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Table of Contents

Overview

On Jul. 25, 2022 Jeff Kern asked K. Scott Rowe to head a tiger team to investigate the various issues that have affected the ALMA Archive hosted in CV for the past few weeks to months.   The  The team was initially just K. Scott.

Communcation lines

Documented Issues

People (not necessarily team members)

  • K. Scott Rowe - Tiger Team Lead
  • CJ Allen - sysadmin
  • Tom Booth - programmer
  • Liz Sharp - sysadmin
  • Brian Mason - DRM Scientist
  • Zhon Butcher - sysadmin
  • Tracy Halstead - sysadmin
  • Alvaro Aguirre - ALMA software
  • Pat Murphy - CIS lead
  • Rachel Rosen - previous ICT lead
  • Laura Jenson - current ICT lead
  • Catherine Vlahakis - Scientist

Communcation lines

Timeline

  • 2020-03-19: ALMA suspends science observing and stows the array because of COVID-19.
  • 2020-06-24: Archive webapps (aq, asaz, rh, etc, but not SP) moved to new Docker Swarm (na-arc-*) system.  See more.
  • 2021-03-17: ALMA re-starts limited science observations, resuming Cycle 7.  See more.
  • 2021-10-01: ALMA starts Cycle 8 observations.  See more.
  • 2022-02-03: Science Portal (SP) upgraded Plone, Python, RHEL and moved into Docker Swarm.  All other webapps had already been in Docker Swarm.
  • 2022-04-18: First documented report of performance issues.  Webapps moved to pre-production Docker Swarm (natest-arc-*).  See more
  • 2022-05-09: moved Science Portal (SP) from Docker Swarm to an rsync copy on  http://almaportal.cv.nrao.edu/ for performance issues
  • 2022-05-31: moved Science Portal (SP) from rsync copy back to Docker Swarm
  • 2022-06-30: Tracy changed the eth0 MTU on the production docker swarm nodes (na-arc-*) from the default 1500 to 9000. The test swarm is still 1500.

Benchmarks

  • Using Apache Benchmarks every hour to load http://almascience.nrao.edu/ on rastan.aoc.nrao.edu
  • Using download script to get 2013.1.00226.S-small (no ASDM tarballs) every hour on cvpost-master.aoc.nrao.edu
  • Using download script to get 2013.1.00226.S-large (with ASDM tarballs) every hour on testpost-master.aoc.nrao.edu

iperf test between hosts measured in Gb/s.  0 means less than 0.01Gb/s.

There is clearly something wrong with na-arc-3 as it is getting about 0.002Gb/s throughput (reports as 0Gb/s) to the other nodes.

...

na-arc-1

(naasc-vs-4)

...

na-arc-2

(naasc-vs-4)

...

na-arc-3

(naasc-vs-3)

...

na-arc-4

(naasc-vs-4)

...

na-arc-5

(naasc-vs-5)

  • You can see poor performance with a command like
    • wget --no-check-certificate http://almaportal.cv.nrao.edu/dataPortal/member.uid___A001_X1358_Xd2.3C286_sci.spw31.cube.I.pbcor.fits
  • krowe has narrowed this down to the ingress overlay network created by docker swarm which is used to re-route traffic sent to the wrong host.
    • On na-arc-2
      • nsenter --net=/var/run/docker/netns/ingress_sbox
      • iperf -B 10.0.0.21 -s
    • On na-arc-3
      • nsenter --net=/var/run/docker/netns/ingress_sbox
      • iperf3 -B 10.0.0.19 -c 10.0.0.21
    • SOLUTION: Set rx-gro-hw=off on naasc-vs-4.  See Conclusions for more details.
  • 2022-09-19 krowe: With rx-gro-hw=off, retransmissions have reduced, but I still see them when sending to naasc-vs-5 and even more when sending to naasc-vs-2.  Sending to naasc-vs-3 or naasc-vs-4 does not produce retransmissions.  This is surprising given how similar naasc-vs-3 and naasc-vs-5 are.  I expect this is caused by congestion as the retransmissions are not easily reproducable.
    • On naasc-vs-2
      • iperf3 -B 10.2.120.107 -s
    • On naasc-vs-3 or naasc-vs-4 or naasc-vs-5 or naasc-cont-1 or...
      • iperf3 -B <LOCAL_IP> -c 10.2.120.107
    • 2022-09-21 cfultz: Replaced the 10Gb network cable on naasc-vs-2.  "the cable was nearly bent in half at the router".  Sadly, I am still seeing retransmissions.
  • 2022-09-19 krowe: With rx-gro-hw=off, throughput over the vxlan/overlay network (like ingress_sbox) has improved but still ranges from 1Gb/s to 4.6Gb/s.  The network is rated at 10Gb/s.  VLAN and VXLAN introduce about a 10% overhead penalty.  So I would expect throughput to be more like 8Gb/s to 9Gb/s.  Granted this isn't really an issue since at the moment the NGAS servers are on a 1Gb/s network, but that may change someday.

Diagrams

  • naasc-archive-network.pdf - This is probably out of date because the docker services can be moved to a different na-arc host which also changes their IP addresses.  It also doesn't list all the docker containers or VM guests, but it is a good approximation.

Timeline of events

  • 2020-03-19: ALMA suspends science observing and stows the array because of COVID-19.
  • 2020-06-24: Archive webapps (aq, asaz, rh, etc, but not SP) moved to new Docker Swarm (na-arc-*) system.  See more.
  • 2021-03-17: ALMA re-starts limited science observations, resuming Cycle 7.  See more.
  • 2021-10-01: ALMA starts Cycle 8 observations.  See more.
  • 2022-02-03: Science Portal (SP) upgraded Plone, Python, RHEL and moved into Docker Swarm.  All other webapps had already been in Docker Swarm.
  • 2022-04-18: First documented report of performance issues.  Webapps moved to pre-production Docker Swarm (natest-arc-*).  See more
  • 2022-05-09: moved Science Portal (SP) from Docker Swarm to an rsync copy on  http://almaportal.cv.nrao.edu/ for performance issues
  • 2022-05-31: moved Science Portal (SP) from rsync copy back to Docker Swarm
  • 2022-06-30: Tracy changed the eth0 MTU on the production docker swarm nodes (na-arc-*) from the default 1500 to 9000. The test swarm is still 1500.
  •  2022-07-25: Jeff Kern asked K. Scott Rowe to head a tiger team to investigate the various issues that have affected the ALMA Archive.
  • 2022-08-11: cloned na-arc-2 and moved the clone to naasc-vs-3 as na-arc-3 and change MTU to 1500.  Other na-arc nodes are 9000 but changing na-arc-3 to 9000 would require changing naasc-vs-3 which could affect other, non-archive, VM guests.
  • 2022-08-12: setup http://almaportal.cv.nrao.edu/ which uses the five na-arc nodes.  This is for internal testing.  Results show download speed at about 32KB/s regaurdless of which na-arc node the web proxy chooses.
  • 2022-08-17 krowe: Changed eth0 on na-arc-5 from qdisc pfifo_fast to qdisc fq_codel to match all the other na-arc and natest-arc nodes.  This seemed to have no affect on performance.
    • tc qdisc replace dev eth0 root fq_codel
  • 2022-08-19 krowe: For some reason, all the swarm services on na-arc-5 shutdown about 11am Central Aug. 18, 2022.  Now my wget tests are getting about 100MB/s and I tested this five times to walk through all four nodes.  I then moved the httpd to na-arc-5 and now na-arc-[1,2,4] download at ~32KB/s while na-arc-[3,5] download at ~100MB/s.
  • 2022-08-25 krowe: Tracy cahnged the following sysctl options on naasc-vs-5 to match the other VM Hosts.  Sadly it seems to have had no effect on wget performance.  na-arc-1, na-arc-2, na-arc-4 are 32KB/s while na-arc-3 and na-arc-5 are 45MB/s.
    • net.ipv4.conf.all.accept_redirects = 0
    • net.ipv4.conf.all.forwarding = 1
  • 2022-09-01: Tracy rebooted naasc-vs-5 which hosts na-arc-5 just in case this was necessary for the net.ipv4.conf.all.forwarding sysctl change to take effect.  Sadly, no change in performance.
  • 2022-09-07 krowe: rebooted na-arc-5 and now net.ipv4.conf.all.accept_redirects = 0 but no change in performance.
  • 2022-09-16 krowe: Set ethtool -K em1 gro off on naasc-vs-4.

Benchmarks

  • Using Apache Benchmarks every hour to load http://almascience.nrao.edu/ on rastan.aoc.nrao.edu
    • ssh.aoc.nrao.edu:/users/krowe/alma_archive/benchmarks/almascience.nrao.edu/data (times are in milliseconds)
      • Mode load time is 98ms
    • ssh.aoc.nrao.edu:/users/krowe/alma_archive/benchmarks/almaportal.cv.nrao.edu/data (times are in milliseconds)
      • Mode load time is 123ms
  • Using wget to get 2013.1.00226.S-small (about 700MB) every hour on cvpost-master.aoc.nrao.edu
    • ssh.cv.nrao.edu:/lustre/cv/users/krowe/tickets/scg-207/benchmarks/almascience.nrao.edu/2013.1.00226.S-small
      • 2022-08-16: average time to download is about 42 seconds which is about 16MB/s
  • iperf tests using iperf3 -s -B <local IP> and  iperf3 -B <local IP> -c <dest IP>

  • 2022-08-11: After re-creating na-arc-3 (a clone of na-arc-2).  Also set the MTU to 1500.  The VM Host interfaces (p5p1.97 and br97 on naasc-vs-3) were still 1500 so we changed the interface on the VM guest (na-arc-3) to 1500 instead of changing the interfaces on the VM host to 9000 because there was concern that may interfere with other running VM guests on that host.

    Table1: iperf3 to/from hosts (Gb/s)

    na-arc-1

    (naasc-vs-4)

    na-arc-2

    (naasc-vs-4)

    na-arc-3

    (naasc-vs-3)

    na-arc-4

    (naasc-vs-4)

    na-arc-5

    (naasc-vs-5)

    na-arc-1
    		1992110

    na-arc-2

    		22
    		92010
    na-arc-377
    		77
    na-arc-421219
    		10
    na-arc-5109810


    Test docker swarm iperf tests measured in Gb/s

    Table2: iperf3 to/from hosts (Gb/s)

    natest-arc-1

    (naasc-dev-vs)

    natest-arc-2

    (naasc-vs-1)

    natest-arc-3

    (naasc-vs-5)

    natest-arc-1
    		0.90.9
    natest-arc-20.9
    		0.9
    natest-arc-30.50.5

    The test docker swarm (natest-arc-*) are performing as expected.  The VM hosts have 1Gb/s links so getting 80% to 90% bandwidth is about as good as one can expect.

  • 2022-08-15 krowe: I had tcpdump running on each na-arc-{1..5} nodes watching for traffic from almaportal tcpdump dst almaportal.  Then I would run the following wget on cvpost-master.  The first execution would be shown by tcpdump on na-arc-1, the second execution on na-arc-2 and so forth.  This is because of the round-robin nature of the web proxy on almaportal and was a nice confirmation of that process.  However, each execution also downloaded at about 32KB/s (0.3Mb/s) after a minute or so of downloading, which is about 300 times slower than expected.  Using the test swarm (natest-arc-{1..3}) I can download the same file at about 10MB/s (100Mb/s). Also, I did not see any difference in performance across the five nodes which was also surprising given that one of the nodes runs the downloader container and the other four need to forward traffic to the one download container.
    • cvpost-master wget --no-check-certificate https://almaportal.cv.nrao.edu/dataPortal/2013.1.00226.S_uid___A001_X122_X1f1_001_of_001.tar
  • 2022-08-15 krowe: I ran iperf tests from end to end and don't see any unexpected performance.
    • [nangas11] -- ~900Mb/s --> [rh-download container on na-arc-5] -- ~8,000Mb/s --> [almaportal] -- ~900Mb/s --> [cvpost-master]
    • [nangas11] -- ~900Mb/s --> [na-arc-5] -- ~8,000Mb/s --> [almaportal] -- ~900Mb/s --> [cvpost-master]
  • 2022-08-17 krowe: doing scp tests of a 784MB file
    • [root@rh-download-na-production-2022jun tmp]# scp krowe@nangas13:/NGAS1/volume1/afa/2022-08-17/1/member.uid___A001_X158f_X90c.IRAS_09022-3615_sci.spw29.cube.I.pb.fits.gz /tmp (93MB/s)
    • [root@rh-download-na-production-2022jun tmp]# scp member.uid___A001_X158f_X90c.IRAS_09022-3615_sci.spw29.cube.I.pb.fits.gz krowe@almaportal:/tmp (70MB/s)
    • almaportal krowe >scp /tmp/member.uid___A001_X158f_X90c.IRAS_09022-3615_sci.spw29.cube.I.pb.fits.gz krowe@cvpost-master:/tmp (110MB/s)
  • tcpdump bandwidth tests
    • When I download a file from na-arc-5 like so `wget --no-check-certificate http://na-arc-5.cv.nrao.edu:8088/dataPortal/member.uid___A001_X122_X1f1.LKCA_15_13CO_cube.image.fits` which lives on nangas13, to cvpost-master, the download runs at about 32KB/s.
      • On nangas13 I see about that much traffic (32KB/s to 50KB/s) almost all of it going to na-arc-5.
      • on na-arc-5 (rh-download container) I see between about 200KB/s and 300KB/s of traffic.
      • on na-arc-2 (httpd container) I see between about 100KB/s and 150KB/s of traffic.  It seems like it is about half the traffic na-arc-5 sees.
  • 2022-08-19 krowe: For some reason, all the swarm services on na-arc-5 shutdown about 11am Central Aug. 18, 2022.  Now my wget tests are getting about 100MB/s and I tested this five times to walk through all four nodes.
    • na-arc-5 was running
      • acralmaprod001.azurecr.io/offline-production/asax-elasticsearch:2022.02.01.2022feb (now on na-arc-3)
      • acralmaprod001.azurecr.io/offline-production/asax-explorer:2022.04.01.2022apr (now on na-arc-2)
      • acralmaprod001.azurecr.io/offline-production/asax-ingestor:2022.06.01.2022jun (now on na-arc-3)
      • acralmaprod001.azurecr.io/offline-production/rh-download:2022.06.01.2022jun (now on na-arc-2)
      • acralmaprod001.azurecr.io/offline-production/rh-logging:2022.06.01.2022jun (now on na-arc-4)
    • Looks like na-arc-5 lost its heartbeat with the swarm.  This is around the time I learned that setting net.ipv4.tcp_timestamps = 0 makes wget performance drop to 0.0KB/s.  So it may have been me that caused na-arc-5 to loose its heartbeat with the swarm although setting net.ipv4.tcp_timestamps=0 on na-arc-5 again didn't cause docker to move the service off it this time.

      • Aug 18 13:34:16 na-arc-5 dockerd: time="2022-08-18T13:34:14.131474019-04:00" level=warning msg="memberlist: Refuting a suspect message (from: c30261b68826)"

        Aug 18 13:34:16 na-arc-5 dockerd: time="2022-08-18T13:34:15.929428007-04:00" level=info msg="memberlist: Suspect 886f1454e2b4 has failed, no acks received"

        Aug 18 13:34:16 na-arc-5 dockerd: time="2022-08-18T13:34:16.061224152-04:00" level=error msg="heartbeat to manager {xojanp58fu1ysx3yk0rpvjsft 10.2.97.71:2377} failed" error="rpc error: code = DeadlineExceeded desc = context deadline exceeded" method="(*session).heartbeat" module=node/agent node.id=1l5cnfmt16f6hyg5it0rq39rr session.id=fl2thh44rmjfxgu7xidnakjg8 sessionID=fl2thh44rmjfxgu7xidnakjg8

    • I moved the rh-download service back to na-arc-5 with docker service update --force production_requesthandler_download and wget performance is back to about 32KB/s.
    • I moved rh-download from na-arc-5 back to na-arc-2 by draining na-arc-5 docker node update --availability drain na-arc-5 and wget performance was back to about 100MB/s.  I ran it four times to make sure.
    • Then I moved rh-download from na-arc-2 to na-arc-1 by forcing a rebalance again with docker service update --force production_requesthandler_download.  This is because na-arc-5 was still drained.  wget performance was back to about 100MB/s.  I ran it four times to make sure.  I wanted to make sure the performance was good because rh-download wasn't on na-arc-5 and not because it was on na-arc-2.  I think I have shown that.  So, the question is why is performance so poor when rh-download is on na-arc-5?
    • I moved production_httpd from na-arc-2 to na-arc-5 and wget performance is vaiable.
      • wget --no-check-certificate http://na-arc-1.cv.nrao.edu:8088/dataPortal/member.uid___A001_X122_X1f1.LKCA_15_13CO_cube.image.fits is about 32KB/s
      • wget --no-check-certificate http://na-arc-2.cv.nrao.edu:8088/dataPortal/member.uid___A001_X122_X1f1.LKCA_15_13CO_cube.image.fits is about 32KB/s
      • wget --no-check-certificate http://na-arc-3.cv.nrao.edu:8088/dataPortal/member.uid___A001_X122_X1f1.LKCA_15_13CO_cube.image.fits is about 100MB/s
      • wget --no-check-certificate http://na-arc-4.cv.nrao.edu:8088/dataPortal/member.uid___A001_X122_X1f1.LKCA_15_13CO_cube.image.fits is about 32KB/s
      • wget --no-check-certificate http://na-arc-5.cv.nrao.edu:8088/dataPortal/member.uid___A001_X122_X1f1.LKCA_15_13CO_cube.image.fits is about 100MB/s
      • My first thought was this has something to do with naasc-vs-4 since na-arc-[1,2,4] are on that VM host.  But iperf tests still show about 900MB/s between all hosts and cvpost-master.
        • There are some differences in the VM hosts sysctl settings
          • naasc-vs-3

            • net.ipv4.conf.all.accept_redirects = 0

            • net.ipv4.conf.all.forwarding = 1
          • naasc-vs-4
            • net.ipv4.conf.all.accept_redirects = 0
            • net.ipv4.conf.all.forwarding = 1
          • naasc-vs-5
            • net.ipv4.conf.all.accept_redirects = 1
            • net.ipv4.conf.all.forwarding = 0
  • 2022-08-31 krowe: I have learned how to do iperf tests ingress network (docker mesh).
    • Login to an VM guest and run the following to get a shell in the ingress_sbox namespace
      • nsenter --net=/var/run/docker/netns/ingress_sbox
    • You can now run ip -c addr to see the IPs of the ingress network
    • Below is a table using default iperf3 test.  The values are rounded for simplicity.  Hosts accross the top row are receiving while hosts along the left column are transmitting.


Table3: iperf3 to/from ingress_sbox (Mb/s)


na-arc-1

10.0.0.2

na-arc-2

10.0.0.21

na-arc-3

10.0.0.19


na-arc-4

10.0.0.5

na-arc-5

10.0.0.6

na-arc-1
4,0002,0004,0003,000
na-arc-24,000
2,0004,0003,000
na-arc-30.30.3
0.33,000
na-arc-44,0004,0002,000
3,000
na-arc-50.30.32,0000.3
Table4: iperf3 to/from ingress_sbox (Mb/s)

natest-arc-1

10.0.0.2

natest-arc-2

10.0.0.8

natest-arc-3

10.0.0.4

natest-arc-1
900700
natest-arc-2900
700
natest-arc-3300300


  • 2022-09-08 krowe: I have tested the other overlay networks (production_agent_network 10.0.1.0/24 and production_default 10.0.2.0/24) and they perform similarly to the ingress overlay network 10.0.0.0/24.
  • 2022-09-09 krowe: na-arc-6 is now online served from naasc-vs-2. Here are the iperf3 tests from ingress_sbox to ingress_sbox.  When throughput is slow (Kb/s) I see that the congestion window size is reduced from about 1MB to about 2.73KB.


    Table6: iperf3 TCP throughput from/to ingress_sbox (Mb/s)

    na-arc-1

    (naasc-vs-4)

    na-arc-2

    (naasc-vs-4)

    na-arc-3

    (naasc-vs-3)

    na-arc-4

    (naasc-vs-4)

    na-arc-5

    (naasc-vs-5)

    na-arc-6

    (naasc-vs-2)

    na-arc-1
    		39202300420031103280
    na-arc-23950
    		2630400033503530
    na-arc-30.20.3
    		0.227202810
    na-arc-4386035802410
    		33903290
    na-arc-50.20.224800.2
    		2550
    na-arc-60.0050.00527900.0053290
  • 2022-09-09 krowe: The ingress network (docker mesh) that I have been testing using the ingress_sbox namespace uses a veth interface (this is like a pipe) that connects to its corrosponding veth interface in another namespace on the same host which connects to a vxlan over a bridge in that second namespace.  vxlan is a tunneling protocol that uses UDP over port 4789.  This is why I am seeing my TCP packets turn into UDP packets.  Using tcpdump in the ingress_sbox to watch iperf TCP traffic going from na-arc-2 to na-arc-3 looks clean.  Watching traffic going from na-arc-3 to na-arc-2, which is slow (32KB/s), shows lots of TCP Retransmission and TCP Out-Of-Order packets.

TCP Retransmissions

  • 2022-09-15 krowe: Even with rx-gro-hw=off on naasc-vs-4, I am still seeing some retransmissions in iper3 tests.  These are the same as TCP Retransmissions seen previously.  On a modern, well-designed network I would expect to see almost no TCP Retransmissions.  So this may indicate that there are still improvements to be made.  The number of retransmissions seems to vary over time from 0 retransmissions to over a thousand retransmissions on certain directions.  This makes me think there is something else using the 10Gb network that is interfering with my tests.

  • This is a 10 second iper3 test using TCP from the host in the left column to the host in the top row.

    TableXX iperf3 Retransmissions over 10Gb and rx-gro-hw=off

    naasc-vs-2

    (10.2.120.107)

    naasc-vs-3

    (10.2.120.109)

    naasc-vs-4

    (10.2.120.110)

    naasc-vs-5

    (10.2.120.112)

    naasc-vs-2
    		0, 0, 00, 0, 045, 52, 59
    naasc-vs-387, 0, 19, 1734
    		0, 0, 074, 52, 56
    naasc-vs-40, 342, 1147, 3630, 0, 0
    		83, 51, 50
    naasc-vs-5494, 0, 1296, 240, 0, 00, 0, 0

    This looks like some sort of misconfiguration on the receiving ends of naasc-vs-2 and naasc-vs-5.  This may be congestion.  For example if I start an iper3 test from naasc-vs-4 to naasc-vs-2 I can often see 0 retransmissions every second.  But then while doing that I also start in iper3 test from na-arc-1 (a guest on naasc-vs-4) to na-arc-6 (a guest on naasc-vs-2), I can see around 20 to 70 retransmissions per second on both naasc-vs-4 and na-arc-1.  They are clearly interfering with each other.  I don't see congestion when I reverse the test (naasc-vs-2 to naasc-vs-4 while na-arc-6 to na-arc-1).  Doing the same test from naasc-vs-5 to naasc-vs-3 while doing na-arc-5 (a guest on naasc-vs-5) to na-arc-3 (a guest on naasc-vs-3) I don't see any congestion.  If I turn off TSO on naasc-vs-2 with ethtool -K ens1f0np0 tx-tcp-segmentation off I then no longer can create congestion by doing two simultaneous iperf3 tests but I still get occational retransmissions (like 100+ per second) when testing from naasc-vs-{3..5} to naasc-vs-2.  Disabling TSO also doesn't seem to reduce the number of retransmissions when testing from na-arc-* to na-arc-6.

    TableXX iperf3 Retransmissions over 10Gb and rx-gro-hw=off

    na-arc-1

    10.2.97.71

    (naasc-vs-4)

    na-arc-2

    10.2.97.72

    (naasc-vs-4)

    na-arc-3

    10.2.97.73

    (naasc-vs-3)

    na-arc-4

    10.2.97.74

    (naasc-vs-4)

    na-arc-5

    10.2.97.75

    (naasc-vs-5)

    na-arc-6

    10.2.97.76

    (naasc-vs-2)

    na-arc-1
    		0, 0, 00, 0, 00, 0, 055, 75, 50323, 501, 538
    na-arc-20, 0, 0
    		0, 0, 00, 0, 068, 81, 64768, 1050, 658
    na-arc-31692, 1627, 20710, 1326, 592
    		1471, 3376, 686360, 2477, 6641873, 1872, 2384
    na-arc-40, 0, 00, 0, 00, 0, 0
    		58, 86, 654, 9, 38
    na-arc-5108, 6, 66, 6, 62, 1, 16, 6, 6
    		1293, 1197, 33
    na-arc-6106, 0, 280, 0, 210, 88, 07, 0, 2889, 75, 52


    • I see a lot of dropped packets on the Rx side of all the naasc-vs hosts.
  • I think the large number of retransmissions when transmissing from naasc-vs-* to naasc-vs-2 the cause for the large number of retransmissions when transmitting from na-arc-* to na-arc-6.
  • I don't know what explains the retransmissions when transmitting from na-arc-3 to na-arc-*.

  • I don't think the retransmissions from na-arc-3 to na-arc-* can be atributed to MTU.  Sure eth0 on na-arc-3 is 1500 while all the other na-arc nodes are 9000 but that should not cause a problem.  If anything it sould be a problem the other way around.  Also I tested changing na-arc-6 to 1500 and retransmissions didn't change.  The lack of retransmissions between na-arc-1, na-arc-2, and na-arc-4 is because they are all on the same VM Host (naasc-vs-4).

    • You can use ping to see if your packet size actually gets through.  This is a good way to test MTU sizes.

      • ping -c 3 -M do -s 1500 na-arc-1

  • Try increasing Rx buffers (ethtool -G) and see if that helps retransmits
    • ethtool -G ens1f0np0 rx 4096
    • ethtool -G ens1f0np0 tx 2048
    • Setting these didn't seem to help with the TCP Retransmissions.
    • 2022-09-28 krowe: Not so fast.  I was running a long iperf3 test from naasc-vs-4 to naasc-vs-2 and while seeing over 100 TCP Retransmissions per second I ran the following on naasc-vs-2 ethtool -G ens1f0np0 rx 4096 and immediatly saw the TCP Retransmissions drop to 0.  I put the rx ring parameter back to 1024 and performed the test again and saw an immediate drop to 0.  So there may be something here.  Perhaps it helps but does not do away with all the TCP Retransmissions.  Theoretically, there will always be some TCP Retransmissions over a long enough sample.  I then succeded in two more tests.  I think there is something here.  Though I can still produce TCP retransmissions by running an iper3 test from na-arc-4 to na-arc-6 while running a test from naasc-vs-4 to naasc-vs-2.
    • 2022-09-28 krowe: But more iper3 tests once rx=4096 show occational bouts of over 100 TCP Retransmissions per second.  So perhaps increasing the ring parameter just reduces that perticular storm but other storms still occur.
  • Map the retransmissions.  Is there a pattern over time?  A regular cadence?
  • map background traffic
  • Is the fact that APIPA (zeroconf) is configured an indication that some network device was not brought up properly
    • 2022-09-28 krowe: No.  APIPA routes are created via /etc/sysconfig/network-scripts/ifup-eth which is installed from the network-scripts RPM.  This RPM is legacy for RHEL8 (naasc-vs-2 is RHEL8.6) and must have been installed specificly.  It is not installed on any other RHEL8 machine I have checked.
    • 2022-09-28 krowe: NO.  I think APIPA is a red herring.  I created routes on naasc-vs-3 against p5p1, p5p1.120, and br97 and didn't see any TCP retransmissions.  I also didn't see any increase in dropped packets.  I also removed the routes from naasc-vs-2 and still occationally see 110 TCP Retransmissions per second.
  • What about ethtool -K ens1f0np0 tx-tcp-segmentation off
    • 2022-09-26 krowe: didn't make a difference.
  • What about net.core.netdev_budget
  • https://access.redhat.com/articles/1391433
  • dropwatch - Couldn't get it to compile on naasc-vs-2 or any other RHEL8 machine because of missing libraries
  • naasc-vs-2 is RHEL8.  Could that be the problem?
  • Solarflare card is a slightly newer model.  Could that be the problem?
    • 2022-09-28 krowe: Don't know.  CV tried putting the same model card in naasc-vs-3 and 5 but then naasc-vs-2 wouldn't boot.
  • Replace the Solarflare card with a different card of the same model.  Perhaps this card has bad RAM or somesuch.
  • 2022-09-29 krowe: BCC https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/configuring_and_managing_networking/index
  • 2022-09-30 krowe: I set all three of these on naasc-vs-2 sysctl -w net.core.rmem_max=26214400 and sysctl -w net.ipv4.tcp_rmem="4096 87380 26214400" and ethtool -G ens1f0np0 rx 4096.  I can't say if it reduced the likehood of TCP Retransmissions but I still saw them eventually.
  • 2022-10-03 krowe: dhart and thalstead inserted a second 10Gb/s card in naasc-vs-2.  This one is supposedly a Solarflare SNF8522 even though Linux detects it as the same model as the original card (Solarflare Communications SFC9220 10/40G Ethernet Controller [1924:0a03]).  Tracy configured this card to be the 10Gb/s NIC of naasc-vs-2 (ens2f0np0).  I don't know why they didn't just remove the original card an insert the new card thus requiring no changes to the configuration but whatever.  My iperf3 tests still show over 100 TCP Retransmissions per second.  So the idea that the original card had some hardware flaw (like bad memory or something) is disproven.
  • 2022-10-04 krowe: thalstea updated the sfc driver on naasc-vs-2 using dkms to version 5.3.12.1021.  Sadly I still see occational periods of TCP Retransmissions on the order of 100 per second.
  • 2022-10-05 krowe: now with the new sfc driver, I set ethtool -G ens1f0np0 rx 4096 but still see TCP Retransmissions.
  • 2022-10-05 krowe: I think it is also interesting that when I run my iperf3 tests for 400 seconds (which often produced TCP retransmissions on naasc-vs-2) the Congestion window (Cwnd) never gets above 0.578MB while with tests to naasc-vs-4 the Cwnd gets up to 2.2MB.
  • 2022-10-06 krowe: thalstea re-installed naasc-vs-2.  It was RHEL8 and it is now RHEL7.  Since the re-installation I have been unable to reproduce the 100+ TCP retransmissions per second.  However I do see times where the throughput to naasc-vs-2 drops to zero bytes per second.  I see reports in /var/log/messages on naasc-vs-2 of the p1p1 NIC's link going down and up at the same times my throughput drops to zero.
    • Later this same day I finally saw 100+ TCP retransmissions per second.  Dang.  So now we have both TCP retransmissinos and flapping NIC.  Sigh.
    • I increased both Rx and Tx ring buffers on naasc-vs-2 from 1024 to 2048 to see if that helps with TCP retransmissions.  It seems that the downgrade to RHEL7 may have reduced the number of TCP retransmissions, but I am still occationally seeing them.  And shortly after doing this I saw the 100+ TCP retransmissions per second.
  • 2022-10-12: thalstea tried adding an old solarflare card to naasc-vs-2 but it wouldn't even get past the BIOS.  Here is a screenshot.
  • 2022-10-12: thalstea upgraded the firmware on the solarflare card (SFN8511) from 6.5.1.1023 to 8.5.0.1002
  • 2022-10-12 krowe: Sadly I have still seen periods of 100+ TCP retransmissions per second when doing iper3 tests.  I have noticed that when I see these periods, if I quickly kill and restart the iper3 test, the TCP retransmissions drop back to 0.  So it is possible that these TCP retransmissions are just a side effect of my iperf3 tests and may not happen during normal usage.  Also, the throughput doesn't drop below 9Gb/s when during these periods so while I am sad that I don't understand why this happens, I am thinking this may not be as much of an issue as I once feared.
  • 2022-10-14 krowe: I noticed that while these TCP retransmissions are happening, if I quickly kill and restart the iper3 test they go back to zero.  This is starting to make me think these TCP retransmissions are only a problem when the network is significantly stressed, and when they do happen it is like a firestorm where the kernel or the NIC loose ground and can't ever catch up. This could mean that we may never see these TCP retransmissions in production, or if we do it will be rare enough to not worry about.  I also found another tool, /usr/share/bcc/tools/tcpretrans, which is part of a suite of tools called BPF Compiler Collection (BCC).  There are several usefull tools in there.  With tcpretrans, I can see the TCP retransmissions happening on naasc-vs-3 or naasc-vs-4 or whatever the source host is in my iper3 tests.  This also means we can watch for them in production.

Dropped packets

I see dropped Rx packets on interface ens1f0np0 on naasc-vs-2 at a rate of about 100 packets per minute.  You can see this with watch ifconfig ens1f0np0.  This is especially interesting given that there isn't much traffic on naasc-vs-2 right now.  It is only hosting one VM guest (na-arc-6) and that guest is only running the docker agent container.  I am not seeing any dropped packets on na-arc-6.

  • 2022-09-26 krowe: ethtool -G ens1f0np0 tx 2048 and ethtool -G ens1f0np0 rx 4096 made no difference.
  • 2022-09-26 krowe: ethtool -K ens1f0np0 tx-tcp-segmentation off made no difference

I see dropped Rx packets on all the other naasc-vs hosts as well.  Hosts naasc-vs-3 and naasc-vs-5 show only about 2 packets dropped per minute while naasc-vs-4 shows about 100 packets per minute.  I don't think this is related to the TCP Retransmissions as I don't see any of them when sending to naasc-vs-4.

  • I don't think this is because of broadcast noise on the 10Gb/s network (10.2.120.0/24) as I don't see see large dropped packet counts on all naasc-vs hosts.
  • 2022-09-26 krowe: Interestingly, if I watch the number of packets dropped per minute (I worte a script) and run the scripts at the same time on all four naasc-vs hosts, I see patterns.  The number of dropped packets each minute is identical between naasc-vs-2 and naasc-vs-4 and hovers around 100.  The number of dropped packets each minute is identical between naasc-vs-3 and naasc-vs-5 and hovers around 2.  This tells me that naasc-vs-2 and naasc-vs-4 are getting the same traffic and dropping it the same way.  What is this traffic?
  • 2022-09-26 krowe: I set na-arc-6, the only guest on naasc-vs-2, to drain in docker swarm to see if that reduced the number of dropped packets seen on naasc-vs-2.  Thinking it was docker swarm creating this traffic.  There was no change in dropped packet rate.  It continued to match naasc-vs-4.
  • 2022-09-26 krowe: On naasc-vs-3 and naasc-vs-5 I see the dropped packet count per minute at about 2 but every 5 or 6 minutes the count inreases to 10 or 11.
  • 2022-09-26 krowe: I tried looking at other nodes on the 10Gb 10.2.120.0/24 network but I couldn't login to most of them.  One I could login to is cv-vs-4 and it is also seeing dropped Rx packets on its 10Gb interface at about the same rate as naasc-vs-3 and naasc-vs-5.  This makes me think that these dropped packets have nothing to do with docker swarm.  Perhaps there is just something on that network (some misconfigured Windows box or something) that is throwing bad packets around.  That doesn't explain the difference in the dropped packet rates though.
  • 2022-09-27 krowe: try clearing the ARP cache on the switch?  Perhaps the switch is sending packets to the node to an IP address that is no longer there like because the container moved.
  • use tcpdump and sort by destination looking for the number of dropped packets per minute.
  • 2022-10-03 krowe: dhart and thalstead inserted a second 10Gb/s card in naasc-vs-2.  This one is supposedly a Solarflare SNF8522 even though Linux detects it as the same model as the original card (Solarflare Communications SFC9220 10/40G Ethernet Controller [1924:0a03]).  Tracy configured this card to be the 10Gb/s NIC of naasc-vs-2 (ens2f0np0).  I don't know why they didn't just remove the original card an insert the new card thus requiring no changes to the configuration but whatever.  I am still seeing about 60 dropped packets per minute, and it still matches the dropped packets on naasc-vs-4.  So the idea that the original card had some hardware flaw (like bad memory or something) is disproven.
  • 2022-10-14 krowe: I may have a line on what is causing the dropped packets.  Several times now when I do tcpdumps on either naasc-vs-2 or naasc-vs-4, tcpdump at the end tells me how many packets were dropped by the interface.  This number matches what my droprate.sh script shows (it gets its information from ifconfig which is probably what tcpdump does also).  Looking at these tcpdumps, I see a number of LLMNR (that's the protocol) packets which is about twice this number.  Half of these packets are IPV4 and half are IPV6.  They are both going to multicast addresses (224.0.0.252 and ff02::1:2).  This is leading me to think naasc-vs-2 and naasc-vs-4 are dropping packets either because the are from IPV6 addresses or they are destened for IPV6 multicast addresses.  Not sure which or even if that is correct.  But so far these sorts of packets fit the number of dropped packets.  I see these same LLMNR packets, both IPV4 and IPV6 on naasc-vs-3 but that host reports almost no dropped packets.  Configuration difference?
    • This page https://access.redhat.com/articles/22304 has a python script that will join a multicast group.
    • I see with netstat -ng naasc-vs-3 and naasc-vs-5 are in the special multicast group 224.0.0.251 while naasc-vs-2 and naasc-vs-4 are not.  This configuration difference lines up with seeing dropped packets on naasc-vs-2 and naasc-vs-4 but not on naasc-vs-3 and naasc-vs-5 (or at least a lot fewer dropped packets).  But joining this multicast group on naasc-vs-2 didn't change the dropped packet rate.
    • I will ask if the LLMNR protocol on cvsccm can be disabled.  Looking around the internet it seems that this is a pretty old way for Windows to share hostnames and is largely deprecated.
    • 2022-10-17 krowe: Actually, I see a strong correlation between IPV6 packets in tcpdump and dropped packets reported by both my script and tcpdump itself on naasc-vs-2 and naasc-vs-4.  But I don't understand why these two hosts would be dropping IPV6 packets while naasc-vs-3 would not.  If I tcpdump all three hosts, I see the same IPV6 packets on all three (usually LLMNR multicast or DHCP6 broadcast).  And all three hosts have ipv6.disable=1 in /proc/cmdline.
    • 2022-10-17 krowe: I see an even stronger correlation between dropped packets and IPV6 packets on VLAN ID 96.  This could explain the dropped packets as neither naasc-vs-2 nor naasc-vs-4 have VLAN 96 configured while both naasc-vs-3 and naasc-vs-5 do have VLAN 96 configured.  This should be an easy test.  Just configure VLAN 96 on naasc-vs-2 and see if the dropped packet rate goes from about 1 per second to less than 1 per minute.
    • Here is a PCAP file.  tcpdump reported 85 packets dropped by the interface while capturing these packets.  If you use wireshark to look at this file you can see there are 86 IPV6 packets (ipv6.src) and all but one of them were on VLAN 96 (ipv6.src and vlan.id == 96).
    • 2022-10-18 krowe: Tracy created VLAN96 interfaces (p1p1.96, br96) on naasc-vs-2 and the dropped packet rate on naasc-vs-2 is now very similar to that of naasc-vs-3 and naasc-vs-5, which is about 2 packets per minute as opposed to 1 or more packets per second.  This means naasc-vs-2 was dropping packets that were both IPV6, which is disabled, and VLAN96, which wasn't configured.  I find it strange that it took both features to drop a packet (IPV6 and VLAN96).  I would have thought either would be sufficient for the packet to be dropped.  This is good to know for future reference when putting a Linux machine on a trunking port.  Doing tcpdumps now, I expect the remaining packets, 1 or 2 per minute, are likely DHCP6 IPV6 packets for VLAN192.

    • We should decide if we want to configure all possible VLANs these hosts may see so that the dropped packet count remains zero or live with an ever increasing dropped packet count and document that this is probably caused by unconfigured VLANs.


Comparisons

naasc-vs-2, 3, 4, 5

Identical

  • 2022-09-02 krowe: sysctl -a | grep br97 across naasc-vs-{3..5} are identical.
  • 2022-09-02 krowe: sysctl -a | grep <vnet> across naasc-vs-{3..5} are identical except for the vnet name (e.g. vnet2, vnet4, etc)
  • 2022-09-02 krowe: sysctl -a across naasc-vs-3 and naasc-vs-5 have no significant differences.
  • 2022-09-06 krowe: CV-NEXUS switch port capabilities for naasc-vs-{3..5} are identical.
  • 2022-09-06 krowe: CV-NEXUS9K switch port capabilities for naasc-vs-{2..5} are identical.
  • 2022-09-06 krowe: ethtool -k <NIC> across naasc-vs-3 and naasc-vs-5 are identical execpt for the NIC name.
  • 2022-09-07 krowe: iptables -L and iptables -S across naasc-vs-{3..5} are identical.
  • 2022-09-02 krowe: sysctl -a | grep <10Gb NIC> across naasc-vs-3 and naasc-vs-5 are identical except for the name of the NIC.
  • 2022-09-19 krowe: ethtool -g <NIC> across naasc-vs-3 and naasc-vs-5 are identical.

Differences

  • 2022-09-02 krowe: sysctl -a | grep <10Gb NIC> between naasc-vs-3/naasc-vs-5 and naasc-vs-4 are different
    • naasc-vs-4 has entries for VLANs 101 and 140 while naasc-vs-3 and naasc-vs-5 have entries for VLANs 192 and 96.
  • 2022-09-02 krowe: sysctl -a on naasc-vs-4 and naasc-vs-5 and found many questionable differences
    • naasc-vs-4: net.iw_cm.default_backlog = 256
      • Is this because the IB modules are loaded?
    • naasc-vs-4: net.rdma_ucm.max_backlog = 1024
      • Is this because the IB modules are loaded?
    • naasc-vs-4: sunrpc.rdma*
      • Is this because the IB modules are loaded?
    • naasc-vs-4: net.netfilter.nf_log.2 = nfnetlink_log
      • nfnetlink is a module for packet mangling.  Could this interfear with the docker swarm networking?
    • Though the recorded output rate of naasc-vs-5 is about 500 Mb/s while naasc-vs-{3..4} is about 300Kb/s.
    • And the recorded input rate of naasc-vs-5 is about 500 Mb/s while naasc-vs{3..4} is about 5 Mb/s.
    • This is very strange as it seemed naasc-vs-5 was the limiting factor but the switch ports suggest not.  Perhaps this data rate is caused by other VM guests on naasc-vs-5 (helpdesk-prod, naascweb2-prod, cartaweb-prod, natest-arc-3, cobweb2-dev)
  • 2022-09-06 krowe: ethtool -k <NIC> for naasc-vs-3/naasc-vs-5 are very different from naasc-vs-4.
    • hw-tc-offload: off vs hw-tc-offload: on
    • rx-gro-hw: off vs rx-gro-hw: on
    • rx-vlan-offload: off vs rx-vlan-offload: on
    • rx-vlan-stag-hw-parse: off vs rx-vlan-stag-hw-parse: on
    • tcp-segmentation-offload: off vs tcp-segmentation-offload: on
    • tx-gre-csum-segmentation: off vs tx-gre-csum-segmentation: on
    • tx-gre-segmentation: off vs tx-gre-segmentation: on
    • tx-gso-partial: off vs x-gso-partial: on
    • tx-ipip-segmentation: off vs tx-ipip-segmentation: on
    • tx-sit-segmentation: off vs tx-sit-segmentation: on
    • tx-tcp-segmentation: off vs tx-tcp-segmentation: on
    • tx-udp_tnl-csum-segmentation: off vs tx-udp_tnl-csum-segmentation: on
    • tx-udp_tnl-segmentation: off vs tx-udp_tnl-segmentation: on
    • tx-vlan-offload: off vs tx-vlan-offload: on
    • tx-vlan-stag-hw-insert: off vs tx-vlan-stag-hw-insert: on
  • 2022-09-12 krowe: I found the rx and tx buffers for em1 on naasc-vs-4 were 511 while on naasc-vs-2, 3, and 5 were 1024.  You can see this with ethtool -g em1.  I changed naasc-vs-4 with the following ethtool -G em1 rx 1024 tx 1024 but it didn't change iperf performance.
  • 2022-09-12 krowe: I found an article suggesting that gro can make traffic slower when it is enabled.  I see that rx-gro-hw is enabled on naasc-vs-4 but disabled on naasc-vs-3 and 5.  You can see this with ethtool -k em1 | grep gro.So I disabled it on naasc-vs-4 with ethtool -K em1 gro off and iperf3 tests now show about 2Gb/s both directions!!!
  • 2022-09-15 krowe: The VM Hosts have different 10Gb network cards
    • naasc-vs-2 uses a Solarflare Communications SFC9220
    • naasc-vs-3 uses a Solarflare Communications SFC9020
    • naasc-vs-4 uses a Broadcom BCM57412 NetXtreme-E
    • naasc-vs-5 uses a Solarflare Communications SFC9020
  • 2022-10-07 krowe: bare metal differences
    • naasc-vs-2: Dell PowerEdge R7525, dual AMD EPYC 7352 24-Core Processor
    • naasc-vs-3: Dell PowerEdge R730, dual Intel(R) Xeon(R) CPU E5-2650 v4 @ 2.20GHz
    • naasc-vs-4: Dell PowerEdge R740, dual Intel(R) Xeon(R) Gold 6152 CPU @ 2.10GHz
    • naasc-vs-5: Dell PowerEdge R740, dual Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz


Questions

  • 2022-09-26 krowe: Can someone who is able to login, login to the nodes on the 10.2.120 network and see if those interfaces are showing dropped Rx packets?  I would, but I can't login to most of them because CV.
  • Why does naasc-vs-4 have all the infiniband modules loaded?  I don't see an IB card.  naasc-vs-1 and naasc-dev-vs also have some IB modules loaded but naasc-vs-3 and naasc-vs-5 don't have any IB modules loaded.
    • Tracy will look into this
    • 2022-10-05 krowe: I don't think this is a significant issue.
  • Why is nfnetlink logging enabled on naasc-vs-4?  You can see this with cat /proc/net/netfilter/nf_log and lsmod|grep -i nfnet
    • nfnetlink is a module for packet mangling.  Could this interfear with the docker swarm networking?
    • 2022-10-05 krowe: I don't think this is a significant issue.
  • why is the eth1 interfaces in all the containers and docker_gwbridge on na-arc-1 in the 172.18.x.x range while all the other na-arcs are in the 172.19.x.x range?  Does it matter?
  • Here are some diffs in sysctl on na-arc nodes.  I tried changing na-arc-4 and na-arc-5 to match the others but performance was the same.  I then changed all the nodes to match na-arc-{1..3} and still no change in performance.  I still don't understand how na-arc-{4..5} got different setttings.  I did find that there is another directory for sysctl settings in /usr/lib/sysctl.d but that isn't why these are different.
    • na-arc-1, na-arc-2, na-arc-3, natest-arc-1, natest-arc-2, natest-arc-3

      • net.bridge.bridge-nf-call-arptables = 0

        net.bridge.bridge-nf-call-ip6tables = 0

        net.bridge.bridge-nf-call-iptables = 1

    • na-arc-4, na-arc-5

      • net.bridge.bridge-nf-call-arptables = 1

        net.bridge.bridge-nf-call-ip6tables = 1

        net.bridge.bridge-nf-call-iptables = 1

  • Why does almaportal use ens3 while almascience uses eth0?

To Do

  • Set ethtool -K em1 gro off perminantly on naasc-vs-4 and document it.  How do we do this?
  • Strawman proposal for reassigning VM guests
  • 2022-10-05 krowe: Change the NIC Model on natest-arc-3.  It is currently rtl8139 instead of virtio and is its speed 100Mb/s instead of 1000Mb/s.
    • You can see this with virsh domiflist natest-arc-3 on naasc-vs-5.
    • 2022-10-05 krowe: This should be fixed but after the test swarm is no longer acting as the production swarm

  • Decide if we want to configure all possible VLANs these hosts may see so that the dropped packet count remains zero or live with an ever increasing dropped packet count and document that this is probably caused by unconfigured VLANs.


Answers

  • Why does iperf show 10Gb/s between na-arc-5 and na-arc-[1,2,4]?  How is this possible if the default interface on the respective VM Hosts is 1Gb/s?
    • ANSWER: The vnets for the VM guests are tied to the 10Gb/s NICs on the VM hosts not the 1Gb/s NICs.
  • Why do natest-arc-{1..3} have 9 veth* interfaces in ip addr show while na-arc-{1..5} don't have any veth* interfaces?
    • Each container creates a veth* interface.
  • Why does na-arc-3 have such poor network performance to the other na-arc nodes?
    • ping na-arc-[1,2,4,5] with anything larger than -s 1490 drops all packets
    • iperf tests show 10Gb/s between the VM host of na-arc-3 (naasc-vs-3 p5p1.120) and the VM host of na-arc-5 (naasc-vs-5 p2p1.120).  So it isn't a bad card in either of the VM hosts.
    • iptables on na-arc-3 looks different than iptables on na-arc-[2,3,5].  na-arc-1 also looks a bit different.
    • docker_gwbridge interface on na-arc-[1,2,4,5] shows NO_CARRIER but not on na-arc-3.
    • na-arc-3 has a veth10fd1da@if37 interface.  None of the other na-arc-* nodes have a veth interface.

    • Production docker swarm iperf tests measured in Gb/s.


      na-arc-1

      (naasc-vs-4)

      na-arc-2

      (naasc-vs-4)

      na-arc-3

      (naasc-vs-3)

      na-arc-4

      (naasc-vs-4)

      na-arc-5

      (naasc-vs-5)

      na-arc-1
      		180.0022010

      na-arc-2

      		20
      		0.0022010
      na-arc-30.0020.002
      		0.0020.002
      na-arc-420190.002

      na-arc-510100.0021010

      There is clearly something wrong with na-arc-3

    • ANSWER: Since there were so many problems with na-arc-3, it was decided to recreate it.  It was recreated from a clone of na-arc-2.
  • Is putting all the 1Gb/s production docker swarm nodes on the same ASIC on the same Fabric Extender of the cv-nexus switch a good idea?
    • I am thinking it does not matter because it looks like the production docker swarm nodes use the 10Gb/s network which is on cv-nexus9k
  • Can we set up a test archive query that uses the "other" docker swarm which in this case would be the production swarm (na-arc-*)?
  • Why are there VLANs on the VM hosts.  e.g. em1.97 on naasc-vs-4?

    • 2022-08-12 dhart: If you want all of your guest VMs to be on the same subnet as the VM host, then VLAN awareness isn't needed.  However, in most cases we want the flexibility of being able to have VM guests on different networks (from one another and/or the VM host) so the VM host is configured with a trunk interface to the network to allow for any VLAN to be passed to the underlying VM guests housed on that VM host machine

    • 2022-08-12 dhart: 10.2.97.x (and 10.2.96.x) = internal VLAN for servers (primarily) 10.2.99.x = internal VLAN for server management
    • 10.2.120.x = internal VLAN for 10 GE connections
  • Where is the main docker config (yaml file)?
  • 2022-09-20 krowe: Why does naasc-vs-2 have APIPA configured networks (169.254.0.0)?  Aren't these usually created only if there are misconfigured network(s)?
    • [root@naasc-vs-2 ~]# netstat -nr
      Kernel IP routing table
      Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
      0.0.0.0         10.2.99.1       0.0.0.0         UG        0 0          0 eno1
      10.2.99.0       0.0.0.0         255.255.255.0   U         0 0          0 eno1
      10.2.120.0      0.0.0.0         255.255.255.0   U         0 0          0 ens1f0np0.120
      169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 ens1f0np0
      169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 ens1f0np0.120
      169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 br97
      169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 br101
      192.168.122.0   0.0.0.0         255.255.255.0   U         0 0          0 virbr0
    • 2022-09-28 krowe: APIPA routes are created via /etc/sysconfig/network-scripts/ifup-eth which is installed from the network-scripts RPM.  This RPM is legacy for RHEL8 (naasc-vs-2 is RHEL8.6) and must have been installed specificly.  It is not installed on any other RHEL8 machine I have checked.
  • 2022-09-26 krowe: Can an older solarflare card (Solarflare Communications SFC9020) replace the card in naasc-vs-2 to see if that helps with the TCP Retransmissions? 
  • Why can't I download via na-arc-6?  I don't think it is properly setup yet.
  • Why do I see cv-6509 when tracerouting from na-arc-5 to nangas13 but not on natest-arc-1
    • [root@na-arc-5 ~]# traceroute nangas13
      traceroute to nangas13 (10.2.140.33), 30 hops max, 60 byte packets
       1  cv-6509-vlan97.cv.nrao.edu (10.2.97.1)  0.426 ms  0.465 ms  0.523 ms
       2  cv-6509.cv.nrao.edu (10.2.254.5)  0.297 ms  0.277 ms  0.266 ms
       3  nangas13.cv.nrao.edu (10.2.140.33)  0.197 ms  0.144 ms  0.109 ms
       
    • [root@natest-arc-1 ~]# traceroute nangas13
      traceroute to nangas13 (10.2.140.33), 30 hops max, 60 byte packets
       1  cv-6509-vlan96.cv.nrao.edu (10.2.96.1)  0.459 ms  0.427 ms  0.402 ms
       2  nangas13.cv.nrao.edu (10.2.140.33)  0.184 ms  0.336 ms  0.311 ms
    • Derek wrote that 10.2.99.1 = CV-NEXUS and 10.2.96.1 = CV-6509
  • 2022-09-28 krowe: Why was the network-scripts RPM installed on naasc-vs-2?  No other RHEL8 machine has this RPM.  Was it because nobody knew how to configure vlans and other complicated networking using NetworkManager, which is the new standard in RHEL8?
    • 2022-10-05 krowe: Yes. RHEL8 makes bridges and vlans really complicated so Tracy installed the network-scripts RPM and configured things the old way.
  • 2022-09-21 krowe: Why are there stuck inventory processes on naasc-vs-2?
    • 2022-10-05 krowe: This is an RHEL8 issue, not a network issue.  All the RHEL8 machines in CV have this problem.
  • Why does naasc-vs-3 have a br120 in state UNKNOWN?  none of the other naasc-vs nodes have a br120.
    • 2022-10-05 krowe: This is because it is easier to create and not use then not create.
  • Why does natest-arc-3 have ens3 instead of eth0 and why is its speed 100Mb/s?
    • virsh domiflist natest-arc-3 shows the Model as rtl8139 instead of virtio
    • When I run ethtool eth0 on nar-arc-{1..5} natest-arc-{1..2} as root, the result is just Link detected: yes instead of the full report with speed while na-arc-3 shows 100Mb/s.
    • 2022-10-05 krowe: This should be fixed but after the test swarm is no longer acting as the production swarm.
    • I think this is just another example of why CV needs good documentation to create VMs


Done

  • Recreate na-arc-3 so it gets the same performance as other na-arc-* nodes which is apparently at least 10Gb/s. (pmurphy)
    1. 2022-08-11: cloned na-arc-2 and moved the clone to naasc-vs-3 (zbutcher)
    2. 2022-08-11: moved old na-arc-3 to na-arc-3-OLD (thalstea)
    3. 2022-08-11: Renamed the clone to na-arc-3.  We connected it to the swarm successfully, but it had a low connection speed.
    4. 2022-08-11: Changed the model of  na-arc-3's vnet5 interface on naasc-vs-3 from rtl8139 to virtio to match all the other na-arc-* nodes.  Performance was still poor.
    5. 2022-08-11: Changed the MTU of na-arc-3 eth0 to 1500.  This is different than all the other na-arc-* nodes but it was either that or change the p5p1.120 and br97 on naasc-vs-3 from 9000 to 1500 which my have impacted other VM guests on that host.  Performance was now reasonable.  7Gb/s.  I was expecting about 9Gb/s but perhaps the 1500 MTU is affecting performance.
    6. 2022-08-11: Joined na-arc-3 to the swarm and started services (sbooth)
  • Launch services on production swarm (sbooth)
    1. 2022-08-11: Joined na-arc-3 to the swarm and started services (sbooth)
  • Test the production docker swarm with a test web interface. (lsharp)
    1. 2022-08-12: http://almaportal.cv.nrao.edu/
    2. 2022-08-12 krowe: ran tcpdump on all five na-arc-{1..5} nodes tcpdump dst almaportal and then downloaded a datafile wget --no-check-certificate https://almaportal.cv.nrao.edu/dataPortal/2013.1.00226.S_uid___A001_X122_X1f1_001_of_001.tar and with each execution of the wget, I could see the next na-arc host report the traffic.  This is because the web proxy on almaportal will select the next na-arc node via round-robin.  All five nodes were providing about 6KB/s speeds to cvpost-master.
    3. 2022-08-12 krowe: I did iperf tests from host to host in the entire chain (nangas14 -> na-arc-{1..5} -> almaportal -> cvpost-master) and each step the performance was at least 900Mb/s yet downloading with wget was about 0.06Mb/s.
  • Ask other ARC if they use MTU 9000 on 10Gb. (krowe)
    1. JAO uses MTU of 1500
    2. ESO uses two VM hosts running VMware with 10Gb/s and MTU of 1500
  • 2022-08-17 krowe: Changed eth0 on na-arc-5 from qdisc pfifo_fast to qdisc fq_codel to match all the other na-arc and natest-arc nodes.  This seemed to have no affect on performance.
    • tc qdisc replace dev eth0 root fq_codel
  • 2022-08-25 krowe: Tracy cahnged the following sysctl options on na-arc-5 to match the other VM Hosts.  Sadly it seems to have had no effect on wget performance.  na-arc-1, na-arc-2, na-arc-4 are 32KB/s while na-arc-3 and na-arc-5 are 45MB/s.
    • net.ipv4.conf.all.accept_redirects = 0
    • net.ipv4.conf.all.forwarding = 1
  • 2022-09-01: Tracy rebooted naasc-vs-5 which hosts na-arc-5 just in case this was necessary for the net.ipv4.conf.all.forwarding sysctl change to take effect.  Sadly, no change in performance.
  • Why does na-arc-5 still have net.ipv4.conf.all.accept_redirects = 1 even after a reboot while all the other na-arc nodes have this set to 0?
    • 2022-09-06 krowe: probably because na-arc-5 didn't reboot when naasc-vs-5 rebooted.  I expect it was suspended instead of rebooted.  Yet natest-arc-3 and naascweb2-prod were rebooted.  I just checked virt-manager and na-arc-5 is hosted by naasc-vs-5.  Can we reboote na-arc-5?
    • 2022-09-07 krowe: rebooted na-arc-5 and now net.ipv4.conf.all.accept_redirects = 0
  • 2022-09-21 cfultz: Replaced the 10Gb network cable on naasc-vs-2.  "the cable was nearly bent in half at the router".
  • Create na-arc-6 on new naasc-vs-2 (https://support.nrao.edu/show-ticket.php?ticketid=144552)
  • Test iperf between ingress_sbox on new na-arc-6 when it is available
  • Double check switch port settings for naasc-vs-2.  I am seeing many TCP retransmissions (dhart)
  • Check and perhaps replace 10Gb network cable to naas-vs-2.  Does that help with TCP retransmissions?
    • The cable was very bent and therefore was replaced.  Sadly, it didn't help with TCP retransmissions.
  • 2022-10-06: thalstead switched naasc-vs-2 from RHEL8 to RHEL7.
  • 2022-10-12: thalstead upgraded the firmware on the solarflare card (SFN8511) from 6.5.1.1023 to 8.5.0.1002

Conclusions

NAASC Archive Stabilization Solutions


People (not necessarily team members)

  • K. Scott Rowe - Tiger Team Lead
  • CJ Allen - sysadmin
  • Tom Booth - programmer
  • Liz Sharp - sysadmin
  • Brian Mason - DRM Scientist
  • Zhon Butcher - sysadmin
  • Tracy Halstead - sysadmin
  • Alvaro Aguirre - ALMA software
  • Pat Murphy - CIS lead
  • Rachel Rosen - previous ICT lead
  • Laura Jenson - current ICT lead
  • Catherine Vlahakis - Scientist

...

na-arc-2

...

The test docker swarm (natest-arc-*) are performing as expected.  The VM hosts have 1Gb/s links so getting 80% to 90% bandwidth is about as good as one can expect.

...

natest-arc-1

(naasc-dev-vs)

...

natest-arc-2

(naasc-vs-1)

...

natest-arc-3

(naasc-vs-5)

...

Questions

  • Why does iperf show 9Gb/s between na-arc-4 (which is on naasc-vs-4) and na-testcarta-2 (which is on naasc-vs-3) when there is only a 1Gb/s link between those two VM Hosts?
  • Why does na-arc-3 have such poor network performance to the other na-arc nodes?
  • Is putting all the production docker swarm nodes on the same ASIC on the same Fabric Extender of the Nexus switch a good idea?
  • When I run ethtool eth0 on nar-arc-{1..5} natest-arc-{1..2} as root, the result is just Link detected: yes instead of the full report with speed.  Yet natest-arc-3, which has ens3 instead of eth0, shows speed of 100Mb/s?
  • Why do natest-arc-{1..3} have 9 veth* interfaces in ip addr show while na-arc-{1..5} don't have any veth* interfaces?

To Do

  • Switch the production docker swarm back to MTU 1500.  Since the test docker swarm uses MTU 1500 and is performing better.

References