2021-09-26: Intermittent networking issues with some shared runner jobs

Current Status

We have been seeing intermittent outbound network connectivity issues especially around accessing package registries and repositories due to a networking issue with our cloud provider.

https://status.cloud.google.com/incidents/QSirAFiyN5yMeeE6GNxq

Known Workarounds

There are two workarounds which have been helping mitigate this while we investigate a root cause:

• FF_NETWORK_PER_BUILD: 1 - #5590 (comment 687202472)
• docker build --network host ... - #5589 (comment 687173570)
• start docker:dind container with custom command with --mtu=1460 or lower, as described at #5590 (comment 688032420)

Timeline

Recent Events (available internally only):

• Deployments
• Feature Flag Changes
• Infrastructure Configurations

All times UTC.

2021-09-26

• 20:05 - @nnelson declares incident in Slack.

2021-09-27

• 03:19 +1 - @thiagocsf runs docker build tests in an attempt to find error patterns with @devin's help
• 04:33 +1 - @thiagocsf suggests that the cause might be a connectivity issue between google cloud and Fastly
• 05:11 +1 - @stanhu suggests Runner upgrade from 5 days ago might be a possible cause
• 05:30 +1 - upgraded to severity2 after @ggillies confirmed this is now a deployment blocker
• 06:10 +1 - public status update by @arihantar
• 06:49 +1 - @devin submitted a GCP Support Ticket, link.
• 07:11 +1 - to rule-out the Runner upgrade, @jarv is going to downgrade it to 14.2.0 https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/627
• 11:45 +1 - Enabled FF_NETWORK_PER_BUILD FF globally: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/628.
• 12:09 +1 - Receiving reports of a new error Couldn't connect to Docker daemon.
• 12:47 +1 - Verified reports and change impact.
• 13:07 +1 - Revert the change, disabling FF_NETWORK_PER_BUILD FF globally: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/629.
• 13:32 +1 - @rehab submitted a Fastly Support Ticket, link.
• 22:30 +1 - @stanhu is experimenting with MTU 1500 setting on google cloud VPC.

2021-09-28

• 03:41 +2 - @stanhu confirms that the MTU changes resolved the issue in his tests (internal slack message)
• 03:53 +2 - @thiagocsf created draft CR 5601 to apply Stan's fix.
• 15:05 +2 - GCP recognizes a general network connectivity issue that is causing this problem - https://status.cloud.google.com/incidents/QSirAFiyN5yMeeE6GNxq.

2021-09-29

• 10:40 +3 - @tmaczukin closed CR 5601 as we're awaiting GCP fix to be fully rolled out.

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