Got paged about this.

Looks like this happens both on mac_chromium_rel_ng and ios-simulator. Doesn't seem super widespread. Also weird that the same pattern happened on both builders. Hopefully this was an isolated incident.

Sample builds:

https://ci.chromium.org/p/chromium/builders/luci.chromium.try/mac_chromium_rel_ng/167867
https://ci.chromium.org/p/chromium/builders/luci.chromium.try/ios-simulator/119539
Click on the swarming task to see more. Error log:

[I 2018-10-22 10:09:29] "system" account is bots-chrome@chromium-swarm.iam.gserviceaccount.com (git_auth: true, devshell: true, docker:true, firebase: false)
[I 2018-10-22 10:09:29] "task" account is chromium-try-builder@chops-service-accounts.iam.gserviceaccount.com (git_auth: true, devshell: true, docker:true, firebase: false)
[I 2018-10-22 10:09:29] Using LogDog URL: {logs.chromium.org chromium buildbucket/cr-buildbucket.appspot.com/8931947438406038832/+/annotations}
[I 2018-10-22 10:09:29] Creating POSIX server socket Listener.      {"namedPipePath":"/b/s/w/ir/tmp/ld.sock"}
[E 2018-10-22 10:10:00] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"200ms"}
[E 2018-10-22 10:10:30] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"400ms"}
[E 2018-10-22 10:11:01] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"800ms"}
[E 2018-10-22 10:11:31] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"1.6s"}
[E 2018-10-22 10:12:03] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"3.2s"}
[E 2018-10-22 10:12:36] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"6.4s"}
[E 2018-10-22 10:13:13] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"10s"}
[E 2018-10-22 10:13:53] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"10s"}
[E 2018-10-22 10:14:33] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"10s"}
[E 2018-10-22 10:15:13] Failed to check if topic exists; retrying... {"error":"context deadline exceeded", "delay":"10s"}
[E 2018-10-22 10:15:53] Failed to check for Pub/Sub topic.          {"error":"context deadline exceeded", "project":"luci-logdog", "topic":"logs"}
[I 2018-10-22 10:15:53] Exiting serve loop.                         {"namedPipePath":"/b/s/w/ir/tmp/ld.sock", "totalConnections":0}
----------------------------------- RESULTS ------------------------------------
infra_failure: <
  text: "failed to run recipe: failed to create LogDog Output instance: failed to check for Pub/Sub topic"