I will look into it

Chan, mind investigating further down here?

It appears there is a recent change on the LogDog path format for LUCI builds:

Previous: "bb/{master_name}/{builder_name}/{build_number}/+/annotations"
Now: "buildbucket/cr-buildbucket.appspot.com/build_id/+/annotations"

+nodir +tandrii in case there are other changes as well

this change isn't recent. This is the format of logdog prefixes used in LUCI builds for 6mo+.

Ideally FindIt does not hard code the logdog stream format. The buildbucket API returns it. For example, in https://cr-buildbucket.appspot.com/_ah/api/buildbucket/v1/builds/8948260456238727472
you can see "swarming_tag:log_location:logdog://logs.chromium.org/chromium/buildbucket/cr-buildbucket.appspot.com/8948260456238727472/+/annotations"
build api v2 will return the logdog stream prefix too.

Hi Nodir, about your suggestion: what should be the best way to get buildbucket_id for a LUCI build currently?  My plan is to get buildbucket property from milo's GetBuildbotBuildJSON API. Is there an easier way to do that?

And also, do you have any suggestion on what could be the best way to get log_location for a buildbot build? I see log_location property in buildbot builds, maybe I should directly use that?

I think you could reuse the code that you already wrote to fetch the buildbucket build using buildbucket search api and build_address tag, unless making one more RPC is a problem in that code path

This is for LUCI build right? what about buildbot build? 

Nothing changed for Buildbot build. The problem is specific to LUCI, right?

Right. I was thinking to find a way to handle both LUCI builds and buildbot builds. But it sgtm to not invest too much for buildbot builds but rather use the old function.

We may still have a problem: for analysis requested by SoM, Findit gets a master_url in the format as: http://build.chromium.prg/p/chromium.mac, so Findit can gets the buildbot master_name directly without query buildbucket.search(Or even we couldn't because the lack of bucket info in request).

+seanmccullough to check how easy is the change to also include bucket info in request to Findit.

In the meantime, I'm thinking should using the suboptimal solution I mentioned in #6 for a quick fix, because this bug is blocking Findit to auto-revert compile culprits. 

retrieving build id from buildbucket property is fine too. That is not going to change.

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/8a1f788944d5fbd63bbc0a0962364a66267299a6

commit 8a1f788944d5fbd63bbc0a0962364a66267299a6
Author: Chan <chanli@chromium.org>
Date: Fri Apr 27 00:00:14 2018

[Findit] Fix the bug to get step logs for a LUCI build.

LUCI builds have a different log_location from buildbot build. This change will get log_locations for both kinds of builds more reliably.

Bug:  836430 
Change-Id: I714683df400489c12e4e33fc6d356e8d43d3cf5f
Reviewed-on: https://chromium-review.googlesource.com/1031383
Commit-Queue: Chan Li <chanli@chromium.org>
Reviewed-by: Shuotao Gao <stgao@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>

[modify] https://crrev.com/8a1f788944d5fbd63bbc0a0962364a66267299a6/appengine/findit/waterfall/build_util.py
[modify] https://crrev.com/8a1f788944d5fbd63bbc0a0962364a66267299a6/appengine/findit/infra_api_clients/logdog_util.py
[modify] https://crrev.com/8a1f788944d5fbd63bbc0a0962364a66267299a6/appengine/findit/waterfall/test/build_util_test.py
[modify] https://crrev.com/8a1f788944d5fbd63bbc0a0962364a66267299a6/appengine/findit/model/wf_build.py
[modify] https://crrev.com/8a1f788944d5fbd63bbc0a0962364a66267299a6/appengine/findit/infra_api_clients/test/logdog_util_test.py