fix(memcached): panic on send on closed channel.
#7817
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Our memcached client has race between closing `inputCh` and submitting work to it (writing to channel) by different goroutines. This PR fix it by having `closed` channel to track if `inputCh` is closed and make it visible to other writter go-routines. Before: ``` === RUN TestMemcached_fetchKeysBatched panic: send on closed channel goroutine 29 [running]: github.com/grafana/loki/pkg/storage/chunk/cache.(*Memcached).fetchKeysBatched.func1() /home/kavirajk/src/loki/pkg/storage/chunk/cache/memcached.go:167 +0x87 created by github.com/grafana/loki/pkg/storage/chunk/cache.(*Memcached).fetchKeysBatched /home/kavirajk/src/loki/pkg/storage/chunk/cache/memcached.go:164 +0x165 FAIL github.com/grafana/loki/pkg/storage/chunk/cache 0.015s FAIL ``` After: ``` loki$ go test -v ./pkg/storage/chunk/cache/... -run TestMemcached_fetchKeysBatched === RUN TestMemcached_fetchKeysBatched --- PASS: TestMemcached_fetchKeysBatched (0.00s) PASS ok github.com/grafana/loki/pkg/storage/chunk/cache 0.013s ``` Signed-off-by: Kaviraj <[email protected]>
Signed-off-by: Kaviraj <[email protected]>
kavirajk
force-pushed
the
kavirajk/fix-panic-memcache-send-on-closed-chan
branch
from
b21bfc0
to
5ae4ab3
Compare
Signed-off-by: Kaviraj <[email protected]>
5 tasks
|
./tools/diff_coverage.sh ../loki-target-branch/test_results.txt test_results.txt ingester,distributor,querier,querier/queryrange,iter,storage,chunkenc,logql,loki Change in test coverage per package. Green indicates 0 or positive change, red indicates that test coverage for a package fell. + ingester 0%
+ distributor 0%
+ querier 0%
+ querier/queryrange 0%
+ iter 0%
+ storage 0%
+ chunkenc 0%
+ logql 0%
+ loki 0% |
dannykopping
approved these changes
Dec 1, 2022
dannykopping
deleted the
kavirajk/fix-panic-memcache-send-on-closed-chan
branch
Abuelodelanada
pushed a commit
to canonical/loki
that referenced
this pull request
Dec 1, 2022
kavirajk
added a commit
that referenced
this pull request
Dec 2, 2022
Follow up to #7817 This PR uses `default` branch instead of `inputCh <- work` to make sure we are writing to closed `inputCh`. Signed-off-by: Kaviraj <[email protected]>
kavirajk
added a commit
that referenced
this pull request
Dec 2, 2022
) Signed-off-by: Kaviraj <[email protected]> **What this PR does / why we need it**: Follow up to #7817 This PR uses `default` branch instead of `inputCh <- work` to make sure we are writing to closed `inputCh`. Gist is, `default` run [only when none of the branch is ready](https://go.dev/tour/concurrency/6). which makes more sense rather than to have `inputCh <- work` (writing to closed channel on the branch condition) These can be explained by these two tiny snippets. * [with `default`](https://go.dev/play/p/-FspbTZd20I) * [without `default`](https://go.dev/play/p/Ag4WznOaEq0) **Which issue(s) this PR fixes**: Fixes #NA **Special notes for your reviewer**: We already have test `TestMemcached_fetchKeysBatched` to catch this behaviour. In fact this test caught this probabilistic behaviour in some CI failures. [here ](https://drone.grafana.net/grafana/loki/17853/3/4) and[ here](https://drone.grafana.net/grafana/loki/17854/3/4) Thanks @DylanGuedes for catching this CI failures. **Checklist** Signed-off-by: Kaviraj <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
What this PR does / why we need it:
Our memcached client has race between closing
inputChand submitting work to it (writing to channel) by different goroutines.This PR fix it by having
closedchannel to track ifinputChis closed and make it visible to other writter go-routines.Before:
After:
Which issue(s) this PR fixes:
Fixes #
Special notes for your reviewer:
Found this panic on lots of internal Loki prod clusters.
Checklist
CHANGELOG.mdupdated