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fix: k8s agent fails to tail logs starving the cpu

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Proposal to fix https://github.com/woodpecker-ci/woodpecker/issues/2253

We have observed several possibly-related issues on a Kubernetes
backend:

1. Agents behave erractly when dealing with certain log payloads. A common
   observation here is that steps that produce a large volume of logs will cause
   some steps to be stuck "pending" forever.

2. Agents use way more CPU than should be expected, we often see 200-300
   millicores of CPU per Workflow per agent (as reported on #2253).

3. We commonly see Agents displaying thousands of error lines about
   parsing logs, often with very close timestamps, which may explain issues 1
   and 2 (as reported on #2253).

```
{"level":"error","error":"rpc error: code = Internal desc = grpc: error while marshaling: string field contains invalid UTF-8","time":"2024-04-05T21:32:25Z","caller":"/src/agent/rpc/client_grpc.go:335","message":"grpc error: log(): code: Internal"}
{"level":"error","error":"rpc error: code = Internal desc = grpc: error while marshaling: string field contains invalid UTF-8","time":"2024-04-05T21:32:25Z","caller":"/src/agent/rpc/client_grpc.go:335","message":"grpc error: log(): code: Internal"}
{"level":"error","error":"rpc error: code = Internal desc = grpc: error while marshaling: string field contains invalid UTF-8","time":"2024-04-05T21:32:25Z","caller":"/src/agent/rpc/client_grpc.go:335","message":"grpc error: log(): code: Internal"}
```

4. We've also observed that agents will sometimes drop out of the worker queue,
also as reported on #2253.

Seeing as the logs point to `client_grpc.go:335`, this pull request
fixes the issue by:

1. Removing codes.Internal from being a retryable GRPC status. Now agent GRPC
calls that fail with codes. Internal will not be retried. There's not an
agreement on what GRPC codes should be retried but Internal does not seem to be
a common one to retry -- if ever.

2. Add a timeout of 30 seconds to any retries. Currently, the exponential
retries have a maximum timeout of _15 minutes_. I assume this might be
required by some other functions so Agents resume their operation in
case the webserver restarts. Still this is likely the cause behind the
large cpu increase as agents can be stuck trying thousands of requests for
a large windown of time. The previous change alone should be enough to
solve this issue but I think this might be a good idea to prevent
similar problems from arising in the future.
This commit is contained in:
Fernando Barbosa 2024-04-05 19:22:59 -03:00
parent d0e63375fa
commit 01699eaaab
2 changed files with 5 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
agent/rpc/client_grpc.go
View file

@ -97,7 +97,6 @@ func (c *client) Next(ctx context.Context, f rpc.Filter) (*rpc.Workflow, error)
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -143,7 +142,6 @@ func (c *client) Wait(ctx context.Context, id string) (err error) {
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -184,7 +182,6 @@ func (c *client) Init(ctx context.Context, id string, state rpc.State) (err erro
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -225,7 +222,6 @@ func (c *client) Done(ctx context.Context, id string, state rpc.State) (err erro
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -259,7 +255,6 @@ func (c *client) Extend(ctx context.Context, id string) (err error) {
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -300,7 +295,6 @@ func (c *client) Update(ctx context.Context, id string, state rpc.State) (err er
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -339,7 +333,6 @@ func (c *client) Log(ctx context.Context, logEntry *rpc.LogEntry) (err error) {
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:
@ -386,7 +379,6 @@ func (c *client) ReportHealth(ctx context.Context) (err error) {
codes.Aborted,
codes.DataLoss,
codes.DeadlineExceeded,
codes.Internal,
codes.Unavailable:
// non-fatal errors
default:

6
pipeline/rpc/log_entry.go
View file

@ -88,7 +88,11 @@ func (w *LineWriter) Write(p []byte) (n int, err error) {
Type: LogEntryStdout,
Line: w.num,
}
if err := w.peer.Log(context.Background(), line); err != nil {
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
if err := w.peer.Log(ctx, line); err != nil {
log.Error().Err(err).Str("step-uuid", w.stepUUID).Msg("fail to write pipeline log to peer")
}
w.num++