Add ReusePort config to confighttp #14058

sinkingpoint · 2025-10-21T09:23:00Z

Description

This adds in a new field, ReusePort that, if set, sets the SO_REUSEPORT socket option on the listener port. If we're on non unix, this errors out instead as AFAIK SO_REUSEPORT isn't available. Cursory googling says that SO_REUSEADDR might work, but I don't have a windows machine to test on.

Link to tracking issue

#14046

Testing

We add a new test, TestServerReusePort which checks the behaviour of both setting and unsetting the ReusePort config with the expectation of an error if it isn't set and it not erroring when binding twice to the same port

codecov · 2025-10-21T09:50:55Z

Codecov Report

❌ Patch coverage is 71.42857% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.26%. Comparing base (a646a2e) to head (6a5a94c).

Files with missing lines	Patch %	Lines
config/confighttp/server.go	55.55%	2 Missing and 2 partials ⚠️
config/confighttp/listen_config_other.go	83.33%	1 Missing and 1 partial ⚠️

❌ Your patch check has failed because the patch coverage (71.42%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14058      +/-   ##
==========================================
- Coverage   92.27%   92.26%   -0.01%     
==========================================
  Files         656      657       +1     
  Lines       41050    41070      +20     
==========================================
+ Hits        37877    37892      +15     
- Misses       2172     2175       +3     
- Partials     1001     1003       +2

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sinkingpoint · 2025-10-21T10:26:53Z

Contrib test failure fixed here: open-telemetry/opentelemetry-collector-contrib#43681

Without a valid `runCtx`, anything that attempts to use the context segfaults. In open-telemetry/opentelemetry-collector#14058 I am using the context, so this test borks. This adds the runCtx to fix it. Signed-off-by: sinkingpoint <[email protected]>

#### Description Without a valid `runCtx`, anything that attempts to use the context segfaults. In open-telemetry/opentelemetry-collector#14058 I am using the context, so this test borks. This adds the runCtx to fix it.  #### Link to tracking issue open-telemetry/opentelemetry-collector#14058  #### Testing  #### Documentation  Signed-off-by: sinkingpoint <[email protected]>

axw · 2025-10-22T01:28:34Z

Should we have this for configgrpc too? And non-HTTP/gRPC?

I'm wondering if we should make a breaking change to confighttp.ServerConfig to use confignet.AddrConfig, similar to configgrpc:

opentelemetry-collector/config/configgrpc/configgrpc.go

Line 176 in c657d5d

NetAddr confignet.AddrConfig `mapstructure:",squash"`

Then we could add ReusePort to confignet.AddrConfig and have it in one place.

(Not necessarily all in this PR, just thinking out loud about how to generalise this change.)

sinkingpoint · 2025-10-22T08:27:07Z

Should we have this for configgrpc too? And non-HTTP/gRPC?

I was going to do those in a separate PR, but rely on "A little copying is better than a little dependency" and just copy the same config changes across. Breaking changes scare me

axw · 2025-10-22T10:19:13Z

@sinkingpoint 👍 that seems fine, we can always make a breaking change independently if desired.

sinkingpoint · 2025-10-22T13:02:47Z

Actually, looking at it a bit more: configgrpc provides .Serve(net.Listener), and all the uses in the contrib repo actually use confighttps ToListener to create the listener to pass into that, so this handles both

dmathieu · 2025-10-22T13:18:01Z

config/confighttp/server_test.go

+
+func TestServerReusePort(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping test: SO_REUSEPORT is not supported on windows")


Could you add a test checking that we do get an error when trying to use SoReuse on windows?

.chloggen/so-reuse-port.yaml

dmathieu · 2025-10-22T13:50:18Z

Could you avoid force-pushing? That breaks the GitHub review interface.

sinkingpoint · 2025-10-22T13:57:32Z

Apologies 😬 I think I've fixed it up now anyway

axw · 2025-10-23T07:21:41Z

Actually, looking at it a bit more: configgrpc provides .Serve(net.Listener), and all the uses in the contrib repo actually use confighttps ToListener to create the listener to pass into that, so this handles both

Where did you see that being done? I found the stef receiver is not using confighttp, for example: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/e3f1205a034ff05c1c31e1e1b84a8bf735563d91/receiver/stefreceiver/stef.go#L57-L77

sinkingpoint · 2025-10-23T08:24:01Z

Oh hrm.. I checked several, like https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/skywalkingreceiver/skywalking_receiver.go#L144 , but you're right - missed the ones that use confignet. Want me to update that here? Or put in a seperate PR?

axw · 2025-10-23T08:28:11Z

Ah I see. That receiver probably should be updated, but I digress

A separate PR sounds good to me, maybe change the description so the issue doesn't get closed when this PR is merged

sinkingpoint · 2025-10-23T08:50:28Z

Done. Is there anything blocking this PR then? I see the CodeCov, but those lines are covered, just in the windows tests (which tracks the error flow)

axw · 2025-10-24T03:18:34Z

@sinkingpoint nope, looks good to go. I've marked it ready to merge, just needs a look from a maintainer now.

bogdandrutu · 2025-10-27T16:29:02Z

config/confighttp/listen_config_windows.go

+func (sc *ServerConfig) getListenConfig() (net.ListenConfig, error) {
+	if sc.ReusePort {
+		return net.ListenConfig{}, errors.New("ReusePort is not supported on this platform")
+	}
+
+	return net.ListenConfig{}, nil
+}


I would also like to have this in Validate and fail during dry-run.

@bogdandrutu The ServerConfig doesn't have a Validate yet - are you proposing I add one?

IMHO, introducing Validate should be another PR.

IMHO, introducing Validate should be another PR.

why?

The ServerConfig doesn't have a Validate yet - are you proposing I add one?

Yes please, every time we add fields that need to be validated we should validate them and if that needs a Validate func we add it.

Added @bogdandrutu

why?

Because that's a separate change that would need its own changelog entry, and having atomic PRs facilitates reviews.

This adds in a new field, `ReusePort` that, if set, sets the SO_REUSEPORT socket option on the listener port. If we're on non unix, this errors out instead as AFAIK SO_REUSEPORT isn't available. Cursory testing says that SO_REUSEADDR _might_ work, but I don't have a windows machine to test on. Signed-off-by: sinkingpoint <[email protected]>

Signed-off-by: sinkingpoint <[email protected]>

This adds a new Validate method that checks the getListenConfig call so that the new SO_REUSEPORT stuff fails in dry run on Windows Signed-off-by: sinkingpoint <[email protected]>

sinkingpoint requested a review from a team as a code owner October 21, 2025 09:23

sinkingpoint requested a review from dmitryax October 21, 2025 09:23

sinkingpoint force-pushed the sinkingpoint/so-reuse-port branch 5 times, most recently from 636ae93 to 344b948 Compare October 21, 2025 09:39

sinkingpoint force-pushed the sinkingpoint/so-reuse-port branch from 344b948 to bac556b Compare October 21, 2025 10:20

sinkingpoint mentioned this pull request Oct 21, 2025

[chore] Pass runCtx into supervisor Health check test open-telemetry/opentelemetry-collector-contrib#43681

Merged

sinkingpoint force-pushed the sinkingpoint/so-reuse-port branch from bac556b to 8f6079d Compare October 22, 2025 12:55

dmathieu reviewed Oct 22, 2025

View reviewed changes

sinkingpoint force-pushed the sinkingpoint/so-reuse-port branch 2 times, most recently from 3d1484b to e063074 Compare October 22, 2025 13:49

dmathieu approved these changes Oct 22, 2025

View reviewed changes

axw added the ready-to-merge Code review completed; ready to merge by maintainers label Oct 24, 2025

axw mentioned this pull request Oct 24, 2025

Stabilize module confighttp #9380

Open

8 tasks

bogdandrutu reviewed Oct 27, 2025

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dmathieu removed the ready-to-merge Code review completed; ready to merge by maintainers label Oct 28, 2025

sinkingpoint added 3 commits October 28, 2025 09:23

ci fix

d713c54

Signed-off-by: sinkingpoint <[email protected]>

Add Validate method to ServerConfig

6a5a94c

This adds a new Validate method that checks the getListenConfig call so that the new SO_REUSEPORT stuff fails in dry run on Windows Signed-off-by: sinkingpoint <[email protected]>

sinkingpoint force-pushed the sinkingpoint/so-reuse-port branch from 1073d97 to 6a5a94c Compare October 28, 2025 09:23

Add ReusePort config to confighttp #14058

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Add ReusePort config to confighttp #14058

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