fix(api): restart api server during reload with address from the new config if necessary by garryliu-stripe · Pull Request #25131 · vectordotdev/vector

garryliu-stripe · 2026-04-06T19:31:59Z

Summary

Vector configuration

During config reload, the API server was started using self.topology.config() (the old config) instead of new_config. This meant that changing api.address in the config and triggering a reload would either:

Start the API server on the old/default address (port 8686) when enabling the API during reload
Not restart the API server at all when only the address changed, since the old code only started the server when self.api_server.is_none()

This fix passes &new_config to GrpcServer::start() and adds logic to detect address changes, stopping the old server and starting a new one on the correct port.

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Is this a breaking change?

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No

Does this PR include user facing changes?

Yes. Please add a changelog fragment based on our guidelines.
No. A maintainer will apply the no-changelog label to this PR.

References

Closes: api server binds to the wrong port during config reloading #25129

Notes

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github-actions · 2026-04-06T19:32:14Z

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pront · 2026-04-06T19:33:59Z

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pront · 2026-04-06T19:34:46Z

Hi @garryliu-stripe please sign the CLA and we will take a look. To sign post a PR comment with the following:

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src/topology/controller.rs

garryliu-stripe · 2026-04-06T19:41:24Z

@pront checking with our legal for CLA. will update shortly

garryliu-stripe · 2026-04-07T01:54:41Z

I have read the CLA Document and I hereby sign the CLA

garryliu-stripe · 2026-04-07T01:55:00Z

recheck

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src/topology/controller.rs

Move the API server start/stop/restart logic to run only after the topology reload succeeds. This prevents the API server from being bounced when the topology rolls back, keeping it consistent with the active config. Also compare configured addresses (old vs new) instead of the bound socket address, which avoids spurious restarts when port 0 or similar configs resolve to a different address on bind. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Committed-By-Agent: claude

garryliu-stripe · 2026-04-10T17:01:11Z

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chatgpt-codex-connector · 2026-04-10T17:05:03Z

src/topology/controller.rs

+                        if let Some(server) = self.api_server.take() {
+                            debug!("Stopping gRPC API server for restart with new address.");
+                            drop(server);


Await API shutdown before starting replacement listener

When api.address changes and a server already exists, this block drops the old GrpcServer and then immediately starts a new one. GrpcServer shutdown is asynchronous (src/api/grpc_server.rs, the listener lives in a spawned task and only exits after the oneshot is observed), so on reloads like 0.0.0.0:8686 -> 127.0.0.1:8686 the old socket can still be bound when restart happens, causing a transient EADDRINUSE and ReloadOutcome::FatalError (process shutdown) even though the new config is valid. The restart path needs to wait for listener teardown (or otherwise coordinate) before rebinding.

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I think we should disallow hot reload of api server. If we want to change the address, we should first set api.enable: false and then set new address and re-enable api-server

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Committed-By-Agent: claude

Pass &new_config instead of self.topology.config() when starting the API server during a reload (disabled->enabled). The old code used the pre-reload config, so the server would bind to the old address instead of the newly configured one. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Committed-By-Agent: claude

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chatgpt-codex-connector · 2026-04-10T17:21:55Z

src/topology/controller.rs


            match api::GrpcServer::start(
-                self.topology.config(),
+                &new_config,


Start gRPC server only after reload succeeds

Passing &new_config to GrpcServer::start before reload_config_and_respawn means a later ReloadOutcome::RolledBack can leave self.api_server running with settings from a rejected config while the topology stays on the previous config. Fresh evidence in this commit is the changed argument at this call site, which now applies new API settings prior to confirming reload success; this can expose or move the API endpoint even though the reload failed.

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I think this is an acceptable compromise? The current behavior can cause vector to bind the wrong port during hot reload.

Since only allow changing address when the api is disabled (the existing behaviour), the api server will be dropped during Rollback

I think we will have to do something better here, either throw a hard error to indicate it's not support or even better, detect proper grpc server shutdown and rebind.

garryliu-stripe · 2026-04-10T17:37:29Z

@pront mind taking a look?

Move the API server start/stop logic into the Ok arm of the topology reload so it only runs after a successful reload. Use self.topology.config() (which reflects the new config post-reload) to bind to the correct address. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Committed-By-Agent: claude

garryliu-stripe · 2026-04-10T18:19:12Z

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chatgpt-codex-connector · 2026-04-10T18:23:58Z

src/topology/controller.rs

+                        debug!("Stopping gRPC API server.");
+                        drop(server);
+                    }
+                } else if self.api_server.is_none() {


Restart API server when enabled address changes

The reload path still skips API restart whenever a server is already running because it only starts in the self.api_server.is_none() branch. In the common case where api.enabled stays true and only api.address changes, reload succeeds but the gRPC server remains bound to the old address, so the configured new endpoint is not actually applied until a full process restart.

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pront · 2026-04-13T15:26:31Z

changelog.d/fix_api_address_reload.fix.md

@@ -0,0 +1 @@
+Fixed a bug where the API server would not respect a configured `api.address` on config reload. The API server now starts with the correct address when re-enabled, and only starts after a successful topology reload to prevent inconsistent state on rollback.


Does this PR handle the case where the API is already running and the address changes?

it does not. It still follow the current behavior that if the API is already running, address change will no bounce the server. To change address, need to first disable api, then re-enable with updated address.

The change primarily solves below situation

initial config:

# not actually set, below are default values # api: # enabled: false # address: 127.0.0.1:8686

try enable api server on port 18686 with reload

api: enabled: true address: 127.0.0.1:18686

however, since we are starting the server with self.topology.config() instead of new_config

match api::GrpcServer::start( self.topology.config(), self.topology.watch(), Arc::clone(&self.topology.running), )

the server will be using the default address.

In addition, it solves potential inconsistent address when topology needs to rollback.

properly restart api server if address is changed

1f0d45b

garryliu-stripe requested a review from a team as a code owner April 6, 2026 19:32

github-actions bot added the domain: topology Anything related to Vector's topology code label Apr 6, 2026

pront added the domain: api Anything related to Vector's GraphQL API label Apr 6, 2026

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Merge branch 'master' into garryliu/fix_server_addr_reloading

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garryliu-stripe and others added 2 commits April 10, 2026 12:50

Merge branch 'master' into garryliu/fix_server_addr_reloading

a8d1f42

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garryliu-stripe and others added 2 commits April 10, 2026 13:08

docs: update changelog for API server reload fix

6103e0a

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Committed-By-Agent: claude

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Merge branch 'master' into garryliu/fix_server_addr_reloading

db84c21

		@@ -0,0 +1 @@
		Fixed a bug where the API server would not respect a configured `api.address` on config reload. The API server now starts with the correct address when re-enabled, and only starts after a successful topology reload to prevent inconsistent state on rollback.

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garryliu-stripe commented Apr 6, 2026

Summary

Vector configuration

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