Add stats of client and pool to be accessible through agent #4157

tdeekens · 2025-04-12T11:37:23Z

This relates to:

This relates to the issue #4149

Rationale

Integrating existing and exposed Pool stats into a telemetry system is a bit cumbersome. Right now we can hook into the factory function and observe the created pool there. It would be beneficial if a Pool's and Client's stats would be exposed by the Agent owning the Pool or Client respectively.

Changes

Exposing stats through the Agent makes it easier to integrate telemetry systems as we do not have to "hook" into the factory to receive the Pool or Client used by an Agent.

Features

Exposes a new getter called stats on an Agent. The method returns an Array of Arrays with stats by origin.

Additionally, the Client now also exposes available stats similar to a Pool. The initial implementation of Pool stats happened in this PR while the implementation for a Client here follows the Pool's implementation pattenr.

Bug Fixes

Breaking Changes and Deprecations

Status

tdeekens · 2025-04-12T11:37:44Z

lib/core/symbols.js

  kHttpProxyAgent: Symbol('http proxy agent'),
-  kHttpsProxyAgent: Symbol('https proxy agent')
+  kHttpsProxyAgent: Symbol('https proxy agent'),
+  kStats: Symbol('stats')


This is used now by Pool and Client. Hence it should be shared in my opinion.

lib/dispatcher/agent.js

tdeekens · 2025-04-12T11:39:18Z

lib/dispatcher/client-stats.js

@@ -0,0 +1,28 @@
+'use strict'


Follows implementation of PoolStats. Clients however expose a subset of stats. Hence the separate class.

I'll put this class in utils or so, as the files within the dispatcher/ dir are mostly mean for classes that shares dispatcher interface.

Sounds good. Same for the PoolStats then which prior to this change lived here too, right?

tdeekens · 2025-04-12T11:39:26Z

lib/dispatcher/client.js

    this[kResume] = (sync) => resume(this, sync)
    this[kOnError] = (err) => onError(this, err)
+
+    this[kStats] = new ClientStats(this)


Same as with Pools.

metcoder95

Can we add testing for it?

lib/dispatcher/agent.js

metcoder95 · 2025-04-13T08:53:06Z

lib/dispatcher/client-stats.js

@@ -0,0 +1,28 @@
+'use strict'


I'll put this class in utils or so, as the files within the dispatcher/ dir are mostly mean for classes that shares dispatcher interface.

tdeekens · 2025-04-13T12:15:56Z

Can we add testing for it?

Yip. I followed the Pool Stats addition PR in terms of depth of testing on only existing through tsd.

tdeekens · 2025-04-13T19:50:52Z

Hi @metcoder95!

In ab942e4 I've moved the pool stats both of pool and client into a utils/stats.js. Happy for feedback.
Furthermore in f2452c4 I added some tests. Let me know if the direction is right and if the depth needs to be expanded on.

Should we also add docs and maybe an example?

tdeekens · 2025-04-15T21:34:42Z

👋🏼 @metcoder95 in 15bc63b I started adding some documentation where I thought it would help.

mise.toml

tdeekens · 2025-04-22T06:46:46Z

Anything else you see should be improved @metcoder95? Thanks!

tdeekens · 2025-04-22T06:59:15Z

@metcoder95 can you approve the workflows again. There was a type issue on the connected stat of a client which is a boolean compared to a pool where it is a number. Thanks!

tdeekens · 2025-04-23T12:38:32Z

@metcoder95 I can't see that tests fail due to my changes with

Error: Cannot find module '../../deps/undici/src/index.js'
Require stack:
- /home/runner/work/undici/undici/node-v23.11.0/test/parallel/test-inspector-network-fetch.js
    at Function._resolveFilename (node:internal/modules/cjs/loader:1405:15)
    at defaultResolveImpl (node:internal/modules/cjs/loader:1061:19)
    at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1066:22)
    at Function._load (node:internal/modules/cjs/loader:1215:37)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:235:24)
    at Module.require (node:internal/modules/cjs/loader:1491:12)
    at require (node:internal/modules/helpers:135:16)
    at Object.<anonymous> (/home/runner/work/undici/undici/node-v23.11.0/test/parallel/test-inspector-network-fetch.js:15:16)
    at Module._compile (node:internal/modules/cjs/loader:1734:14) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [
    '/home/runner/work/undici/undici/node-v23.11.0/test/parallel/test-inspector-network-fetch.js'
  ]
}

or

✖ SqliteCacheStore works nicely with multiple stores (22.842ms)
✔ SqliteCacheStore maxEntries (4.6677ms)
✔ SqliteCacheStore two writes (0.8061ms)
✔ SqliteCacheStore write & read (1.3409ms)
Error: [Error [ERR_TEST_FAILURE]: failed running after hook] { code: 'ERR_TEST_FAILURE', failureType: 'hookFailed', cause: [Error: EBUSY: resource busy or locked, unlink 'D:\a\undici\undici\cache-interceptor.sqlite'] { errno: -4082, code: 'EBUSY', syscall: 'unlink', path: 'D:\\a\\undici\\undici\\cache-interceptor.sqlite' } }

is that something you can help with? I've little to no experience with the CI setup of this repository.

lib/dispatcher/agent.js

mcollina · 2025-04-23T13:23:07Z

lib/util/stats.js

+  get size () {
+    return this[kPool][kSize]
+  }
+}


I don't really understand this design. Instead of using getters, I would allocate new objects. This ensures that data is stable in time without having to copy them.

To be fair I also didn't but this it the current implementation and I am following it assuming it has reasoning. In that this code is just moved from elsewhere as requested by @metcoder95.

Do you wish to have this changed here or as a follow up?

👋🏼 What's the implicit agreement here? Refactor as a follow-up, not at all or here? I understand the issue that the using getters can cause inconsistent as a whole with single values. I assume we would return an object of a "stats bag" in the pool and agent. Just not sure when/where to implement it.

@metcoder95 what's missing on this PR to land this? Anything expected from my side?

Just applying the suggested refactor from getters to a plain object (it can also come from a class, but avoiding the getters/setters).

Sure. From what I understand 7ac13ff is what you had in mind?

tdeekens · 2025-04-29T20:53:09Z

lib/core/symbols.js

  kNoProxyAgent: Symbol('no proxy agent'),
  kHttpProxyAgent: Symbol('http proxy agent'),
-  kHttpsProxyAgent: Symbol('https proxy agent'),
-  kStats: Symbol('stats')


Not needed anymore. Not assigned as property any longer.

tdeekens · 2025-04-29T20:53:23Z

lib/dispatcher/client.js


  get stats () {
-    return this[kStats]
+    return new ClientStats(this)


New class every time accessed.

tdeekens · 2025-04-29T20:53:33Z

lib/util/stats.js

-    this[kClient] = client
-  }
-
-  get connected () {


Not getters just instance properties.

tdeekens · 2025-04-30T10:21:15Z

@metcoder95 the failing tests appear to be unrelated.

✔ SqliteCacheStore (16.3615ms)
✖ SqliteCacheStore works nicely with multiple stores (19.9884ms)
✔ SqliteCacheStore maxEntries (4.9747ms)
✔ SqliteCacheStore two writes (0.8221ms)
✔ SqliteCacheStore write & read (1.2954ms)
Error: [Error [ERR_TEST_FAILURE]: failed running after hook] { code: 'ERR_TEST_FAILURE', failureType: 'hookFailed', cause: [Error: EBUSY: resource busy or locked, unlink 'D:\a\undici\undici\cache-interceptor.sqlite'] { errno: -4082, code: 'EBUSY', syscall: 'unlink', path: 'D:\\a\\undici\\undici\\cache-interceptor.sqlite' } }

Is this a known issue. Something I have to or you could have a look into?

mcollina

lgtm

mcollina · 2025-04-30T17:24:42Z

PTAL @ronag @metcoder95

metcoder95

lgtm

tdeekens · 2025-05-02T06:10:43Z

@metcoder95 I need some help with the failing tests. I can't see them as relating to the proposed changes. Can you provide some guidance?

metcoder95 · 2025-05-02T07:48:42Z

Feel free them, they are not related to your changes as you suggests; I'm starting to dig deeper into it to see if can sort it out.

tdeekens · 2025-05-07T19:42:17Z

@metcoder95 sorry to nudge but did you end up anywhere? I tried to understand what's going on but can not find the root cause.

metcoder95 · 2025-05-08T07:55:58Z

They are not a blocker for your PR but rather due to other reasons; feel free to ignore them

tdeekens · 2025-05-08T07:59:14Z

They are not a blocker for your PR but rather due to other reasons; feel free to ignore them

@metcoder95 Does that mean you would merge the PR or is something else missing to land this?

metcoder95 · 2025-05-08T08:02:56Z

LGTM, waiting for @ronag review

tdeekens · 2025-05-08T12:17:31Z

Whooop. Thanks all. All approvals are there. I am excited. /cc @metcoder95

tdeekens · 2025-05-11T11:24:48Z

Thanks for the support and release. The next version of @promster/undici will support exporting agent metrics to Prometheus.

tdeekens/promster#1385

…dejs#4157)

Ethan-Arrowood · 2025-07-15T20:40:27Z

Was it intentional to omit stats from Client directly? I didn't read through every thread here, but I've been loving pool.stats I expected it to exist on client as well but it seems only on agent? Happy to contribute this unless there was a reason it was omitted in the first place.

Ethan-Arrowood · 2025-07-15T21:02:39Z

Lol please ignore me. I didn't realize I was using undici v6 and this was added in v7. 🤦‍♂️

tdeekens added 9 commits April 12, 2025 13:16

Add shared stats symbol

2661544

Add client stats class

28ec198

Use client stats in client

df86d9b

Adjust pool and expose stats from agent

4370e3d

Add types for changes

2947cba

Add test for client

39c7617

Fix formatting changes

651eb86

Add types for agent stats getter

0c22ba5

fixup! Fix formatting changes

8855ecb

tdeekens commented Apr 12, 2025

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tdeekens mentioned this pull request Apr 12, 2025

How should Agent pools exposed and stats be integrated into e.g. Prometheus #4149

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metcoder95 changed the title ~~Add stats of client and pool to be expored through agent~~ feat: Add stats of client and pool to be expored through agent Apr 13, 2025

metcoder95 reviewed Apr 13, 2025

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tdeekens added 2 commits April 13, 2025 20:40

Move pool and client stats into util/stats

ab942e4

Add tests and fix implementation

f2452c4

Adds documentation and fixes

15bc63b

tdeekens requested a review from metcoder95 April 15, 2025 21:34

tdeekens changed the title ~~feat: Add stats of client and pool to be expored through agent~~ Add stats of client and pool to be expored through agent Apr 16, 2025

metcoder95 reviewed Apr 20, 2025

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mise.toml Outdated Show resolved Hide resolved

Fix to remove mise

5a93529

tdeekens requested a review from metcoder95 April 22, 2025 06:46

tdeekens marked this pull request as ready for review April 22, 2025 06:46

Restore docs list star

435acc8

metcoder95 approved these changes Apr 22, 2025

View reviewed changes

Fix boolean type

373736e

mcollina reviewed Apr 23, 2025

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Refactor to return object over list of list

52e7d94

tdeekens requested a review from mcollina April 26, 2025 20:12

tdeekens changed the title ~~Add stats of client and pool to be expored through agent~~ Add stats of client and pool to be accessible through agent Apr 29, 2025

Refactor to not use getters but object

7ac13ff

tdeekens force-pushed the add-agent-pool-client-stats branch from 55566bb to 7ac13ff Compare April 29, 2025 20:52

tdeekens commented Apr 29, 2025

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metcoder95 approved these changes Apr 30, 2025

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mcollina approved these changes Apr 30, 2025

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metcoder95 approved these changes May 1, 2025

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ronag approved these changes May 8, 2025

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metcoder95 merged commit c9f50c4 into nodejs:main May 9, 2025
28 of 31 checks passed

github-actions bot mentioned this pull request May 10, 2025

[Release] v7.9.0 #4204

Merged

github-actions bot mentioned this pull request May 12, 2025

[Release] v6.21.3 #4211

Closed

caitp pushed a commit to caitp/undici that referenced this pull request May 15, 2025

feat: Add stats of client and pool to be accessible through agent (no…

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…dejs#4157)

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