Add Dio interceptor for capturing network events with Posthog #220

TabooSun · 2025-11-23T14:24:05Z

💡 Motivation and Context

Close #169

Didn't manage to test the code because when I check the Posthog dashboard, none of the events are recorded in the Activity pane, not sure if it is filtered, might need help here.

💚 How did you test it?

📝 Checklist

I reviewed the submitted code.
I added tests to verify the changes.
I updated the docs if needed.
No breaking change or entry added to the changelog.

Copilot

Pull request overview

This PR adds a Dio interceptor to enable automatic capturing of network events for session replay and network performance monitoring with PostHog. The interceptor integrates with Dio's request/response lifecycle to track HTTP requests and responses.

Adds PosthogDioInterceptor class that extends Dio's Interceptor
Captures network events on both successful responses and errors
Transforms request/response data into PostHog-compatible snapshot events
Adds Dio as a direct dependency

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
`pubspec.yaml`	Adds Dio 5.9.0 as a new dependency to support the network interceptor
`lib/src/replay/network_performance/dio_interceptor.dart`	Implements the `PosthogDioInterceptor` class that captures network events from Dio requests/responses and sends them to PostHog as snapshot events

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

lib/src/replay/network_performance/dio_interceptor.dart

pubspec.yaml

lib/src/replay/network_performance/dio_interceptor.dart

marandaneto · 2025-11-24T08:06:12Z

pubspec.yaml

  # plugin_platform_interface depends on meta anyway
  meta: ^1.3.0
  stack_trace: ^1.12.0
+  dio: ^5.9.0


this has to be a new package within the posthog-flutter repo so users that dont use dio dont need to have this as a dependency

marandaneto · 2025-11-24T08:06:26Z

lib/src/replay/network_performance/dio_interceptor.dart

+import 'package:dio/dio.dart';
+import 'package:posthog_flutter/posthog_flutter.dart';
+
+class PosthogDioInterceptor extends Interceptor {


Suggested change

class PosthogDioInterceptor extends Interceptor {

class PostHogDioInterceptor extends Interceptor {

marandaneto · 2025-11-24T08:15:04Z

lib/src/replay/network_performance/dio_interceptor.dart

+          if (publishableRequest != null) 'request': publishableRequest,
+          if (publishableResponse != null) 'response': publishableResponse,


i think we should skip this for now, or we should check its body size and type before appending to the properties.
events that are large will be dropped, and it has to be json serializable, so better to skip for a 1st version

Size concern: May I know what's the size limit here? If you let me know, I can drop it.

json serializable ensurance: actually _tryTransformDataToPublishableObject has already transformed them to publishable object that is ensured to be json serializable

Kinda need this for my usage, so if possible I plan to have it in the 1st version.

Kinda need this for my usage, so if possible I plan to have it in the 1st version.

Expose a ctor param when creating a PosthogDioInterceptor instance, so users can optin/out of attaching payloads.
like attachBodies or attachPayloads with default false due to PII risk

Size concern: May I know what's the size limit here? If you let me know, I can drop it.

lets dow hat the JS SDK does
https://github.com/PostHog/posthog-js/blob/962649dcc87ff67da2e80e7dfb776020b903bc7b/packages/browser/src/extensions/replay/external/config.ts#L130-L170
you can inspire from this implementation

marandaneto · 2025-11-24T08:15:27Z

lib/src/replay/network_performance/dio_interceptor.dart

+      },
+      'timestamp': DateTime.now().millisecondsSinceEpoch,
+    };
+    await Posthog().capture(


you dont need to await this, so you can remove the Future<void> from this method

Still need it after the latest change.

marandaneto · 2025-11-24T08:17:32Z

lib/src/replay/network_performance/dio_interceptor.dart

+    Response<dynamic> response,
+    ResponseInterceptorHandler handler,
+  ) async {
+    await _captureNetworkEvent(


we should only call this method if (check ScreenshotCapturer):

final isSessionReplayActive = await _nativeCommunicator.isSessionReplayActive();

so we dont try to capture snapshot network requests if replay is deactivated, this method is private, we'd need to expose internally at least

marandaneto · 2025-11-24T08:18:31Z

Didn't manage to test the code because when I check the Posthog dashboard, none of the events are recorded in the Activity pane, not sure if it is filtered, might need help here.

they are not analytics events, they are session replay metata, it wont appear in the Activity page, they will be part of a recording in the session replay recordings

ioannisj · 2025-11-24T09:02:09Z

lib/src/replay/network_performance/dio_interceptor.dart

+  ) async {
+    final Response<dynamic>? response = err.response;
+    if (response != null) {
+      await _captureNetworkEvent(response: response);


We are checking response here, but I think this will miss network connection errors, connection timeouts etc which may not have a response object returned

Hmm, isn't this supposed to be captured by the Error Tracking automatically (unless user catch the error)?

yes but not with the same level of details as you have here (you have more context in this method).
what you could do is: try catch, read what you need and rethrow the error.

I don't really think we should rethrow the error here, the interceptor is supposed to just send whatever we want here.

If we throw here, the next interceptor that user configures will not be called.

if _captureNetworkEvent throws, we wont catch/log anything.
if we try catch and rethrow, this is the behaviour that would happen anyway.
same approach i've done before https://github.com/getsentry/sentry-dart/blob/20faa47cb637900f4a6112a89bd71419fd7bc16d/packages/dio/lib/src/tracing_client_adapter.dart#L68-L80

I am confused about the comment after a few replies. Let me try and restructure first.

So, initially the ask is to handle the errors from the overriding method: onError, in which it contains network connection errors, connection timeouts etc. I didn't want to handle it because I feel that this is supposed to be handled by the Error Tracking.

Then I was asked to catch the error here:

yes but not with the same level of details as you have here (you have more context in this method).
what you could do is: try catch, read what you need and rethrow the error.

which is weird because technically this is different ask compared to the original handling of the DioException from the onError method.

If we throw here, the next interceptor that user configures will not be called.

This will no longer be true after my latest changes of moving the call of _captureNetworkEvent after super.onError.

All in all, I don't mind handling the err from onError but I need a sample of implementing it, do I just send the stack trace along or just the error message? If we want stack trace then I still think it's better to use Posthog.captureException as this is the easiest way for me.

I think there's a misunderstanding here.

We're not talking about onError
We're talking about being able to create a network request snapshot even if there's an error.
Not talking about network errors, but rather API errors eg 4xx or 5xx, you still want network request snapshots.
If dio throws an exception in this use case, we have to try-catch-rethrow so you are able to do so.

TabooSun · 2025-11-24T14:16:15Z

Didn't manage to test the code because when I check the Posthog dashboard, none of the events are recorded in the Activity pane, not sure if it is filtered, might need help here.

they are not analytics events, they are session replay metata, it wont appear in the Activity page, they will be part of a recording in the session replay recordings

Still don't see it, this is the sample data I observe from Proxyman:

{
  "api_key": "",
  "uuid": "",
  "properties": {
    "$window_id": "",
    "$snapshot_data": {
      "type": 6,
      "data": {
        "payload": {
          "method": "POST",
          "status_code": 200,
          "url": "",
          "request": {
          },
          "response": {
          }
        },
        "plugin": "rrweb/network@1"
      },
      "timestamp": 1763992397179
    },
    "$snapshot_source": "mobile",
    "$lib": "posthog-flutter",
    "distinct_id": "",
    "$lib_version": "5.9.0",
    "$screen_name": "",
    "$session_id": "019AB623-E12C-7C70-A9DD-53B345EE89BF"
  },
  "event": "$snapshot",
  "timestamp": "2025-11-24T13:53:17.221Z",
  "distinct_id": ""
}

marandaneto · 2025-11-24T14:17:27Z

packages/posthog_dio_interceptor/pubspec.yaml

+
+# Add regular dependencies here.
+dependencies:
+  dio: ^5.9.0


Suggested change

dio: ^5.9.0

dio: ^5.0.0

if we dont use anything new, we can target the major instead of the latest

marandaneto · 2025-11-24T14:18:22Z

packages/posthog_dio_interceptor/pubspec.yaml

+# Add regular dependencies here.
+dependencies:
+  dio: ^5.9.0
+  posthog_flutter: ^5.9.0


Suggested change

posthog_flutter: ^5.9.0

posthog_flutter: ^5.0.0

same here

packages/posthog_dio_interceptor/lib/src/dio_interceptor.dart

marandaneto · 2025-11-24T14:21:37Z

packages/posthog_dio_interceptor/lib/src/dio_interceptor.dart

+            final hasExceededLimit = await _hasExceededSizeLimit(
+              data: response.requestOptions.data,
+              header: response.requestOptions.headers,
+            );
+            return (
+              value,
+              hasExceededLimit,
+            );
+          },
+        ),
+      if (attachPayloads)
+        _tryTransformDataToPublishableObject(
+          data: response.data,
+        ).then(
+          (value) async {
+            final hasExceededLimit = await _hasExceededSizeLimit(


you have to sum the request payload + response payload to tell if hasExceededLimit or not since what matters is the size of the final posthog event built here snapshotData

marandaneto · 2025-11-24T14:45:39Z

packages/posthog_dio_interceptor/lib/src/dio_interceptor.dart

+
+/// A Dio interceptor that captures network events and sends them to PostHog.
+class PostHogDioInterceptor extends Interceptor {
+  final NativeCommunicator _nativeCommunicator = NativeCommunicator();


instead of creating a new instance for this, we should expose and reuse this class

posthog-flutter/lib/src/replay/screenshot/screenshot_capturer.dart

Line 40 in f8ea523

final _nativeCommunicator = NativeCommunicator();

example: https://github.com/PostHog/posthog-android/blob/743a341365f5d9c1cf254a7b01882b59c3089e30/posthog/src/main/java/com/posthog/PostHog.kt#L1096-L1102
we expose a public method in the posthog class so we can call it directly from here

marandaneto · 2025-11-24T14:47:07Z

now i think our example should depend on the new package and add a button in the sample for testing
also we should fix the release process and CI now https://github.com/PostHog/posthog-flutter/tree/main/.github/workflows to consider the new package
maybe the current package should move under the packages folder as well since its a mono repo with multiple packages

TabooSun · 2025-11-25T10:50:34Z

now i think our example should depend on the new package and add a button in the sample for testing also we should fix the release process and CI now https://github.com/PostHog/posthog-flutter/tree/main/.github/workflows to consider the new package maybe the current package should move under the packages folder as well since its a mono repo with multiple packages

Done moving to package and adding button for testing. But can you help with the workflow? It seems that it requires approval, not sure if this is a one-time thing or the approval has to be granted every time, if it's latter, I think it's better that the maintainer handles this.

marandaneto · 2025-11-25T15:41:22Z

@TabooSun I'm handling an incident now, but will follow up on comments/maybe open a PR on top of yours with suggestions later on (later this week or early next week), so we avoid the back and forth since I am focusing on other tasks that have higher priority for now, sorry about that.

ioannisj · 2025-12-19T08:48:50Z

@marandaneto ping on this one

marandaneto · 2025-12-19T12:41:47Z

@TabooSun mind fixing conflicts after your changes? so i can do a final review/release if all good?

…ialization to separate isolates

…lculateSizeLimit` and improve payload size validation logic

…unicator` with `Posthog` in Dio interceptor

…`_callApiWithDio` example to showcase usage

…package

TabooSun · 2025-12-19T13:38:01Z

@TabooSun mind fixing conflicts after your changes? so i can do a final review/release if all good?

Hi, updated~

Copilot AI review requested due to automatic review settings November 23, 2025 14:24

TabooSun requested a review from a team as a code owner November 23, 2025 14:24

Copilot started reviewing on behalf of TabooSun November 23, 2025 14:24 View session

Copilot finished reviewing on behalf of TabooSun November 23, 2025 14:26

Copilot AI reviewed Nov 23, 2025

View reviewed changes

marandaneto reviewed Nov 24, 2025

View reviewed changes

marandaneto requested a review from ioannisj November 24, 2025 08:18

ioannisj reviewed Nov 24, 2025

View reviewed changes

marandaneto reviewed Nov 24, 2025

View reviewed changes

packages/posthog_dio_interceptor/lib/src/dio_interceptor.dart Show resolved Hide resolved

marandaneto reviewed Nov 24, 2025

View reviewed changes

TabooSun added 6 commits December 19, 2025 21:22

Add Dio interceptor for capturing network events with Posthog

1389249

Extract PostHog Dio interceptor into a standalone package

bbe3b7d

Enhance Dio interceptor to handle large payloads and offload JSON ser…

5479dd9

…ialization to separate isolates

Downgrade posthog_flutter dependency to version ^5.0.0 in pubspec.yaml

eecf16f

Downgrade dio dependency to version ^5.0.0 in pubspec.yaml

094a4a6

Refactor Dio interceptor to replace _hasExceededSizeLimit with `_ca…

8b5b072

…lculateSizeLimit` and improve payload size validation logic

TabooSun added 2 commits December 19, 2025 21:22

Integrate session replay check into Posthog and replace `NativeComm…

09afba8

…unicator` with `Posthog` in Dio interceptor

Refactor Dio interceptor to streamline session replay checks and add …

9b410ec

…`_callApiWithDio` example to showcase usage

TabooSun force-pushed the add-dio-interceptor branch from 167a0d9 to 9616f39 Compare December 19, 2025 13:24

TabooSun added 3 commits December 19, 2025 21:37

Restructure package

812c9ce

Update CI configuration to set working directory for Posthog Flutter …

ce70f82

…package

Update .gitignore to correctly ignore Packages folder

18cb2f7

TabooSun force-pushed the add-dio-interceptor branch from ad638e3 to 18cb2f7 Compare December 19, 2025 13:37

	class PosthogDioInterceptor extends Interceptor {
	class PostHogDioInterceptor extends Interceptor {

		if (publishableRequest != null) 'request': publishableRequest,
		if (publishableResponse != null) 'response': publishableResponse,

Add Dio interceptor for capturing network events with Posthog #220

Are you sure you want to change the base?

Add Dio interceptor for capturing network events with Posthog #220

Uh oh!

Conversation

TabooSun commented Nov 23, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

💡 Motivation and Context

💚 How did you test it?

📝 Checklist

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

marandaneto Nov 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

marandaneto commented Nov 24, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

TabooSun Nov 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

TabooSun commented Nov 24, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

TabooSun commented Nov 23, 2025 •

edited

Loading

marandaneto Nov 24, 2025 •

edited

Loading

TabooSun Nov 24, 2025 •

edited

Loading