Add callback to record the type and amount of data discarded before reaching Sentry #4612

alexander-alderman-webb · 2025-08-07T11:43:35Z

📜 Description

Adds a callback field to SentryOptions, which is invoked in the ClientReportRecorder when some data is discarded.

The callback accepts the discard reason, the type of discarded data, and the number of items discarded as parameters (although the number of items dropped is 1 unless the items are spans). The former two parameters are (currently) strings because the deserializer only returns strings if an envelope containing a ClientReport is processed.

💡 Motivation and Context

Client reports, introduced by #1982, are currently sent to Sentry. As per the issue below, users migrating from a former Java SDK version have requested a way to hook into the SDK to track when data is discarded before reaching Sentry. They can thus implement custom methods to alert them about issues, for example, with their network configuration.

Closes #3652

💚 How did you test it?

Unit tests, and I ran the console sample.

📝 Checklist

I added tests to verify the changes.
No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
I updated the docs if needed.
I updated the wizard if needed.
Review from the native team if needed.
No breaking change or entry added to the changelog.
No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

…eaching Sentry

github-actions · 2025-08-07T11:44:06Z

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against edccc48

sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java

github-actions · 2025-08-07T12:14:27Z

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	492.24 ms	507.43 ms	15.18 ms
Size	1.58 MiB	2.10 MiB	530.93 KiB

Previous results on branch: feat/callback-on-discard

Startup times

Revision	Plain	With Sentry	Diff
`161f873`	417.88 ms	448.72 ms	30.84 ms
`25f281c`	428.48 ms	463.63 ms	35.15 ms
`a884d63`	439.94 ms	493.38 ms	53.44 ms

App size

Revision	Plain	With Sentry	Diff
`161f873`	1.58 MiB	2.10 MiB	530.94 KiB
`25f281c`	1.58 MiB	2.09 MiB	522.42 KiB
`a884d63`	1.58 MiB	2.10 MiB	530.95 KiB

lcian

Unless there's a strong reason for it, I would prefer if we moved the DiscardReason and DataCategory out of ApiStatus.INTERNAL, that way we could pass those enums to the callback instead of plain strings.

This probably needs also a refactoring of the intermediate function to take the enums and then convert to string when necessary, but that's a private function so it's fine.

sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java

CHANGELOG.md

alexander-alderman-webb · 2025-08-07T15:11:35Z

sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java

@@ -124,6 +124,18 @@ private void recordLostEventInternal(
      @NotNull String reason, @NotNull String category, @NotNull Long countToAdd) {
    final ClientReportKey key = new ClientReportKey(reason, category);
    storage.addCount(key, countToAdd);
+    if (options.getOnDiscard() != null) {
+      try {
+        options.getOnDiscard().execute(reason, category, countToAdd);


There may be duplicate invocations of onDiscard() after restoreCountsFromClientReport() is reached. We're discussing whether to change the signature on the callback, so I will address this when we have a decision.

See my comment above

adinauer

Can we also add a test that proves, we don't double count when restoring counts from a previous ClientReport envelope item please?

sentry/src/main/java/io/sentry/SentryOptions.java

sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java

adinauer · 2025-08-08T06:31:29Z

sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java

@@ -124,6 +124,18 @@ private void recordLostEventInternal(
      @NotNull String reason, @NotNull String category, @NotNull Long countToAdd) {
    final ClientReportKey key = new ClientReportKey(reason, category);
    storage.addCount(key, countToAdd);
+    if (options.getOnDiscard() != null) {
+      try {
+        options.getOnDiscard().execute(reason, category, countToAdd);


See my comment above

sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java

…e signature of onDiscard callback, and avoid duplicate invocation

…y-java into feat/callback-on-discard

lcian

Nice, looks good to me!

adinauer

LGTM. Thanks for taking care of this!

…gelog

alexander-alderman-webb added 3 commits August 7, 2025 13:21

Add callback to record the type and amount of data discarded before r…

dd8f7bb

…eaching Sentry

Merge branch 'main' into feat/callback-on-discard

8deac8c

Remove empty test file

bfb7f0d

alexander-alderman-webb requested review from adinauer, romtsn, stefanosiano, markushi and lcian as code owners August 7, 2025 11:43

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alexander-alderman-webb added 3 commits August 7, 2025 13:52

Use long variable in sample usage of onDiscard

1b53c4e

Wrap onDiscard callback in a try-catch and fix docstring

6baf63e

Reference pull request instead of issue in the changelog

a436bf2

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alexander-alderman-webb self-assigned this Aug 7, 2025

lcian reviewed Aug 7, 2025

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sentry/src/main/java/io/sentry/clientreport/ClientReportRecorder.java Outdated Show resolved Hide resolved

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alexander-alderman-webb commented Aug 7, 2025

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adinauer reviewed Aug 8, 2025

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alexander-alderman-webb and others added 2 commits August 8, 2025 11:03

Remove Internal annotation from DiscardReason and DataCategory, updat…

88fbca6

…e signature of onDiscard callback, and avoid duplicate invocation

Format code

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alexander-alderman-webb added 3 commits August 8, 2025 11:16

Add stub for using onDiscard to the changelog

6e1b2b0

Switch samples to use enums instead of strings and lint

80aa565

Merge branch 'feat/callback-on-discard' of github.com:getsentry/sentr…

900fdd9

…y-java into feat/callback-on-discard

alexander-alderman-webb requested a review from adinauer August 8, 2025 10:50

lcian approved these changes Aug 8, 2025

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adinauer approved these changes Aug 11, 2025

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Merge branch 'main' into feat/callback-on-discard

ecb41ca

alexander-alderman-webb added 4 commits August 12, 2025 08:40

Move feature out of release that appeared by merging main in the chan…

8b18e8f

…gelog

Merge branch 'main' into feat/callback-on-discard

efcd846

merge main again

32d5205

merge main

edccc48

alexander-alderman-webb mentioned this pull request Aug 12, 2025

Add documentation for onDiscard callback in Java, Android, and Spring Boot getsentry/sentry-docs#14632

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3 tasks

alexander-alderman-webb merged commit 2091db3 into main Aug 12, 2025
37 of 41 checks passed

alexander-alderman-webb deleted the feat/callback-on-discard branch August 12, 2025 14:10

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Add callback to record the type and amount of data discarded before reaching Sentry #4612

Add callback to record the type and amount of data discarded before reaching Sentry #4612

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📜 Description

💡 Motivation and Context

💚 How did you test it?

📝 Checklist

🔮 Next steps

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Performance metrics 🚀

Previous results on branch: feat/callback-on-discard

Startup times

App size

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alexander-alderman-webb commented Aug 7, 2025 •

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