fix(queue): preserve durable records across retries

[dustinbyrne]

💡 Motivation and Context

Durable event and replay queues currently couple retention to flush retry exhaustion: repeated retryable failures can clear every persisted record. Queue filenames also reuse payload UUIDs, so duplicate payload identities do not represent distinct durable entries.

This aligns the shared file-backed queue with PostHog/sdk-specs#53: retryable transport and HTTP failures retain bounded durable records, known-offline periods consume no attempts, and every enqueue has a stable queue-entry identity. HTTP 413 continues shrinking to a singleton poison record.

Cross-SDK implementation: PostHog/posthog-ios#788

💚 How did you test it?

• ./gradlew :posthog:test --tests 'com.posthog.internal.PostHogQueueTest'
• make testJava
• make checkFormat
• make api — no API snapshot changes
• git diff --check
• independent read-only implementation and cross-SDK reviews found no blockers

📝 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.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented with Pi using isolated implementation, scout, and review subagents. The human directed the durability contract and cross-SDK scope. Queue capacity and bounded backoff remain the resource controls; no public option or default was added.

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix(queue): preserve durable records acr..." | Re-trigger Greptile}

[github-actions]

posthog-android Compliance Report

Date: 2026-09-07 20:53:42 UTC
Duration: 118399ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	387ms
Format Validation.Event Has Uuid	✅	32ms
Format Validation.Event Has Lib Properties	✅	28ms
Format Validation.Distinct Id Is String	✅	27ms
Format Validation.Token Is Present	✅	22ms
Format Validation.Custom Properties Preserved	✅	25ms
Format Validation.Event Has Timestamp	✅	24ms
Retry Behavior.Retries On 503	✅	7033ms
Retry Behavior.Does Not Retry On 400	✅	4026ms
Retry Behavior.Does Not Retry On 401	✅	4025ms
Retry Behavior.Respects Retry After Header	✅	7027ms
Retry Behavior.Implements Backoff	✅	17035ms
Retry Behavior.Retries On 500	✅	7014ms
Retry Behavior.Retries On 502	✅	7021ms
Retry Behavior.Retries On 504	✅	7020ms
Retry Behavior.Max Retries Respected	✅	17035ms
Deduplication.Generates Unique Uuids	✅	36ms
Deduplication.Preserves Uuid On Retry	✅	7016ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	12021ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7017ms
Deduplication.No Duplicate Events In Batch	✅	37ms
Deduplication.Different Events Have Different Uuids	✅	25ms
Compression.Sends Gzip When Enabled	✅	20ms
Batch Format.Uses Proper Batch Structure	✅	20ms
Batch Format.Flush With No Events Sends Nothing	✅	14ms
Batch Format.Multiple Events Batched Together	✅	34ms
Error Handling.Does Not Retry On 403	✅	4021ms
Error Handling.Does Not Retry On 413	✅	4021ms
Error Handling.Retries On 408	✅	5027ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	32ms
Request Payload.Flags Request Uses V2 Query Param	✅	24ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	20ms
Request Payload.Flags Request Omits Authorization Header	✅	23ms
Request Payload.Token In Flags Body Matches Init	✅	23ms
Request Payload.Groups Round Trip	✅	33ms
Request Payload.Groups Default To Empty Object	✅	25ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	21ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	21ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	20ms
Request Lifecycle.No Flags Request On Init Alone	✅	12ms
Request Lifecycle.No Flags Request On Normal Capture	✅	20ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	38ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	23ms
Retry Behavior.Retries Flags On 502	✅	321ms
Retry Behavior.Retries Flags On 504	✅	321ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	23ms

[greptile-apps]

_{Reviews (2): Last reviewed commit: "fix(queue): preserve durable records acr..." | Re-trigger Greptile}

[dustinbyrne]

PostHog/posthog-ios#788 (comment)