chore(engine): provide detailed error for invalid serverless sse event #3881

NathanFlurry · 2026-01-14T02:40:51Z

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railway-app · 2026-01-14T02:40:58Z

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NathanFlurry · 2026-01-14T02:41:07Z

chore(engine): provide detailed error for invalid serverless sse event #3881 : 2 dependent PRs (#3890 , #3891 ) 👈 (View in Graphite)
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claude · 2026-01-14T02:42:31Z

PR Review: Improved Serverless SSE Error Handling

Overview

This PR consolidates the error handling for serverless SSE events by:

Merging ServerlessInvalidBase64 and ServerlessInvalidPayload into a single ServerlessInvalidSsePayload error
Adding raw_payload to the error for better debugging
Extracting SSE parsing logic into dedicated helper functions
Handling the ping event type

Positive Changes ✅

1. Better Error Reporting

Adding raw_payload (truncated to 512 chars) significantly improves debuggability when invalid SSE messages are received
Using safe_slice correctly prevents panics on invalid UTF-8 boundaries

2. Code Organization

Extracting parse_to_serverless_server_event() and get_raw_event_data() improves readability and eliminates duplication
The new functions have clear single responsibilities

3. Handling Edge Cases

Now properly handles ping events (line 647-648)
Warns about unknown event types instead of crashing (line 658-660)

Issues & Recommendations 🔧

1. CRITICAL: Breaking Change - Test Must Be Updated

The test at engine/packages/engine/tests/actors_scheduling_errors.rs:964-974 still references the old error variants:

rivet_types::actor::RunnerPoolError::ServerlessInvalidPayload { message } => { ... }
rivet_types::actor::RunnerPoolError::ServerlessInvalidBase64 => { ... }

This needs to be updated to:

rivet_types::actor::RunnerPoolError::ServerlessInvalidSsePayload { message, raw_payload } => {
    tracing::info!(?message, ?raw_payload, "got ServerlessInvalidSsePayload as expected");
}

Action Required: Update the test before merging, or verify tests are passing in CI.

2. Documentation Out of Date

docs/engine/ACTOR_ERRORS.md:38-39 still documents the old error types:

- `ServerlessInvalidBase64` - Invalid base64 in SSE message
- `ServerlessInvalidPayload` - Invalid protocol payload

Should be updated to:

- `ServerlessInvalidSsePayload` - Invalid SSE payload (base64 or protocol deserialization error)

3. SDK Regeneration Required

The grep results show that the old error types are embedded in generated SDKs:

engine/sdks/go/api-full/types.go
engine/sdks/typescript/api-full/src/
engine/sdks/rust/api-full/

Action Required: Regenerate SDKs to include the new ServerlessInvalidSsePayload type with the raw_payload field. This is a breaking API change that affects SDK consumers.

4. Minor: Incomplete Logging Context

At line 659, when logging unknown event types:

tracing::warn!(event, "received unknown serverless sse message event kind");

Consider adding more context:

tracing::warn!(event, ?msg, "received unknown serverless sse message event kind");

This would help debugging by showing the full message, not just the event type string.

5. Code Style: Match Arms Consistency

The refactored code at lines 327-336 has inconsistent indentation. The nested if runner_id.is_none() check should perhaps be pulled out for clarity, or kept as-is for consistency with the draining path.

Current:

match payload {
    protocol::mk2::ToServerlessServer::ToServerlessServerInit(init) => {
        if runner_id.is_none() {
            runner_id = Some(...);
            // ...
        }
    }
}

This is fine, but note that in finish_non_critical_draining (line 480-489), the comment explicitly states why the if runner_id.is_none() is checked. Consider adding a similar comment here for consistency:

// Only initialize the runner once
if runner_id.is_none() {

Performance Considerations ⚡

Positive:

No performance regressions
safe_slice is efficient (single pass through char boundaries)
Raw payload is only captured on error path, not hot path

Security Considerations 🔒

Positive:

Truncating raw_payload to 512 chars prevents memory exhaustion from malicious payloads
Using safe_slice prevents potential panics from invalid UTF-8

Note: The raw payload could contain sensitive information. Consider whether this data should be logged or included in error responses. Since it is only included on error and truncated, the current approach seems reasonable.

Test Coverage 📊

Action Required:

Update existing test in actors_scheduling_errors.rs
Verify test passes after the update
Consider adding a test case for the ping event handling

Summary

This is a solid refactoring that improves error handling and debuggability. However, there are blocking issues that must be addressed:

✅ Update the test to use new error variant
✅ Update documentation
✅ Regenerate SDKs (breaking API change)

Once these are addressed, this PR will be ready to merge.

Checklist for Author

Update test in actors_scheduling_errors.rs:964-974
Update docs/engine/ACTOR_ERRORS.md:38-39
Regenerate SDKs to include ServerlessInvalidSsePayload
Run cargo test to verify all tests pass
Consider adding comment at line 328: // Only initialize the runner once
Consider enhancing logging at line 659 to include ?msg

pkg-pr-new · 2026-01-14T02:43:10Z

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@rivetkit/engine-runner-protocol

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commit: 41511a3

graphite-app · 2026-01-14T20:52:30Z

Merge activity

Jan 14, 8:52 PM UTC: NathanFlurry added this pull request to the Graphite merge queue.
Jan 14, 8:52 PM UTC: CI is running for this pull request on a draft pull request (#3898) due to your merge queue CI optimization settings.
Jan 14, 8:53 PM UTC: Merged by the Graphite merge queue via draft PR: #3898.

#3881)

railway-app bot temporarily deployed to rivet-frontend / rivet-pr-3881 January 14, 2026 02:41 Destroyed

NathanFlurry force-pushed the 01-13-chore_engine_provide_detailed_error_for_invalid_serverless_sse_event branch from 6e8950e to 8e7fba5 Compare January 14, 2026 04:10

railway-app bot temporarily deployed to rivet-frontend / rivet-pr-3881 January 14, 2026 04:10 Destroyed

NathanFlurry mentioned this pull request Jan 14, 2026

DO NOT MERGE: cloudflare w/o do support #3890

Draft

NathanFlurry requested a review from MasterPtato January 14, 2026 04:13

NathanFlurry mentioned this pull request Jan 14, 2026

feat(rivetkit): allow defining public namespace & token for client redirects via metadata endpoint #3891

Closed

chore(engine): provide detailed error for invalid serverless sse event

41511a3

MasterPtato approved these changes Jan 14, 2026

View reviewed changes

NathanFlurry force-pushed the 01-13-chore_engine_provide_detailed_error_for_invalid_serverless_sse_event branch from 8e7fba5 to 41511a3 Compare January 14, 2026 08:21

railway-app bot temporarily deployed to rivet-frontend / rivet-pr-3881 January 14, 2026 08:21 Destroyed

This was referenced Jan 14, 2026

chore(rivetkit): update welcome message #3893

Closed

chore(rivetkit): validate incoming serverless request endpoint/namespace #3894

Closed

doc: configuring rivet endpoints #3895

Closed

doc: update railway integration guide for serverless #3897

Closed

graphite-app bot pushed a commit that referenced this pull request Jan 14, 2026

chore(engine): provide detailed error for invalid serverless sse event (

b4e904e

#3881)

graphite-app bot closed this Jan 14, 2026

graphite-app bot deleted the 01-13-chore_engine_provide_detailed_error_for_invalid_serverless_sse_event branch January 14, 2026 20:53

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PR Review: Improved Serverless SSE Error Handling

Overview

Positive Changes ✅

Issues & Recommendations 🔧

1. CRITICAL: Breaking Change - Test Must Be Updated

2. Documentation Out of Date

3. SDK Regeneration Required

4. Minor: Incomplete Logging Context

5. Code Style: Match Arms Consistency

Performance Considerations ⚡

Security Considerations 🔒

Test Coverage 📊

Summary

Checklist for Author

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