fix(pb): backport serverless fix

[MasterPtato]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[MasterPtato]

• fix(epoxy): use vbare #4616
• fix: dont upsert for ensure if missing #4615
• fix(envoy): require runner config for ws conn #4612
• fix(pb): backport serverless fix #4611 👈 (View in Graphite)
• fix(pb): optimize actor key allocation #4610
• fix: move runner configs to epoxy #4605
• chore(epoxy): clean up kv get #4604
• fix(pb-envoy): reduce round trips for ws connection #4603
• fix(envoy-client): fix handling actor event ack #4599
• fix(envoy-client): add tls #4595 : 1 other dependent PR (#4597 )
• chore: fix driver test suite #4591
• chore: tunnel auth #4588
• chore: remove udb as a dependency of envoy-client #4587
• chore: revert actor v2 hack #4586
• fix: fix pool metadata protocol version refresh, rivetkit native ws #4585
• feat: US-001 - Define SqliteKv trait in rivetkit-sqlite-native #4584
• feat(rust/engine-runner): minimal rust engine runner #4289
• chore: delete kv channel #4583
• feat(engine): rust runner #4582
• chore: remove non-engine drivers #4574 : 1 other dependent PR (#4581 )
• feat: dynamic actors #4397
• fix: driver test suite & sqlite reliability #4559
• fix: remove serverless token #4572
• fix: misc token fixes #4569
• fix(pb): clean up actor stop decision handling #4566
• fix(envoy): use global instance, add signal handlers #4565
• chore: misc fixes, add pb snapshot test #4561
• fix(cache): make in memory cache global #4560
• main

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[claude]

PR Review: fix(pb): backport serverless fix

This is a clean, minimal bug fix that removes incorrect drain signal handling from within an activity.

Summary

The PR removes a Drain message subscription from the outbound_req activity in the serverless Pegboard connection workflow. Activities in this workflow engine are not the right place to receive durable messages — that responsibility belongs to the surrounding workflow context.

Changes Analysis

conn.rs — Correct removal

Removing drain_sub and its select! branch from outbound_req_inner is the right call. Activities run with #[timeout = u64::MAX] and cannot durably handle signals. The drain detection path that remains — is_runner_draining polling at the start of each outbound_req_inner call and ctx.listen_with_timeout::<Drain> in the loope retry body — is architecturally sound for the activity-based model.

receiver.rs — Correct cleanup

Removing the ctx.msg(conn::Drain {}).send() call is consistent: once the activity no longer subscribes to that message, sending it is a no-op. The signal pathway (ctx.signal(conn::Drain {}).to_workflow_id(conn_wf_id)) remains and is the correct mechanism for waking the connection workflow between retries.

The ctx.removed::<Message<conn::Drain>>() call is correctly retained for workflow-engine bookkeeping to clean up the message type from durable state.

Verdict

The fix is minimal, well-targeted, and correct. No new logic is introduced — only dead/incorrect code is removed. No issues found.

[MasterPtato]

Merge activity

• Apr 13, 12:21 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 13, 12:38 AM UTC: Graphite rebased this pull request as part of a merge.
• Apr 13, 12:38 AM UTC: @MasterPtato merged this pull request with Graphite.