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tarantool-etcd-1rs No ErrWatcherDuplicateID; watch ids are globally scoped, so two streams collide Lined Up

status: open P2 bug etcd-changelog-sweep
bd update tarantool-etcd-1rs --claim bd close tarantool-etcd-1rs
Created byEugene Blikh
Ownerbigbes@gmail.com
Created2026-07-17T13:20:16Z
Updated2026-07-17T13:20:16Z
Description
etcd rejects a reused or negative watch id with created=true, canceled=true, cancel_reason='duplicate watch ID' (mvcc/watcher.go).

app/etcd/watch.lua:331 does 'watchers[watch_id] = w' with no in-use check, and the registry (watch.lua:42-44) is MODULE-GLOBAL rather than per-stream. So two different client connections that both choose the same custom watch id collide — stream A's fiber can drain stream B's events. Cross-connection data leak between unrelated clients, not just a protocol nicety.

Route-level: grpc.lua:448.
Design
Key the registry by (stream, watch_id) rather than watch_id alone, and reject in-use/negative ids with the etcd-shaped cancel. The global registry may have other consumers — check before re-keying.
Acceptance criteria
Two streams using the same custom watch id do not interfere; reused id on one stream returns the duplicate-ID cancel; negative id rejected; test covers the cross-stream case.

Depends on

No outgoing dependencies.

Depended on by

Nothing depends on this issue.

No comments.

  • Eugene Blikh created the issue · 2026-07-17T16:20:16Z
  • Eugene Blikh added label etcd-changelog-sweep · 2026-07-17T16:20:16Z
Stored rows — what this pane was built from, as read
issues 1 row
id tarantool-etcd-1rs
content_hash b3af9b9653f2aefab78554f22ffe2433f695a04c58411920ae4c1915f6a71c5b
title No ErrWatcherDuplicateID; watch ids are globally scoped, so two streams collide
description etcd rejects a reused or negative watch id with created=true, canceled=true, cancel_reason='duplicate watch ID' (mvcc/watcher.go). app/etcd/watch.lua:331 does 'watchers[watch_id] = w' with no in-use check, and the registry (watch.lua:42-44) is MODULE-GLOBAL rather than per-stream. So two different client connections that both choose the same custom watch id collide — stream A's fiber can drain stream B's events. Cross-connection data leak between unrelated clients, not just a protocol nicety. Route-level: grpc.lua:448.
design Key the registry by (stream, watch_id) rather than watch_id alone, and reject in-use/negative ids with the etcd-shaped cancel. The global registry may have other consumers — check before re-keying.
acceptance_criteria Two streams using the same custom watch id do not interfere; reused id on one stream returns the duplicate-ID cancel; negative id rejected; test covers the cross-stream case.
notes
status open
priority 2
issue_type bug
assignee NULL
estimated_minutes NULL
created_at 2026-07-17T13:20:16Z
created_by Eugene Blikh
owner bigbes@gmail.com
updated_at 2026-07-17T13:20:16Z
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created_at 2026-07-17T16:20:16Z
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comment Added label: etcd-changelog-sweep
created_at 2026-07-17T16:20:16Z