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docs: say Limit is not used in the remaining settings tables (2.1) - #297

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Backport of #296 to 2.1.x. Same three lines; #295 fixed the prose on 2.1.

The settings tables in the broadcast guide and the settings reference, and the sample's full settings file, still described RedisStreamsTopicOptions.Limit as the number of entries one read returns. Nothing reads Limit: the reader asks for PollBatchSize entries, and the publisher trims with MaxLength only. #294 (main) fixed the guide's prose. This fixes the three remaining places, so the docs no longer contradict each other.

Docs only.

The broadcast guide's table, the settings reference and the sample's full settings file still described Limit as the number of entries one read returns. Nothing reads it.

Signed-off-by: Cosmin Staicu <cosmin.staicu@uipath.com>
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Signed-off-by: Cosmin Staicu <cosmin.staicu@uipath.com>
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Folded into #293.

cosmin-staicu added a commit that referenced this pull request Oct 26, 2026
…caught-up groups (2.1) (#293)

One PR for the stream reader fixes on 2.1.x, the backport of #291. It
folds in #292 (caught-up consumer groups) and #297 (the `Limit` docs),
which are closed.

## Pending entries after a failed read

When an `XREADGROUP` times out on the client, Redis has already moved
the group past the entries and put them in the consumer's pending list.
The reader only ever read new entries (`>`) and never read its pending
list, so those entries were never dispatched. Their invalidations were
lost, and the node kept the old values in its local tier until they
expired.

Changes in `RedisStreamSubjectWriter`:
- **Pending read:** when it starts, and after every failed read, the
reader reads its own pending entries from `0` before going back to `>`.
A full batch continues from its last ID rather than restarting from `0`,
so an entry that never gets acknowledged is not read in a loop. The
consumer name (the `SourceUri`) stays the same for the writer's whole
life, so the pending list it reads is its own, as long as the
`SourceUri` is unique per process.
- **Deleted entries:** a pending entry trimmed or deleted from the
stream before it was read comes back with no fields. Its invalidation is
lost. It is acknowledged and logged as a Warning; 2.1 has no
missed-message signal to raise.
- **Undecodable entries:** an entry that decodes to null, or whose
decode throws, is acknowledged and dropped. It is not reported as a
missed message: a bad payload is not a lost invalidation, and reporting
it would let one bad writer clear the local tier on every node. Each one
is tracked as the
`Caching.RedisStreamSubjectWriter.DispatchEventsAsync.UndecodableEvent`
telemetry event and logged as a Warning once per 100, at Debug
otherwise.
- **Timeouts:** a read timeout is logged as a Warning once per 100, at
Debug otherwise, instead of as an Error every time.

Not changed: the background poll still uses the connection's request
timeout. StackExchange.Redis has no per-command timeout on a shared
connection.

Tests:
- Unit tests:
  - pending entries are read first, and only once
  - a failed read is followed by a pending read
  - a full pending batch continues from its last ID
  - deleted and undecodable pending entries are acknowledged
- undecodable entries are tracked, rate-limited, and acknowledged even
when the telemetry sink throws
  - timeouts give a Warning once per 100 and never an Error
- `RedisStreamSubjectWriterIntegrationTests`: entries handed out by a
read whose answer was thrown away are dispatched and acknowledged
against a real Redis.
- Each weaker version fails at least one test: no pending read at start,
no pending read after a failure, re-reading from `0` until empty,
deleted entries not acknowledged, timeouts still logged as errors. The
undecodable-entry rate limit was red-checked on #291.
- The full suite passes on net8.0 and net10.0 with the Redis integration
tests on. The Release `-warnaserror` build is clean.

Differences from #291, where 2.1's code differs:
- 2.1 has no gap-check script, so new entries are always read with a
plain `XREADGROUP`, and the pending read has no gap-check state to keep
in step.
- No existing 2.1 test counted every read, so 2.1 needs no `StreamReads`
helper.

## Caught-up consumer groups on a quiet stream

The stream maintainer counted a consumer group with consumers as stale
once its `last-delivered-id` was older than `MaintainerTrimInterval`. It
never checked whether anything newer had been written. On a stream with
no traffic, every live group was quarantined, deleted after
`MaintainerQuarantineInterval`, and recreated by its reader on the next
`NOGROUP`. That repeated every cycle, with warnings,
`LogRecreatingTopic`, and `XGROUP` calls that sometimes timed out.

A group whose `last-delivered-id` has reached the stream's
`last-generated-id` is now healthy, and a quarantine it was under is
cleared.
- Both parts of the ID are compared, so a group behind by one entry in
the same millisecond still counts as behind.
- If either ID can't be parsed, the old rule applies.
- A caught-up group whose consumer is dead is no longer removed on a
quiet stream. It is quarantined and deleted as before once the stream
gets a new entry.

Tests:
- Unit tests: a caught-up group is not quarantined; a caught-up group
under an elapsed quarantine is released, not deleted; a group behind in
the same millisecond is still quarantined; a stream head that can't be
read keeps the old rule.
- Integration test against Redis: on a quiet stream, a caught-up group
is kept and a group that is behind is deleted.
- The tests fail with the old code, and with a check that compares only
milliseconds.
- The full suite passes on net8.0 and net10.0 with the Redis integration
tests on. The Release `-warnaserror` build is clean.

The code is the same as #290. Only the CHANGELOG entry differs, because
it goes into 2.1's own Unreleased section.

## `Limit` docs

The settings tables in the broadcast guide and the settings reference,
and the sample's full settings file, still described
`RedisStreamsTopicOptions.Limit` as the number of entries one read
returns. Nothing reads `Limit`: the reader asks for `PollBatchSize`
entries, and the publisher trims with `MaxLength` only. #294 (main)
fixed the guide's prose. This fixes the three remaining places, so the
docs no longer contradict each other.

Docs only.

Signed-off-by: Cosmin Staicu <cosmin.staicu@uipath.com>
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