wenjin272 commented on code in PR #887:
URL: https://github.com/apache/flink-agents/pull/887#discussion_r3719200583
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docs/content/docs/development/memory/sensory_and_short_term_memory.md:
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@@ -291,9 +291,13 @@ Short-term memory can be configured with a time-to-live
(TTL) so that older stat
Set `short-term-memory.state-ttl.ms` to a value greater than 0 in milliseconds
to enable TTL. You can also configure how the TTL is refreshed and whether
expired state can be returned before Flink cleans it up:
-- `short-term-memory.state-ttl.update-type`: controls whether TTL is refreshed
on create/write or on read/write.
+- `short-term-memory.state-ttl.update-type`: controls whether TTL is refreshed
on create/write (`ON_CREATE_AND_WRITE`) or on read/write (`ON_READ_AND_WRITE`,
the default).
- `short-term-memory.state-ttl.visibility`: controls whether expired memory is
never returned or may be returned if it has not been cleaned up yet.
+{{< hint warning >}}
+The default `ON_READ_AND_WRITE` update type extends an entry's lifetime
whenever it is read. This also applies when producing the run-begin snapshot
used by [Memory Events]({{< ref "docs/development/memory/memory_events" >}}):
if you opt in through `agent-run.begin-event`, each input scans the key's
short-term memory and refreshes TTL for the entries it reads, although only
value nodes are included in the event. Choose `ON_CREATE_AND_WRITE` when
entries should expire based only on writes.
Review Comment:
The last sentence skips the direct option of leaving the run-begin event
disabled. Could we make the choices explicit?
> With the default update type `ON_READ_AND_WRITE`, every read refreshes an
entry's TTL. Enabling `agent-run.begin-event` introduces an additional source
of reads: each input scans the key's short-term memory to produce the run-begin
snapshot, which may extend the lifetime of the scanned entries even though only
value nodes are included in the event. Leave `agent-run.begin-event` disabled
if the snapshot is not needed. If the snapshot is needed but reads should not
extend TTL, use `ON_CREATE_AND_WRITE`.
The corresponding warning in `memory_events.md` should be aligned as well.
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