Limit the details field length we store for each SLM invocation

[andreidan]

The XContent representation of a SnapshotInvocationRecord is used to store an SLM
invocation record in the cluster state.

The details field could be very large, so large we cannot deserialise it anymore when a
node starts.

This adds a limit of maximum 1000 characters for the details field.

Fixes #96918

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[elasticsearchmachine]

Hi @andreidan, I've created a changelog YAML for you.

[andreidan]

@elasticmachine update branch

[dakrone]

LGTM, is 1000 enough characters? Should it be 2000? (I don't actually know, just curious how it was chosen)

[andreidan]

@dakrone I've picked 1000 due to paranoia :)
So 1000 characters is the exception type, message and a bit of the stack trace (depends on the Exception message length too) e.g.

org.elasticsearch.xcontent.XContentParseException: [-1:6050591] [snapshot_policy_invocation_record] failed to parse field [details]	at org.elasticsearch.xcontent.ObjectParser.throwFailedToParse(ObjectParser.java:616) ~[elasticsearch-x-content-8.8.1.jar:?]	at org.elasticsearch.xcontent.ObjectParser.parseValue(ObjectParser.java:611) ~[elasticsearch-x-content-8.8.1.jar:?]	at org.elasticsearch.xcontent.ObjectParser.parseSub(ObjectParser.java:657) ~[elasticsearch-x-content-8.8.1.jar:?]	at org.elasticsearch.xcontent.ObjectParser.parse(ObjectParser.java:315) ~[elasticsearch-x-content-8.8.1.jar:?]	at org.elasticsearch.xcontent.ConstructingObjectParser.parse(ConstructingObjectParser.java:166) ~[elasticsearch-x-content-8.8.1.jar:?]	at org.elasticsearch.xcontent.ConstructingObjectParser.apply(ConstructingObjectParser.java:158) ~[elasticsearch-x-content-8.8.1.jar:?]	at org.elasticsearch.xpack.core.slm.SnapshotInvocationRecord.parse(SnapshotInvocationRecord.java:54) ~[?:?]	at org.elasticsearch.xcontent.ObjectParser.lambda$decla 

To me it feels that the stracktrace should not be in there at all (but just logged) but happy to bump the limit further if it's useful to have more?

[dakrone]

It's nice to see what 1000 characters gets us, I think it's a fine limit to use.

[elasticsearchmachine]

💚 Backport successful

Status	Branch	Result
✅	8.9