Roy Teeuwen created SLING-13212:
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Summary: LogStoreListener push API on the in-memory log store
Key: SLING-13212
URL: https://issues.apache.org/jira/browse/SLING-13212
Project: Sling
Issue Type: Improvement
Components: Commons
Affects Versions: Commons Log 6.1.2
Reporter: Roy Teeuwen
SLING-13188 added an optional in-memory LogStore queryable via
LogStore.getRecent(Pattern, LogLevel, int). The query API is well suited to
occasional inspection (e.g., a web console panel), but consumers that want to
forward log events elsewhere — telemetry pipelines, alerting, audit shipping —
are forced into a polling loop with manual de-duplication and a race against
the ring buffer's eviction policy.
Proposal: add a whiteboard-style consumer interface in
org.apache.sling.commons.log.logback.store:
{code:java}
@ConsumerType
public interface LogStoreListener {
void onEntry(LogEntry entry);
}
{code}
LogStoreRegistrar tracks LogStoreListener services with a ServiceTracker. Each
appended entry is fanned out to the currently-registered listeners
synchronously on the appender thread, after the entry has been added to the
store and outside its internal lock. Listeners registered before the LogStore
PID is configured are remembered and attached when the store activates;
listeners registered later are attached immediately.
Listeners are documented to be cheap and non-blocking; if a listener throws,
the throwable propagates to the caller (the Logback appender thread) and
Logback handles it, which keeps the contract simple and matches how Logback
already treats appender exceptions.
This change is additive: the existing LogStore.getRecent(...) API is untouched,
and consumers that don't register a LogStoreListener see no behavioural
difference.
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