[mauroservienti]

The event log query was the last dynamic query in the error database. RavenDB served it with the auto index Auto/EventLogItems/ByRaisedAt. Same problem as #5953 for retry batches and #6099 for the throughput database.

Analysis

• EventLogDataStore.GetEventLogItems ran session.Query<EventLogItem>() sorted by RaisedAt, without a static index. ServicePulse reads the event log, so the auto index exists on most error databases. A customer case reported it after migrating to Lucene.
• An auto index follows the database setting Indexing.Auto.SearchEngineType and has no per-index search engine setting. The search engine custom check and the start-up warning keep reporting it after all static indexes use Lucene.
• Sweep of the error database, by code: every other Query<T>, DocumentQuery<T> and by-query operation in ServiceControl.Persistence.RavenDB and ServiceControl.RavenDB uses a static index, or is a collection query without a filter or sort (ExternalIntegrationRequestsDataStore.TryDispatchEventBatch), which creates no index. Nothing outside the RavenDB persistence projects opens a session.
• Sweep of the error database, by running the RavenDB persistence suite and listing the auto indexes each test leaves behind: Auto/EventLogItems/ByRaisedAt was the only one.

Changes

• New static index EventLogItems_ByRaisedAt, mapping RaisedAt. GetEventLogItems queries through it.
• PersistenceTestsContext.TearDown lists the auto indexes in the error database of each test and fails the test if there are any. This catches a new dynamic query in any data store that a test exercises. Without the index change, the EventLogDataStoreTests fail with Auto/EventLogItems/ByRaisedAt.
• Approval files: the new index definition, and EventLogItem in RavenPersistedTypes.

Existing databases

• RavenDB builds the new index once over the event log, which retention keeps small. No existing index is rebuilt.
• The code does not delete the existing auto index. RavenDB marks it idle after 30 minutes without queries and deletes it 72 hours later. It can also be deleted in RavenDB Studio.
• IndexDefinitionApprovals changed. Following docs/testing.md, the upgrade guide of the next release needs an entry in docs.particular.net.

Testing

• ServiceControl.Persistence.Tests.RavenDB, full suite: 368/370. The two failures are setup failures with a refused connection to the shared embedded server on port 33334, which also happen on master, a different set on each run.

Open points

• Add an upgrade guide entry for the new index in docs.particular.net.
• Extend the teardown check to the throughput database once Query the throughput endpoints through a static index #6099 is merged.