Suppress polling logs by event name

[Rohit Ranjan (RohitRanjanMS)]

Issue describing the changes in this PR

Follow-up to #11603.

Moves FunctionsLogs noise suppression into SystemLogger, where category, level, and EventName are available together. The standard ILoggingBuilder.AddFilter callback only receives category and level, so it cannot distinguish individual events — which is why the previous approach had to drop every Debug/Trace log in a category.

Suppression is driven by a single declarative table. An empty event list suppresses the whole category; otherwise only the listed EventNames are suppressed:

Category	Suppressed events
Host.Executor	all (unchanged from #11603)
Microsoft.Azure.WebJobs.EventHubs.EventHubProducerClientImpl	all (unchanged from #11603)
Microsoft.Azure.WebJobs.Extensions.Storage.Common.Listeners.QueueListener	GetMessages, BackoffDelay
Microsoft.Azure.WebJobs.Host.Queues.Listeners.QueueListener	GetMessages, BackoffDelay
Microsoft.Azure.WebJobs.Extensions.Storage.Blobs.Listeners.BlobListener	PollBlobContainer, BlobAlreadyProcessed, BlobDoesNotMatchPattern

Adding a category or event requires only a new line in that table.

Compared to the original approach, this preserves queue/blob listener start/stop lifecycle logs, HandlingStorageException, BlobMessageEnqueued, ContainerDoesNotExist, FunctionNotFound, BlobHasNoETag, and the other low-volume diagnostics that share these categories.

Telemetry data

A 30-minute production FunctionsLogs sample contained ~992.5M Debug/Trace rows. The queue rules cover 13.52% and the blob rules 4.76%; together with the existing Event Hub producer suppression the targeted rules cover ~20.6% of Debug/Trace volume, while the retained blob diagnostics are 3–4 orders of magnitude smaller (for example BlobMessageEnqueued at ~118K).

Event Hub PartitionProcessor (8.87%) and Kafka (2.40%) are intentionally not suppressed. Their Debug logs carry no EventName, so they cannot be filtered without discarding partition lifecycle, checkpoint, batching, and native-initialization diagnostics. Targeting those requires the extensions to emit stable named EventIds first.

Scope and safety

• Applies only to the internal SystemLogger sink, so customer-configured providers (Application Insights, OpenTelemetry, console) continue to honor host.json.
• Only affects Debug/Trace; Information and above are untouched.
• Diagnostic mode bypasses suppression entirely.
• The suppression check runs before the message formatter, so suppressed logs are not formatted.

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

• Backporting to the in-proc branch is not required
• My changes do not require documentation changes
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
• My changes do not require diagnostic events changes
• I have added all required tests (Unit tests, E2E tests)

[Copilot]

Pull request overview

This PR extends the existing log-category suppression filter to reduce high-volume polling noise by dropping Debug/Trace logs for additional well-known listener categories, while preserving Information+ events. It builds on the earlier telemetry noise suppression work from #11603.

Changes:

• Added four additional polling-related logging categories to the suppressed-category set (Debug/Trace only).
• Expanded unit test coverage to assert suppression behavior (Debug/Trace suppressed; Information+ allowed) for the newly added categories.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/WebJobs.Script/Extensions/ScriptLoggingBuilderExtensions.cs	Adds new high-volume polling categories to the suppression allowlist (Info+) / denylist (Debug/Trace).
test/WebJobs.Script.Tests/Extensions/ScriptLoggingBuilderExtensionsTests.cs	Adds unit test cases validating the new categories are suppressed at Debug/Trace and allowed at Information+.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.