improvement(client-presence): improve join response scalability and reliability

[jason-ha]

• In broadcast join responses:
  • include list of Client Connection Ids that the broadcast response covers. This will prevent hole where existing client sees a broadcast result too soon after a Join message and assumes it contains all sufficient and timely data.
  • potential join respondents will only reply if they have received a join response (or appear to have same or more requests that other audience members indicating complete knowledge)
• Increase trust of Audience (dictated by service) and select some of its member for named (primary) join responders when no Quorum members are known.
• Delay Join response messages for scalability
  • Important Do not broadcast a join response immediately even when selected as a named responder. Wait 200ms for others that may join.
• Add telemetry events for join handling:
  • JoinRequested - client has broadcast Join signal
  • JoinResponse - client is responding to join request
    Each event includes attendee and connection ids. JoinResponse additionally contains lists for whom they are responding to.

Update tests for higher client counts and delayed join responses and enable previously failing test. Limit higher client count (longer duration) tests to dedicated CI pipelines.

AB#45620

[Copilot]

Pull Request Overview

This PR improves the scalability and reliability of the join response mechanism in the presence framework by implementing delayed broadcasting, audience-based selection, and enhanced tracking capabilities.

Key changes:

• Implements delayed join responses with configurable timing (200ms for named responders, 40ms increments for backup responders)
• Adds comprehensive telemetry tracking with events for join deferrals, requests, and responses
• Updates test infrastructure to support scale testing with higher client counts (up to 100 clients) when FLUID_TEST_SCALE=true

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tools/pipelines/test-service-clients.yml	Adds environment variable to enable scale testing in CI
tools/pipelines/test-real-service.yml	Adds pipeline documentation link
packages/service-clients/end-to-end-tests/azure-client/src/test/multiprocess/presenceTest.spec.ts	Updates test configuration for conditional scale testing and removes previous test skip
packages/framework/presence/src/test/schemaValidation/protocol.spec.ts	Updates test expectations for new join response protocol with delays and response tracking
packages/framework/presence/src/test/presenceDatastoreManager.spec.ts	Comprehensive test updates for new join handling logic including delayed responses and audience management
packages/framework/presence/src/protocol.ts	Adds joinResponseFor field to track which clients a response satisfies
packages/framework/presence/src/presenceManager.ts	Updates event handling and adds disconnect callback to datastore manager
packages/framework/presence/src/presenceDatastoreManager.ts	Major implementation changes for delayed joins, audience-based responder selection, and enhanced broadcast timing
.changeset/floppy-sides-hammer.md	Documents the feature addition for improved join scalability

[alexvy86]

Approving for docs with a suggestion. Didn't look at the rest in detail.

[WillieHabi]

nit: pushing selfClientID to othersWorthIgnoring is a bit confusing here. Maybe could replace the line with quorumMembers.delete(selfClientId) instead if I understand correctly.

[jason-ha]

We could but getAudienceInformation doesn't guarantee that self is removed. It happens to do so currently. This seems more robust. The comment didn't make it clear?

[jason-ha]

JsonString related changes will be merged separately. Currently PRs #25501 and #25522.

[github-actions]

🔗 Found some broken links! 💔

Run a link check locally to find them. See
https://github.com/microsoft/FluidFramework/wiki/Checking-for-broken-links-in-the-documentation for more information.

linkcheck output

> [email protected] ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> [email protected] serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> [email protected] check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

 ELIFECYCLE  Command failed with exit code 1.