[rmcdaniel]

Part of #325.

Contract (published Server 2.11.7, Workflow 2.15.7)

• Batches. WorkflowTaskPoller::claimReadyTask and ActivityTaskPoller::claimReadyTask read a batch of candidates: limit max(10, max_tasks_per_poll * 10), 10 by default. The workflow bridge filters workflow types in SQL, and pages forward until a batch holds an eligible task.
• Order. The poll tries the batch in TaskFairnessScheduler::reorder order:
  • tiers keep their priority order;
  • within a tier, the next candidate comes from the class with the fewest picks per unit of weight, ties going to the earliest-seen class;
  • tasks without a key share one default class.
• State. The fairness state is InMemoryTaskFairnessState, which starts empty on every request of the Apache image. So only the batch's own picks count, and the first candidate never moves. The order decides which candidate a poll tries next when an earlier one can't be claimed.

Evidence. Raw worker HTTP against published 2.11.7, using a worker that can't replay typed search attributes:

• ready tasks in time order were A1 (skipped), C (no key) and A2 (key a);
• PHP claimed A2, then C. Time order would have claimed C.

Change

• priority_fairness::fairness_order: the reorder, starting from empty state.
• Store::fairness_batches: the claim loop drops candidates of an unsupported workflow type, as PHP's SQL does. It splits the rest into batches of 10 and tries each batch in that order.

Why no shared fixture

The skipped candidate in a recording is always a resume task, since a first task has no history to be skipped for. Published PHP gives resume tasks, and timer tasks, the default priority and no fairness key. That contradicts its own published inheritance rule (workflow_task => inherits_priority_and_fairness_from_parent_run), filed as durable-workflow/workflow#971. Native follows the rule, so the two servers place that task in different classes. With the same keys, native reproduced PHP's order.

Remaining

These are documented in the checkpoint:

• PHP's activity poll stops after its first batch; native keeps looking.
• Native's activity batches also hold other activity types, which PHP's SQL leaves out.

Checks

• Unit tests. fairness_order pins the order: alternation, weights and tiers.
• Native test. a_skipped_candidate_is_followed_by_another_fairness_class pins the claim path: A1 (a, skipped), A2 (a), B1 (b) gives B1, then A2.
• Rust suites. Library 365 and integration 647, all passing.
• Node unit suite. 6445 pass. The one failure is the known local PhpImageContextTest.

Checkpoint.

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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