bulkhead-pattern

Bulkhead Pattern: Isolating Requests by Service Priority

When all requests share one thread pool, a slow premium client's batch job can starve real-time API calls. The bulkhead pattern isolates requests into separate concurrency pools. This workflow classifies incoming requests by service name and priority, allocates a pool slot, executes the request in isolation, and releases the slot when done.

Workflow

serviceName, priority, request
              |
              v
+------------------------+     +----------------------+     +------------------------+     +----------------------+
| bh_classify_request    | --> | bh_allocate_pool     | --> | bh_execute_request     | --> | bh_release_pool      |
+------------------------+     +----------------------+     +------------------------+     +----------------------+
  pool assigned based on        slot allocated with          request processed              slot released
  serviceName + priority        maxConcurrency limit         in isolated pool               poolId returned

Workers

ClassifyRequestWorker -- Takes serviceName and priority. Assigns a pool name and maxConcurrency limit based on the priority level.

AllocatePoolWorker -- Allocates a slot in the assigned pool. Returns poolId: "POOL-{hashCode}", allocated: true.

ExecuteRequestWorker -- Processes the request within the pool. Returns response: {status: "ok"}.

ReleasePoolWorker -- Releases the pool slot. Returns released: true.

Tests

4 unit tests cover request classification, pool allocation, execution, and release.

Running

See ../../RUNNING.md for setup and execution instructions.