Add ShutdownWorker internal API (#443)

* Add ShutdownWorker internal API. 

This API will allow workers to signal shutdown/restart, which Matching can use to unload the shutdown worker's sticky task queue. This will effectively remove the latency incurred from tasks being pushed to a sticky worker after that worker has already been shutdown.

openapi/openapiv2.json

@@ -10091,6 +10091,9 @@
       ],
       "default": "SEVERITY_UNSPECIFIED"
     },
+    "v1ShutdownWorkerResponse": {
+      "type": "object"
+    },
     "v1SignalExternalWorkflowExecutionCommandAttributes": {
       "type": "object",
       "properties": {

temporal/api/workflowservice/v1/request_response.proto

@@ -871,6 +871,16 @@ message ResetStickyTaskQueueRequest {
 message ResetStickyTaskQueueResponse {
 }
 
+message ShutdownWorkerRequest {
+    string namespace = 1;
+    string sticky_task_queue = 2;
+    string identity = 3;
+    string reason = 4;
+}
+
+message ShutdownWorkerResponse {
+}
+
 message QueryWorkflowRequest {
     string namespace = 1;
     temporal.api.common.v1.WorkflowExecution execution = 2;

temporal/api/workflowservice/v1/service.proto

@@ -521,11 +521,31 @@ service WorkflowService {
     // 1. StickyTaskQueue
     // 2. StickyScheduleToStartTimeout
     //
+    // When possible, ShutdownWorker should be preferred over
+    // ResetStickyTaskQueue (particularly when a worker is shutting down or
+    // cycling).
+    //
     // (-- api-linter: core::0127::http-annotation=disabled
     //     aip.dev/not-precedent: We do not expose worker API to HTTP. --)
     rpc ResetStickyTaskQueue (ResetStickyTaskQueueRequest) returns (ResetStickyTaskQueueResponse) {
     }
 
+    // ShutdownWorker is used to indicate that the given sticky task
+    // queue is no longer being polled by its worker. Following the completion of
+    // ShutdownWorker, newly-added workflow tasks will instead be placed
+    // in the normal task queue, eligible for any worker to pick up.
+    //
+    // ShutdownWorker should be called by workers while shutting down,
+    // after they've shut down their pollers. If another sticky poll
+    // request is issued, the sticky task queue will be revived.
+    //
+    // As of Temporal Server v1.25.0, ShutdownWorker hasn't yet been implemented.
+    //
+    // (-- api-linter: core::0127::http-annotation=disabled
+    //     aip.dev/not-precedent: We do not expose worker API to HTTP. --)
+    rpc ShutdownWorker (ShutdownWorkerRequest) returns (ShutdownWorkerResponse) {
+    }
+
     // QueryWorkflow requests a query be executed for a specified workflow execution.
     rpc QueryWorkflow (QueryWorkflowRequest) returns (QueryWorkflowResponse) {
         option (google.api.http) = {