Merge bitcoin/bitcoin#22361: refactor: Make httpserver work queue a unique_ptr

fa92e60 refactor: Make httpserver work queue a unique_ptr (MarcoFalke)

Pull request description:

  This simplifies the code a bit because `if (p) { delete p; p = nullptr; }` can be replaced by a call to the `reset()` member.

ACKs for top commit:
  promag:
    Core review ACK fa92e60.
  jonatack:
    ACK fa92e60 code review, debug build clean, ran test/functional/interface*.py tests locally as a sanity check
  hebasto:
    ACK fa92e60, I have reviewed the code and it looks OK, I agree it can be merged.

Tree-SHA512: 6b122162317dd4ad6889341745c7ac1903a3ee510f6548f46dc356308442a6eff13eb8dc604c38ba18783e7a66d2b836d641a8594ff980a010c12c97f3856684

Author: MarcoFalke

src/httpserver.cpp

@@ -136,7 +136,7 @@ static struct evhttp* eventHTTP = nullptr;
 //! List of subnets to allow RPC connections from
 static std::vector<CSubNet> rpc_allow_subnets;
 //! Work queue for handling longer requests off the event loop thread
-static WorkQueue<HTTPClosure>* workQueue = nullptr;
+static std::unique_ptr<WorkQueue<HTTPClosure>> g_work_queue{nullptr};
 //! Handlers for (sub)paths
 static std::vector<HTTPPathHandler> pathHandlers;
 //! Bound listening sockets
@@ -256,10 +256,10 @@ static void http_request_cb(struct evhttp_request* req, void* arg)
     // Dispatch to worker thread
     if (i != iend) {
         std::unique_ptr<HTTPWorkItem> item(new HTTPWorkItem(std::move(hreq), path, i->handler));
-        assert(workQueue);
-        if (workQueue->Enqueue(item.get()))
+        assert(g_work_queue);
+        if (g_work_queue->Enqueue(item.get())) {
             item.release(); /* if true, queue took ownership */
-        else {
+        } else {
             LogPrintf("WARNING: request rejected because http work queue depth exceeded, it can be increased with the -rpcworkqueue= setting\n");
             item->req->WriteReply(HTTP_SERVICE_UNAVAILABLE, "Work queue depth exceeded");
         }
@@ -392,7 +392,7 @@ bool InitHTTPServer()
     int workQueueDepth = std::max((long)gArgs.GetArg("-rpcworkqueue", DEFAULT_HTTP_WORKQUEUE), 1L);
     LogPrintf("HTTP: creating work queue of depth %d\n", workQueueDepth);
 
-    workQueue = new WorkQueue<HTTPClosure>(workQueueDepth);
+    g_work_queue = std::make_unique<WorkQueue<HTTPClosure>>(workQueueDepth);
     // transfer ownership to eventBase/HTTP via .release()
     eventBase = base_ctr.release();
     eventHTTP = http_ctr.release();
@@ -424,7 +424,7 @@ void StartHTTPServer()
     g_thread_http = std::thread(ThreadHTTP, eventBase);
 
     for (int i = 0; i < rpcThreads; i++) {
-        g_thread_http_workers.emplace_back(HTTPWorkQueueRun, workQueue, i);
+        g_thread_http_workers.emplace_back(HTTPWorkQueueRun, g_work_queue.get(), i);
     }
 }
 
@@ -435,16 +435,17 @@ void InterruptHTTPServer()
         // Reject requests on current connections
         evhttp_set_gencb(eventHTTP, http_reject_request_cb, nullptr);
     }
-    if (workQueue)
-        workQueue->Interrupt();
+    if (g_work_queue) {
+        g_work_queue->Interrupt();
+    }
 }
 
 void StopHTTPServer()
 {
     LogPrint(BCLog::HTTP, "Stopping HTTP server\n");
-    if (workQueue) {
+    if (g_work_queue) {
         LogPrint(BCLog::HTTP, "Waiting for HTTP worker threads to exit\n");
-        for (auto& thread: g_thread_http_workers) {
+        for (auto& thread : g_thread_http_workers) {
             thread.join();
         }
         g_thread_http_workers.clear();
@@ -467,10 +468,7 @@ void StopHTTPServer()
         event_base_free(eventBase);
         eventBase = nullptr;
     }
-    if (workQueue) {
-        delete workQueue;
-        workQueue = nullptr;
-    }
+    g_work_queue.reset();
     LogPrint(BCLog::HTTP, "Stopped HTTP server\n");
 }