Bug 1703934 - P2: Use another parallel limit for backup speculative connection, r=dragana,necko-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D112349

modules/libpref/init/StaticPrefList.yaml

@@ -9417,6 +9417,12 @@
   value: 100
   mirror: always
 
+# The global half open sockets allowed for creating a backup connection.
+- name: network.http.http3.parallel_fallback_conn_limit
+  type: RelaxedAtomicUint32
+  value: 32
+  mirror: always
+
 # When true, a http request will be upgraded to https when HTTPS RR is
 # available.
 - name: network.dns.upgrade_with_https_rr

netwerk/protocol/http/nsHttpConnectionMgr.cpp

@@ -3304,7 +3304,8 @@ void nsHttpConnectionMgr::DoSpeculativeConnection(
   } else {
     LOG(
         ("OnMsgSpeculativeConnect Transport "
-         "not created due to existing connection count\n"));
+         "not created due to existing connection count:%d",
+         parallelSpeculativeConnectLimit));
   }
 }
 

netwerk/protocol/http/nsHttpTransaction.cpp

@@ -3229,6 +3229,21 @@ void nsHttpTransaction::OnBackupConnectionReady(bool aHTTPSRRUsed) {
   }
 }
 
+static void CreateBackupConnection(
+    nsHttpConnectionInfo* aBackupConnInfo, nsIInterfaceRequestor* aCallbacks,
+    uint32_t aCaps, std::function<void(bool)>&& aResultCallback) {
+  RefPtr<SpeculativeTransaction> trans = new SpeculativeTransaction(
+      aBackupConnInfo, aCallbacks, aCaps | NS_HTTP_DISALLOW_HTTP3,
+      std::move(aResultCallback));
+  uint32_t limit =
+      StaticPrefs::network_http_http3_parallel_fallback_conn_limit();
+  if (limit) {
+    trans->SetParallelSpeculativeConnectLimit(limit);
+    trans->SetIgnoreIdle(true);
+  }
+  gHttpHandler->ConnMgr()->DoSpeculativeConnection(trans, false);
+}
+
 void nsHttpTransaction::OnHttp3BackupTimer() {
   LOG(("nsHttpTransaction::OnHttp3BackupTimer [%p]", this));
   MOZ_ASSERT(OnSocketThread(), "not on socket thread");
@@ -3246,10 +3261,8 @@ void nsHttpTransaction::OnHttp3BackupTimer() {
     }
   };
 
-  RefPtr<SpeculativeTransaction> trans = new SpeculativeTransaction(
-      mBackupConnInfo, mCallbacks, mCaps | NS_HTTP_DISALLOW_HTTP3,
+  CreateBackupConnection(mBackupConnInfo, mCallbacks, mCaps,
                          std::move(callback));
-  gHttpHandler->ConnMgr()->DoSpeculativeConnection(trans, false);
 }
 
 void nsHttpTransaction::OnFastFallbackTimer() {
@@ -3283,10 +3296,8 @@ void nsHttpTransaction::OnFastFallbackTimer() {
     self->OnBackupConnectionReady(true);
   };
 
-  RefPtr<SpeculativeTransaction> trans = new SpeculativeTransaction(
-      mBackupConnInfo, mCallbacks, mCaps | NS_HTTP_DISALLOW_HTTP3,
+  CreateBackupConnection(mBackupConnInfo, mCallbacks, mCaps,
                          std::move(callback));
-  gHttpHandler->ConnMgr()->DoSpeculativeConnection(trans, false);
 }
 
 void nsHttpTransaction::HandleFallback(

netwerk/test/unit/test_http3_fast_fallback.js

@@ -61,6 +61,9 @@ registerCleanupFunction(async () => {
   );
   Services.prefs.clearUserPref("network.http.http3.backup_timer_delay");
   Services.prefs.clearUserPref("network.http.speculative-parallel-limit");
+  Services.prefs.clearUserPref(
+    "network.http.http3.parallel_fallback_conn_limit"
+  );
   if (trrServer) {
     await trrServer.stop();
   }
@@ -154,34 +157,6 @@ add_task(async function test_fast_fallback_with_speculative_connection() {
   await fast_fallback_test();
 });
 
-let HTTPObserver = {
-  observeActivity(
-    aChannel,
-    aType,
-    aSubtype,
-    aTimestamp,
-    aSizeData,
-    aStringData
-  ) {
-    aChannel.QueryInterface(Ci.nsIChannel);
-    if (aChannel.URI.spec == `https://foo.example.com:${h2Port}/`) {
-      if (
-        aType == Ci.nsIHttpActivityDistributor.ACTIVITY_TYPE_HTTP_TRANSACTION &&
-        aSubtype ==
-          Ci.nsIHttpActivityDistributor.ACTIVITY_SUBTYPE_REQUEST_HEADER
-      ) {
-        // We need to enable speculative connection again, since the backup
-        // connection is done by using speculative connection.
-        Services.prefs.setIntPref("network.http.speculative-parallel-limit", 6);
-        let observerService = Cc[
-          "@mozilla.org/network/http-activity-distributor;1"
-        ].getService(Ci.nsIHttpActivityDistributor);
-        observerService.removeObserver(HTTPObserver);
-      }
-    }
-  },
-};
-
 // Test the case when speculative connection is disabled. In this case, when the
 // back connection is ready, the http transaction is already activated,
 // but the socket is not ready to write.
@@ -193,11 +168,6 @@ add_task(async function test_fast_fallback_without_speculative_connection() {
   Services.obs.notifyObservers(null, "network:reset-http3-excluded-list");
   Services.prefs.setIntPref("network.http.speculative-parallel-limit", 0);
 
-  let observerService = Cc[
-    "@mozilla.org/network/http-activity-distributor;1"
-  ].getService(Ci.nsIHttpActivityDistributor);
-  observerService.addObserver(HTTPObserver);
-
   await fast_fallback_test();
 
   Services.prefs.clearUserPref(
@@ -647,9 +617,10 @@ add_task(async function testH3FallbackWithMultipleTransactions() {
 
   // Disable fast fallback.
   Services.prefs.setIntPref(
-    "network.dns.httpssvc.http3_fast_fallback_timeout",
+    "network.http.http3.parallel_fallback_conn_limit",
     0
   );
+  Services.prefs.setIntPref("network.http.speculative-parallel-limit", 0);
 
   await trrServer.registerDoHAnswers("test.multiple_trans.org", "HTTPS", {
     answers: [
@@ -684,8 +655,10 @@ add_task(async function testH3FallbackWithMultipleTransactions() {
 
   let promises = [];
   for (let i = 0; i < 2; ++i) {
-    let chan = makeChan(`https://test.multiple_trans.org:${h2Port}/server-timing`);
-    promises.push(channelOpenPromise(chan))
+    let chan = makeChan(
+      `https://test.multiple_trans.org:${h2Port}/server-timing`
+    );
+    promises.push(channelOpenPromise(chan));
   }
 
   let res = await Promise.all(promises);