Merge pull request #1767 from Expensify/dsilva_useCorrectCancelAfterW…

…henResourcesAreExhausted

Use correct cancelAfter broadcast when resources are exhausted

sqlitecluster/SQLiteNode.cpp

@@ -1716,6 +1716,12 @@ void SQLiteNode::_onMESSAGE(SQLitePeer* peer, const SData& message) {
                     uint64_t threadAttemptStartTimestamp = STimeNow();
                     thread(&SQLiteNode::_replicate, this, peer, message, _dbPool->getIndex(false), threadAttemptStartTimestamp).detach();
                 } catch (const system_error& e) {
+                    // If the server is strugling and falling behind on replication, we might have too many threads
+                    // causing a resource exhaustion. If that happens, all the transactions that are already threaded
+                    // and waiting for the transaction that failed will be stuck in an infinite loop. To prevent that
+                    // we're changing the state to SEARCHING and sending the cancelAfter property to drop all threads
+                    // that depend on the transaction that failed to be threaded.
+                    _changeState(SQLiteNodeState::SEARCHING, message.calcU64("NewCount") - 1);
                     SWARN("Caught system_error starting _replicate thread with " << _replicationThreadCount.load() << " threads. e.what()=" << e.what());
                     STHROW("Error starting replicate thread so giving up and reconnecting.");
                 }
@@ -1921,7 +1927,7 @@ void SQLiteNode::_sendToAllPeers(const SData& message, bool subscribedOnly) {
     }
 }
 
-void SQLiteNode::_changeState(SQLiteNodeState newState) {
+void SQLiteNode::_changeState(SQLiteNodeState newState, uint64_t commitIDToCancelAfter) {
     SINFO("[NOTIFY] setting commit count to: " << _db.getCommitCount());
     _localCommitNotifier.notifyThrough(_db.getCommitCount());
 
@@ -1932,7 +1938,7 @@ void SQLiteNode::_changeState(SQLiteNodeState newState) {
         // If we were following, and now we're not, we give up an any replications.
         if (_state == SQLiteNodeState::FOLLOWING) {
             _replicationThreadsShouldExit = true;
-            uint64_t cancelAfter = _leaderCommitNotifier.getValue();
+            uint64_t cancelAfter = commitIDToCancelAfter ? commitIDToCancelAfter : _leaderCommitNotifier.getValue();
             SINFO("Replication threads should exit, canceling commits after current leader commit " << cancelAfter);
             _localCommitNotifier.cancel(cancelAfter);
             _leaderCommitNotifier.cancel(cancelAfter);

sqlitecluster/SQLiteNode.h

@@ -226,7 +226,7 @@ class SQLiteNode : public STCPManager {
     // Add required headers for messages being sent to peers.
     SData _addPeerHeaders(SData message);
 
-    void _changeState(SQLiteNodeState newState);
+    void _changeState(SQLiteNodeState newState, uint64_t commitIDToCancelAfter = 0);
 
     // Handlers for transaction messages.
     void _handleBeginTransaction(SQLite& db, SQLitePeer* peer, const SData& message, bool wasConflict);