MXS-2026 Separate QC process and thread initialization

qc_thread_init() must now explicitly be called in every thread
and not just in other threads but the one where qc_process_init()
is called.

This change was caused by QC_INIT_SELF initialization actually
being performed in query_classifier.cc. Before this change, there
actually was a leak in the routing worker running in the main
thread, the query classification cache was created twice.

include/maxscale/query_classifier.h

@@ -198,16 +198,14 @@ typedef struct query_classifier
     void (*qc_process_end)(void);
 
     /**
-     * Called once per each thread, except for the thread for which @c qc_process_init
+     * Called once per each thread.
-     * was called.
      *
      * @return QC_RESULT_OK, if the thread initialization succeeded.
      */
     int32_t (*qc_thread_init)(void);
 
     /**
-     * Called once when a thread finishes, except for the thread for which @c qc_process_init
+     * Called once when a thread finishes.
-     * was called.
      */
     void (*qc_thread_end)(void);
 
@@ -499,9 +497,9 @@ bool qc_process_init(uint32_t kind);
 /**
  * Finalizes the query classifier.
  *
- * A successful call of qc_init() should before program exit be followed
+ * A successful call of @c qc_process_init should before program exit be
- * by a call to this function. MaxScale calls this function, so plugins
+ * followed by a call to this function. MaxScale calls this function, so
- * should not do that.
+ * plugins should not do that.
  *
  * @param kind  What kind of finalization should be performed.
  *              Combination of qc_init_kind_t.
@@ -537,8 +535,7 @@ void qc_unload(QUERY_CLASSIFIER* classifier);
 
 /**
  * Performs thread initialization needed by the query classifier. Should
- * be called in every thread, except the one where qc_process_init()
+ * be called in every thread.
- * was called.
  *
  * MaxScale calls this function, so plugins should not do that.
  *
@@ -553,8 +550,8 @@ bool qc_thread_init(uint32_t kind);
 
 /**
  * Performs thread finalization needed by the query classifier.
- * A successful call to qc_thread_init() should at some point be followed
+ * A successful call to @c qc_thread_init should at some point be
- * by a call to this function.
+ * followed by a call to this function.
  *
  * MaxScale calls this function, so plugins should not do that.
  *

query_classifier/test/classify.c

@@ -317,9 +317,9 @@ int main(int argc, char** argv)
 
         if (mxs_log_init(NULL, ".", MXS_LOG_TARGET_DEFAULT))
         {
-            if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, lib, NULL) &&
+            if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, lib, NULL)
-                qc_process_init(QC_INIT_BOTH) &&
+                && qc_process_init(QC_INIT_BOTH)
-                qc_thread_init(QC_INIT_BOTH))
+                && qc_thread_init(QC_INIT_BOTH))
             {
                 //  Version encoded as MariaDB encodes the version, i.e.:
                 //  version = major * 10000 + minor * 100 + patch
@@ -327,6 +327,8 @@ int main(int argc, char** argv)
 
                 qc_set_server_version(version);
                 rc = run(input_name, expected_name);
+
+                qc_thread_end(QC_INIT_BOTH);
                 qc_process_end(QC_INIT_BOTH);
             }
             else

server/core/query_classifier.cc

@@ -441,19 +441,11 @@ bool qc_process_init(uint32_t kind)
         }
     }
 
-    bool rc = qc_thread_init(QC_INIT_SELF);
+    bool rc = true;
 
-    if (rc)
+    if (kind & QC_INIT_PLUGIN)
     {
-        if (kind & QC_INIT_PLUGIN)
+        rc = this_unit.classifier->qc_process_init() == 0;
-        {
-            rc = this_unit.classifier->qc_process_init() == 0;
-
-            if (!rc)
-            {
-                qc_thread_end(QC_INIT_SELF);
-            }
-        }
     }
 
     return rc;
@@ -468,8 +460,6 @@ void qc_process_end(uint32_t kind)
     {
         this_unit.classifier->qc_process_end();
     }
-
-    qc_thread_end(QC_INIT_SELF);
 }
 
 QUERY_CLASSIFIER* qc_load(const char* plugin_name)
@@ -502,12 +492,19 @@ bool qc_thread_init(uint32_t kind)
 
     bool rc = false;
 
-    this_thread.pInfo_cache = new (std::nothrow) QCInfoCache;
+    if (kind & QC_INIT_SELF)
-
+    {
-    if (this_thread.pInfo_cache)
+        mxb_assert(!this_thread.pInfo_cache);
+        this_thread.pInfo_cache = new (std::nothrow) QCInfoCache;
+        rc = true;
+    }
+    else
     {
         rc = true;
+    }
 
+    if (rc)
+    {
         if (kind & QC_INIT_PLUGIN)
         {
             rc = this_unit.classifier->qc_thread_init() == 0;
@@ -515,8 +512,11 @@ bool qc_thread_init(uint32_t kind)
 
         if (!rc)
         {
-            delete this_thread.pInfo_cache;
+            if (kind & QC_INIT_SELF)
-            this_thread.pInfo_cache = nullptr;
+            {
+                delete this_thread.pInfo_cache;
+                this_thread.pInfo_cache = nullptr;
+            }
         }
     }
 
@@ -533,8 +533,11 @@ void qc_thread_end(uint32_t kind)
         this_unit.classifier->qc_thread_end();
     }
 
-    delete this_thread.pInfo_cache;
+    if (kind & QC_INIT_SELF)
-    this_thread.pInfo_cache = nullptr;
+    {
+        delete this_thread.pInfo_cache;
+        this_thread.pInfo_cache = nullptr;
+    }
 }
 
 qc_parse_result_t qc_parse(GWBUF* query, uint32_t collect)

server/core/test/test_trxcompare.cc

@@ -186,9 +186,9 @@ int main(int argc, char* argv[])
             set_libdir(strdup("../../../query_classifier/qc_sqlite"));
 
             // We have to setup something in order for the regexes to be compiled.
-            if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, "qc_sqlite", NULL) &&
+            if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, "qc_sqlite", NULL)
-                qc_process_init(QC_INIT_BOTH) &&
+                && qc_process_init(QC_INIT_BOTH)
-                qc_thread_init(QC_INIT_BOTH))
+                && qc_thread_init(QC_INIT_BOTH))
             {
                 Tester tester(verbosity);
 
@@ -218,6 +218,7 @@ int main(int argc, char* argv[])
                     }
                 }
 
+                qc_thread_end(QC_INIT_BOTH);
                 qc_process_end(QC_INIT_BOTH);
             }
             else

server/core/test/test_trxtracking.cc

@@ -423,9 +423,9 @@ int main(int argc, char* argv[])
             set_libdir(strdup("../../../query_classifier/qc_sqlite"));
 
             // We have to setup something in order for the regexes to be compiled.
-            if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, "qc_sqlite", NULL) &&
+            if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, "qc_sqlite", NULL)
-                qc_process_init(QC_INIT_BOTH) &&
+                && qc_process_init(QC_INIT_BOTH)
-                qc_thread_init(QC_INIT_BOTH))
+                && qc_thread_init(QC_INIT_BOTH))
             {
                 rc = EXIT_SUCCESS;
 
@@ -451,6 +451,7 @@ int main(int argc, char* argv[])
                     cout << endl;
                 }
 
+                qc_thread_end(QC_INIT_BOTH);
                 qc_process_end(QC_INIT_BOTH);
             }
             else

server/modules/filter/cache/test/testrules.cc

@@ -397,13 +397,14 @@ int main()
         pConfig->n_threads = 1;
 
         set_libdir(MXS_STRDUP_A("../../../../../query_classifier/qc_sqlite/"));
-        if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, "qc_sqlite", "") &&
+        if (qc_setup(NULL, QC_SQL_MODE_DEFAULT, "qc_sqlite", "")
-            qc_process_init(QC_INIT_BOTH) &&
+            && qc_process_init(QC_INIT_BOTH)
-            qc_thread_init(QC_INIT_BOTH))
+            && qc_thread_init(QC_INIT_BOTH))
         {
             set_libdir(MXS_STRDUP_A("../"));
             rc = test();
 
+            qc_thread_end(QC_INIT_BOTH);
             qc_process_end(QC_INIT_BOTH);
         }
         else