Allow avrorouter converstion to be started and stopped

The modulecmd functionality allows the avrorouter to easily control the
conversion process with one command. The conversion can now be started and
stopped by the user.

This also fixes a bug where the conversion would stop if there were no
binlog files present when the service was started.

server/modules/routing/avro/avro.c

@@ -50,6 +50,7 @@
 #include <binlog_common.h>
 #include <avro/errors.h>
 #include <maxscale/alloc.h>
+#include <maxscale/modulecmd.h>
 
 #ifndef BINLOG_NAMEFMT
 #define BINLOG_NAMEFMT      "%s.%06d"
@@ -93,6 +94,7 @@ bool avro_save_conversion_state(AVRO_INSTANCE *router);
 static void stats_func(void *);
 void avro_index_file(AVRO_INSTANCE *router, const char* path);
 void avro_update_index(AVRO_INSTANCE* router);
+static bool conversion_task_ctl(AVRO_INSTANCE *inst, bool start);
 
 /** The module object definition */
 static ROUTER_OBJECT MyObject =
@@ -123,6 +125,26 @@ version()
     return version_str;
 }
 
+bool avro_handle_convert(const MODULECMD_ARG *args)
+{
+    bool rval = false;
+
+    if (strcmp(args->argv[1].value.string, "start") == 0 &&
+        conversion_task_ctl(args->argv[0].value.service->router_instance, true))
+    {
+        MXS_NOTICE("Started conversion for service '%s'.", args->argv[0].value.service->name);
+        rval = true;
+    }
+    else if (strcmp(args->argv[1].value.string, "stop") == 0 &&
+             conversion_task_ctl(args->argv[0].value.service->router_instance, false))
+    {
+        MXS_NOTICE("Stopped conversion for service '%s'.", args->argv[0].value.service->name);
+        rval = true;
+    }
+
+    return rval;
+}
+
 /**
  * The module initialisation routine, called when the module
  * is first loaded.
@@ -133,6 +155,13 @@ ModuleInit()
     MXS_NOTICE("Initialized avrorouter module %s.\n", version_str);
     spinlock_init(&instlock);
     instances = NULL;
+
+    modulecmd_arg_type_t args[] =
+    {
+        { MODULECMD_ARG_SERVICE, "The avrorouter service" },
+        { MODULECMD_ARG_STRING, "Action, whether to 'start' or 'stop' the conversion process" }
+    };
+    modulecmd_register_command("avrorouter", "convert", avro_handle_convert, 2, args);
 }
 
 /**
@@ -224,22 +253,29 @@ bool create_tables(sqlite3* handle)
     return true;
 }
 
-static bool add_conversion_task(AVRO_INSTANCE *inst)
+static bool conversion_task_ctl(AVRO_INSTANCE *inst, bool start)
 {
+    bool rval = false;
+
+    if (!inst->service->svc_do_shutdown)
+    {
         char tasknm[strlen(avro_task_name) + strlen(inst->service->name) + 2];
         snprintf(tasknm, sizeof(tasknm), "%s-%s", inst->service->name, avro_task_name);
-    if (inst->service->svc_do_shutdown)
+
+        /** Remove old task and create a new one */
+        hktask_remove(tasknm);
+
+        if (!start || hktask_add(tasknm, converter_func, inst, inst->task_delay))
         {
-        MXS_INFO("AVRO converter task is not added due to MaxScale shutdown");
+            rval = true;
-        return false;
         }
-    MXS_INFO("Setting task for converter_func");
+        else
-    if (hktask_oneshot(tasknm, converter_func, inst, inst->task_delay) == 0)
         {
             MXS_ERROR("Failed to add binlog to Avro conversion task to housekeeper.");
-        return false;
         }
-    return true;
+    }
+
+    return rval;
 }
 
 /**
@@ -566,7 +602,7 @@ createInstance(SERVICE *service, char **options)
      */
 
     /* Start the scan, read, convert AVRO task */
-    add_conversion_task(inst);
+    conversion_task_ctl(inst, true);
 
     MXS_INFO("AVRO: current MySQL binlog file is %s, pos is %lu\n",
              inst->binlog_name, inst->current_pos);
@@ -1047,7 +1083,7 @@ void converter_func(void* data)
     if (binlog_end == AVRO_LAST_FILE)
     {
         router->task_delay = MXS_MIN(router->task_delay + 1, AVRO_TASK_DELAY_MAX);
-        if (add_conversion_task(router))
+        if (conversion_task_ctl(router, true))
         {
             MXS_INFO("Stopped processing file %s at position %lu. Waiting until"
                      " more data is written before continuing. Next check in %d seconds.",