MXS-1576: Add purge command to avrorouter

The `purge` command can be used to reset the conversion
process. Currently, executing the `purge` module command and restarting
MaxScale is the only correct way to reset the conversion process.

Documentation/Routers/Avrorouter.md

@@ -179,6 +179,18 @@ Start or stop the binary log to Avro conversion. The first parameter is the name
 of the service to stop and the second parameter tells whether to start the
 conversion process or to stop it.
 
+### `avrorouter::purge SERVICE`
+
+This command will delete all files created by the avrorouter. This includes all
+.avsc schema files and .avro data files as well as the internal state tracking
+files. Use this to completely reset the conversion process.
+
+**Note:** Once the command has completed, MaxScale must be restarted to restart
+the conversion process. Issuing a `convert start` command **will not work**.
+
+**WARNING:** You will lose any and all converted data when this command is
+  executed.
+
 # Files Created by the Avrorouter
 
 The avrorouter creates two files in the location pointed by _avrodir_:

server/modules/routing/avrorouter/avro.c

@@ -31,6 +31,10 @@
 #include <string.h>
 #include <ctype.h>
 #include <time.h>
+#include <glob.h>
+#include <ini.h>
+#include <sys/stat.h>
+#include <avro/errors.h>
 #include <maxscale/service.h>
 #include <maxscale/server.h>
 #include <maxscale/router.h>
@@ -39,20 +43,13 @@
 #include <maxscale/dcb.h>
 #include <maxscale/spinlock.h>
 #include <maxscale/housekeeper.h>
-#include <time.h>
-
 #include <maxscale/log_manager.h>
-
 #include <maxscale/protocol/mysql.h>
-#include <ini.h>
-#include <sys/stat.h>
-
-#include <maxscale/random_jkiss.h>
-#include <binlog_common.h>
-#include <avro/errors.h>
 #include <maxscale/alloc.h>
 #include <maxscale/modulecmd.h>
 #include <maxscale/paths.h>
+#include <maxscale/random_jkiss.h>
+#include <binlog_common.h>
 
 #ifndef BINLOG_NAMEFMT
 #define BINLOG_NAMEFMT      "%s.%06d"
@@ -120,6 +117,70 @@ bool avro_handle_convert(const MODULECMD_ARG *args)
     return rval;
 }
 
+static bool do_unlink(const char* format, ...)
+{
+    va_list args;
+    va_start(args, format);
+
+    char filename[PATH_MAX + 1];
+    vsnprintf(filename, sizeof(filename), format, args);
+
+    va_end(args);
+
+    int rc = unlink(filename);
+    return rc == 0 || rc == ENOENT;
+}
+
+static bool do_unlink_with_pattern(const char* format, ...)
+{
+    bool rval = true;
+    va_list args;
+    va_start(args, format);
+
+    char filename[PATH_MAX + 1];
+    vsnprintf(filename, sizeof(filename), format, args);
+
+    va_end(args);
+
+    glob_t g;
+    int rc = glob(filename, 0, NULL, &g);
+
+    if (rc == 0)
+    {
+        for (size_t i = 0; i < g.gl_pathc; i++)
+        {
+            if (!do_unlink("%s", g.gl_pathv[i]))
+            {
+                rval = false;
+            }
+        }
+    }
+    else if (rc != GLOB_NOMATCH)
+    {
+        modulecmd_set_error("Failed to search '%s': %d, %s",
+                            filename, errno, mxs_strerror(errno));
+        rval = false;
+    }
+
+    globfree(&g);
+
+    return rval;
+}
+
+static bool avro_handle_purge(const MODULECMD_ARG *args)
+{
+    AVRO_INSTANCE* inst = (AVRO_INSTANCE*)args->argv[0].value.service->router_instance;
+
+    // First stop the conversion service
+    conversion_task_ctl(inst, false);
+
+    // Then delete the files
+    return do_unlink("%s/%s", inst->avrodir, AVRO_PROGRESS_FILE) && // State file
+           do_unlink("/%s/%s", inst->avrodir, avro_index_name) &&   // Index database
+           do_unlink_with_pattern("/%s/*.avro", inst->avrodir) &&   // .avro files
+           do_unlink_with_pattern("/%s/*.avsc", inst->avrodir);     // .avsc files
+}
+
 /**
  * The module entry point routine. It is this routine that
  * must populate the structure that is referred to as the
@@ -133,12 +194,21 @@ MXS_MODULE* MXS_CREATE_MODULE()
     spinlock_init(&instlock);
     instances = NULL;
 
-    static modulecmd_arg_type_t args[] =
+    static modulecmd_arg_type_t args_convert[] =
     {
         { MODULECMD_ARG_SERVICE | MODULECMD_ARG_NAME_MATCHES_DOMAIN, "The avrorouter service" },
         { MODULECMD_ARG_STRING, "Action, whether to 'start' or 'stop' the conversion process" }
     };
-    modulecmd_register_command(MXS_MODULE_NAME, "convert", avro_handle_convert, 2, args);
+    modulecmd_register_command(MXS_MODULE_NAME, "convert", avro_handle_convert, 2, args_convert);
+
+    static modulecmd_arg_type_t args_purge[] =
+    {
+        {
+            MODULECMD_ARG_SERVICE | MODULECMD_ARG_NAME_MATCHES_DOMAIN,
+            "The avrorouter service to purge (NOTE: THIS REMOVES ALL CONVERTED FILES)"
+        }
+    };
+    modulecmd_register_command(MXS_MODULE_NAME, "purge", avro_handle_purge, 1, args_purge);
 
     static MXS_ROUTER_OBJECT MyObject =
     {