feature/changelog: Avoid thread creation if xlator is not enabled

Problem:
Changelog creates threads even if the changelog is not enabled

Background:
Changelog xlator broadly does two things
  1. Journalling - Cosumers are geo-rep and glusterfind
  2. Event Notification for registered events like (open, release etc) -
     Consumers are bitrot, geo-rep

The existing option "changelog.changelog" controls journalling and
there is no option to control event notification and is enabled by
default. So when bitrot/geo-rep is not enabled on the volume, threads
and resources(rpc and rbuf) related to event notifications consumes
resources and cpu cycle which is unnecessary.

Solution:
The solution is to have two different options as below.
 1. changelog-notification : Event notifications
 2. changelog : Journalling

This patch introduces the option "changelog-notification" which is
not exposed to user. When either bitrot or changelog (journalling)
is enabled, it internally enbales 'changelog-notification'. But
once the 'changelog-notification' is enabled, it will not be disabled
for the life time of the brick process even after bitrot and changelog
is disabled. As of now, rpc resource cleanup has lot of races and is
difficult to cleanup cleanly. If allowed, it leads to memory leaks
and crashes on enable/disable of bitrot or changelog (journal) in a
loop. Hence to be safer, the event notification is not disabled within
lifetime of process once enabled.

Change-Id: Ifd00286e0966049e8eb9f21567fe407cf11bb02a
Updates: #475
Signed-off-by: Mohit Agrawal <moagrawal@redhat.com>

3 files changed, 116 insertions, 40 deletions

diff --git a/xlators/features/changelog/src/changelog-helpers.h b/xlators/features/changelog/src/changelog-helpers.h
index 0906b164a78..0d06d98c9e1 100644
--- a/xlators/features/changelog/src/changelog-helpers.h
+++ b/xlators/features/changelog/src/changelog-helpers.h
@@ -190,8 +190,12 @@ typedef struct changelog_ev_selector {
 
 /* changelog's private structure */
 struct changelog_priv {
+    /* changelog journalling */
     gf_boolean_t active;
 
+    /* changelog live notifications */
+    gf_boolean_t rpc_active;
+
     /* to generate unique socket file per brick */
     char *changelog_brick;
 
diff --git a/xlators/features/changelog/src/changelog-rpc-common.c b/xlators/features/changelog/src/changelog-rpc-common.c
index afcc3a873c8..125246a17e1 100644
--- a/xlators/features/changelog/src/changelog-rpc-common.c
+++ b/xlators/features/changelog/src/changelog-rpc-common.c
@@ -262,6 +262,9 @@ changelog_rpc_server_destroy(xlator_t *this, rpcsvc_t *rpc, char *sockfile,
     struct rpcsvc_program *prog = NULL;
     rpc_transport_t *trans = NULL;
 
+    if (!rpc)
+        return;
+
     while (*progs) {
         prog = *progs;
         (void)rpcsvc_program_unregister(rpc, prog);
diff --git a/xlators/features/changelog/src/changelog.c b/xlators/features/changelog/src/changelog.c
index 0a03cfa3673..75d5ae267fd 100644
--- a/xlators/features/changelog/src/changelog.c
+++ b/xlators/features/changelog/src/changelog.c
@@ -34,6 +34,12 @@ static struct changelog_bootstrap cb_bootstrap[] = {
     },
 };
 
+static int
+changelog_init_rpc(xlator_t *this, changelog_priv_t *priv);
+
+static int
+changelog_init(xlator_t *this, changelog_priv_t *priv);
+
 /* Entry operations - TYPE III */
 
 /**
@@ -1997,6 +2003,11 @@ notify(xlator_t *this, int event, void *data, ...)
     uint64_t clntcnt = 0;
     changelog_clnt_t *conn = NULL;
     gf_boolean_t cleanup_notify = _gf_false;
+    char sockfile[UNIX_PATH_MAX] = {
+        0,
+    };
+    rpcsvc_listener_t *listener = NULL;
+    rpcsvc_listener_t *next = NULL;
 
     INIT_LIST_HEAD(&queue);
 
@@ -2010,23 +2021,40 @@ notify(xlator_t *this, int event, void *data, ...)
                "cleanup changelog rpc connection of brick %s",
                priv->victim->name);
 
-        this->cleanup_starting = 1;
-        changelog_destroy_rpc_listner(this, priv);
-        conn = &priv->connections;
-        if (conn)
-            changelog_ev_cleanup_connections(this, conn);
-        xprtcnt = GF_ATOMIC_GET(priv->xprtcnt);
-        clntcnt = GF_ATOMIC_GET(priv->clntcnt);
-
-        if (!xprtcnt && !clntcnt) {
-            LOCK(&priv->lock);
-            {
-                cleanup_notify = priv->notify_down;
-                priv->notify_down = _gf_true;
+        if (priv->rpc_active) {
+            this->cleanup_starting = 1;
+            changelog_destroy_rpc_listner(this, priv);
+            conn = &priv->connections;
+            if (conn)
+                changelog_ev_cleanup_connections(this, conn);
+            xprtcnt = GF_ATOMIC_GET(priv->xprtcnt);
+            clntcnt = GF_ATOMIC_GET(priv->clntcnt);
+            if (!xprtcnt && !clntcnt) {
+                LOCK(&priv->lock);
+                {
+                    cleanup_notify = priv->notify_down;
+                    priv->notify_down = _gf_true;
+                }
+                UNLOCK(&priv->lock);
+                list_for_each_entry_safe(listener, next, &priv->rpc->listeners,
+                                         list)
+                {
+                    if (listener->trans) {
+                        rpc_transport_unref(listener->trans);
+                    }
+                }
+                CHANGELOG_MAKE_SOCKET_PATH(priv->changelog_brick, sockfile,
+                                           UNIX_PATH_MAX);
+                sys_unlink(sockfile);
+                if (priv->rpc) {
+                    rpcsvc_destroy(priv->rpc);
+                    priv->rpc = NULL;
+                }
+                if (!cleanup_notify)
+                    default_notify(this, GF_EVENT_PARENT_DOWN, data);
             }
-            UNLOCK(&priv->lock);
-            if (!cleanup_notify)
-                default_notify(this, GF_EVENT_PARENT_DOWN, data);
+        } else {
+            default_notify(this, GF_EVENT_PARENT_DOWN, data);
         }
         goto out;
     }
@@ -2405,6 +2433,22 @@ changelog_barrier_pthread_destroy(changelog_priv_t *priv)
     LOCK_DESTROY(&priv->bflags.lock);
 }
 
+static void
+changelog_cleanup_rpc(xlator_t *this, changelog_priv_t *priv)
+{
+    /* terminate rpc server */
+    if (!this->cleanup_starting)
+        changelog_destroy_rpc_listner(this, priv);
+
+    (void)changelog_cleanup_rpc_threads(this, priv);
+    /* cleanup rot buffs */
+    rbuf_dtor(priv->rbuf);
+
+    /* cleanup poller thread */
+    if (priv->poller)
+        (void)changelog_thread_cleanup(this, priv->poller);
+}
+
 int
 reconfigure(xlator_t *this, dict_t *options)
 {
@@ -2413,6 +2457,9 @@ reconfigure(xlator_t *this, dict_t *options)
     changelog_priv_t *priv = NULL;
     gf_boolean_t active_earlier = _gf_true;
     gf_boolean_t active_now = _gf_true;
+    gf_boolean_t rpc_active_earlier = _gf_true;
+    gf_boolean_t rpc_active_now = _gf_true;
+    gf_boolean_t iniate_rpc = _gf_false;
     changelog_time_slice_t *slice = NULL;
     changelog_log_data_t cld = {
         0,
@@ -2434,6 +2481,7 @@ reconfigure(xlator_t *this, dict_t *options)
 
     ret = -1;
     active_earlier = priv->active;
+    rpc_active_earlier = priv->rpc_active;
 
     /* first stop the rollover and the fsync thread */
     changelog_cleanup_helper_threads(this, priv);
@@ -2467,6 +2515,29 @@ reconfigure(xlator_t *this, dict_t *options)
         goto out;
 
     GF_OPTION_RECONF("changelog", active_now, options, bool, out);
+    GF_OPTION_RECONF("changelog-notification", rpc_active_now, options, bool,
+                     out);
+
+    /* If journalling is enabled, enable rpc notifications */
+    if (active_now && !active_earlier) {
+        if (!rpc_active_earlier)
+            iniate_rpc = _gf_true;
+    }
+
+    if (rpc_active_now && !rpc_active_earlier) {
+        iniate_rpc = _gf_true;
+    }
+
+    /* TODO: Disable of changelog-notifications is not supported for now
+     * as there is no clean way of cleaning up of rpc resources
+     */
+
+    if (iniate_rpc) {
+        ret = changelog_init_rpc(this, priv);
+        if (ret)
+            goto out;
+        priv->rpc_active = _gf_true;
+    }
 
     /**
      * changelog_handle_change() handles changes that could possibly
@@ -2597,6 +2668,7 @@ changelog_init_options(xlator_t *this, changelog_priv_t *priv)
         goto dealloc_2;
 
     GF_OPTION_INIT("changelog", priv->active, bool, dealloc_2);
+    GF_OPTION_INIT("changelog-notification", priv->rpc_active, bool, dealloc_2);
     GF_OPTION_INIT("capture-del-path", priv->capture_del_path, bool, dealloc_2);
 
     GF_OPTION_INIT("op-mode", tmp, str, dealloc_2);
@@ -2635,22 +2707,6 @@ error_return:
     return -1;
 }
 
-static void
-changelog_cleanup_rpc(xlator_t *this, changelog_priv_t *priv)
-{
-    /* terminate rpc server */
-    if (!this->cleanup_starting)
-        changelog_destroy_rpc_listner(this, priv);
-
-    (void)changelog_cleanup_rpc_threads(this, priv);
-    /* cleanup rot buffs */
-    rbuf_dtor(priv->rbuf);
-
-    /* cleanup poller thread */
-    if (priv->poller)
-        (void)changelog_thread_cleanup(this, priv->poller);
-}
-
 static int
 changelog_init_rpc(xlator_t *this, changelog_priv_t *priv)
 {
@@ -2747,10 +2803,13 @@ init(xlator_t *this)
     INIT_LIST_HEAD(&priv->queue);
     priv->barrier_enabled = _gf_false;
 
-    /* RPC ball rolling.. */
-    ret = changelog_init_rpc(this, priv);
-    if (ret)
-        goto cleanup_barrier;
+    if (priv->rpc_active || priv->active) {
+        /* RPC ball rolling.. */
+        ret = changelog_init_rpc(this, priv);
+        if (ret)
+            goto cleanup_barrier;
+        priv->rpc_active = _gf_true;
+    }
 
     ret = changelog_init(this, priv);
     if (ret)
@@ -2762,7 +2821,9 @@ init(xlator_t *this)
     return 0;
 
 cleanup_rpc:
-    changelog_cleanup_rpc(this, priv);
+    if (priv->rpc_active) {
+        changelog_cleanup_rpc(this, priv);
+    }
 cleanup_barrier:
     changelog_barrier_pthread_destroy(priv);
 cleanup_options:
@@ -2788,9 +2849,10 @@ fini(xlator_t *this)
     priv = this->private;
 
     if (priv) {
-        /* terminate RPC server/threads */
-        changelog_cleanup_rpc(this, priv);
-
+        if (priv->active || priv->rpc_active) {
+            /* terminate RPC server/threads */
+            changelog_cleanup_rpc(this, priv);
+        }
         /* call barrier_disable to cancel timer */
         if (priv->barrier_enabled)
             __chlog_barrier_disable(this, &queue);
@@ -2859,6 +2921,13 @@ struct volume_options options[] = {
      .flags = OPT_FLAG_SETTABLE,
      .level = OPT_STATUS_BASIC,
      .tags = {"journal", "georep", "glusterfind"}},
+    {.key = {"changelog-notification"},
+     .type = GF_OPTION_TYPE_BOOL,
+     .default_value = "off",
+     .description = "enable/disable changelog live notification",
+     .op_version = {3},
+     .level = OPT_STATUS_BASIC,
+     .tags = {"bitrot", "georep"}},
     {.key = {"changelog-brick"},
      .type = GF_OPTION_TYPE_PATH,
      .description = "brick path to generate unique socket file name."