features/changelog: RPC'fy {libgf}changelog

This patch introduces RPC based communication between the changelog
translator and libgfchangelog. It replaces the old pathetic stream
based interaction that existed earlier (due to time constraints :-/).

Changelog, upon initialization starts a RPC server (rpcsvc) allowing
clients to invoke a probe API as a bootup mechanism to request for
event notifications. During probe, clients can choose an event
filter specifying the type(s) of events they are interested in. As
of now there is no way to change the event notification set once
the probe RPC call is made, but that is easier to implement.

The actual event notifications is done on a separate RPC session.
The client (libgfchangelog) itself starts and RPC server which the
changelog translator "connects back" during probe. Notifications
are dispatched by a bunch of threads from the server (translator)
and the client optionally orders them if ordered notifications
are requried. FOPs fill in their respective event details in a
buffer (rot-buffs to be particular) and a bunch of threads
(consumers) swap the buffers out of roatation and dispatch them
via RPC. To avoid writer starvation, then number of dispatcher
threads is one less than the number of buffer list in rot-buffs.x

libgfchangelog becomes purely callback based -- upon event
notification from the server (and re-ordering them if required)
invoke a callback routine specified by consumer(s).

A major part of the patch is also aimed at providing backward
compatibility for geo-replication, which was one of the main
consumer of the stream based API. Also, this patch does not\
"turn on" event notifications for all fops, just a bunch which
is currently in requirement. Another pain point is that the
server does not filter events before dispatching it to the
clients. That load is taken up by the client itself (although
it's done at the library layer rather than making it hard on
the callback implementor). This needs improvement and care
needs to be taken to not load the server up with expensive
filtering mechanisms.

Change-Id: Ibf60a432b68f2dfa60c6f9add2bcfd37a9c41395
BUG: 1170075
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-on: http://review.gluster.org/9708
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 300 insertions, 0 deletions

diff --git a/xlators/features/changelog/src/changelog-rpc.c b/xlators/features/changelog/src/changelog-rpc.c
new file mode 100644
index 00000000000..04326456d31
--- /dev/null
+++ b/xlators/features/changelog/src/changelog-rpc.c
@@ -0,0 +1,300 @@
+/*
+   Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com>
+   This file is part of GlusterFS.
+
+   This file is licensed to you under your choice of the GNU Lesser
+   General Public License, version 3 or any later version (LGPLv3 or
+   later), or the GNU General Public License, version 2 (GPLv2), in all
+   cases as published by the Free Software Foundation.
+*/
+
+#include "changelog-rpc.h"
+#include "changelog-mem-types.h"
+#include "changelog-ev-handle.h"
+
+struct rpcsvc_program *changelog_programs[];
+
+static void
+changelog_cleanup_dispatchers (xlator_t *this,
+                               changelog_priv_t *priv, int count)
+{
+        for (; count >= 0; count--) {
+                (void) changelog_thread_cleanup
+                        (this, priv->ev_dispatcher[count]);
+        }
+}
+
+static int
+changelog_cleanup_rpc_threads (xlator_t *this, changelog_priv_t *priv)
+{
+        int ret = 0;
+        changelog_clnt_t *conn = NULL;
+
+        conn = &priv->connections;
+        if (!conn)
+                return 0;
+
+        /** terminate RPC thread(s) */
+        ret = changelog_thread_cleanup (this, priv->connector);
+        if (ret != 0)
+                goto error_return;
+        /** terminate dispatcher thread(s) */
+        changelog_cleanup_dispatchers (this, priv, priv->nr_dispatchers);
+
+        /* TODO: what about pending and waiting connections? */
+        changelog_ev_cleanup_connections (this, conn);
+
+        /* destroy locks */
+        ret = pthread_mutex_destroy (&conn->pending_lock);
+        if (ret != 0)
+                goto error_return;
+        ret = pthread_cond_destroy (&conn->pending_cond);
+        if (ret != 0)
+                goto error_return;
+        ret = LOCK_DESTROY (&conn->active_lock);
+        if (ret != 0)
+                goto error_return;
+        ret = LOCK_DESTROY (&conn->wait_lock);
+        if (ret != 0)
+                goto error_return;
+        return 0;
+
+ error_return:
+        return -1;
+}
+
+static int
+changelog_init_rpc_threads (xlator_t *this, changelog_priv_t *priv,
+                            rbuf_t *rbuf, int nr_dispatchers)
+{
+        int               j    = 0;
+        int               ret  = 0;
+        changelog_clnt_t *conn = NULL;
+
+        conn = &priv->connections;
+
+        conn->this = this;
+        conn->rbuf = rbuf;
+        conn->sequence = 1; /* start with sequence number one */
+
+        INIT_LIST_HEAD (&conn->pending);
+        INIT_LIST_HEAD (&conn->active);
+        INIT_LIST_HEAD (&conn->waitq);
+
+        ret = pthread_mutex_init (&conn->pending_lock, NULL);
+        if (ret)
+                goto error_return;
+        ret = pthread_cond_init (&conn->pending_cond, NULL);
+        if (ret)
+                goto cleanup_pending_lock;
+
+        ret = LOCK_INIT (&conn->active_lock);
+        if (ret)
+                goto cleanup_pending_cond;
+        ret = LOCK_INIT (&conn->wait_lock);
+        if (ret)
+                goto cleanup_active_lock;
+
+        /* spawn reverse connection thread */
+        ret = pthread_create (&priv->connector,
+                              NULL, changelog_ev_connector, conn);
+        if (ret != 0)
+                goto cleanup_wait_lock;
+
+        /* spawn dispatcher thread(s) */
+        priv->ev_dispatcher = GF_CALLOC (nr_dispatchers, sizeof(pthread_t),
+                                         gf_changelog_mt_ev_dispatcher_t);
+        if (!priv->ev_dispatcher)
+                goto cleanup_connector;
+
+        /* spawn dispatcher threads */
+        for (; j < nr_dispatchers; j++) {
+                ret = pthread_create (&priv->ev_dispatcher[j],
+                                      NULL, changelog_ev_dispatch, conn);
+                if (ret != 0) {
+                        changelog_cleanup_dispatchers (this, priv, --j);
+                        break;
+                }
+        }
+
+        if (ret != 0)
+                goto cleanup_connector;
+
+        priv->nr_dispatchers = nr_dispatchers;
+        return 0;
+
+ cleanup_connector:
+        (void) pthread_cancel (priv->connector);
+ cleanup_wait_lock:
+        (void) LOCK_DESTROY (&conn->wait_lock);
+ cleanup_active_lock:
+        (void) LOCK_DESTROY (&conn->active_lock);
+ cleanup_pending_cond:
+        (void) pthread_cond_destroy (&conn->pending_cond);
+ cleanup_pending_lock:
+        (void) pthread_mutex_destroy (&conn->pending_lock);
+ error_return:
+        return -1;
+}
+
+int
+changelog_rpcsvc_notify (rpcsvc_t *rpc,
+                         void *xl, rpcsvc_event_t event, void *data)
+{
+        return 0;
+}
+
+void
+changelog_destroy_rpc_listner (xlator_t *this, changelog_priv_t *priv)
+{
+        char sockfile[UNIX_PATH_MAX] = {0,};
+
+        /* sockfile path could have been saved to avoid this */
+        CHANGELOG_MAKE_SOCKET_PATH (priv->changelog_brick,
+                                    sockfile, UNIX_PATH_MAX);
+        changelog_rpc_server_destroy (this,
+                                      priv->rpc, sockfile,
+                                      changelog_rpcsvc_notify,
+                                      changelog_programs);
+        (void) changelog_cleanup_rpc_threads (this, priv);
+}
+
+rpcsvc_t *
+changelog_init_rpc_listner (xlator_t *this, changelog_priv_t *priv,
+                            rbuf_t *rbuf, int nr_dispatchers)
+{
+        int ret = 0;
+        char sockfile[UNIX_PATH_MAX] = {0,};
+
+        ret = changelog_init_rpc_threads (this, priv, rbuf, nr_dispatchers);
+        if (ret)
+                return NULL;
+
+        CHANGELOG_MAKE_SOCKET_PATH (priv->changelog_brick,
+                                    sockfile, UNIX_PATH_MAX);
+        return changelog_rpc_server_init (this, sockfile, NULL,
+                                          changelog_rpcsvc_notify,
+                                          changelog_programs);
+}
+
+void
+changelog_rpc_clnt_cleanup (changelog_rpc_clnt_t *crpc)
+{
+        if (!crpc)
+                return;
+        crpc->c_clnt = NULL;
+        (void) LOCK_DESTROY (&crpc->lock);
+        GF_FREE (crpc);
+}
+
+inline changelog_rpc_clnt_t *
+changelog_rpc_clnt_init (xlator_t *this,
+                         changelog_probe_req *rpc_req, changelog_clnt_t *c_clnt)
+{
+        int ret = 0;
+        changelog_rpc_clnt_t *crpc = NULL;
+
+        crpc = GF_CALLOC (1, sizeof (*crpc), gf_changelog_mt_rpc_clnt_t);
+        if (!crpc)
+                goto error_return;
+        INIT_LIST_HEAD (&crpc->list);
+
+        crpc->ref = 0;
+        changelog_set_disconnect_flag (crpc, _gf_false);
+
+        crpc->filter = rpc_req->filter;
+        (void) memcpy (crpc->sock, rpc_req->sock, strlen (rpc_req->sock));
+
+        crpc->this = this;
+        crpc->c_clnt = c_clnt;
+        crpc->cleanup = changelog_rpc_clnt_cleanup;
+
+        ret = LOCK_INIT (&crpc->lock);
+        if (ret != 0)
+                goto dealloc_crpc;
+        return crpc;
+
+ dealloc_crpc:
+        GF_FREE (crpc);
+ error_return:
+        return NULL;
+}
+
+/**
+ * Actor declarations
+ */
+
+/**
+ * @probe_handler
+ * A probe RPC call spawns a connect back to the caller. Caller also
+ * passes an hint which acts as a filter for selecting updates.
+ */
+
+int
+changelog_handle_probe (rpcsvc_request_t *req)
+{
+        int                   ret     = 0;
+        xlator_t             *this    = NULL;
+        rpcsvc_t             *svc     = NULL;
+        changelog_priv_t     *priv    = NULL;
+        changelog_clnt_t     *c_clnt  = NULL;
+        changelog_rpc_clnt_t *crpc    = NULL;
+
+        changelog_probe_req   rpc_req = {0,};
+        changelog_probe_rsp   rpc_rsp = {0,};
+
+        ret = xdr_to_generic (req->msg[0],
+                              &rpc_req, (xdrproc_t)xdr_changelog_probe_req);
+        if (ret < 0) {
+                gf_log ("", GF_LOG_ERROR, "xdr decoding error");
+                req->rpc_err = GARBAGE_ARGS;
+                goto handle_xdr_error;
+        }
+
+        /* ->xl hidden in rpcsvc */
+        svc    = rpcsvc_request_service (req);
+        this   = svc->mydata;
+        priv   = this->private;
+        c_clnt = &priv->connections;
+
+        crpc = changelog_rpc_clnt_init (this, &rpc_req, c_clnt);
+        if (!crpc)
+                goto handle_xdr_error;
+
+        changelog_ev_queue_connection (c_clnt, crpc);
+        rpc_rsp.op_ret = 0;
+
+        goto submit_rpc;
+
+ handle_xdr_error:
+        rpc_rsp.op_ret = -1;
+ submit_rpc:
+        (void) changelog_rpc_sumbit_reply (req, &rpc_rsp, NULL, 0, NULL,
+                                           (xdrproc_t)xdr_changelog_probe_rsp);
+        return 0;
+}
+
+/**
+ * RPC declarations
+ */
+
+rpcsvc_actor_t changelog_svc_actors[CHANGELOG_RPC_PROC_MAX] = {
+        [CHANGELOG_RPC_PROBE_FILTER] = {
+                "CHANGELOG PROBE FILTER", CHANGELOG_RPC_PROBE_FILTER,
+                changelog_handle_probe, NULL, 0, DRC_NA
+        },
+};
+
+struct rpcsvc_program changelog_svc_prog = {
+        .progname  = CHANGELOG_RPC_PROGNAME,
+        .prognum   = CHANGELOG_RPC_PROGNUM,
+        .progver   = CHANGELOG_RPC_PROGVER,
+        .numactors = CHANGELOG_RPC_PROC_MAX,
+        .actors    = changelog_svc_actors,
+        .synctask  = _gf_true,
+};
+
+struct rpcsvc_program *changelog_programs[] = {
+        &changelog_svc_prog,
+        NULL,
+};