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, 334 insertions, 0 deletions

diff --git a/xlators/features/changelog/src/changelog-rpc-common.c b/xlators/features/changelog/src/changelog-rpc-common.c
new file mode 100644
index 00000000000..76db6696ae8
--- /dev/null
+++ b/xlators/features/changelog/src/changelog-rpc-common.c
@@ -0,0 +1,334 @@
+/*
+   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-common.h"
+
+/**
+*****************************************************
+                  Client Interface
+*****************************************************
+*/
+
+/**
+ * Initialize and return an RPC client object for a given unix
+ * domain socket.
+ */
+
+void *
+changelog_rpc_poller (void *arg)
+{
+        xlator_t *this = arg;
+
+        (void) event_dispatch (this->ctx->event_pool);
+        return NULL;
+}
+
+struct rpc_clnt *
+changelog_rpc_client_init (xlator_t *this, void *cbkdata,
+                           char *sockfile, rpc_clnt_notify_t fn)
+{
+        int              ret         = 0;
+        struct rpc_clnt *rpc         = NULL;
+        dict_t          *options     = NULL;
+
+        if (!cbkdata)
+                cbkdata = this;
+
+        options = dict_new ();
+        if (!options)
+                goto error_return;
+
+        ret = rpc_transport_unix_options_build (&options, sockfile, 0);
+        if (ret) {
+                gf_log (this->name, GF_LOG_ERROR,
+                        "failed to build rpc options");
+                goto dealloc_dict;
+        }
+
+        rpc = rpc_clnt_new (options, this->ctx, this->name, 16);
+        if (!rpc)
+                goto dealloc_dict;
+
+        ret = rpc_clnt_register_notify (rpc, fn, cbkdata);
+        if (ret) {
+                gf_log (this->name, GF_LOG_ERROR, "failed to register notify");
+                goto dealloc_rpc_clnt;
+        }
+
+        ret = rpc_clnt_start (rpc);
+        if (ret) {
+                gf_log (this->name, GF_LOG_ERROR, "failed to start rpc");
+                goto dealloc_rpc_clnt;
+        }
+
+        return rpc;
+
+ dealloc_rpc_clnt:
+        rpc_clnt_unref (rpc);
+ dealloc_dict:
+        dict_unref (options);
+ error_return:
+        return NULL;
+}
+
+/**
+ * Generic RPC client routine to dispatch a request to an
+ * RPC server.
+ */
+int
+changelog_rpc_sumbit_req (struct rpc_clnt *rpc, void *req,
+                          call_frame_t *frame, rpc_clnt_prog_t *prog,
+                          int procnum, struct iovec *payload, int payloadcnt,
+                          struct iobref *iobref, xlator_t *this,
+                          fop_cbk_fn_t cbkfn, xdrproc_t xdrproc)
+{
+        int           ret        = 0;
+        int           count      = 0;
+        struct iovec  iov        = {0, };
+        struct iobuf *iobuf      = NULL;
+        char          new_iobref = 0;
+        ssize_t       xdr_size   = 0;
+
+        GF_ASSERT (this);
+
+        if (req) {
+                xdr_size = xdr_sizeof (xdrproc, req);
+
+                iobuf = iobuf_get2 (this->ctx->iobuf_pool, xdr_size);
+                if (!iobuf) {
+                        goto out;
+                };
+
+                if (!iobref) {
+                        iobref = iobref_new ();
+                        if (!iobref) {
+                                goto out;
+                        }
+
+                        new_iobref = 1;
+                }
+
+                iobref_add (iobref, iobuf);
+
+                iov.iov_base = iobuf->ptr;
+                iov.iov_len  = iobuf_size (iobuf);
+
+                /* Create the xdr payload */
+                ret = xdr_serialize_generic (iov, req, xdrproc);
+                if (ret == -1) {
+                        goto out;
+                }
+
+                iov.iov_len = ret;
+                count = 1;
+        }
+
+        ret = rpc_clnt_submit (rpc, prog, procnum, cbkfn, &iov, count,
+                               payload, payloadcnt, iobref, frame, NULL,
+                               0, NULL, 0, NULL);
+
+ out:
+        if (new_iobref)
+                iobref_unref (iobref);
+        if (iobuf)
+                iobuf_unref (iobuf);
+        return ret;
+}
+
+/**
+ * Entry point to perform a remote procedure call
+ */
+int
+changelog_invoke_rpc (xlator_t *this, struct rpc_clnt *rpc,
+                      rpc_clnt_prog_t *prog, int procidx, void *arg)
+{
+        int                   ret   = 0;
+        call_frame_t         *frame = NULL;
+        rpc_clnt_procedure_t *proc  = NULL;
+
+        if (!this || !prog)
+                goto error_return;
+
+        frame = create_frame (this, this->ctx->pool);
+        if (!frame) {
+                gf_log (this->name, GF_LOG_ERROR, "failed to create frame");
+                goto error_return;
+        }
+
+        proc = &prog->proctable[procidx];
+        if (proc->fn)
+                ret = proc->fn (frame, this, arg);
+
+        STACK_DESTROY (frame->root);
+        return ret;
+
+ error_return:
+        return -1;
+}
+
+/**
+*****************************************************
+                  Server Interface
+*****************************************************
+*/
+
+struct iobuf *
+__changelog_rpc_serialize_reply (rpcsvc_request_t *req, void *arg,
+                                 struct iovec *outmsg, xdrproc_t xdrproc)
+{
+        struct iobuf *iob      = NULL;
+        ssize_t       retlen   = 0;
+        ssize_t       rsp_size = 0;
+
+        rsp_size = xdr_sizeof (xdrproc, arg);
+        iob = iobuf_get2 (req->svc->ctx->iobuf_pool, rsp_size);
+        if (!iob)
+                goto error_return;
+
+        iobuf_to_iovec (iob, outmsg);
+
+        retlen = xdr_serialize_generic (*outmsg, arg, xdrproc);
+        if (retlen == -1)
+                goto unref_iob;
+
+        outmsg->iov_len = retlen;
+        return iob;
+
+ unref_iob:
+        iobuf_unref (iob);
+ error_return:
+        return NULL;
+}
+
+int
+changelog_rpc_sumbit_reply (rpcsvc_request_t *req,
+                            void *arg, struct iovec *payload, int payloadcount,
+                            struct iobref *iobref, xdrproc_t xdrproc)
+{
+        int           ret        = -1;
+        struct iobuf *iob        = NULL;
+        struct iovec  iov        = {0,};
+        char          new_iobref = 0;
+
+        if (!req)
+                goto return_ret;
+
+        if (!iobref) {
+                iobref = iobref_new ();
+                if (!iobref)
+                        goto return_ret;
+                new_iobref = 1;
+        }
+
+        iob = __changelog_rpc_serialize_reply (req, arg, &iov, xdrproc);
+        if (!iob)
+                gf_log ("", GF_LOG_ERROR, "failed to serialize reply");
+        else
+                iobref_add (iobref, iob);
+
+        ret = rpcsvc_submit_generic (req, &iov,
+                                     1, payload, payloadcount, iobref);
+
+        if (new_iobref)
+                iobref_unref (iobref);
+        if (iob)
+                iobuf_unref (iob);
+ return_ret:
+        return ret;
+}
+
+void
+changelog_rpc_server_destroy (xlator_t *this, rpcsvc_t *rpc, char *sockfile,
+                              rpcsvc_notify_t fn, struct rpcsvc_program **progs)
+{
+        rpcsvc_listener_t      *listener = NULL;
+        rpcsvc_listener_t      *next    = NULL;
+        struct rpcsvc_program *prog    = NULL;
+
+        while (*progs) {
+                prog = *progs;
+                (void) rpcsvc_program_unregister (rpc, prog);
+        }
+
+        list_for_each_entry_safe (listener, next, &rpc->listeners, list) {
+                rpcsvc_listener_destroy (listener);
+        }
+
+        (void) rpcsvc_unregister_notify (rpc, fn, this);
+        unlink (sockfile);
+
+        GF_FREE (rpc);
+}
+
+rpcsvc_t *
+changelog_rpc_server_init (xlator_t *this, char *sockfile, void *cbkdata,
+                           rpcsvc_notify_t fn, struct rpcsvc_program **progs)
+{
+        int                    j       = 0;
+        int                    ret     = 0;
+        rpcsvc_t              *rpc     = NULL;
+        dict_t                *options = NULL;
+        struct rpcsvc_program *prog    = NULL;
+
+        if (!cbkdata)
+                cbkdata = this;
+
+        options = dict_new ();
+        if (!options)
+                goto error_return;
+
+        ret = rpcsvc_transport_unix_options_build (&options, sockfile);
+        if (ret)
+                goto dealloc_dict;
+
+        rpc = rpcsvc_init (this, this->ctx, options, 8);
+        if (rpc == NULL) {
+                gf_log (this->name, GF_LOG_ERROR, "failed to init rpc");
+                goto dealloc_dict;
+        }
+
+        ret = rpcsvc_register_notify (rpc, fn, cbkdata);
+        if (ret) {
+                gf_log (this->name,
+                        GF_LOG_ERROR, "failed to register notify function");
+                goto dealloc_rpc;
+        }
+
+        ret = rpcsvc_create_listeners (rpc, options, this->name);
+        if (ret != 1) {
+                gf_log (this->name,
+                        GF_LOG_DEBUG, "failed to create listeners");
+                goto dealloc_rpc;
+        }
+
+        while (*progs) {
+                prog = *progs;
+                ret = rpcsvc_program_register (rpc, prog);
+                if (ret) {
+                        gf_log (this->name,
+                                GF_LOG_ERROR, "cannot register program "
+                                "(name: %s, prognum: %d, pogver: %d)",
+                                prog->progname, prog->prognum, prog->progver);
+                        goto dealloc_rpc;
+                }
+
+                progs++;
+        }
+
+        dict_unref (options);
+        return rpc;
+
+ dealloc_rpc:
+        GF_FREE (rpc);
+ dealloc_dict:
+        dict_unref (options);
+ error_return:
+        return NULL;
+}