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, 114 insertions, 0 deletions

diff --git a/xlators/features/changelog/lib/src/gf-changelog-journal.h b/xlators/features/changelog/lib/src/gf-changelog-journal.h
new file mode 100644
index 00000000000..9a0f0b28956
--- /dev/null
+++ b/xlators/features/changelog/lib/src/gf-changelog-journal.h
@@ -0,0 +1,114 @@
+/*
+   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.
+*/
+
+#ifndef __GF_CHANGELOG_JOURNAL_H
+#define __GF_CHANGELOG_JOURNAL_H
+
+#include <unistd.h>
+#include <pthread.h>
+
+#include "changelog.h"
+
+enum api_conn {
+        JNL_API_CONNECTED,
+        JNL_API_CONN_INPROGESS,
+        JNL_API_DISCONNECTED,
+};
+
+typedef struct gf_changelog_entry {
+        char path[PATH_MAX];
+
+        struct list_head list;
+} gf_changelog_entry_t;
+
+typedef struct gf_changelog_processor {
+        pthread_mutex_t  lock;     /* protects ->entries */
+        pthread_cond_t   cond;     /* waiter during empty list */
+        gf_boolean_t     waiting;
+
+        pthread_t processor;       /* thread-id of journal processing thread */
+
+        struct list_head entries;
+} gf_changelog_processor_t;
+
+typedef struct gf_changelog_journal {
+        DIR *jnl_dir;                       /* 'processing' directory stream */
+
+        int jnl_fd;                         /* fd to the tracker file */
+
+        char jnl_brickpath[PATH_MAX];       /* brick path for this end-point */
+
+        gf_changelog_processor_t *jnl_proc;
+
+        char *jnl_working_dir;              /* scratch directory */
+
+        char jnl_current_dir[PATH_MAX];
+        char jnl_processed_dir[PATH_MAX];
+        char jnl_processing_dir[PATH_MAX];
+
+        char rfc3986[256];                  /* RFC 3986 string encoding */
+
+        struct gf_changelog_journal *hist_jnl;
+        int hist_done;                      /* holds 0 done scanning,
+                                               1 keep scanning and -1 error */
+
+        pthread_spinlock_t lock;
+        int connected;
+} gf_changelog_journal_t;
+
+#define JNL_SET_API_STATE(jnl, state)  (jnl->connected = state)
+#define JNL_IS_API_DISCONNECTED(jnl)  (jnl->connected == JNL_API_DISCONNECTED)
+
+/* History API */
+typedef struct gf_changelog_history_data {
+        int           len;
+
+        int           htime_fd;
+
+        /* parallelism count */
+        int           n_parallel;
+
+        /* history from, to indexes */
+        unsigned long from;
+        unsigned long to;
+} gf_changelog_history_data_t;
+
+typedef struct gf_changelog_consume_data {
+        /** set of inputs */
+
+        /* fd to read from */
+        int             fd;
+
+        /* from @offset */
+        off_t           offset;
+
+        xlator_t       *this;
+
+        gf_changelog_journal_t *jnl;
+
+        /** set of outputs */
+
+        /* return value */
+        int retval;
+
+        /* journal processed */
+        char changelog[PATH_MAX];
+} gf_changelog_consume_data_t;
+
+/* event handler */
+CALLBACK gf_changelog_handle_journal;
+
+/* init, connect & disconnect handler */
+INIT gf_changelog_journal_init;
+FINI gf_changelog_journal_fini;
+CONNECT gf_changelog_journal_connect;
+DISCONNECT gf_changelog_journal_disconnect;
+
+#endif