[PATCH] Ceph RADOS cluster mutex helper for Samba CTDB

[David Disseldorp <ddiss@suse.de>]

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Hi,

The attached patch-set implements a cluster mutex helper for Samba CTDB
using Ceph librados.

ctdb_mutex_ceph_rados_helper_lock can be used as a recovery lock provider
for CTDB.  When configured, split brain avoidance during CTDB recovery
will be handled using locks against an object located in a Ceph RADOS
pool.

I've also attached a standalone test script - @Martin: does this belong
in the ctdb test suite, or can I just commit it as a standalone test?
It has a few non-standard dependencies: a running Ceph cluster, the
rados and jq binaries.

Feedback appreciated.

Cheers, David

--

 ctdb/doc/Makefile                           |   3 +-
 ctdb/doc/ctdb_mutex_ceph_rados_helper.7.xml |  90 ++++++
 ctdb/tools/ctdb_mutex_ceph_rados_helper.c   | 334 ++++++++++++++++++++
 ctdb/wscript                                |  19 ++
 4 files changed, 445 insertions(+), 1 deletion(-)


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[-- Attachment #2: ctdb_reclock_ceph.patchset --]
[-- Type: text/x-patch, Size: 17146 bytes --]

From 47e653373073f1564844465eb416cdebb1dc4aa6 Mon Sep 17 00:00:00 2001
From: David Disseldorp <ddiss@samba.org>
Date: Thu, 1 Dec 2016 13:33:22 +0100
Subject: [PATCH 1/2] ctdb: cluster mutex helper using Ceph RADOS

ctdb_mutex_ceph_rados_helper implements the cluster mutex helper API
atop Ceph using the librados rados_lock_exclusive()/rados_unlock()
functionality.

Once configured, split brain avoidance during CTDB recovery will be
handled using locks against an object located in a Ceph RADOS pool.

Signed-off-by: David Disseldorp <ddiss@samba.org>
---
 ctdb/tools/ctdb_mutex_ceph_rados_helper.c | 334 ++++++++++++++++++++++++++++++
 ctdb/wscript                              |  19 ++
 2 files changed, 353 insertions(+)
 create mode 100644 ctdb/tools/ctdb_mutex_ceph_rados_helper.c

diff --git a/ctdb/tools/ctdb_mutex_ceph_rados_helper.c b/ctdb/tools/ctdb_mutex_ceph_rados_helper.c
new file mode 100644
index 0000000..8d19965
--- /dev/null
+++ b/ctdb/tools/ctdb_mutex_ceph_rados_helper.c
@@ -0,0 +1,334 @@
+/*
+   CTDB mutex helper using Ceph librados locks
+
+   Copyright (C) David Disseldorp 2016
+
+   Based on ctdb_mutex_fcntl_helper.c, which is:
+   Copyright (C) Martin Schwenke 2015
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "replace.h"
+#include "system/filesys.h"
+#include "system/network.h"
+
+/* protocol.h is just needed for ctdb_sock_addr, which is used in system.h */
+#include "protocol/protocol.h"
+#include "common/system.h"
+#include "lib/util/time.h"
+#include "tevent.h"
+#include "talloc.h"
+#include "rados/librados.h"
+
+#define CTDB_MUTEX_CEPH_LOCK_NAME	"ctdb_reclock_mutex"
+#define CTDB_MUTEX_CEPH_LOCK_COOKIE	CTDB_MUTEX_CEPH_LOCK_NAME
+#define CTDB_MUTEX_CEPH_LOCK_DESC	"CTDB recovery lock"
+
+#define CTDB_MUTEX_STATUS_HOLDING "0"
+#define CTDB_MUTEX_STATUS_CONTENDED "1"
+#define CTDB_MUTEX_STATUS_TIMEOUT "2"
+#define CTDB_MUTEX_STATUS_ERROR "3"
+
+static char *progname = NULL;
+
+static int ctdb_mutex_rados_ctx_create(const char *ceph_cluster_name,
+				       const char *ceph_auth_name,
+				       const char *pool_name,
+				       rados_t *_ceph_cluster,
+				       rados_ioctx_t *_ioctx)
+{
+	rados_t ceph_cluster = NULL;
+	rados_ioctx_t ioctx = NULL;
+	int ret;
+
+	ret = rados_create2(&ceph_cluster, ceph_cluster_name, ceph_auth_name, 0);
+	if (ret < 0) {
+		fprintf(stderr, "%s: failed to initialise Ceph cluster %s as %s"
+			" - (%s)\n", progname, ceph_cluster_name, ceph_auth_name,
+			strerror(-ret));
+		return ret;
+	}
+
+	/* path=NULL tells librados to use default locations */
+	ret = rados_conf_read_file(ceph_cluster, NULL);
+	if (ret < 0) {
+		fprintf(stderr, "%s: failed to parse Ceph cluster config"
+			" - (%s)\n", progname, strerror(-ret));
+		rados_shutdown(ceph_cluster);
+		return ret;
+	}
+
+	ret = rados_connect(ceph_cluster);
+	if (ret < 0) {
+		fprintf(stderr, "%s: failed to connect to Ceph cluster %s as %s"
+			" - (%s)\n", progname, ceph_cluster_name, ceph_auth_name,
+			strerror(-ret));
+		rados_shutdown(ceph_cluster);
+		return ret;
+	}
+
+
+	ret = rados_ioctx_create(ceph_cluster, pool_name, &ioctx);
+	if (ret < 0) {
+		fprintf(stderr, "%s: failed to create Ceph ioctx for pool %s"
+			" - (%s)\n", progname, pool_name, strerror(-ret));
+		rados_shutdown(ceph_cluster);
+		return ret;
+	}
+
+	*_ceph_cluster = ceph_cluster;
+	*_ioctx = ioctx;
+
+	return 0;
+}
+
+static void ctdb_mutex_rados_ctx_destroy(rados_t ceph_cluster,
+					 rados_ioctx_t ioctx)
+{
+	rados_ioctx_destroy(ioctx);
+	rados_shutdown(ceph_cluster);
+}
+
+static int ctdb_mutex_rados_lock(rados_ioctx_t *ioctx,
+				 const char *oid)
+{
+	int ret;
+
+	ret = rados_lock_exclusive(ioctx, oid,
+                                   CTDB_MUTEX_CEPH_LOCK_NAME,
+				   CTDB_MUTEX_CEPH_LOCK_COOKIE,
+				   CTDB_MUTEX_CEPH_LOCK_DESC,
+                                   NULL, /* infinite duration */
+                                   0);
+	if ((ret == -EEXIST) || (ret == -EBUSY)) {
+		/* lock contention */
+		return ret;
+	} else if (ret < 0) {
+		/* unexpected failure */
+		fprintf(stderr,
+			"%s: Failed to get lock on RADOS object '%s' - (%s)\n",
+			progname, oid, strerror(-ret));
+		return ret;
+	}
+
+	/* lock obtained */
+	return 0;
+}
+
+static int ctdb_mutex_rados_unlock(rados_ioctx_t *ioctx,
+				   const char *oid)
+{
+	int ret;
+
+	ret = rados_unlock(ioctx, oid,
+			   CTDB_MUTEX_CEPH_LOCK_NAME,
+			   CTDB_MUTEX_CEPH_LOCK_COOKIE);
+	if (ret < 0) {
+		fprintf(stderr,
+			"%s: Failed to drop lock on RADOS object '%s' - (%s)\n",
+			progname, oid, strerror(-ret));
+		return ret;
+	}
+
+	return 0;
+}
+
+struct ctdb_mutex_rados_state {
+	bool holding_mutex;
+	const char *ceph_cluster_name;
+	const char *ceph_auth_name;
+	const char *pool_name;
+	const char *object;
+	int ppid;
+	struct tevent_context *ev;
+	struct tevent_signal *sig_ev;
+	struct tevent_timer *timer_ev;
+	rados_t ceph_cluster;
+	rados_ioctx_t ioctx;
+};
+
+static void ctdb_mutex_rados_sigterm_cb(struct tevent_context *ev,
+					struct tevent_signal *se,
+					int signum,
+					int count,
+					void *siginfo,
+					void *private_data)
+{
+	struct ctdb_mutex_rados_state *cmr_state = private_data;
+	int ret;
+
+	if (!cmr_state->holding_mutex) {
+		fprintf(stderr, "Sigterm callback invoked without mutex!\n");
+		ret = -EINVAL;
+		goto err_ctx_cleanup;
+	}
+
+	ret = ctdb_mutex_rados_unlock(cmr_state->ioctx, cmr_state->object);
+err_ctx_cleanup:
+	ctdb_mutex_rados_ctx_destroy(cmr_state->ceph_cluster,
+				     cmr_state->ioctx);
+	talloc_free(cmr_state);
+	exit(ret ? 1 : 0);
+}
+
+static void ctdb_mutex_rados_timer_cb(struct tevent_context *ev,
+				      struct tevent_timer *te,
+				      struct timeval current_time,
+				      void *private_data)
+{
+	struct ctdb_mutex_rados_state *cmr_state = private_data;
+	int ret;
+
+	if (!cmr_state->holding_mutex) {
+		fprintf(stderr, "Timer callback invoked without mutex!\n");
+		ret = -EINVAL;
+		goto err_ctx_cleanup;
+	}
+
+	if ((kill(cmr_state->ppid, 0) == 0) || (errno != ESRCH)) {
+		/* parent still around, keep waiting */
+		cmr_state->timer_ev = tevent_add_timer(cmr_state->ev, cmr_state,
+						       timeval_current_ofs(5,0),
+						      ctdb_mutex_rados_timer_cb,
+						       cmr_state);
+		if (cmr_state->timer_ev == NULL) {
+			fprintf(stderr, "Failed to create timer event\n");
+			/* rely on signal cb */
+		}
+		return;
+	}
+
+	/* parent ended, drop lock and exit */
+	ret = ctdb_mutex_rados_unlock(cmr_state->ioctx, cmr_state->object);
+err_ctx_cleanup:
+	ctdb_mutex_rados_ctx_destroy(cmr_state->ceph_cluster,
+				     cmr_state->ioctx);
+	talloc_free(cmr_state);
+	exit(ret ? 1 : 0);
+}
+
+int main(int argc, char *argv[])
+{
+	int ret;
+	struct ctdb_mutex_rados_state *cmr_state;
+
+	progname = argv[0];
+
+	if (argc != 5) {
+		fprintf(stderr, "Usage: %s <Ceph Cluster> <Ceph user> "
+				"<RADOS pool> <RADOS object>\n",
+			progname);
+		ret = -EINVAL;
+		goto err_out;
+	}
+
+	ret = setvbuf(stdout, NULL, _IONBF, 0);
+	if (ret != 0) {
+		fprintf(stderr, "Failed to configure unbuffered stdout I/O\n");
+	}
+
+	cmr_state = talloc_zero(NULL, struct ctdb_mutex_rados_state);
+	if (cmr_state == NULL) {
+		fprintf(stdout, CTDB_MUTEX_STATUS_ERROR);
+		ret = -ENOMEM;
+		goto err_out;
+	}
+
+	cmr_state->ceph_cluster_name = argv[1];
+	cmr_state->ceph_auth_name = argv[2];
+	cmr_state->pool_name = argv[3];
+	cmr_state->object = argv[4];
+
+	cmr_state->ppid = getppid();
+	if (cmr_state->ppid == 1) {
+		/*
+		 * The original parent is gone and the process has
+		 * been reparented to init.  This can happen if the
+		 * helper is started just as the parent is killed
+		 * during shutdown.  The error message doesn't need to
+		 * be stellar, since there won't be anything around to
+		 * capture and log it...
+		 */
+		fprintf(stderr, "%s: PPID == 1\n", progname);
+		ret = -EPIPE;
+		goto err_state_free;
+	}
+
+	cmr_state->ev = tevent_context_init(cmr_state);
+	if (cmr_state->ev == NULL) {
+		fprintf(stderr, "tevent_context_init failed\n");
+		fprintf(stdout, CTDB_MUTEX_STATUS_ERROR);
+		ret = -ENOMEM;
+		goto err_state_free;
+	}
+
+	/* wait for sigterm */
+	cmr_state->sig_ev = tevent_add_signal(cmr_state->ev, cmr_state, SIGTERM, 0,
+					      ctdb_mutex_rados_sigterm_cb,
+					      cmr_state);
+	if (cmr_state->sig_ev == NULL) {
+		fprintf(stderr, "Failed to create signal event\n");
+		fprintf(stdout, CTDB_MUTEX_STATUS_ERROR);
+		ret = -ENOMEM;
+		goto err_state_free;
+	}
+
+	/* periodically check parent */
+	cmr_state->timer_ev = tevent_add_timer(cmr_state->ev, cmr_state,
+					       timeval_current_ofs(5,0),
+					       ctdb_mutex_rados_timer_cb,
+					       cmr_state);
+	if (cmr_state->timer_ev == NULL) {
+		fprintf(stderr, "Failed to create timer event\n");
+		fprintf(stdout, CTDB_MUTEX_STATUS_ERROR);
+		ret = -ENOMEM;
+		goto err_state_free;
+	}
+
+	ret = ctdb_mutex_rados_ctx_create(cmr_state->ceph_cluster_name,
+					  cmr_state->ceph_auth_name,
+					  cmr_state->pool_name,
+					  &cmr_state->ceph_cluster,
+					  &cmr_state->ioctx);
+	if (ret < 0) {
+		fprintf(stdout, CTDB_MUTEX_STATUS_ERROR);
+		goto err_state_free;
+	}
+
+	ret = ctdb_mutex_rados_lock(cmr_state->ioctx, cmr_state->object);
+	if ((ret == -EEXIST) || (ret == -EBUSY)) {
+		fprintf(stdout, CTDB_MUTEX_STATUS_CONTENDED);
+		goto err_ctx_cleanup;
+	} else if (ret < 0) {
+		fprintf(stdout, CTDB_MUTEX_STATUS_ERROR);
+		goto err_ctx_cleanup;
+	}
+
+	cmr_state->holding_mutex = true;
+	fprintf(stdout, CTDB_MUTEX_STATUS_HOLDING);
+
+	/* wait for the signal / timer events to do their work */
+	ret = tevent_loop_wait(cmr_state->ev);
+	if (ret < 0) {
+		goto err_ctx_cleanup;
+	}
+err_ctx_cleanup:
+	ctdb_mutex_rados_ctx_destroy(cmr_state->ceph_cluster,
+				     cmr_state->ioctx);
+err_state_free:
+	talloc_free(cmr_state);
+err_out:
+	return ret ? 1 : 0;
+}
diff --git a/ctdb/wscript b/ctdb/wscript
index f4bccef..75ddee2 100644
--- a/ctdb/wscript
+++ b/ctdb/wscript
@@ -69,6 +69,9 @@ def set_options(opt):
     opt.add_option('--enable-pmda',
                    help=("Turn on PCP pmda support (default=no)"),
                    action="store_true", dest='ctdb_pmda', default=False)
+    opt.add_option('--enable-ceph-reclock',
+                   help=("Enable Ceph CTDB recovery lock helper (default=no)"),
+                   action="store_true", dest='ctdb_ceph_reclock', default=False)
 
     opt.add_option('--with-logdir',
                    help=("Path to log directory"),
@@ -159,6 +162,15 @@ def configure(conf):
         conf.env.CTDB_PMDADIR = os.path.join(conf.env.LOCALSTATEDIR,
                                              'lib/pcp/pmdas/ctdb')
 
+    if Options.options.ctdb_ceph_reclock:
+        if (conf.CHECK_HEADERS('rados/librados.h', False, False, 'rados') and
+					conf.CHECK_LIB('rados', shlib=True)):
+            Logs.info('Building with Ceph librados recovery lock support')
+            conf.define('HAVE_LIBRADOS', 1)
+        else:
+            Logs.error("Missing librados for Ceph recovery lock support")
+            sys.exit(1)
+
     have_infiniband = False
     if Options.options.ctdb_infiniband:
         ib_support = True
@@ -517,6 +529,13 @@ def build(bld):
         bld.INSTALL_FILES('${CTDB_PMDADIR}', 'utils/pmda/README',
                           destname='README')
 
+    if bld.env.HAVE_LIBRADOS:
+        bld.SAMBA_BINARY('ctdb_mutex_ceph_rados_helper',
+                         source='tools/ctdb_mutex_ceph_rados_helper.c',
+			 deps='ctdb-system rados',
+			 includes='include',
+			 install_path='${CTDB_HELPER_BINDIR}')
+
     sed_expr1 = 's|/usr/local/var/lib/ctdb|%s|g'  % (bld.env.CTDB_VARDIR)
     sed_expr2 = 's|/usr/local/etc/ctdb|%s|g'      % (bld.env.CTDB_ETCDIR)
     sed_expr3 = 's|/usr/local/var/log|%s|g'       % (bld.env.CTDB_LOGDIR)
-- 
2.10.2


From fb53f42d1e02e0f33d1a1304c7d708203d75a14d Mon Sep 17 00:00:00 2001
From: David Disseldorp <ddiss@samba.org>
Date: Thu, 1 Dec 2016 14:22:45 +0100
Subject: [PATCH 2/2] ctdb/doc: man page for Ceph RADOS cluster mutex helper

Signed-off-by: David Disseldorp <ddiss@samba.org>
---
 ctdb/doc/Makefile                           |  3 +-
 ctdb/doc/ctdb_mutex_ceph_rados_helper.7.xml | 90 +++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 ctdb/doc/ctdb_mutex_ceph_rados_helper.7.xml

diff --git a/ctdb/doc/Makefile b/ctdb/doc/Makefile
index f0f8215..5bbd748 100644
--- a/ctdb/doc/Makefile
+++ b/ctdb/doc/Makefile
@@ -8,7 +8,8 @@ DOCS = ctdb.1 ctdb.1.html \
 	ctdbd.conf.5 ctdbd.conf.5.html \
 	ctdb.7 ctdb.7.html \
 	ctdb-statistics.7 ctdb-statistics.7.html \
-	ctdb-tunables.7 ctdb-tunables.7.html
+	ctdb-tunables.7 ctdb-tunables.7.html \
+	ctdb_mutex_ceph_rados_helper.7 ctdb_mutex_ceph_rados_helper.7.html
 
 all: $(DOCS)
 
diff --git a/ctdb/doc/ctdb_mutex_ceph_rados_helper.7.xml b/ctdb/doc/ctdb_mutex_ceph_rados_helper.7.xml
new file mode 100644
index 0000000..e5dedc7
--- /dev/null
+++ b/ctdb/doc/ctdb_mutex_ceph_rados_helper.7.xml
@@ -0,0 +1,90 @@
+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE refentry
+	PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+	"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
+<refentry id="ctdb_mutex_ceph_rados_helper.7">
+
+  <refmeta>
+    <refentrytitle>Ceph RADOS Mutex</refentrytitle>
+    <manvolnum>7</manvolnum>
+    <refmiscinfo class="source">ctdb</refmiscinfo>
+    <refmiscinfo class="manual">CTDB - clustered TDB database</refmiscinfo>
+  </refmeta>
+
+  <refnamediv>
+    <refname>ctdb_mutex_ceph_rados_helper</refname>
+    <refpurpose>Ceph RADOS cluster mutex helper</refpurpose>
+  </refnamediv>
+
+  <refsect1>
+    <title>DESCRIPTION</title>
+    <para>
+      ctdb_mutex_ceph_rados_helper_lock can be used as a recovery lock provider
+      for CTDB.  When configured, split brain avoidance during CTDB recovery
+      will be handled using locks against an object located in a Ceph RADOS
+      pool.
+      To enable this functionality, include the following line in your CTDB
+      config file:
+    </para>
+    <screen format="linespecific">
+CTDB_RECOVERY_LOCK="!ctdb_mutex_ceph_rados_helper_lock [Cluster] [User] [Pool] [Object]"
+
+Cluster: Ceph cluster name (e.g. ceph)
+User: Ceph cluster user name (e.g. client.admin)
+Pool: Ceph RADOS pool name
+Object: Ceph RADOS object name
+    </screen>
+    <para>
+      The Ceph cluster <parameter>Cluster</parameter> must be up and running,
+      with a configuration, and keyring file for <parameter>User</parameter>
+      located in a librados default search path (e.g. /etc/ceph/).
+      <parameter>Pool</parameter> must already exist.
+    </para>
+  </refsect1>
+
+  <refsect1>
+    <title>SEE ALSO</title>
+    <para>
+      <citerefentry><refentrytitle>ctdb</refentrytitle>
+      <manvolnum>7</manvolnum></citerefentry>,
+
+      <citerefentry><refentrytitle>ctdbd</refentrytitle>
+      <manvolnum>1</manvolnum></citerefentry>,
+
+      <ulink url="http://ctdb.samba.org/"/>
+    </para>
+  </refsect1>
+
+  <refentryinfo>
+    <author>
+      <contrib>
+	This documentation was written by David Disseldorp
+      </contrib>
+    </author>
+
+    <copyright>
+      <year>2016</year>
+      <holder>David Disseldorp</holder>
+    </copyright>
+    <legalnotice>
+      <para>
+	This program is free software; you can redistribute it and/or
+	modify it under the terms of the GNU General Public License as
+	published by the Free Software Foundation; either version 3 of
+	the License, or (at your option) any later version.
+      </para>
+      <para>
+	This program is distributed in the hope that it will be
+	useful, but WITHOUT ANY WARRANTY; without even the implied
+	warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+	PURPOSE.  See the GNU General Public License for more details.
+      </para>
+      <para>
+	You should have received a copy of the GNU General Public
+	License along with this program; if not, see
+	<ulink url="http://www.gnu.org/licenses"/>.
+      </para>
+    </legalnotice>
+  </refentryinfo>
+
+</refentry>
-- 
2.10.2


[-- Attachment #3: test_ceph_rados_reclock.sh --]
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