Author: aconway
Date: Mon Jul 23 14:27:31 2012
New Revision: 1364646
URL: http://svn.apache.org/viewvc?rev=1364646&view=rev
Log:
NO-JIRA: HA documentation update.
Added:
qpid/branches/0.18/qpid/doc/book/src/cpp-broker/.gitignore
Modified:
qpid/branches/0.18/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml
Added: qpid/branches/0.18/qpid/doc/book/src/cpp-broker/.gitignore
URL:
http://svn.apache.org/viewvc/qpid/branches/0.18/qpid/doc/book/src/cpp-broker/.gitignore?rev=1364646&view=auto
==============================================================================
--- qpid/branches/0.18/qpid/doc/book/src/cpp-broker/.gitignore (added)
+++ qpid/branches/0.18/qpid/doc/book/src/cpp-broker/.gitignore Mon Jul 23
14:27:31 2012
@@ -0,0 +1 @@
+/output
Modified:
qpid/branches/0.18/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml
URL:
http://svn.apache.org/viewvc/qpid/branches/0.18/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml?rev=1364646&r1=1364645&r2=1364646&view=diff
==============================================================================
--- qpid/branches/0.18/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml
(original)
+++ qpid/branches/0.18/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml
Mon Jul 23 14:27:31 2012
@@ -27,64 +27,35 @@ under the License.
<section>
<title>Overview</title>
<para>
- This release provides a preview of a new module for High Availability
(HA).
- This module is intended to eventually replace the existing cluster
module.
+
+ The High Availability (HA) module provides
+ <firstterm>active-passive</firstterm>, <firstterm>hot-standby</firstterm>
+ messaging clusters to provide fault tolerant message delivery.
</para>
<para>
- The old cluster module takes an <firstterm>active-active</firstterm>
approach, i.e. all the
- brokers in a cluster are able to handle client requests simultaneously.
The new HA module
- takes an <firstterm>active-passive</firstterm>,
<firstterm>hot-standby</firstterm> approach.
+ In an active-passive cluster only one broker, known as the
+ <firstterm>primary</firstterm>, is active and serving clients at a time.
The other
+ brokers are standing by as <firstterm>backups</firstterm>. Changes on
the primary
+ are replicated to all the backups so they are always up-to-date or
"hot". Backup
+ brokers reject client connection attempts, to enforce the requirement
that clients
+ only connect to the primary.
</para>
<para>
- In an active-passive cluster only one broker, known as the
<firstterm>primary</firstterm>, is
- active and serving clients at a time. The other brokers are standing by
as
- <firstterm>backups</firstterm>. Changes on the primary are immediately
replicated to all the
- backups so they are always up-to-date or "hot". If the primary fails,
one of the backups is
- promoted to take over as the new primary. Clients fail-over to the new
primary
- automatically. If there are multiple backups, the backups also fail-over
to become backups of
- the new primary. Backup brokers reject connection attempts, to enforce
the requirement that
- only the primary be active. Clients fail-over till the successfully
connect to the primary broker.
+ If the primary fails, one of the backups is promoted to take over as the
new
+ primary. Clients fail-over to the new primary automatically. If there
are multiple
+ backups, the other backups also fail-over to become backups of the new
primary.
</para>
<para>
- This approach requires on an external <firstterm>cluster resource
- manager</firstterm> to detect failures and choose the new primary. <ulink
- url="https://fedorahosted.org/cluster/wiki/RGManager";>Rgmanager</ulink>
is
- supported initially, but others may be supported in the future.
+ This approach relies on an external <firstterm>cluster resource
manager</firstterm>
+ to detect failures, choose the new primary and handle network
partitions. <ulink
+ url="https://fedorahosted.org/cluster/wiki/RGManager";>Rgmanager</ulink>
is supported
+ initially, but others may be supported in the future.
</para>
<section>
- <title>Why the new approach?</title>
- <para>
- The new active-passive approach has several advantages compared to the
- existing active-active cluster module.
- <itemizedlist>
- <listitem>
- It does not depend directly on openais or corosync. It does not use
multicast
- which simplifies deployment.
- </listitem>
- <listitem>
- It is more portable: in environments that don't support corosync,
it can be
- integrated with a resource manager available in that environment.
- </listitem>
- <listitem>
- Replication to a <firstterm>disaster recovery</firstterm> site can
be handled as
- simply another node in the cluster, it does not require a separate
replication
- mechanism.
- </listitem>
- <listitem>
- It can take advantage of features provided by the resource manager,
for example
- virtual IP addresses.
- </listitem>
- <listitem>
- Improved performance and scalability due to better use of multiple
CPUs
- </listitem>
- </itemizedlist>
- </para>
- </section>
- <section>
- <title>Avoiding messge loss</title>
+ <title>Avoiding message loss</title>
<para>
In order to avoid message loss, the primary broker <emphasis>delays
- acknowledgement</emphasis> of messages received from clients until the
+ acknowledgment</emphasis> of messages received from clients until the
message has been replicated to and acknowledged by all of the back-up
brokers.
</para>
@@ -93,11 +64,10 @@ under the License.
a fail-over.
<footnote>
<para>
- Clients must use 'at-least-once' reliability to enable re-send of
- unacknowledged messages. This is the default behavior, no options
- need be set to enable it. For details of client addressing options see
- "Using the Qpid Messaging API" in <citetitle>Programming in
Apache
- Qpid</citetitle>
+ Clients must use "at-least-once" reliability to enable re-send of
unacknowledged
+ messages. This is the default behavior, no options need be set to
enable it. For
+ details of client addressing options see "Using the Qpid
Messaging API"
+ in <citetitle>Programming in Apache Qpid</citetitle>
</para>
</footnote>
If the primary crashes before a message is replicated to
@@ -112,7 +82,7 @@ under the License.
</para>
<para>
When a new primary is promoted after a fail-over it is initially in
- "recovering" mode. In this mode, it delays acknowledgement of messages
+ "recovering" mode. In this mode, it delays acknowledgment of messages
on behalf of all the backups that were connected to the previous
primary. This protects those messages against a failure of the new
primary until the backups have a chance to connect and catch up.
@@ -164,6 +134,37 @@ under the License.
</variablelist>
</section>
<section>
+ <title>Replacing the old cluster module</title>
+ <para>
+ The High Availability (HA) module replaces the previous
+ <firstterm>active-active</firstterm> cluster module. The new
active-passive
+ approach has several advantages compared to the existing active-active
cluster
+ module.
+ <itemizedlist>
+ <listitem>
+ It does not depend directly on openais or corosync. It does not use
multicast
+ which simplifies deployment.
+ </listitem>
+ <listitem>
+ It is more portable: in environments that don't support corosync,
it can be
+ integrated with a resource manager available in that environment.
+ </listitem>
+ <listitem>
+ Replication to a <firstterm>disaster recovery</firstterm> site can
be handled as
+ simply another node in the cluster, it does not require a separate
replication
+ mechanism.
+ </listitem>
+ <listitem>
+ It can take advantage of features provided by the resource manager,
for example
+ virtual IP addresses.
+ </listitem>
+ <listitem>
+ Improved performance and scalability due to better use of multiple
CPUs
+ </listitem>
+ </itemizedlist>
+ </para>
+ </section>
+ <section>
<title>Limitations</title>
<para>
There are a number of known limitations in the current preview
implementation. These
@@ -266,7 +267,7 @@ under the License.
</para>
</footnote>
used by cluster brokers to connect to each other. The URL can
- contain a list of all the brokers' addresses or it can contain
a single
+ contain a list of all the broker addresses or it can contain a
single
virtual IP address. If a list is used it is comma separated,
for example
<literal>amqp:node1.exaple.com,node2.exaple.com,node3.exaple.com</literal>
</para>
@@ -276,7 +277,7 @@ under the License.
<entry><literal>--ha-public-url
<replaceable>URL</replaceable></literal> </entry>
<entry>
<para>
- The URL that is advertized to clients. This defaults to the
+ The URL that is advertised to clients. This defaults to the
<literal>--ha-brokers-url</literal> URL above, and has the same
format. A
virtual IP address is recommended for the public URL as it
simplifies
deployment and hides changes to the cluster membership from
clients.
@@ -371,7 +372,7 @@ under the License.
clustered services using <command>cman</command> and
<command>rgmanager</command>. It will show you how to configure an
active-passive,
hot-standby <command>qpidd</command> HA cluster with
<command>rgmanager</command>.
- </para>
+ </para>
<para>
You must provide a <literal>cluster.conf</literal> file to configure
<command>cman</command> and <command>rgmanager</command>. Here is
@@ -731,12 +732,12 @@ NOTE: fencing is not shown, you must con
<section>
<title>Security.</title>
<para>
- You can secure your cluster using the authenticiation and authorization
features
+ You can secure your cluster using the authentication and authorization
features
described in <xref linkend="chap-Messaging_User_Guide-Security"/>.
</para>
<para>
Backup brokers connect to the primary broker and subscribe for management
- events and queue contents. You can specifiy the identity used to connect
+ events and queue contents. You can specify the identity used to connect
to the primary with the following options:
</para>
<table frame="all" id="ha-broker-security-options">
@@ -780,7 +781,7 @@ NOTE: fencing is not shown, you must con
To integrate with a different resource manager you must configure it to:
<itemizedlist>
<listitem>Start a qpidd process on each node of the cluster.</listitem>
- <listitem>Restart qpidd if it crases.</listitem>
+ <listitem>Restart qpidd if it crashes.</listitem>
<listitem>Promote exactly one of the brokers to primary.</listitem>
<listitem>Detect a failure and promote a new primary.</listitem>
</itemizedlist>
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