diff options
| -rw-r--r-- | qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml | 90 |
1 files changed, 86 insertions, 4 deletions
diff --git a/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml b/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml index 9fcadbcbe9..c13640ac31 100644 --- a/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml +++ b/qpid/doc/book/src/cpp-broker/Active-Passive-Cluster.xml @@ -81,6 +81,79 @@ under the License. </para> </section> <section> + <title>Avoiding messge loss</title> + <para> + In order to avoid message loss, the primary broker <emphasis>delays + acknowledgement</emphasis> of messages received from clients until the + message has been replicated to and acknowledged by all of the back-up + brokers. + </para> + <para> + Clients buffer unacknowledged messages and re-send them in the event of + a fail-over. If the primary crashes before a message is replicated to + all the backups, the client will re-send the message when it fails over + to the new primary. + </para> + <para> + Note that this means it is possible for messages to be + <emphasis>duplicated</emphasis>. In the event of a failure it is + possible for a message to be both received by the backup that becomes + the new primary <emphasis>and</emphasis> re-sent by the client. + </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 + 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. + </para> + <variablelist> + <title>Status of a HA broker</title> + <varlistentry> + <term>Joining</term> + <listitem> + <para> + Initial status of a new broker that has not yet connected to the primary. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>Catch-up</term> + <listitem> + <para> + A backup broker that is connected to the primary and catching up + on queues and messages. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>Ready</term> + <listitem> + <para> + A backup broker that is fully caught-up and ready to take over as + primary. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>Recovering</term> + <listitem> + <para> + The newly-promoted primary, waiting for backups to connect and catch up. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>Active</term> + <listitem> + <para> + The active primary broker with all backups connected and caught-up. + </para> + </listitem> + </varlistentry> + </variablelist> + </section> + <section> <title>Limitations</title> <para> There are a number of known limitations in the current preview implementation. These @@ -135,7 +208,7 @@ under the License. virtual IP addresses for clients or brokers. </para> </section> - + <section> <title>Configuring the Brokers</title> <para> @@ -208,7 +281,7 @@ under the License. <entry><literal>--ha-replicate</literal></entry> <foo/> <entry> - <para> + <para> Specifies whether queues and exchanges are replicated by default. For details see <xref linkend="ha-creating-replicated"/> </para> @@ -227,6 +300,15 @@ under the License. then this user must have all permissions. </entry> </row> + <row> + <entry><literal>--ha-backup-timeout <replaceable>SECONDS</replaceable></literal> </entry> + <entry> + <para> + Maximum time that a recovering primary will wait for an expected + backup to connect and become ready. + </para> + </entry> + </row> </tbody> </tgroup> </table> @@ -374,7 +456,7 @@ NOTE: fencing is not shown, you must configure fencing appropriately for your cl <para> The <literal>resources</literal> section also defines a pair of virtual IP addresses on different sub-nets. One will be used for broker-to-broker - communication, the other for client-to-broker. + communication, the other for client-to-broker. </para> <para> To take advantage of the virtual IP addresses, <filename>qpidd.conf</filename> @@ -426,7 +508,7 @@ NOTE: fencing is not shown, you must configure fencing appropriately for your cl command line. </para> </section> - + <section id="ha-creating-replicated"> <title>Creating replicated queues and exchanges</title> <para> |