Allow replication in <filename>pg_hba.conf</filename>:

Make sure the <filename>pg_hba.conf</filename> file allows

<parameter>id</parameter>, <type>integer</type>

</para>

<para>Node ID.

</para>

</listitem>

<listitem>

<para>

<parameter>enabled</parameter>, <type>boolean</type>

</para>

<para>Shows whether the node is excluded from the cluster. The node can only be disabled if responses to heartbeats are not received within the <varname>heartbeat_recv_timeout</> time interval. When the node starts responding to heartbeats, <filename>multimaster</filename> can automatically restore the node and switch it back to the enabled state.

Automatic recovery is only possible if the replication slot is still active. Otherwise, you can <link linkend="multimaster-restoring-a-node-manually">restore the node manually</link>.</para>

</listitem>

<listitem>

<para>

<parameter>connected</parameter>, <type>boolean</type>

</para>

<para>

Shows whether the node is connected to the WAL sender.

<parameter>slot_active</parameter>, <type>boolean</type>

</para>

<para>Shows whether the node has an active replication slot. For a disabled node, the slot remains active until the <varname>max_recovery_lag</varname> value is reached.

<parameter>stopped</parameter>, <type>boolean</type>

</para>

<para>Shows whether replication to this node was stopped by the <function>mtm.stop_node()</function> function. A stopped node acts as a disabled one, but cannot be automatically recovered. Call <function>mtm.recover_node()</function> to re-enable such a node.

<parameter>catchUp</parameter>, <type>boolean</type>

</para>

<para>During the node recovery, shows whether the data is recovered up to the <varname>min_recovery_lag</varname> value.

<parameter>slotLag</parameter>, <type>bigint</type>

</para>

<para>The size of WAL data that the replication slot holds for a disabled/stopped node. The slot is dropped when <literal>slotLag</literal> reaches the <literal>max_recovery_lag</literal> value.

<parameter>avgTransDelay</parameter>, <type>bigint</type>

</para>

<para>An average commit delay caused by this node, in microseconds.

<parameter>lastStatusChange</parameter>, <type>timestamp</type>

<para>Last time when the node changed its status (enabled/disabled).</para>

<parameter>oldestSnapshot</parameter>, <type>bigint</type>

<para>The oldest global snapshot existing on this node.</para>

<parameter>SenderPid</parameter>, <type>integer</type>

<para>Process ID of the WAL sender.</para>

<parameter>SenderStartTime</parameter>, <type>timestamp</type>

<para>WAL sender start time.</para>

<parameter>ReceiverPid</parameter>, <type>integer</type>

<para>Process ID of the WAL receiver.</para>

<parameter>ReceiverStartTime</parameter>, <type>timestamp</type>

<para>WAL receiver start time.</para>

<parameter>connStr</parameter>, <type>text</type>

<para>Connection string to this node.</para>

<parameter>connectivityMask</parameter>, <type>bigint</type>

<para>Bitmask representing connectivity to neighbor nodes. Each bit represents a connection to node.</para>

</listitem>

<listitem>

<para><parameter>nHeartbeats</parameter>, <type>integer</type></para>

<para>The number of heartbeat responses received from this node.</para>

<varlistentry>

<term>

<function>mtm.collect_cluster_state()</function>

<indexterm>

<primary><function>mtm.collect_cluster_state</></primary>

</indexterm>

</term>

<listitem>

<para>Collects the data returned by the <function>mtm.get_cluster_state()</function> function from all available nodes. For this function to work, in addition to replication connections, <filename>pg_hba.conf</filename> must allow ordinary connections to the node with the specified connection string.

</para>

</listitem>

</varlistentry>

<para>Shows the status of the <filename>multimaster</filename> extension. Returns a tuple of the following values:

<parameter>status</parameter>, <type>text</type>

</para>

<para>Node status. Possible values are: <literal>Initialization</literal>, <literal>Offline</literal>, <literal>Connected</literal>, <literal>Online</literal>, <literal>Recovery</literal>, <literal>Recovered</literal>, <literal>InMinor</literal>, <literal>OutOfService</literal>.</para>

</listitem>

<listitem>

<para>

<parameter>disabledNodeMask</parameter>, <type>bigint</type>

<para>Bitmask of disabled nodes.</para>

<parameter>disconnectedNodeMask</parameter>, <type>bigint</type>

<para>Bitmask of disconnected nodes.</para>

<parameter>catchUpNodeMask</parameter>, <type>bigint</type>

<para>Bitmask of nodes that completed the recovery.</para>

<parameter>liveNodes</parameter>, <type>integer</type>

<para>Number of enabled nodes.</para>

<parameter>allNodes</parameter>, <type>integer</type>

<para>Number of nodes in the cluster. The majority of alive nodes is calculated based on this parameter.</para>

<parameter>nActiveQueries</parameter>, <type>integer</type>

<para>Number of queries being currently processed on this node.</para>

<parameter>nPendingQueries</parameter>, <type>integer</type>

<para>Number of queries waiting for execution on this node.</para>

<parameter>queueSize</parameter>, <type>bigint</type>

<para>Size of the pending query queue, in bytes.</para>

<parameter>transCount</parameter>, <type>bigint</type>

<para>The total number of replicated transactions processed by this node.</para>

<parameter>timeShift</parameter>, <type>bigint</type>

<para>Global snapshot shift caused by unsynchronized clocks on nodes, in microseconds.</para>

<parameter>recoverySlot</parameter>, <type>integer</type>

<para>The node from which a failed node gets data updates during automatic recovery.</para>

<parameter>xidHashSize</parameter>, <type>bigint</type>

<para>Size of xid2state hash.</para>

<parameter>gidHashSize</parameter>, <type>bigint</type>

<para>Size of gid2state hash.</para>

<parameter>oldestXid</parameter>, <type>bigint</type>

<para>The oldest transaction ID on this node.</para>

<parameter>configChanges</parameter>, <type>integer</type>

<para>Number of state changes (enabled/disabled) since the last reboot.</para>

<parameter>stalledNodeMask</parameter>, <type>biint</type>

</para>

<para>Bitmask of nodes for which replication slots were dropped.

</para>

</listitem>

<listitem>

<para>

<parameter>stoppedNodeMask</parameter>, <type>bigint</type>

</para>

<para>Bitmask of nodes that were stopped by <function>mtm.stop_node()</function>.

</para>

</listitem>

<listitem>

<para>

<parameter>lastStatusChange</parameter>, <type>timestamp</type>

</para>

<para>Timestamp of the last state change.

providing full compatibility with the standard <productname>PostgreSQL</productname>.