Step 5 - Creating the PGD cluster ================================= Creating the PGD cluster ------------------------ - **Create connection strings for each node**. For each node, create a connection string that will allow PGD to perform replication. The connection string is a key/value string that starts with a ``host=`` and the IP address of the host. (If you have resolvable named hosts, the name of the host is used instead of the IP address.) That’s followed by the name of the database. In this case, use ``dbname=bdrdb`` , as a ``bdrdb`` database was created when :ref:`installing the software ` . We recommend you also add the port number of the server to your connection string as ``port=5444`` for EDB Postgres Advanced Server and ``port=5432`` for EDB Postgres Extended and community PostgreSQL. - **Prepare the first node.** To create the cluster, select and log in to the ``bdrdb`` database on any host’s Postgres server. - **Create the first node.** Run ``bdr.create_node`` and give the node a name and its connection string where *other* nodes can connect to it. - Create the top-level group. Create a top-level group for the cluster with ``bdr.create_node_group`` , giving it a single parameter: the name of the top-level group. - Create a subgroup. Create a subgroup as a child of the top-level group with ``bdr.create_node_group`` , giving it two parameters: the name of the subgroup and the name of the parent (and top-level) group. This process initializes the first node. - **Add the second node.** - Create the second node. Log in to another initialized node’s ``bdrdb`` database. Run ``bdr.create_node`` and give the node a different name and its connection string where *other* nodes can connect to it. - Join the second node to the cluster. Next, run ``bdr.join_node_group`` , passing two parameters: the connection string for the first node and the name of the subgroup you want the node to join. - **Add the third node.** - Create the third node. Log in to another initialized node’s ``bdrdb`` database. Run ``bdr.create_node`` and give the node a different name and its connection string where *other* nodes can connect to it. - Join the third node to the cluster. Next, run ``bdr.join_node_group`` , passing two parameters: the connection string for the first node and the name of the subgroup you want the node to join. Worked example -------------- So far, this example has: - Created three hosts. - Installed a Postgres server on each host. - Installed Postgres Distributed on each host. - Configured the Postgres server to work with PGD on each host. To create the cluster, you tell host-one’s Postgres instance that it’s a PGD node—node-one—and create PGD groups on that node. Then you tell host-two and host-three’s Postgres instances that they are PGD nodes—node-two and node-three—and that they must join a group on node-one. Create connection strings for each node ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Calculate the connection strings for each of the nodes in advance. Following are the connection strings for this 3-node example. .. csv-table:: :header: Name,Node name,Private IP,Connection string :widths: 15,12,12,20 :align: left :class: longtable host-one,node-one,192.168.254.166,host=host-one dbname=bdrdb port=5444 host-two,node-two,192.168.254.247,host=host-two dbname=bdrdb port=5444 host-three,node-three,192.167.254.135,host=host-three dbname=bdrdb port=5444 Preparing the first node ^^^^^^^^^^^^^^^^^^^^^^^^ Log in to host-one’s Postgres server. :: ssh admin@host-one sudo -iu enterprisedb psql bdrdb Create the first node ^^^^^^^^^^^^^^^^^^^^^ Call the :ref:`bdr.create_node ` function to create a node, passing it the node name and a connection string that other nodes can use to connect to it. :: select bdr.create_node(node-one,host=host-one dbname=bdrdb port=5444); Create the top-level group ^^^^^^^^^^^^^^^^^^^^^^^^^^ Call the :ref:`bdr.create_node_group ` function to create a top-level group for your PGD cluster. Passing a single string parameter creates the top-level group with that name. This example creates a top-level group named ``pgd`` . :: select bdr.create_node_group(pgd); Create a subgroup ^^^^^^^^^^^^^^^^^ Using subgroups to organize your nodes is preferred, as it allows services like PGD Proxy, which you’ll configure later, to coordinate their operations. In a larger PGD installation, multiple subgroups can exist. These subgroups provide organizational grouping that enables geographical mapping of clusters and localized resilience. For that reason, this example creates a subgroup for the first nodes to enable simpler expansion and the use of PGD Proxy. Call the :ref:`bdr.create_node_group ` function again to create a subgroup of the top-level group. The subgroup name is the first parameter, and the parent group is the second parameter. This example creates a subgroup ``dc1`` as a child of ``pgd`` . :: select bdr.create_node_group(dc1,pgd); Adding the second node ^^^^^^^^^^^^^^^^^^^^^^ Log in to host-two’s Postgres server :: ssh admin@host-two sudo -iu enterprisedb psql bdrdb Create the second node ^^^^^^^^^^^^^^^^^^^^^^ Call the :ref:`bdr.create_node ` function to create this node, passing it the node name and a connection string that other nodes can use to connect to it. :: select bdr.create_node(node-two,host=host-two dbname=bdrdb port=5444); Join the second node to the cluster ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Using :ref:`bdr.join_node_group ` , you can ask node-two to join node-one’s ``dc1`` group. The function takes as a first parameter the connection string of a node already in the group and the group name as a second parameter. :: select bdr.join_node_group(host=host-one dbname=bdrdb port=5444,dc1); Add the third node ^^^^^^^^^^^^^^^^^^ Log in to host-three’s Postgres server. :: ssh admin@host-three sudo -iu enterprisedb psql bdrdb Create the third node ^^^^^^^^^^^^^^^^^^^^^ Call the :ref:`bdr.create_node ` function to create this node, passing it the node name and a connection string that other nodes can use to connect to it. :: select bdr.create_node(node-three,host=host-three dbname=bdrdb port=5444); Join the third node to the cluster ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Using :ref:`bdr.join_node_group ` , you can ask node-three to join node-one’s ``dc1`` group. The function takes as a first parameter the connection string of a node already in the group and the group name as a second parameter. :: select bdr.join_node_group(host=host-one dbname=bdrdb port=5444,dc1); A PGD cluster is now created.