This chapter describes groups in MarkLogic Server, and includes the following sections:
This chapter describes how to use the Admin Interface to create and configure groups. For details on how to create and configure groups programmatically, see Creating and Configuring Groups in the Scripting Administrative Tasks Guide.
The basic definitions for group, host, and cluster are the following:
For single-node configurations, you can only use one group at a time (because there is only one host). For clusters configurations with multiple hosts, you can have as many group configurations as makes sense in your environment.
Groups allow you to have several configurations, each of which applies to a distinct set of hosts. Different configurations are often needed when different hosts perform different tasks, or when the hosts have different system capabilities (disk space, memory, and so on). In cluster configurations, a common configuration is to have one group defined for the evaluator nodes (hosts that service query requests) and another group defined for the data nodes (hosts to which forests are attached).
HTTP, ODBC, XDBC, and WebDAV servers are defined at the group level and apply to all hosts within the group. Schemas and namespaces can also be defined at the group level to apply group-wide.
The Configure tab of the Group Administration section of the Admin Interface enables you to define configuration information for memory settings, SMTP server settings, and other configuration settings. The values for the settings are set at installation time based on your system memory configuration at the time of the installation. For a description of each configuration option, see the Help tab of the Group Administration section of the Admin Interface.
The relationships between a cluster, a group and a host in MarkLogic Server may be best illustrated with an example.
In this example, each machine is set up as a host within the example cluster. Specifically, hosts E1
, E2
and E3
belong to a group called Evaluator-Nodes
. They are configured with HTTP servers and XDBC servers to run user applications. All hosts in the Evaluator-Nodes
group have the same MarkLogic Server configuration.
Hosts D1
, D2
and D3
belong to a group called Data-Nodes
. Hosts in the Data-Nodes
group are configured with data forests and interact with the nodes in the Evaluator-Nodes
group to service data requests. See the sections on databases, forests and hosts for details on configuring data forests.
For more information about clusters, see the Scalability, Availability, and Failover Guide.
If you are administering a single-host MarkLogic environment, the host is automatically added to a Default group during the installation process. You will only have one host in the group and will not be able to add other hosts to the group.
The following procedures describe how to create and manage groups in MarkLogic Server:
To create a new group, perform the following steps:
For information about auditing, including how to configure various audit events, see Auditing Events.
Adding a group is a 'hot' administrative task; the changes are reflected immediately without a restart.
You must drop all hosts assigned to a group before you can delete a group. To delete a group, perform the following steps:
Deleting a group is a hot operation; the server does not need to restart to reflect your changes.
To enable encrypted SSL communication between hosts in the group, set xdqp ssl enabled
to true
. All communications to and from hosts in the group will be secured, even if the other end of the socket is in a group that does not have SSL enabled.
The SSL keys and certificates used by the hosts are automatically generated when you install or upgrade MarkLogic Server. No outside authority is used to sign certificates used between servers communicating over the internal XDQP connections in a cluster. Such certificates are self-signed and trusted by each server in the cluster.
For details on configuring SSL communication between web browsers and App Servers, see Configuring SSL on App Servers. For details on configuring FIPS 140-2 mode for SSL communication, see OpenSSL FIPS 140-2 Mode.
The following screen capture shows the options related to configuring SSL for intra-cluster XDQP communication.
The installation process configures an SMTP server based on the environment at installation time. A single SMTP server is configured for all of the hosts in a group. The SMTP configuration is used when applications use the xdmp:email function.
To change the SMTP server or the SMTP timeout for the system (the time after which SMTP requests fail with an error), perform the following steps:
Changing any SMTP settings is a hot operation; the server does not need to restart to reflect your changes.
Perform the following steps to restart all the hosts in a group from the Admin Interface:
The restart operation normally completes within a few seconds. It is possible, however, for it to take longer under some conditions (for example, if the Security database needs to run recovery or if the connectivity between hosts in a cluster is slow). If it takes longer than a few seconds for MarkLogic Server to restart, than the Admin Interface might return a 503: Service Unavailable
message. If you encounter this situation, wait several seconds and then reload the Admin Interface.