Defining the topology

The Lifecycle Manager (LCM) topology consists of cluster, datacenter, and node models. LCM uses the topology for installing and configuring DataStax Enterprise (DSE) at these levels. When installing and configuring DSE clusters, the topology provides flexibility and powerful inheritance mechanisms.

LCM requires defining the cluster topology using either the OpsCenter interface or the OpsCenter API when creating a new DSE cluster. For existing clusters, import the cluster topology automatically and LCM will add the cluster models on your behalf in the Clusters workspace, provided all target nodes use a single SSH credential. The logical LCM model should reflect the actual physical topology of a cluster.

If someone manually changes the cluster topology without using LCM, you must update the logical topology model in LCM to reflect the physical changes. Manually changing the cluster topology is not a recommended best practice, but might be necessary under certain circumstances. For instance, when a node is decommissioned in OpsCenter, you must manually delete the node in the topology. It is not currently possible to decommission systems directly using LCM.

After decommissioning a node, you must delete the corresponding node model in LCM prior to running the next configure or install job. Otherwise, LCM attempts to restore the old topology, with unpredictable results.

When deleting (that is, ceasing to manage) a model from the topology in LCM, you are simply removing management of the model from LCM. Deleting a cluster, datacenter, or node in LCM does not affect the physical systems. Deleting models from the LCM topology causes LCM to stop managing and ignore them. In addition to deleting the model, you must decommission the target nodes outside of LCM. The physical cluster, datacenters, nodes, and the corresponding topologies in OpsCenter are not affected.

The data (cluster topology, configuration profiles, credentials, repositories, job history, and so forth) for Lifecycle Manager is stored in the lcm.db database. Your organization is responsible for backing up the lcm.db database. You must also configure failover to mirror the lcm.db database. The location of the Lifecycle Manager database lcm.db depends on the type of installation:

  • Package installations: /var/lib/opscenter/lcm.db

  • Tarball installations: install_location/lcm.db

For further instructions, see Defining DSE topologies.

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