Description

Displays information about each registered node in the replication cluster. This command polls each registered server and shows its role (primary / standby) and status. It polls each server directly and can be run on any node in the cluster; this is also useful when analyzing connectivity from a particular node.

Node availability is tested by connecting from the node where ltcluster cluster show is executed, and does not necessarily imply the node is down. See ltcluster cluster matrix and ltcluster cluster crosscheck to get better overviews of connections between nodes.

Execution

This command requires either a valid ltcluster.conf file or a database connection string to one of the registered nodes; no additional arguments are needed.

To show database connection errors when polling nodes, run the command in --verbose mode.

Example

    $ ltcluster -f /etc/ltcluster.conf cluster show
     ID | Name  | Role    | Status    | Upstream | Location | Priority | Timeline | Connection string
    ----+-------+---------+-----------+----------+----------+----------+----------+-----------------------------------------
     1  | node1 | primary | * running |          | default  | 100      | 1        | host=db_node1 dbname=ltcluster user=ltcluster
     2  | node2 | standby |   running | node1    | default  | 100      | 1        | host=db_node2 dbname=ltcluster user=ltcluster
     3  | node3 | standby |   running | node1    | default  | 100      | 1        | host=db_node3 dbname=ltcluster user=ltcluster
     4  | node4 | standby |   running | node1    | default  | 100      | 1        | host=db_node4 dbname=ltcluster user=ltcluster
     5  | node5 | witness | * running | node1    | default  | 0        | n/a      | host=db_node5 dbname=ltcluster user=ltcluster

Notes

The column Role shows the expected server role according to the ltcluster metadata.

Status shows whether the server is running or unreachable. If the node has an unexpected role not reflected in the ltcluster metadata, e.g. a node was manually promoted to primary, this will be highlighted with an exclamation mark. If a connection to the node cannot be made, this will be highlighted with a question mark. Note that the node will only be shown as ? unreachable if a connection is not possible at network level; if the LightDB instance on the node is pingable but not accepting connections, it will be shown as ? running.

In the following example, executed on node3, node1 is not reachable at network level and assumed to be down; node2 has been promoted to primary (but node3 is not attached to it, and its metadata has not yet been updated); node4 is running but rejecting connections (from node3 at least).

     ID | Name  | Role    | Status               | Upstream | Location | Priority | Timeline | Connection string
    ----+-------+---------+----------------------+----------+----------+----------+----------+----------------------------------------------------
     1  | node1 | primary | ? unreachable        |          | default  | 100      |          | host=db_node1 dbname=ltcluster user=ltcluster
     2  | node2 | standby | ! running as primary | ? node1  | default  | 100      | 2        | host=db_node2 dbname=ltcluster user=ltcluster
     3  | node3 | standby |   running            | ? node1  | default  | 100      | 1        | host=db_node3 dbname=ltcluster user=ltcluster
     4  | node4 | standby | ? running            | ? node1  | default  | 100      |          | host=db_node4 dbname=ltcluster user=ltcluster

    WARNING: following issues were detected
      - unable to connect to node "node1" (ID: 1)
      - node "node1" (ID: 1) is registered as an active primary but is unreachable
      - node "node2" (ID: 2) is registered as standby but running as primary
      - unable to connect to node "node2" (ID: 2)'s upstream node "node1" (ID: 1)
      - unable to determine if node "node2" (ID: 2) is attached to its upstream node "node1" (ID: 1)
      - unable to connect to node "node3" (ID: 3)'s upstream node "node1" (ID: 1)
      - unable to determine if node "node3" (ID: 3) is attached to its upstream node "node1" (ID: 1)
      - unable to connect to node "node4" (ID: 4)
    HINT: execute with --verbose option to see connection error messages

To diagnose connection issues, execute ltcluster cluster show with the --verbose option; this will display the error message for each failed connection attempt.

Options

Exit codes

One of the following exit codes will be emitted by ltcluster cluster show:

See also

ltcluster node status, ltcluster node check, ltcluster service status