ltcluster cluster show — display information about each registered node in the replication cluster
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.
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.
$ 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
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.
Use ltcluster cluster matrix and ltcluster cluster crosscheck to diagnose connection issues across the whole replication cluster.
--csv
ltcluster cluster show
accepts an optional parameter --csv
, which
outputs the replication cluster's status in a simple CSV format, suitable for
parsing by scripts, e.g.:
$ ltcluster -f /etc/ltcluster.conf cluster show --csv 1,-1,-1 2,0,0 3,0,1
The columns have following meanings:
--compact
Suppress display of the conninfo
column.
--terse
Suppress warnings about connection issues.
--verbose
Display the full text of any database connection error messages
One of the following exit codes will be emitted by ltcluster cluster show
:
SUCCESS (0)
No issues were detected.
ERR_BAD_CONFIG (1)
An issue was encountered while attempting to retrieve ltcluster metadata.
ERR_DB_CONN (6)
ltcluster was unable to connect to the local LightDB instance.
ERR_NODE_STATUS (25)
One or more issues were detected with the replication configuration, e.g. a node was not in its expected state.