Performing Health Checks on Domain and Database Status
Periodically, you may want to confirm the state of a specific admin process or database, or a specific Storage Manager (SM) process or Transaction Engine (TE) process.
The following commands provide information on the number of processes and their status:
nuocmd check database --db-name <database name>
| Subcommand | Description |
|---|---|
--check-liveness n
|
Checks that all processes have responded within the specified number (n) of seconds. |
--check-running
|
Checks whether the database is in the RUNNING state. |
--num-processes n
|
Checks the number of processes. |
nuocmd servers
| Subcommand | Description |
|---|---|
--check-active
|
Checks that all servers are ACTIVE. |
--check-connected
|
Checks that all servers are CONNECTED to the server performing the check. |
--check-leader
|
Checks the number of processes. |
--num-servers n |
Check the number of admin processes. |
nuocmd check process --start-id <start_id)
| Subcommand | Description |
|---|---|
check-liveness n
|
Checks that all servers are ACTIVE. |
--check-connected
|
Checks that all servers are CONNECTED to the server performing the check. |
--check-leader
|
Checks the number of processes. |
--num-servers n |
Check the number of admin processes. |
Note: The commands documented here are issued using NuoDB Command (nuocmd). For more information on NuoDB Command and other command line tools, see Command Line Tools.
Note: The commands documented here return 1 if the boolean expression evaluates to true, and return 0 if the boolean expression evaluates to false.
Note: For each subcommand, you may add a --timeout or a --wait-forever option. If neither is provided, the check is run once and the command returns. Use --timeout TIMEOUT to specify how long (in seconds) to wait for the database check to pass. Use --wait-forever to specify no limit to how long to wait for the database check to pass.
Examples
Example 1: Using the --check-running subcommand without timing out
To check whether a database named test is running, and wait until it is running, specify the following:
nuocmd check database --db-name test --check-running --wait-forever
--check-running subcommand
with the timeout option
To check, for a period of 10 seconds before timing out, whether a database named test is running, specify the following:
nuocmd check database --db-name test --check-running --timeout 10
--num-processes subcommand
with the timeout option
To check for a period of 10 seconds before timing out, whether a database named test has four processes ( say two TE processes and two SM processes), specify the following:
nuocmd check database --db-name test --num-processes 4 --timeout 10 --check-running subcommand without timing out
To check whether a database process with a specific start ID is running, and wait until it is running, specify the following:
nuocmd check process --start-id 1 --check-running --wait-forever--check-exited subcommand without timing out
A shutdown process command was issued on start ID 1. To check whether the database process with start ID 1 has exited, and wait until it has, specify the following:
nuocmd check process --start-id 1 --check-exited --wait-forever