Table of Contents
View and handle controller (CMON instance), allows building a highly available cluster of CMON instances to achieve ClusterControl’s high availability.
Note
CMON HA feature is still a beta feature.
This command can help setup CMON with high availability feature using the following simple steps:
- Install a CMON Controller together with the CMON Database serving as permanent storage for the controller. The CMON HA will not replicate the CMON Database, so it has to be accessible from all the controllers and if necessary it has to provide redundancy on itself.
- Enable the CMON HA subsystem using the
--enable-cmon-haon the running controller. This will create one CmonController class object. Check the object using the--listor--statoption. The CMON HA is now enabled, but there is no redundancy, only one controller is running. The one existing controller in this stage should be a leader although there are no followers. - Install additional Cmon Controllers one by one and start them the usual way. The next controllers should use the same CMON Database and should have the same configuration files. When the additional controllers are started they will find the leader in the CMON Database and will ask the leader to let them join. When the join is successful one more CmonController will be created for every joining controller.
Note
See this two-part blog series to see how to install and configure ClusterControl CMON HA, ClusterControl CMON HA for Distributed Database High Availability – Part 1 – Installation and ClusterControl CMON HA for Distributed Database High Availability – Part 2 (GUI Access Setup).
Usage
s9s controller {command} {options}Command
| Name, shorthand | Description |
|---|---|
−−create-snapshot |
Creates a job that will create a controller to controller snapshot of the Cmon HA subsystem. Creating a snapshot manually using this command-line option is not necessary for the Cmon HA to operate, this command-line option is made for testing and repairing. |
−−enable-cmon-ha |
Enabled the CMON HA subsystem. By default, Cmon HA is not enabled for compatibility reasons, so this command-line option is implemented to enable the controller to controller communication. When the CMON HA is enabled CmonController class objects will be created and used to implement the high availability features (e.g. the leader election). So if the controller at least one CmonController object, the CMON HA is enabled, if not, it is not enabled. |
−−get-ldap-config |
Gets the LDAP configuration from the controller and prints it to the standard output. |
−−list |
Lists the CmonController type objects known to the controller. If the CMON HA is not enabled there will be no such objects, if it is enabled one or more controllers will be listed. With the --long option a more detailed list will be shown where the state of the controllers can be checked. |
−−ping |
Sends a ping request to the controller and prints the information received. Please note that there is another ping request for the clusters, but this ping request is quite different from that. This request does not need a cluster, it is never redirected (follower controllers will also reply to this request) and it is replied with some basic information about the Cmon HA subsystem. |
−−stat |
Prints more details about the controller objects. |
Examples
Create a controller to controller snapshot of CMON HA subsystem:
$ s9s controller \
--create-snapshot \
--logEnable CMON HA feature for the current CMON instance:
$ s9s controller --enable-cmon-haThe command line option itself is only a syntactic sugar to save a “true” boolean value into a CDT entry, so for example the following command can also be used:
$ echo "true" | \
s9s tree \
--save \
--cmon-user=system \
--password=secret \
--controller="https://10.10.1.23:9501" \
--batch \
/.runtime/cmon_ha/enabledNote
See this two-part blog series to see how to install and configure ClusterControl CMON HA, ClusterControl CMON HA for Distributed Database High Availability – Part 1 – Installation and ClusterControl CMON HA for Distributed Database High Availability – Part 2 (GUI Access Setup).
Print out LDAP configuration from the controller:
$ s9s controller \
--cmon-user="system" \
--password="XXXXXXXX" \
--get-ldap-config \
--print-jsonList out all controllers participate in the CMON HA cluster:
$ s9s controller \
--list \
--longSend ping request to the controller and print the output in JSON format, with some text filtering on the output:
$ s9s controller \
--ping \
--print-json \
--json-format='status: ${controller_status}\n'Print more details about the controller objects:
$ s9s controller --stat