Docker
Overview
Docker is a set of platform as a service (PaaS) products that uses OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels. All containers are run by a single operating system kernel and therefore use fewer resources than virtual machines.
The service has both free and premium tiers. The software that hosts the containers is called Docker Engine.[8] It was first started in 2013 and is developed by Docker, Inc.
Plugin-pack assets
Monitored objects
- Nodes
- Containers
Monitored metrics
More information about gathered metrics can be found into Docker official API documentation : https://docs.docker.com/engine/api/v1.30/
| Metric name | Description |
|---|---|
| Name | Name of the container. |
| State_name | Real state of the container. |
| read_io | The average number of read bytes from disk per second. Unit: Bytes/Second |
| Write_io | The average number of written bytes on disk per second. Unit: Bytes/Second |
| Cpu_total_usage | The percentage of CPU usage. Unit: Percent |
| Cpu_system_usage | The average amount of time taken per disk I/O write operation. Unit: Seconds |
| Memory_usage | The percentage of memory usage. Units: Percent & Bytes |
| Traffic_in | The percentage of inbound traffic usage. Units: Percent & Bytes/Second |
| Traffic_out | The percentage of outbound traffic usage. Units: Percent & Bytes/Second |
| Metric name | Description |
|---|---|
| Node-status | The status of node. Unit: text |
| Containers-running | The number of running containers. Unit: counter |
| Containers-stopped | The number of stopped containers. Unit: counter |
| Containers_paused | The Number of paused containers. Unit: counter |
Prerequisites
- This monitoring plugin requires at least a Docker API version >= 1.21 (https://docs.docker.com/engine/api/v1.30/).
API connection
Open your favorite ssh client and configure your API to allow connections from the outside:
- vi /lib/systemd/system/docker.service
- Modify the line starting with ExecStart as shown below:
ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock -H=tcp://0.0.0.0:2375
- Save the changes
- Apply the changes made at the systemd level :
systemctl daemon-reload - Restart the Docker engine:
systemctl restart docker
Installation
- Install the plugin on every poller expected to monitor Docker resources:
yum install centreon-plugin-Applications-Docker-Restapi
- Install the "Docker-Restapi" Centreon Plugin-Pack from the "Configuration > Plugin packs > Manager" page
- Install the plugin on every poller expected to monitor Docker resources:
yum install centreon-plugin-Applications-Docker-Restapi
- Install the Centreon Plugin-Pack RPM on your central server:
yum install centreon-pack-applications-docker-restapi
- Install the "Docker-Restapi" Centreon Plugin-Pack from the "Configuration > Plugin packs > Manager" page
Host Configuration
Apply the "App-Docker-Restapi-custom" template to your newly created host. Then fill the macros value fileds marked as mandatory below:
| Mandatory | Name | Description |
|---|---|---|
| X | DOCKERENGINEPORT | Docker API TCP port to use to query the Docker engine |
| DOCKERENGINEEXTRAOPTIONS | Docker API engine extra options |
FAQ
Why are some of my checks are very slow ?
The container stats endpoint can be pretty slow to return a result (between 1 and 2 second), so it's considered as normal that the container-stats check may take some time.
How can I test my plugin through the CLI and what does the main command_line parameters mean ?
Once you've installed your monitoring plugin, you can use the centreon-engine user to test it!
/usr/lib/centreon/plugins//centreon_docker_restapi.pl \
--plugin=cloud::docker::restapi::plugin \
--mode=node-status \
--hostname='192.168.0.50' \
--port='2375' \
--warning-node-status='' \
--critical-node-status='%{status} !~ /ready/ || %{manager_status} !~ /reachable|-/' \
--verbose
OK: Node '192.168.0.50' Containers Running : 7, Containers Stopped : 2, Containers Paused : 0 | 'containers_running'=7;;;0; 'containers_stopped'=2;;;0; 'containers_paused'=0;;;0;
Node '192.168.0.50' Containers Running : 7, Containers Stopped : 2, Containers Paused : 0
This command checks your docker engine node status (--mode=node-status) using tcp port 2375 (--port='2375'). It provides the overall status of the node and state of each container it manages.
A CRITICAL alert is triggered if your node is not considered as ready or the manager cannot be reached (--critical-node-status='%{status} !~ /ready/ || %{manager_status} !~ /reachable|-/')