Each instance in a WLS cluster maintains the configuration for its Prometheus Exporter locally. The coordinator allows them to share changes to the query configurations.
The coordinator is a simple web server, listening on port 8999, which accepts two requests:
- a GET request returns the latest configuration update
- a PUT request provides a new configuration update
The following is an example configuration update:
{
"timestamp": 14567894,
"configuration":
"queries:
- JVMRuntime:
key: name
prefix: jvm_
values: [heapFreeCurrent, heapFreePercent, heapSizeCurrent, heapSizeMax, uptime, processCpuLoad]"
}
An update is a JSON object with two fields:
| Name | Description |
|---|---|
| timestamp | a long value, representing milliseconds since the epoch. |
| configuration | a string representing the new YAML configuration. |
This server is run in a docker container, which is built using
docker build -t config_coordinator .
from the config_coordinator directory, and may be run with
docker run --publish 8999:8999 --name coordinator --rm config_coordinator
The query_sync section of the exporter configuration should point to this server
Passing the option "-db " will cause the coordinator to use the designated file path to persist changes to the configuration. This will preserve changes across container restarts. When running in a container, the file must be in a mounted volume.
For example:
docker run --publish 8999:8999 --name coordinator --rm -v /my/storage:/var/lib/coordinator \
config_coordinator -db /var/lib/coordinator/configs.json
will cause Docker to mount the host machine directory /my/storage at the path /var/lib/coordinator
in the container, and to use a file named configs.json in that directory to persist its state.
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