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cowcheck

A microservice for checking the health of a Rancher node. Presents an HTTP interface on port 5050 for querying health status. Calling / or /health will return 200 OK when healthy and 503 Service Unavailable when one or more of its checks were unhealthy in the most recent evaluation cycle. Additionally, a prometheus endpoint can be found at /metrics. See Prometheus section below.

What does it check/monitor?

  • Rancher Metadata API
  • Rancher DNS
  • Disk space available on the node (both container data space and Docker/Moby metadata space)

How to use

With an auto-scaling group

Run this as a container on each Rancher host that runs your containers. It will assert basic functionality of the Rancher stack is working such as DNS, Metadata API. When combined with a fleet management service such as AWS Auto Scale Groups or Google Cloud Deployment Manager you can replace nodes automatically when they fail. Alternatively you can just monitor and alert by polling the endpoint periodically.

Prometheus Endpoint

Endpoint is available at /metrics on port 5050. Following metrics are available:

  • cowcheck_node_health: The metric will be set to 0 when healthy and 1 when unhealthy.
  • docker_data_storage: Amount of free Docker Data Storage space in bytes
  • docker_metadata_storage: Amount of free Docker Metadata Storage space in bytes

Configuration options

  • POLL_INTERVAL: Time in seconds between evaluating checks
  • LOG_LEVL: Level of logging verbosity
  • ENABLE_STORAGE_CHECK: Enable storage check by setting to true. Disabled by default. Currently only supports devicemapper storage driver.
  • DATA_SPACE_THRESHOLD: Minimum amount of storage in bytes before failing storage checks.
  • METADATA_SPACE_THRESHOLD: Minimum amount of storage in bytes before failing storage checks.
  • DOCKER_API_VERSION: The version of the Docker API to use when connecting to the local docker daemon (only for storage checks)

Building

To build the binary: make build

To create a Docker image: make package

Running

docker run --net=host -p 5050:5050 [image name]

Or schedule with Rancher to run on all hosts as a Global Service (cattle) or Daemonset (kubernetes).

License

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.