Troubleshoot cluster configurations

Estimated reading time: 2 minutes

Docker UCP persists configuration data on an etcd key-value store that is replicated on all controller nodes of the UCP cluster. This key-value store is for internal use only, and should not be used by other applications.

This article shows how you can access the key-value store, for troubleshooting configuration problems in your cluster.

Using the REST API

In this example we’ll be using curl for making requests to the key-value store REST API, and jq to process the responses.

You can install these tools on a Ubuntu distribution by running:

$ sudo apt-get update && apt-get install curl jq
  1. Use a client bundle to authenticate your requests. Learn more.

  2. Use the REST API to access the cluster configurations.

# $DOCKER_HOST and $DOCKER_CERT_PATH are set when using the client bundle
$ export KV_URL="https://$(echo $DOCKER_HOST | cut -f3 -d/ | cut -f1 -d:):12379"

$ curl -s \
    --cert ${DOCKER_CERT_PATH}/cert.pem \
    --key ${DOCKER_CERT_PATH}/key.pem \
    --cacert ${DOCKER_CERT_PATH}/ca.pem \
    ${KV_URL}/v2/keys | jq "."

To learn more about the key-value store rest API check the etcd official documentation.

Using a CLI client

The containers running the key-value store, include etcdctl, a command line client for etcd. You can run it using the docker exec command.

The examples below assume you are logged in with ssh into a UCP controller node.

Check the health of the etcd cluster

$ docker exec -it ucp-kv etcdctl \
        --endpoint \
        --ca-file /etc/docker/ssl/ca.pem \
        --cert-file /etc/docker/ssl/cert.pem \
        --key-file /etc/docker/ssl/key.pem \

member 16c9ae1872e8b1f0 is healthy: got healthy result from
member c5a24cfdb4263e72 is healthy: got healthy result from
member ca3c1bb18f1b30bf is healthy: got healthy result from
cluster is healthy

On failure the command exits with an error code, and no output.

To learn more about the etcdctl utility, check the etcd official documentation.

Where to go next

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