How to monitor your OpenShift cluster

Overview

UKCloud for Red Hat OpenShift enables you to develop, deploy, and manage digital and container-based applications seamlessly across local physical or virtual environments, with full portability to and from UKCloud.

This guide explains how you can set up a simple system to monitor an OpenShift cluster.

Intended audience

This guide assumes familiarity with the Linux command line, and with the oc command set to manage an OpenShift cluster.

Prerequisites

To complete the steps in this guide, you must have the oc command installed and have a suitable account on your OpenShift cluster. Specifically, it is assumed you know the authentication credentials that need to be supplied to oc login.

Generating an authentication token

The first step is to create a service account within your OpenShift cluster that your monitoring system can use, and create an authentication token for it.

Tip

The token may have already been created, so it's worth checking first.

oc login ...
oc project openshift-infra

Check if a monitoring account already exists:
```
oc get serviceaccount --all-namespaces | grep infra | \
grep monitoring
```
If the account exists, the command above prints the name, and you can move on to Reading the authentication token. If it prints nothing, you need to create the account as described in the remaining steps below.
Create the monitoring account if it does not exist:
```
oc create serviceaccount monitoring
```

Add the role cluster-reader to the account:

oc adm policy add-cluster-role-to-user cluster-reader \
system:serviceaccount:openshift-infra:monitoring

Reading the authentication token

Next, you need to retrieve the authentication token that you created in the previous step.

If you haven't already done so, ensure you are logged in to OpenShift and connected to the right project:
```
oc login ...
oc project openshift-infra
```
Find the name of the monitoring account's token IDs:
```
oc describe serviceaccount monitoring
```
This lists the IDs of one or more token names, for example, monitoring-token-1abc2.
Find the actual authentication token by querying the secret by the name given in the previous step, for example:
```
oc describe secret <monitoring-token>
```
Where monitoring-token is the token name you found in the previous step.

This lists a few values, including the 179-character authentication token.

Using the authentication token

The OpenShift API provides a way of determining the health of the cluster; the data required to do this is obtainable by requesting the API at /api/vi/nodes. You must supply the authentication token in the HTTP Authorization header.

The following example shows how to query this data from a shell command using curl.

$ token="<authentication_token>"
$ endpoint= https://ocp.<my-cluster-url>.ukcloud.com:8443
$ curl -k -H "Authorization: Bearer ${token}" \
  -H 'Accept: application/json' ${endpoint}/api/v1/nodes

You'll need to customise the query above by providing the correct values for endpoint and token.

This API call returns a reasonable amount of JSON-encoded data, which may be hard to parse using shell commands. It's also necessary to fetch items from various places within this data. The Python program in the following section shows you how to accomplish this.

Using the OpenShift API to obtain cluster status

The code example below uses the OpenShift API to obtain information about the health of the cluster, and prints a summary showing if each node is healthy. It has been tested using Python 3.7.

Tip

The ENDPOINT parameter in the code is an example for OpenShift v3. For OpenShift v4 clusters, you'll need to change the port number from 8443 to 6443. API URLs for OpenShift v4 begin with https://api. rather than https://ocp..

#!/usr/bin/env python3
import urllib.request
import json
import ssl

def get_all_nodes(endpoint, token):
    """Fetch the nodes data from the openshift cluster"""
    request = urllib.request.Request(endpoint + "/api/v1/nodes")
    request.add_header('Authorization', 'Bearer ' + token)
    request.add_header('Accept', 'application/json')
    ssl_context = None  # or ssl._create_unverified_context()
    result = urllib.request.urlopen(request, context=ssl_context)
    return result.read()

def get_status_from_node(data_item):
    """ Extract the status conditions from the data"""
    addresses = data_item['status']['addresses']
    address = None
    for addr in addresses:
        if addr['type'] == 'Hostname':
            address = addr['address']
    return {'hostname': address,
            'conditions': data_item['status']['conditions']}

def find_faults(cond_data):
    """ find whether each node is in a failed state"""
    cells = []
    for node in cond_data:
        hostname = node['hostname']
        state = 'OK  '
        for cond in node['conditions']:
            if cond['status'] != "False" and cond['type'] != "Ready":
                state = 'FAIL'
            elif cond['status'] != "True" and cond['type'] == "Ready":
                state = 'FAIL'
        cells.append('{} {} '.format(state, hostname))
    return cells

def main():
    all_nodes = json.loads(get_all_nodes(ENDPOINT, TOKEN))
    all_conditions = []
    for node in all_nodes['items']:
        all_conditions.append(get_status_from_node(node))
    print("Status of Cluster at {}".format(ENDPOINT))
    for node in find_faults(all_conditions):
        print(node)

ENDPOINT = 'https://ocp.my-cluster-url.ukcloud.com:8443'
TOKEN = 'eyJhb...the.179.char.token'
main()

Tip

If you encounter problems copying and pasting the source code above, we also provide the code in the following blog post:

https://ukcloud.com/hub/news/simple-openshift-monitoring/

Next steps

For more information about UKCloud for Red Hat OpenShift service, see:

Feedback

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