Cassandra with AxonOps on Kubernetes
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13 Oct, 2020

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Introduction

The following shows how to install AxonOps for monitoring Cassandra. This process specifically requires the official cassandra helm repository.

Using minikube

The deployment should work fine on latest versions of minikube as long as you provide enough memory for it.

minikube start --memory 8192 --cpus=4
minikube addons enable storage-provisioner

⚠️ Make sure you use a recent version of minikube. Also check available drivers and select the most appropriate for your platform

Helmfile

Overview

As this deployment contains multiple applications we recommend you use an automation system such as Ansible or Helmfile to put together the config. The example below uses helmfile.

Install requirements

You would need to install the following components:

Alternatively you can consider using a dockerized version of them both such as https://hub.docker.com/r/chatwork/helmfile

Config files

The values below are set for running on a laptop with minikube, adjust accordingly for larger deployments.

The values below are set for running on a laptop with minikube, adjust accordingly for larger deployments.

helmfile.yaml

---
repositories:
  - name: stable
    url: https://kubernetes-charts.storage.googleapis.com
  - name: incubator
    url: https://kubernetes-charts-incubator.storage.googleapis.com
  - name: axonops-helm
    url: https://repo.axonops.com/public/helm/helm/charts/
  - name: bitnami
    url: https://charts.bitnami.com/bitnami
releases:
  - name: axon-elastic
    namespace: {{ env "NAMESPACE" | default "monitoring" }}
    chart: "bitnami/elasticsearch"
    wait: true
    labels:
      env: minikube
    values:
      - fullnameOverride: axon-elastic
      - imageTag: "7.8.0"
      - data:
          replicas: 1
          persistence:
            size: 1Gi
            enabled: true
            accessModes: [ "ReadWriteOnce" ]
      - curator:
          enabled: true
      - coordinating:
          replicas: 1
      - master:
          replicas: 1
          persistence:
            size: 1Gi
            enabled: true
            accessModes: [ "ReadWriteOnce" ]

  - name: axonops
    namespace: {{ env "NAMESPACE" | default "monitoring" }}
    chart: "axonops-helm/axonops"
    wait: true
    labels:
      env: minikube
    values:
      - values.yaml

  - name: cassandra
    namespace: cassandra
    chart: "incubator/cassandra"
    wait: true
    labels:
      env: dev
    values:
      - values.yaml

values.yaml

---
persistence:
  enabled: true
  size: 1Gi
  accessMode: ReadWriteMany

podSettings:
  terminationGracePeriodSeconds: 300

image:
  tag: 3.11.6
  pullPolicy: IfNotPresent

config:
  cluster_name: minikube
  cluster_size: 3
  seed_size: 2
  num_tokens: 256
  max_heap_size: 512M
  heap_new_size: 512M

env:
  JVM_OPTS: "-javaagent:/var/lib/axonops/axon-cassandra3.11-agent.jar=/etc/axonops/axon-agent.yml"

extraVolumes:
  - name: axonops-agent-config
    configMap:
      name: axonops-agent
  - name: axonops-shared
    emptyDir: {}
  - name: axonops-logs
    emptyDir: {}
  - name: cassandra-logs
    emptyDir: {}

extraVolumeMounts:
  - name: axonops-shared
    mountPath: /var/lib/axonops
    readOnly: false
  - name: axonops-agent-config
    mountPath: /etc/axonops
    readOnly: true
  - name: axonops-logs
    mountPath: /var/log/axonops
  - name: cassandra-logs
    mountPath: /var/log/cassandra

extraContainers:
  - name: axonops-agent
    image: digitalisdocker/axon-agent:latest
    env:
      - name: AXON_AGENT_VERBOSITY
        value: "1"
    volumeMounts:
      - name: axonops-agent-config
        mountPath: /etc/axonops
        readOnly: true
      - name: axonops-shared
        mountPath: /var/lib/axonops
        readOnly: false
      - name: axonops-logs
        mountPath: /var/log/axonops
      - name: cassandra-logs
        mountPath: /var/log/cassandra

axon-server:
  elastic_host: http://axon-elastic-elasticsearch-master
  image:
    repository: digitalisdocker/axon-server
    tag: latest
    pullPolicy: IfNotPresent


axon-dash:
  axonServerUrl: http://axonops-axon-server:8080
  service:
    # use NodePort for minikube, change to ClusterIP or LoadBalancer on fully featured
    # k8s deployments such as AWS or Google
    type: NodePort
  image:
    repository: digitalisdocker/axon-dash
    tag: latest
    pullPolicy: IfNotPresent

axon-agent.yml

axon-server:
    hosts: "axonops-axon-server.monitoring" # Specify axon-server IP axon-server.mycompany.
    port: 1888

axon-agent:
    org: "minikube" # Specify your organisation name
    human_readable_identifier: "axon_agent_ip" # one of the following:

NTP:
    host: "pool.ntp.org" # Specify a NTP to determine a NTP offset

cassandra:
  tier0: # metrics collected every 5 seconds
      metrics:
          jvm_:
            - "java.lang:*"
          cas_:
            - "org.apache.cassandra.metrics:*"
            - "org.apache.cassandra.net:type=FailureDetector"

  tier1:
      frequency: 300 # metrics collected every 300 seconds (5m)
      metrics:
          cas_:
            - "org.apache.cassandra.metrics:name=EstimatedPartitionCount,*"

  blacklist: # You can blacklist metrics based on Regex pattern. Hit the agent on http://agentIP:9916/metricslist to list JMX metrics it is collecting
    - "org.apache.cassandra.metrics:type=ColumnFamily.*" # duplication of table metrics
    - "org.apache.cassandra.metrics:.*scope=Repair#.*" # ignore each repair instance metrics
    - "org.apache.cassandra.metrics:.*name=SnapshotsSize.*" # Collecting SnapshotsSize metrics slows down collection
    - "org.apache.cassandra.metrics:.*Max.*"
    - "org.apache.cassandra.metrics:.*Min.*"
    - ".*999thPercentile|.*50thPercentile|.*FifteenMinuteRate|.*FiveMinuteRate|.*MeanRate|.*Mean|.*OneMinuteRate|.*StdDev"

  JMXOperationsBlacklist:
    - "getThreadInfo"
    - "getDatacenter"
    - "getRack"

  DMLEventsWhitelist: # You can whitelist keyspaces / tables (list of "keyspace" and/or "keyspace.table" to log DML queries. Data is not analysed.
  # - "system_distributed"

  DMLEventsBlacklist: # You can blacklist keyspaces / tables from the DMLEventsWhitelist (list of "keyspace" and/or "keyspace.table" to log DML queries. Data is not analysed.
  # - system_distributed.parent_repair_history

  logSuccessfulRepairs: false # set it to true if you want to log all the successful repair events.

  warningThresholdMillis: 200 # This will warn in logs when a MBean takes longer than the specified value.

  logFormat: "%4$s %1$tY-%1$tm-%1$td %1$tH:%1$tM:%1$tS,%1$tL %5$s%6$s%n"

Start up

Create Axon Agent configuration

kubectl create ns cassandra
kubectl create configmap axonops-agent --from-file=axon-agent.yml -n cassandra

Run helmfile

With locally installed helm and helmfile

cd your/config/directory
hemlfile sync

With docker image

docker run --rm 
    -v ~/.kube:/root/.kube 
    -v ${PWD}/.helm:/root/.helm 
    -v ${PWD}/helmfile.yaml:/helmfile.yaml 
    -v ${PWD}/values.yaml:/values.yaml 
    --net=host chatwork/helmfile sync

Access

Minikube

If you used minikube, identify the name of the service with kubectl get svc -n monitoring and launch it with

minikube service axonops-axon-dash -n monitoring

LoadBalancer

Find the DNS entry for it:

kubectl get svc -n monitoring -o wide

Open your browser and copy and paste the URL.

Troubleshooting

Check the status of the pods:

kubectl get pod -n monitoring
kubectl get pod -n cassandra

Any pod which is not on state Running check it out with

kubectl describe -n NAMESPACE pod POD-NAME

Storage

One common problem is regarding storage. If you have enabled persistent storage you may see an error about persistent volume claims (not found, unclaimed, etc). If you’re using minikube make sure you enable storage with

minikube addons enable storage-provisioner

Memory

The second most common problem is not enough memory (OOMKilled). You will see this often if you’re node does not have enough memory to run the containers or if the heap settings for Cassandra are not right. kubectl describe command will be showing Error 127 when this occurs.

In the values.yaml file adjust the heap options to match your hardware:

max_heap_size: 512M
  heap_new_size: 512M

Minikube

Review the way you have started up minikube and assign more memory if you can. Also check the available drivers and select the appropriate for your platform. On MacOS where I tested hyperkit or virtualbox are the best ones.

minikube start --memory 10240 --cpus=4 --driver=hyperkit

Putting it all together

This short video shows how quickly you can run Cassandra with AxonOps on a Kubernetes cluster. The video uses a “helmfile” to manage the packages and configurations. https://youtu.be/OvRZkS0FNCg

Sergio Rua

Sergio Rua

DevOps Engineer

Sergio has many years experience working on various development projects before joining Digitalis. He worked for large companies with complex networks and infrastructure. ‘This has  helped Sergio gain lots of experience in multiple areas from programming to networks. He especial excels is in DevOps: automation is his day-to-day and Kubernetes his passion.

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