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Sending Kubernetes logs to OpenSearch

The following tutorial shows you how to send Kubernetes logs to OpenSearch.

Prerequisites

You need a Kubernetes cluster. We used minikube with docker driver and Helm. We used a Ubuntu 22.04 (amd64) machine, but it should work on any system that can run minikube (2 CPUs, 2GB of free memory, 20GB of free disk space).

The OpenSearch service needs a large mmap count setting, so set it to at least 262144, for example:

sysctl -w vm.max_map_count=262144

You must have Helm and kubectl installed.

Generate logs

Install kube-logging/log-generator to generate logs. Complete the following steps.

Add the kube-logging repository to Helm.

helm repo add kube-logging https://kube-logging.github.io/helm-charts

Expected output:

"kube-logging" has been added to your repositories

Update your repositories.

helm repo update

The output should look like:

Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "kube-logging" chart repository
Update Complete. ⎈Happy Helming!⎈

Install kube-logging/log-generator.

helm install --generate-name --wait kube-logging/log-generator

The output should look like:

NAME: log-generator-1684694629
LAST DEPLOYED: Sun May 21 20:43:49 2023
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

Check that the log-generator is running:

kubectl get pods

The output should look like:

NAME                                        READY   STATUS        RESTARTS       AGE
log-generator-1681984863-5946c559b9-ftrrn   1/1     Running       0              8s

Set up OpenSearch

Install an OpenSearch cluster with Helm:

helm repo add opensearch https://opensearch-project.github.io/helm-charts/

Expected output:

"opensearch" has been added to your repositories

Update your repositories.

helm repo update

The output should look like:

Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "opensearch" chart repository
Update Complete. ⎈Happy Helming!⎈

Install OpenSearch. This step can take a few minutes.

helm install --generate-name --wait opensearch/opensearch

Install the OpenSearch dashboards.

helm install --generate-name --wait opensearch/opensearch-dashboards

The output should look like:

NAME: opensearch-dashboards-1684695728
LAST DEPLOYED: Sun May 21 21:02:09 2023
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
1. Get the application URL by running these commands:
  export POD_NAME=$(kubectl get pods --namespace default -l "app.kubernetes.io/name=opensearch-dashboards,app.kubernetes.io/instance=opensearch-dashboards-1684695728" -o jsonpath="{.items[0].metadata.name}")
  export CONTAINER_PORT=$(kubectl get pod --namespace default $POD_NAME -o jsonpath="{.spec.containers[0].ports[0].containerPort}")
  echo "Visit http://127.0.0.1:8080 to use your application"
  kubectl --namespace default port-forward $POD_NAME 8080:$CONTAINER_PORT

Now you should have 5 pods. Check that they exist:

kubectl get pods

The output should look like:

NAME                                                READY   STATUS    RESTARTS   AGE
log-generator-1681984863-5946c559b9-ftrrn           1/1     Running   0          3m39s
opensearch-cluster-master-0                         1/1     Running   0          81s
opensearch-cluster-master-1                         1/1     Running   0          81s
opensearch-cluster-master-2                         1/1     Running   0          81s
opensearch-dashboards-1681999620-59f64f98f7-bjwwh   1/1     Running   0          44s

Forward the 5601 port of the OpenSearch Dashboards service (replace the name of the pod with your pod).

kubectl port-forward opensearch-dashboards-1681999620-59f64f98f7-bjwwh 8080:5601

The output should look like:

Forwarding from 127.0.0.1:8080 -> 5601
Forwarding from [::1]:8080 -> 5601

Log in to the dashboard at http://localhost:8080 with admin/admin. You will soon create an Index Pattern here, but first you have to send some logs from syslog-ng.

Set up axosyslog-collector

Add the AxoSyslog Helm repository:

helm repo add axosyslog https://axoflow.github.io/axosyslog-charts
helm repo update

Create a YAML file (called axoflow-demo.yaml in the examples) to configure the collector.

config:
  sources:
    kubernetes:
      # Collect kubernetes logs
      enabled: true
  destinations:
    # Send logs to OpenSearch
    opensearch:
      - address: "opensearch-cluster-master"
        index: "test-axoflow-index"
        user: "admin"
        password: "admin"
        tls:
          # Do not validate the server's TLS certificate.
          peerVerify: false
        # Send the syslog fields + the metadata from .k8s.* in JSON format
        template: "$(format-json --scope rfc5424 --exclude DATE --key ISODATE @timestamp=${ISODATE} k8s=$(format-json .k8s.* --shift-levels 2 --exclude .k8s.log))"

Check how the syslog-ng.conf file looks with your custom values:

helm template -f axoflow-demo.yaml -s templates/config.yaml axosyslog/axosyslog-collector

The output should look like:

# Source: axosyslog-collector/templates/config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  labels:
    helm.sh/chart: axosyslog-collector-0.3.0
    app.kubernetes.io/name: axosyslog-collector
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "4.2.0"
    app.kubernetes.io/managed-by: Helm
  name: release-name-axosyslog-collector
data:
  syslog-ng.conf: |
    @version: current
    @include "scl.conf"

    options {
      stats(
        level(1)
      );
    };

    log {
      source { kubernetes(); };
      destination {
        elasticsearch-http(
          url("https://opensearch-cluster-master:9200/_bulk")
          index("test-axoflow-index")
          type("")
          template("$(format-json --scope rfc5424 --exclude DATE --key ISODATE @timestamp=${ISODATE} k8s=$(format-json .k8s.* --shift-levels 2 --exclude .k8s.log))")
          user("admin")
          password("admin")
          tls(
            peer-verify(no)
          )
        );
      };
    };

Install the axosyslog-collector chart:

helm install --generate-name --wait -f axoflow-demo.yaml axosyslog/axosyslog-collector

The output should look like:

NAME: axosyslog-collector-1682002179
LAST DEPLOYED: Thu Apr 20 16:49:39 2023
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
1. Watch the axosyslog-collector-1682002179 container start.

Check your pods:

kubectl get pods --namespace=default -l app=axosyslog-collector-1682002179 -w
kubectl get pods

The output should look like:

NAME                                                READY   STATUS    RESTARTS   AGE
log-generator-1681984863-5946c559b9-ftrrn           1/1     Running   0          13m
opensearch-cluster-master-0                         1/1     Running   0          11m
opensearch-cluster-master-1                         1/1     Running   0          11m
opensearch-cluster-master-2                         1/1     Running   0          11m
opensearch-dashboards-1681999620-59f64f98f7-bjwwh   1/1     Running   0          10m
axosyslog-collector-1682002179-pjlkn                1/1     Running   0          6s

Check the logs in OpenSearch

Open OpenSearch dashboard at http://localhost:8080/app/management/opensearch-dashboards/.
Create an Index Pattern called test-axoflow-index: http://localhost:8080/app/management/opensearch-dashboards/indexPatterns. At Step 2, set the Time field to @timestamp.
Now you can see your logs on the Discover view at http://localhost:8080/app/discover. Opening the detailed view for a log entry shows you the fields sent to OpenSearch.