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Wycliffe A. Onyango
Wycliffe A. Onyango

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100 Days of DevOps: Day 55

#devops #nginx #kubernetes #containers

Deploying a Sidecar Pattern for Nginx Log Shipping in Kubernetes

Overview

The goal was to run a web server (nginx) inside a Kubernetes Pod and ship its logs to an aggregation service using the Sidecar pattern.

  • Main Container: nginx-container serves web pages and generates access/error logs.
  • Sidecar Container: sidecar-container (Ubuntu) reads the same logs every 30 seconds.
  • Shared Storage: An emptyDir volume allows both containers to share log files during the Pod’s lifetime.

This pattern keeps responsibilities separate:

Nginx focuses on serving web content, while the sidecar focuses on log collection.

Step 1 – Create the Pod Definition

I defined the Pod in a YAML file named webserver.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: webserver
spec:
  volumes:
  - name: shared-logs
    emptyDir: {}
  containers:
  - name: nginx-container
    image: nginx:latest
    volumeMounts:
    - name: shared-logs
      mountPath: /var/log/nginx
  - name: sidecar-container
    image: ubuntu:latest
    command: ["sh","-c","while true; do cat /var/log/nginx/access.log /var/log/nginx/error.log; sleep 30; done"]
    volumeMounts:
    - name: shared-logs
      mountPath: /var/log/nginx
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Step 2 – Apply the Configuration

Command:

kubectl apply -f webserver.yaml
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Output:

pod/webserver created
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This confirmed the Pod was created successfully.

Step 3 – Inspect the Pod

Command:

kubectl describe pod webserver
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Key Output Highlights:

Name:             webserver
Status:           Running
Containers:
  nginx-container:  Running
  sidecar-container: Running
Volumes:
  shared-logs: EmptyDir
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This shows:

  • Both containers (nginx-container and sidecar-container) are Running.
  • The shared-logs emptyDir volume is mounted in both containers at /var/log/nginx.

Step 4 – View Sidecar Logs

Command:

kubectl logs -f webserver -c sidecar-container
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Output (sample):

2025/09/27 07:43:13 [notice] 1#1: using the "epoll" event method
2025/09/27 07:43:13 [notice] 1#1: nginx/1.29.1
2025/09/27 07:43:13 [notice] 1#1: start worker processes
...
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These are the Nginx startup messages and worker process notices being printed from the error log.
Because the sidecar loops every 30 seconds, these lines repeat whenever it re-reads the files.

Final Result

  • Pod Name: webserver

  • Containers Running:

    • nginx-container (serves pages, writes logs)
    • sidecar-container (reads & outputs logs)

  • Shared Volume: shared-logs (type: emptyDir)

  • Behavior: Logs from Nginx are continuously read and displayed by the sidecar every 30 seconds.

Key Takeaways

  1. Separation of Concerns: The main container serves web pages only; the sidecar handles log shipping.
  2. Shared Volumes Enable Communication: emptyDir allows both containers to share log files without persistence.
  3. Scalable Pattern: In production, the sidecar could be replaced with a real log shipper like Fluentd or Filebeat to forward logs to a central system.

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