Log Tailing - Skaffold

Skaffold has built-in support for tailing logs for containers built and deployed by Skaffold on your cluster to your local machine when running in either dev, debug or run mode.

{{< alert title="Note" >}} Log Tailing is enabled by default for [dev]({{<relref "/docs/workflows/dev" >}}) and [debug]({{<relref "/docs/workflows/debug" >}}).

Log Tailing is disabled by default for run mode; it can be enabled with the --tail flag. {{< /alert >}}

Log Structure

To view log structure, run skaffold run --tail in examples/microservices

bash

skaffold run --tail

will produce an output like this

For every log line, skaffold will prefix the pod name and container name if they're not the same.

In the above example, leeroy-web-75ff54dc77-9shwm is the pod name and leeroy-web is container name defined in the spec for this deployment

yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: leeroy-web
  labels:
    app: leeroy-web
spec:
  replicas: 1
  selector:
    matchLabels:
      app: leeroy-web
  template:
    metadata:
      labels:
        app: leeroy-web
    spec:
      containers:
        - name: leeroy-web
          image: gcr.io/k8s-skaffold/leeroy-web
          ports:
            - containerPort: 8080

Skaffold will choose a unique color for each container to make it easy for users to read the logs.

JSON Parsing

In some cases, logs may simply be JSON objects. If you know this ahead of time and know that you'd like to only get specific fields from these objects, you can add a deploy.logs.jsonParse stanza to your skaffold.yaml file to configure which fields you'd like to see.

yaml

apiVersion: skaffold/v2beta27
kind: Config
build:
  artifacts:
  - image: skaffold-example
deploy:
  logs:
    jsonParse:
      fields: ["message", "severity"]
  kubectl:
    manifests:
      - k8s-*

In the above example, only the fields message and severity will be gathered from the incoming JSON logs. So, if the logs coming through were structured like so:

[getting-started] {"timestampSeconds":1643740871,"timestampNanos":446000000,"severity":"INFO","thread":"main","message":"Hello World!","context":"default"}

with the deploy.logs.jsonParse config added, they would look like this:

[getting-started] message: Hello World!, severity: INFO