Add an example that demonstrates waiting for a sidecar to become Ready

examples/taskruns/sidecar-ready.yaml

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+apiVersion: tekton.dev/v1alpha1
+kind: TaskRun
+metadata:
+ generateName: sidecar-ready-
+spec:
+ taskSpec:
+ sidecars:
+ - name: slow-sidecar
+ image: ubuntu
+ command: ['sleep', 'infinity']
+ # The sidecar takes 5s to report as Ready, even after it starts. If the
+ # step runs as soon as the sidecar starts, it will fail because
+ # /shared/ready isn't available yet.
+ readinessProbe:
+ exec:
+ command:
+ - sh
+ - -c
+ - sleep 5 && touch /shared/ready
+ volumeMounts:
+ - name: shared
+ mountPath: /shared
+
+ steps:
+ - name: check-ready
+ image: ubuntu
+ # The step will only succeed if the sidecar has written this file, which
+ # it does 5s after it starts, before it reports Ready.
+ command: ['cat', '/shared/ready']
+ volumeMounts:
+ - name: shared
+ mountPath: /shared
+
+ # Sidecars don't have /workspace mounted by default, so we have to define
+ # our own shared volume.
+ volumes:
+ - name: shared
+ emptyDir: {}