Using IMDS to get the status of a replica

We can use the IMDS to retrieve the current status of the replica from inside the workload. This can be achieved using either the IMDS SDK, or the JSON request endpoint. In this example, we’ll create a Python script using the IMDS SDK to check whether the container is ready, and start a bash script when it is.

​

Using the SDK to retrieve the status

We’ll start by using the IMDS SDK to retrieve the statuses of the currently running container.

Now, if we run this on a container that has passed its startup probe, but not completed its readiness probe, we’ll see this:

{
  "ready": false,
  "started": true
}

​

Starting a script when its ready

Now we know the status of the container, we can use this to start a bash script when it reaches a ready state.

import json
from subprocess import call
from salad_cloud_imds_sdk import SaladCloudImdsSdk, Environment

sdk = SaladCloudImdsSdk(
    base_url=Environment.DEFAULT.value,
    timeout=10000
)

result = sdk.metadata.get_container_status()

#Get the ready status out of the JSON response
data = json.loads(result)

status = data['ready']

if status == True:
  subprocess.call("exampleScript.sh")
else: print("Not Ready Yet!")