Hi,
I got a general question regarding the Kubernetes API: Is it strongly consistent or eventual consistent? Are there any partial guarantees (e.g., strongly consistent on same resource type/object, or similar).
To make it specific: If I successfully post a new resource A of type a, and directly query resources of type a afterwards, is it guaranteed that I see A in the response?
Thanks!
The Kubernetes API is using etcd to store cluster data. You can read more about the read consistency of etcd here[1] and here [2]
You can achieve strong consistency for read-modify-write by using resourceVersion.
Then, if your writer has a side channel to your reader, you can pass over the written version number and watch+block until you see the updated version.
More generally, looking at the whole system: due to the watch+modify pattern, Kubernetes as a whole is eventually consistent - changing your Deployment will not be immediately reflected in the Pod objects, for both unavoidable and intentional reasons
Thank you for your responses!
Most helpful for me was @feloy s answer regarding etcd, which offers sequential consistency.
Which I interpret as: yes.