Large payload for Custom Objects

Question

While I can create custom objects just fine, I am wondering how one is supposed to handle large payloads (Gigabytes) for an object.

CRs are mostly used in order to interface with garbage collection/reference counting in Kubernetes.

Adding the payload via YAML does not work, though (out of memory for large payloads):

apiVersion: "data.foo.bar/v1" 
kind: Dump 
metadata:
  name: my-data
  ownerReferences:
    - apiVersion: apps/v1
      kind: Deploy
      name: my-deploy
      uid: d9607a69-f88f-11e7-a518-42010a800195
spec: 
  payload: dfewfawfjr345434hdg4rh4ut34gfgr_and_so_on_...

One could perhaps add the payload to a PV and just reference that path in the CR. Then I have the problem, that it seems like I cannot clean up the payload file, should the CR get finalized (could not find any info about custom Finalizers).

Have no clear idea how to integrate such a concept into Kubernetes lifetimes.

score 3 · Answer 1 · answered Sep 04 '18 at 17:27

In general the limit on size for any Kube API object is ~1M due to etcd restrictions, but putting more than 20-30k in an object is a bad idea and will be expensive to access (and garbage collection will be expensive as well).

I would recommend storing the data in a object storage bucket and using an RBAC proxy like https://github.com/brancz/kube-rbac-proxy to gate access the bucket contents (use a URL to the proxy as a reference from your object). That gives you all the benefits of tracking the data in the api, but keeps the object size small. If you want a more complex integration you could implement an aggregated API and reuse the core Kubernetes libraries to handle your API, storing the data in the object store.

Can you clarify what you mean by _object storage bucket_? – abergmeier Sep 05 '18 at 08:28 — abergmeier, Sep 05 '18 at 08:28

score 1 · Accepted Answer · answered Sep 10 '18 at 06:38

We still went with using the CO. Alongside, we created a Kubernetes Controller, which handles the lifetime in the PV. For us this works fine, since the Controller can be the single writer to the PV, while the actual Services only need read access to the PV. Combined with ownerReference, this makes for a good integration into the Kubernetes lifetime.

Large payload for Custom Objects

2 Answers2