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Provide flags to use etcd3 backed storage
ref: #24405
What's in this PR?
- Add a new flag "storage-backend" to choose "etcd2" or "etcd3". By default (i.e. empty), it's "etcd2".
- Take out etcd config code into a standalone package and let it create etcd2 or etcd3 storage backend given user input.
Automatic merge from submit-queue
Use the first version as thirdparty resource preferredVersion
First commit is a one-liner, which implements the server-half of #23985.
The other two commits rearrange the test code, and add back a commented out test of thirdparty resource.
@lavalamp @nikhiljindal
Automatic merge from submit-queue
Make etcd cache size configurable
Instead of the prior 50K limit, allow users to specify a more sensible size for their cluster.
I'm not sure what a sensible default is here. I'm still experimenting on my own clusters. 50 gives me a 270MB max footprint. 50K caused my apiserver to run out of memory as it exceeded >2GB. I believe that number is far too large for most people's use cases.
There are some other fundamental issues that I'm not addressing here:
- Old etcd items are cached and potentially never removed (it stores using modifiedIndex, and doesn't remove the old object when it gets updated)
- Cache isn't LRU, so there's no guarantee the cache remains hot. This makes its performance difficult to predict. More of an issue with a smaller cache size.
- 1.2 etcd entries seem to have a larger memory footprint (I never had an issue in 1.1, even though this cache existed there). I suspect that's due to image lists on the node status.
This is provided as a fix for #23323
Automatic merge from submit-queue
Additional go vet fixes
Mostly:
- pass lock by value
- bad syntax for struct tag value
- example functions not formatted properly
Pass down into the server initialization the necessary interface for
handling client/server content type negotiation. Add integration tests
for the negotiation.
