ETCD - Filter out locks from query results

[celian-garcia]

According to the ETCD concurrency code directly https://github.com/etcd-io/etcd/blob/8ac44ffa5fcccc7928876be4682c07f50b5e3b7e/client/v3/concurrency/mutex.go#L114

The value of the lock seems to be "" empty string.

Thus I would like to filter empty values, hoping that it will prevent us from having this kind of issue in query all :

error decoding the value associated with the key '<queried-key>/<one-real-element>/3477f3fdab5002b': unexpected end of JSON input

[celian-garcia]

It is probably not a good idea to check for the value to determinate if we encounter a lock or not. Despite the fact that I'm pretty sure that a lock value is empty string, one can simply set a real object with the empty string and would like to query it.

Probably a better approach would be to use leasing instead. Like if the object contains a lease, then it shouldn't be part of the result, but is there a case where we'd like to retrieve a real object (not a lock) with a lease inside ? I think not.

Another solution would be to not fail on Unmarshal issues, and continue. This is actually the better for me as currently we have a critical failure. You can currently make everything fail with that command etcdctl put <query key>/0 "". Because 0 will appears lexically at first result, and the first result being not parsable, it will fail and not make the rest

[Nexucis]

thanks for the fix, totally make sense.