How to evaluate the etcd value size

[lance5890]

1. As we can get a etcd value by its key like this :

etcdctl get  /kubernetes.io/secrets/xxx

2. But how can we evaluate the specified value size, as we can only see the value data, how can we get its size

[jmhbnz]

Hey @lance5890 - For retrieving the size of a key, how about writing the value to disk and just using ls?

For example:

 james  ~  D  e  bin   main                                                                                   16:16:02 
 ➜ ./etcdctl get --print-value-only /kubernetes.io/secrets/xxx > value.tmp


 james  ~  D  e  bin   main                                                                                   16:17:39 
 ➜ ls -lh
total 73M
drwx------ 3 james james 4.0K Aug 21 16:14 default.etcd
-rwxrwxr-x 1 james james  32M Aug 20 09:45 etcd
-rwxrwxr-x 1 james james  21M Aug 20 09:45 etcdctl
-rwxrwxr-x 1 james james  21M Aug 20 09:45 etcdutl
-rw-rw-r-- 1 james james   13 Aug 21 16:16 value.tmp

[lance5890]

yes, the value can be retrieved by this way. I just wonder if or not the value size have been compacted when restored in etcd boltdb

[jmhbnz]

That's a fair question, I haven't looked into if bbolt is doing any kind of compression / storage optimsation for values stored. @ahrtr might have some knowledge on this part of it.

At the very least you could use the approach I mentioned above as a worst case scenario / highest possible estimate for an individual key value.

[ahrtr]

I just wonder if or not the value size have been compacted when restored in etcd boltdb

bbolt doesn't compact the value. But the key & value stored in bbolt is different from the key & value what users see. The key stored in bbolt is actually a monotonically increasing revision, and the value stored in bbolt includes both the real key & value users see. Please read kvstore_txn.go#L209-L232

If you really want to get the value size programatically, you should use the etcd SDK (call the Get method), and then get the value size using expression something like len(resp.Kvs[0].Value).

[lance5890]

Thanks so much