API to find a key in a etcd cluster

Question

I am trying to write a code where I need to find if a key exists in etcd or not. I tried this:

_, err = kapi.Get(context.Background(), key, nil)
        if err != nil {
          return err      
        } else { ...

But even if the key is not in the cluster, the error is always nil.

Any idea what am I doing wrong here? Or is there any other API call to make?

Answer 1

If you use the go client v3 KV client here: https://godoc.org/go.etcd.io/etcd/clientv3#KV

It returns the following type: https://godoc.org/go.etcd.io/etcd/etcdserver/etcdserverpb#RangeResponse

type RangeResponse struct {
    Header *ResponseHeader `protobuf:"bytes,1,opt,name=header" json:"header,omitempty"`
    // kvs is the list of key-value pairs matched by the range request.
    // kvs is empty when count is requested.
    Kvs []*mvccpb.KeyValue `protobuf:"bytes,2,rep,name=kvs" json:"kvs,omitempty"`
    // more indicates if there are more keys to return in the requested range.
    More bool `protobuf:"varint,3,opt,name=more,proto3" json:"more,omitempty"`
    // count is set to the number of keys within the range when requested.
    Count int64 `protobuf:"varint,4,opt,name=count,proto3" json:"count,omitempty"`
}

So as you see, there is a Count property and a Kvs property, if you want to check that your response contains keys you can just check that Count > 0 or len(res.Kvs) > 0