clientv3: add "WithFragment" OpOption

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

clientv3/op.go

@@ -51,6 +51,12 @@ type Op struct {
 	// for watch, put, delete
 	prevKV bool
 
+	// for watch
+	// fragmentation should be disabled by default
+	// if true, split watch events when total exceeds
+	// "--max-request-bytes" flag value + 512-byte
+	fragment bool
+
 	// for put
 	ignoreValue bool
 	ignoreLease bool
@@ -475,6 +481,17 @@ func WithPrevKV() OpOption {
 	}
 }
 
+// WithFragment to receive raw watch response with fragmentation.
+// Fragmentation is disabled by default. If fragmentation is enabled,
+// etcd watch server will split watch response before sending to clients
+// when the total size of watch events exceed server-side request limit.
+// The default server-side request limit is 1.5 MiB, which can be configured
+// as "--max-request-bytes" flag value + gRPC-overhead 512 bytes.
+// See "etcdserver/api/v3rpc/watch.go" for more details.
+func WithFragment() OpOption {
+	return func(op *Op) { op.fragment = true }
+}
+
 // WithIgnoreValue updates the key using its current value.
 // This option can not be combined with non-empty values.
 // Returns an error if the key does not exist.