feat: add lock.proto (#3)

proto/greptime/v1/meta/lock.proto

@@ -0,0 +1,43 @@
+syntax = "proto3";
+
+package greptime.v1.meta;
+
+import "greptime/v1/meta/common.proto";
+
+service Lock {
+  // Lock acquires a distributed shared lock on a given named lock. On success, it
+  // will return a unique key that exists so long as the lock is held by the caller.
+  rpc Lock(LockRequest) returns (LockResponse);
+
+  // Unlock takes a key returned by Lock and releases the hold on lock.
+  rpc Unlock(UnlockRequest) returns (UnlockResponse);
+}
+
+message LockRequest {
+  RequestHeader header = 1;
+
+  // Name is the identifier for the distributed shared lock to be acquired.
+  bytes name = 2;
+
+  // If the expiration time is exceeded and currently holds the lock, the lock is
+  // aytomatically released. The unit is second.
+  int64 expire = 3;
+}
+
+message LockResponse {
+  ResponseHeader header = 1;
+
+  // Key will exist as long as lock is held by the caller.
+  bytes key = 2;
+}
+
+message UnlockRequest {
+  RequestHeader header = 1;
+
+  // key is the lock ownership key granted by Lock.
+  bytes key = 2;
+}
+
+message UnlockResponse {
+  ResponseHeader header = 1;
+}