Update response to HELLO command (#102)

* Update response to HELLO command

Update response from HELLO command to match the api of redis.

Notes:
- For any protocol version other than 2 an error matching what redis
  returns for !2,3 is returned

* Add test for redis HELLO command

* Extract version building to GetVersion function

* Update contributors file

* Add HELLO command to README readiness matrix

* Revert "Add HELLO command to README readiness matrix"

This reverts commit 069f590ad0.

* Add HELLO command to api_status document

CONTRIBUTORS.md

@@ -4,3 +4,4 @@
   * Helm Chart
 * **[Ryan Russell](https://github.com/ryanrussell)**
   * Docs & Code Readability
+* **[Ali-Akber Saifee](https://github.com/alisaifee)**

doc/api_status.md

@@ -57,6 +57,7 @@ with respect to Memcached and Redis APIs.
   - [X] EXEC
   - [X] FLUSHALL
   - [X] FLUSHDB
+  - [X] HELLO
   - [X] INFO
   - [X] MULTI
   - [X] SHUTDOWN

src/facade/dragonfly_connection.cc

@@ -284,6 +284,10 @@ string Connection::GetClientInfo() const {
   return res;
 }
 
+uint32 Connection::GetClientId() const {
+  return id_;
+}
+
 io::Result<bool> Connection::CheckForHttpProto(FiberSocketBase* peer) {
   size_t last_len = 0;
   do {

src/facade/dragonfly_connection.h

@@ -70,6 +70,7 @@ class Connection : public util::Connection {
   }
 
   std::string GetClientInfo() const;
+  uint32 GetClientId() const;
 
  protected:
   void OnShutdown() override;

src/server/dragonfly_test.cc

@@ -294,6 +294,20 @@ TEST_F(DflyEngineTest, EvalResp) {
   EXPECT_THAT(resp.GetVec(), ElementsAre(IntArg(5), "foo", "17.5"));
 }
 
+TEST_F(DflyEngineTest, Hello) {
+  auto resp_no_param = Run({"hello"});
+  ASSERT_THAT(resp_no_param, ArrLen(12));
+
+  auto resp = Run({"hello", "2"});
+  ASSERT_THAT(resp, ArrLen(12));
+  EXPECT_THAT(resp.GetVec(),
+              ElementsAre("server", "redis", "version", "df-dev", "proto",
+                          IntArg(2), "id", ArgType(RespExpr::INT64), "mode",
+                          "standalone", "role", "master"));
+
+  EXPECT_THAT(Run({"hello", "3"}), ErrArg("ERR NOPROTO unsupported protocol"));
+}
+
 TEST_F(DflyEngineTest, EvalSha) {
   auto resp = Run({"script", "load", "return 5"});
   EXPECT_THAT(resp, ArgType(RespExpr::STRING));

src/server/server_family.cc

@@ -777,7 +777,7 @@ void ServerFamily::Info(CmdArgList args, ConnectionContext* cntx) {
   if (should_enter("SERVER")) {
     ADD_HEADER("# Server");
 
-    append("redis_version", StrCat("df-", kGitTag));
+    append("redis_version", GetVersion());
     append("redis_mode", "standalone");
     append("arch_bits", 64);
     append("multiplexing_api", "iouring");
@@ -950,7 +950,29 @@ void ServerFamily::Info(CmdArgList args, ConnectionContext* cntx) {
 }
 
 void ServerFamily::Hello(CmdArgList args, ConnectionContext* cntx) {
-  return (*cntx)->SendOk();
+  if (args.size() > 1) {
+    string_view proto_version = ArgS(args, 1);
+
+    if (proto_version != "2") {
+      (*cntx)->SendError("NOPROTO unsupported protocol version");
+      return;
+    }
+  }
+
+  (*cntx)->StartArray(12);
+  (*cntx)->SendBulkString("server");
+  (*cntx)->SendBulkString("redis");
+  (*cntx)->SendBulkString("version");
+  (*cntx)->SendBulkString(GetVersion());
+  (*cntx)->SendBulkString("proto");
+  (*cntx)->SendLong(2);
+  (*cntx)->SendBulkString("id");
+  (*cntx)->SendLong(cntx->owner()->GetClientId());
+  (*cntx)->SendBulkString("mode");
+  (*cntx)->SendBulkString("standalone");
+  (*cntx)->SendBulkString("role");
+  (*cntx)->SendBulkString((*ServerState::tlocal()).is_master ? "master" : "slave");
+
 }
 
 void ServerFamily::ReplicaOf(CmdArgList args, ConnectionContext* cntx) {

src/server/version.cc.in

@@ -13,4 +13,6 @@ const char kGitSha[] = "@GIT_SHA1@";
 const char kGitClean[] = "@GIT_CLEAN_DIRTY@";
 const char kBuildTime[] = "@PRJ_BUILD_TIME@";
 
+const char* GetVersion() { return "df-@GIT_VER@"; }
+
 }  // namespace dfly

src/server/version.h

@@ -11,4 +11,6 @@ extern const char kGitSha[];
 extern const char kGitClean[];
 extern const char kBuildTime[];
 
+const char* GetVersion();
+
 }  // namespace dfly