Implement the command hello

src/redis_cmd.cc

@@ -4132,6 +4132,52 @@ class CommandEcho : public Commander {
   }
 };
 
+class CommandHello final : public Commander {
+public:
+  Status Execute(Server *svr, Connection *conn, std::string *output) override {
+    std::cout << "Execute is called" << std::endl;
+    if (args_.size() == 2) {
+      int64_t protocol;
+      try {
+        protocol = std::stoll(args_[1]);
+      } catch (std::exception& e) {
+        // std::invalid_argument or std::out_of_range
+        *output = Redis::Error("Protocol version is not an integer or out of range");
+        return Status::OK();
+      }
+
+      // In redis, it will check protocol < 2 or protocol > 3,
+      // but kvrocks only supports REPL2 by now.
+      if (protocol != 2) {
+        *output = Redis::Error("-NOPROTO unsupported protocol version");
+        return Status::OK();
+      }
+    }
+
+    // TODO(mapleFU): do we need to implement auth and setname?
+
+    std::vector<std::string> output_list;
+    output_list.push_back(Redis::BulkString("server"));
+    output_list.push_back(Redis::BulkString("redis"));
+    output_list.push_back(Redis::BulkString("version"));
+    output_list.push_back(Redis::BulkString("")); // TODO(mapleFU): change it to the real redis version
+    output_list.push_back(Redis::BulkString("proto"));
+    output_list.push_back(Redis::Integer(2));
+    output_list.push_back(Redis::BulkString("id"));
+    output_list.push_back(Redis::Integer(2)); // TODO(mapleFU): fix this
+
+    output_list.push_back(Redis::BulkString("mode"));
+    // Note: sentinel is not supported.
+    if (svr->GetConfig()->cluster_enabled) {
+      output_list.push_back(Redis::BulkString("cluster"));
+    } else {
+      output_list.push_back(Redis::BulkString("standalone"));
+    }
+    *output = Redis::Array(output_list);
+    return Status::OK();
+  }
+};
+
 class CommandScanBase : public Commander {
  public:
   Status ParseMatchAndCountParam(const std::string &type, std::string value) {
@@ -5680,6 +5726,7 @@ CommandAttributes redisCommandTable[] = {
     ADD_CMD("debug", -2, "read-only exclusive", 0, 0, 0, CommandDebug),
     ADD_CMD("command", -1, "read-only", 0, 0, 0, CommandCommand),
     ADD_CMD("echo", 2, "read-only", 0, 0, 0, CommandEcho),
+    ADD_CMD("hello", -1, "read-only", 0, 0, 0, CommandHello),
 
     ADD_CMD("ttl", 2, "read-only", 1, 1, 1, CommandTTL),
     ADD_CMD("pttl", 2, "read-only", 1, 1, 1, CommandPTTL),

src/redis_reply.cc

@@ -45,36 +45,43 @@ std::string MultiLen(int64_t len) {
   return "*"+std::to_string(len)+"\r\n";
 }
 
-std::string MultiBulkString(std::vector<std::string> values, bool output_nil_for_empty_string) {
+std::string MultiBulkString(const std::vector<std::string>& values, bool output_nil_for_empty_string) {
+  std::vector<std::string> copiedStrings;
+  copiedStrings.resize(values.size());
   for (size_t i = 0; i < values.size(); i++) {
     if (values[i].empty() && output_nil_for_empty_string) {
-      values[i] = NilString();
+      copiedStrings[i] = NilString();
     }  else {
-      values[i] = BulkString(values[i]);
+      copiedStrings[i] = BulkString(values[i]);
     }
   }
-  return Array(values);
+  return Array(copiedStrings);
 }
 
 
-std::string MultiBulkString(std::vector<std::string> values, const std::vector<rocksdb::Status> &statuses) {
+std::string MultiBulkString(const std::vector<std::string>& values, const std::vector<rocksdb::Status> &statuses) {
+  std::vector<std::string> copiedStrings;
+  copiedStrings.resize(values.size());
   for (size_t i = 0; i < values.size(); i++) {
     if (i < statuses.size() && !statuses[i].ok()) {
-      values[i] = NilString();
+      copiedStrings[i] = NilString();
     } else {
-      values[i] = BulkString(values[i]);
+      copiedStrings[i] = BulkString(values[i]);
     }
   }
-  return Array(values);
+  return Array(copiedStrings);
 }
-std::string Array(std::vector<std::string> list) {
+
+std::string Array(const std::vector<std::string>& list) {
   std::string::size_type n = std::accumulate(
     list.begin(), list.end(), std::string::size_type(0),
     [] ( std::string::size_type n, const std::string &s ) { return ( n += s.size() ); });
   std::string result = "*" + std::to_string(list.size()) + CRLF;
-  result.reserve(n);
-  return std::accumulate(list.begin(), list.end(), result,
+  std::string::size_type final_size = result.size() + n;
+  result.reserve(final_size);
+  auto s = std::accumulate(list.begin(), list.end(), result,
     [](std::string &dest, std::string const &item) -> std::string& {dest += item; return dest;});
+  return s;
 }
 
 std::string Command2RESP(const std::vector<std::string> &cmd_args) {

src/redis_reply.h

@@ -35,8 +35,8 @@ std::string Integer(int64_t data);
 std::string BulkString(const std::string &data);
 std::string NilString();
 std::string MultiLen(int64_t len);
-std::string Array(std::vector<std::string> list);
-std::string MultiBulkString(std::vector<std::string> values, bool output_nil_for_empty_string = true);
-std::string MultiBulkString(std::vector<std::string> values, const std::vector<rocksdb::Status> &statuses);
+std::string Array(const std::vector<std::string>& list);
+std::string MultiBulkString(const std::vector<std::string>& values, bool output_nil_for_empty_string = true);
+std::string MultiBulkString(const std::vector<std::string>& values, const std::vector<rocksdb::Status> &statuses);
 std::string Command2RESP(const std::vector<std::string> &cmd_args);
 }  // namespace Redis

src/util.cc

@@ -344,7 +344,7 @@ Status DecimalStringToNum(const std::string &str, int64_t *n, int64_t min, int64
   try {
     *n = static_cast<int64_t>(std::stoll(str));
     if (max > min && (*n < min || *n > max)) {
-      return Status(Status::NotOK, "value shoud between "+std::to_string(min)+" and "+std::to_string(max));
+      return Status(Status::NotOK, "value should between "+std::to_string(min)+" and "+std::to_string(max));
     }
   } catch (std::exception &e) {
     return Status(Status::NotOK, "value is not an integer or out of range");
@@ -356,7 +356,7 @@ Status OctalStringToNum(const std::string &str, int64_t *n, int64_t min, int64_t
   try {
     *n = static_cast<int64_t>(std::stoll(str, nullptr, 8));
     if (max > min && (*n < min || *n > max)) {
-      return Status(Status::NotOK, "value shoud between "+std::to_string(min)+" and "+std::to_string(max));
+      return Status(Status::NotOK, "value should between "+std::to_string(min)+" and "+std::to_string(max));
     }
   } catch (std::exception &e) {
     return Status(Status::NotOK, "value is not an integer or out of range");