diff --git a/src/Client.cpp b/src/Client.cpp
index 1265344d..93992e32 100644
--- a/src/Client.cpp
+++ b/src/Client.cpp
@@ -41,6 +41,7 @@ err_code_t Client::get(const char* const* keys, const size_t* keyLens, size_t nK
   dispatchRetrieval(GET_OP, keys, keyLens, nKeys);
   err_code_t rv = waitPoll();
   collectRetrievalResult(results, nResults);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -50,6 +51,7 @@ err_code_t Client::gets(const char* const* keys, const size_t* keyLens, size_t n
   dispatchRetrieval(GETS_OP, keys, keyLens, nKeys);
   err_code_t rv = waitPoll();
   collectRetrievalResult(results, nResults);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -101,6 +103,7 @@ err_code_t Client::M(const char* const* keys, const size_t* keyLens, \
                   valLens, nItems); \
   err_code_t rv = waitPoll(); \
   collectMessageResult(results, nResults); \
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv)); \
   return rv;\
 }
 
@@ -118,6 +121,7 @@ err_code_t Client::_delete(const char* const* keys, const size_t* keyLens,
   dispatchDeletion(keys, keyLens, noreply, nItems);
   err_code_t rv = waitPoll();
   collectMessageResult(results, nResults);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -144,6 +148,7 @@ err_code_t Client::version(broadcast_result_t** results, size_t* nHosts) {
   broadcastCommand(keywords::kVERSION, 7);
   err_code_t rv = waitPoll();
   collectBroadcastResult(results, nHosts);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -152,6 +157,7 @@ err_code_t Client::quit() {
   broadcastCommand(keywords::kQUIT, 4, true);
   err_code_t rv = waitPoll();
   markDeadAll(NULL, keywords::kCONN_QUIT);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -160,6 +166,7 @@ err_code_t Client::stats(broadcast_result_t** results, size_t* nHosts) {
   broadcastCommand(keywords::kSTATS, 5);
   err_code_t rv = waitPoll();
   collectBroadcastResult(results, nHosts);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -170,6 +177,7 @@ err_code_t Client::touch(const char* const* keys, const size_t* keyLens,
   dispatchTouch(keys, keyLens, exptime, noreply, nItems);
   err_code_t rv = waitPoll();
   collectMessageResult(results, nResults);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -193,6 +201,7 @@ err_code_t Client::incr(const char* key, const size_t keyLen, const uint64_t del
   dispatchIncrDecr(INCR_OP, key, keyLen, delta, noreply);
   err_code_t rv = waitPoll();
   collectUnsignedResult(results, nResults);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
@@ -203,6 +212,7 @@ err_code_t Client::decr(const char* key, const size_t keyLen, const uint64_t del
   dispatchIncrDecr(DECR_OP, key, keyLen, delta, noreply);
   err_code_t rv = waitPoll();
   collectUnsignedResult(results, nResults);
+  log_info_if(rv != RET_OK, "[I: %p], err code %s", this, errCodeToString(rv));
   return rv;
 }
 
diff --git a/src/Connection.cpp b/src/Connection.cpp
index 70837dcf..2a1dce07 100644
--- a/src/Connection.cpp
+++ b/src/Connection.cpp
@@ -164,18 +164,15 @@ void Connection::close() {
 
 bool Connection::tryReconnect() {
   if (!m_alive) {
-    time_t now;
-    time(&now);
+    time_t now = time(NULL);
     if (now >= m_deadUntil) {
       int rv = this->connect();
       if (rv == 0) {
-        if (m_deadUntil > 0) {
-          log_info("Connection %s is back to live at %lu", m_name, now);
-        }
+        log_info_if(m_deadUntil > 0, "[I: %p] %s is back to live at %lu", this, m_name, now);
         m_deadUntil = 0;
       } else {
         m_deadUntil = now + m_retryTimeout;
-        // log_info("%s is still dead", m_name);
+        log_info("[I: %p] %s is still dead", this, m_name);
       }
     }
   }
@@ -188,14 +185,16 @@ void Connection::markDead(const char* reason, int delay) {
     m_deadUntil += delay; // check after `delay` seconds, default 0
     this->close();
     if (strcmp(reason, keywords::kCONN_QUIT) != 0) {
-      log_warn("Connection %s is dead(reason: %s, delay: %d), next check at %lu",
-               m_name, reason, delay, m_deadUntil);
+      log_warn("[I: %p] %s is dead(reason: %s, delay: %d), next check at %lu",
+               this, m_name, reason, delay, m_deadUntil);
+#ifndef NDEBUG
       std::queue<struct iovec>* q = m_parser.getRequestKeys();
       if (!q->empty()) {
-        log_warn("%s: first request key: %.*s", m_name,
+        log_debug("[I: %p] %s first request key: %.*s", this, m_name,
                  static_cast<int>(q->front().iov_len),
                  static_cast<char*>(q->front().iov_base));
       }
+#endif
     }
   }
 }
@@ -209,6 +208,7 @@ void Connection::takeBuffer(const char* const buf, size_t buf_len) {
 }
 
 void Connection::addRequestKey(const char* const key, const size_t len) {
+  log_debug("[I: %p] %s add request key: %.*s", this, m_name, static_cast<int>(len), key);
   m_parser.addRequestKey(key, len);
 }
 
@@ -261,7 +261,8 @@ ssize_t Connection::recv() {
   size_t bufferSizeAvailable = m_buffer_reader->prepareWriteBlock(bufferSize);
   char* writePtr = m_buffer_reader->getWritePtr();
   ssize_t bufferSizeActual = ::recv(m_socketFd, writePtr, bufferSizeAvailable, 0);
-  // log_info("%p recv(%lu) %.*s", this, bufferSizeActual, (int)bufferSizeActual, writePtr);
+  log_debug("[I: %p] %s recv(%lu)", this, m_name, bufferSizeActual);
+  // log_debug("[I: %p] %.*s", (int)bufferSizeActual, writePtr);
   if (bufferSizeActual > 0) {
     m_buffer_reader->commitWrite(bufferSizeActual);
   }
diff --git a/src/ConnectionPool.cpp b/src/ConnectionPool.cpp
index f4931dc8..2d9384ae 100644
--- a/src/ConnectionPool.cpp
+++ b/src/ConnectionPool.cpp
@@ -204,6 +204,7 @@ void ConnectionPool::dispatchStorage(op_code_t op,
       conn->getMessageResults()->reserve(conn->m_counter);
     }
   }
+  log_debug("[I: %p] after dispatchStorage, m_nActiveConn: %d", this, m_nActiveConn);
 }
 
 
@@ -248,7 +249,7 @@ void ConnectionPool::dispatchRetrieval(op_code_t op, const char* const* keys,
       conn->getRetrievalResults()->reserve(conn->m_counter);
     }
   }
-  // log_debug("after dispatchRetrieval: m_nActiveConn: %d", this->m_nActiveConn);
+  log_debug("[I: %p] after dispatchRetrieval, m_nActiveConn: %d", this, m_nActiveConn);
 }
 
 
@@ -404,7 +405,7 @@ err_code_t ConnectionPool::waitPoll() {
     if (m_nInvalidKey > 0) {
       return RET_INVALID_KEY_ERR;
     } else {
-      // hard server error
+      log_debug("[I: %p] hard server error", this);
       return RET_MC_SERVER_ERR;
     }
   }
@@ -480,6 +481,7 @@ err_code_t ConnectionPool::waitPoll() {
           // POLLIN recv
           ssize_t nRecv = conn->recv();
           if (nRecv == -1 || nRecv == 0) {
+            log_warn("[I: %p] recv_error, Connection(%p): %s, nRecv: %zd", this, conn, conn->name(), nRecv);
             markDeadConn(conn, keywords::kRECV_ERROR, pollfd_ptr);
             ret_code = RET_RECV_ERR;
             --m_nActiveConn;
@@ -625,6 +627,7 @@ void ConnectionPool::setRetryTimeout(int timeout) {
 
 
 void ConnectionPool::markDeadAll(pollfd_t* pollfds, const char* reason) {
+  log_warn("[I: %p] markDeadAll(reason: %s), m_nActiveConn: %d", this, reason, m_nActiveConn);
   nfds_t fd_idx = 0;
   for (std::vector<Connection*>::iterator it = m_activeConns.begin();
       it != m_activeConns.end();
@@ -643,6 +646,7 @@ void ConnectionPool::markDeadAll(pollfd_t* pollfds, const char* reason) {
 
 
 void ConnectionPool::markDeadConn(Connection* conn, const char* reason, pollfd_t* fd_ptr) {
+  log_warn("[I: %p] markDeadConn(reason: %s), Connection(%p): %s", this, reason, conn, conn->name());
   conn->markDead(reason);
   fd_ptr->events &= ~POLLOUT & ~POLLIN;
   fd_ptr->fd = conn->socketFd();
diff --git a/src/HashkitKetama.cpp b/src/HashkitKetama.cpp
index 1bc45c46..707daf3c 100644
--- a/src/HashkitKetama.cpp
+++ b/src/HashkitKetama.cpp
@@ -133,7 +133,7 @@ std::vector<continuum_item_t>::iterator KetamaSelector::getServerIt(const char*
         }
       } while (--max_iter);
       if (max_iter == 0) {
-        log_warn("no server is avaliable(alive) for key: \"%.*s\"", static_cast<int>(key_len), key);
+        log_warn("no server is available(alive) for key: \"%.*s\"", static_cast<int>(key_len), key);
         return m_continuum.end();
       }
     } else {
diff --git a/src/Parser.cpp b/src/Parser.cpp
index 7004d8df..d5635ede 100644
--- a/src/Parser.cpp
+++ b/src/Parser.cpp
@@ -63,7 +63,6 @@ void PacketParser::setBufferReader(BufferReader* reader) {
 
 
 void PacketParser::addRequestKey(const char* const key, const size_t len) {
-  // log_info("add request key: %.*s", static_cast<int>(len), key);
   struct iovec iov = {const_cast<char*>(key), len};
   m_requestKeys.push(iov);
 }