X-Git-Url: https://git.m6w6.name/?a=blobdiff_plain;f=libmemcached%2Fio.cc;h=837959da5db6696765036ffe5787741c8235658c;hb=674c7578fa870c3b57e81e765c355ce98434b310;hp=f77a097325c84d0c166c5f4149c8d793c54427d5;hpb=7abcaebdc4c3dd11b779eaef58a7371fb82ae888;p=m6w6%2Flibmemcached

diff --git a/libmemcached/io.cc b/libmemcached/io.cc
index f77a0973..837959da 100644
--- a/libmemcached/io.cc
+++ b/libmemcached/io.cc
@@ -38,126 +38,26 @@
 
 
 #include <libmemcached/common.h>
-#include <cassert>
+
+void initialize_binary_request(org::libmemcached::Instance* server, protocol_binary_request_header& header)
+{
+  server->request_id++;
+  header.request.magic= PROTOCOL_BINARY_REQ;
+  header.request.opaque= htons(server->request_id);
+}
 
 enum memc_read_or_write {
   MEM_READ,
   MEM_WRITE
 };
 
-static ssize_t io_flush(memcached_server_write_instance_st ptr,
-                        const bool with_flush,
-                        memcached_return_t *error);
-static void increment_udp_message_id(memcached_server_write_instance_st ptr);
-
-static memcached_return_t io_wait(memcached_server_write_instance_st ptr,
-                                  memc_read_or_write read_or_write)
-{
-  struct pollfd fds;
-  fds.fd= ptr->fd;
-  fds.events= POLLIN;
-
-  if (read_or_write == MEM_WRITE) /* write */
-  {
-    fds.events= POLLOUT;
-    WATCHPOINT_SET(ptr->io_wait_count.write++);
-  }
-  else
-  {
-    WATCHPOINT_SET(ptr->io_wait_count.read++);
-  }
-
-  /*
-   ** We are going to block on write, but at least on Solaris we might block
-   ** on write if we haven't read anything from our input buffer..
-   ** Try to purge the input buffer if we don't do any flow control in the
-   ** application layer (just sending a lot of data etc)
-   ** The test is moved down in the purge function to avoid duplication of
-   ** the test.
- */
-  if (read_or_write == MEM_WRITE)
-  {
-    memcached_return_t rc= memcached_purge(ptr);
-    if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
-    {
-      return MEMCACHED_FAILURE;
-    }
-  }
-
-  if (ptr->root->poll_timeout == 0) // Mimic 0 causes timeout behavior (not all platforms do this)
-  {
-    return memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
-  }
-
-  size_t loop_max= 5;
-  while (--loop_max) // While loop is for ERESTART or EINTR
-  {
-
-    int error= poll(&fds, 1, ptr->root->poll_timeout);
-    switch (error)
-    {
-    case 1: // Success!
-      WATCHPOINT_IF_LABELED_NUMBER(read_or_write && loop_max < 4, "read() times we had to loop, decremented down from 5", loop_max);
-      WATCHPOINT_IF_LABELED_NUMBER(!read_or_write && loop_max < 4, "write() times we had to loop, decremented down from 5", loop_max);
-
-      return MEMCACHED_SUCCESS;
-
-    case 0: // Timeout occured, we let the while() loop do its thing.
-      return memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
-
-    default:
-      WATCHPOINT_ERRNO(get_socket_errno());
-      switch (get_socket_errno())
-      {
-#ifdef TARGET_OS_LINUX
-      case ERESTART:
-#endif
-      case EINTR:
-        break;
-
-      case EFAULT:
-      case ENOMEM:
-        return memcached_set_error(*ptr, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT);
-
-      case EINVAL:
-        return memcached_set_error(*ptr, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT, memcached_literal_param("RLIMIT_NOFILE exceeded, or if OSX the timeout value was invalid"));
-
-      default:
-        if (fds.revents & POLLERR)
-        {
-          int err;
-          socklen_t len= sizeof (err);
-          (void)getsockopt(ptr->fd, SOL_SOCKET, SO_ERROR, &err, &len);
-          memcached_set_errno(*ptr, (err == 0) ? get_socket_errno() : err, MEMCACHED_AT);
-        }
-        else
-        {
-          memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-        }
-        memcached_quit_server(ptr, true);
-
-        return memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-      }
-    }
-  }
-
-  memcached_quit_server(ptr, true);
-
-  return memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-}
-
-memcached_return_t memcached_io_wait_for_write(memcached_server_write_instance_st ptr)
-{
-  return io_wait(ptr, MEM_WRITE);
-}
-
 /**
  * Try to fill the input buffer for a server with as much
  * data as possible.
  *
  * @param ptr the server to pack
  */
-static bool repack_input_buffer(memcached_server_write_instance_st ptr)
+static bool repack_input_buffer(org::libmemcached::Instance* ptr)
 {
   if (ptr->read_ptr != ptr->read_buffer)
   {
@@ -174,24 +74,27 @@ static bool repack_input_buffer(memcached_server_write_instance_st ptr)
   {
     do {
       /* Just try a single read to grab what's available */
-      ssize_t nr= recv(ptr->fd,
-                       ptr->read_ptr + ptr->read_data_length,
-                       MEMCACHED_MAX_BUFFER - ptr->read_data_length,
-                       MSG_DONTWAIT);
-
-      switch (nr)
+      ssize_t nr;
+      if ((nr= recv(ptr->fd,
+                    ptr->read_ptr + ptr->read_data_length,
+                    MEMCACHED_MAX_BUFFER - ptr->read_data_length,
+                    MSG_DONTWAIT)) <= 0)
       {
-      case SOCKET_ERROR:
+        if (nr == 0)
+        {
+          memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT);
+        }
+        else
         {
           switch (get_socket_errno())
           {
           case EINTR:
             continue;
 
+#if EWOULDBLOCK != EAGAIN
           case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-          case EAGAIN:
 #endif
+          case EAGAIN:
 #ifdef TARGET_OS_LINUX
           case ERESTART:
 #endif
@@ -201,24 +104,19 @@ static bool repack_input_buffer(memcached_server_write_instance_st ptr)
             memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
           }
         }
-        break;
 
-      case 0: // Shutdown on the socket has occurred
-        {
-          memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT);
-        }
         break;
+      }
+      else // We read data, append to our read buffer
+      {
+        ptr->read_data_length+= size_t(nr);
+        ptr->read_buffer_length+= size_t(nr);
 
-      default:
-        {
-          ptr->read_data_length+= size_t(nr);
-          ptr->read_buffer_length+= size_t(nr);
-          return true;
-        }
-        break;
+        return true;
       }
-    } while (0);
+    } while (false);
   }
+
   return false;
 }
 
@@ -232,13 +130,13 @@ static bool repack_input_buffer(memcached_server_write_instance_st ptr)
  * @param ptr the server to star processing iput messages for
  * @return true if we processed anything, false otherwise
  */
-static bool process_input_buffer(memcached_server_write_instance_st ptr)
+static bool process_input_buffer(org::libmemcached::Instance* ptr)
 {
   /*
    ** We might be able to process some of the response messages if we
    ** have a callback set up
  */
-  if (ptr->root->callbacks != NULL && ptr->root->flags.use_udp == false)
+  if (ptr->root->callbacks != NULL)
   {
     /*
      * We might have responses... try to read them out and fire
@@ -249,10 +147,8 @@ static bool process_input_buffer(memcached_server_write_instance_st ptr)
     memcached_set_processing_input((memcached_st *)ptr->root, true);
 
     char buffer[MEMCACHED_DEFAULT_COMMAND_SIZE];
-    memcached_return_t error;
     memcached_st *root= (memcached_st *)ptr->root;
-    error= memcached_response(ptr, buffer, sizeof(buffer),
-                              &root->result);
+    memcached_return_t error= memcached_response(ptr, buffer, sizeof(buffer), &root->result);
 
     memcached_set_processing_input(root, false);
 
@@ -262,7 +158,9 @@ static bool process_input_buffer(memcached_server_write_instance_st ptr)
       {
         error= (*cb.callback[x])(ptr->root, &root->result, cb.context);
         if (error != MEMCACHED_SUCCESS)
+        {
           break;
+        }
       }
 
       /* @todo what should I do with the error message??? */
@@ -274,96 +172,341 @@ static bool process_input_buffer(memcached_server_write_instance_st ptr)
   return false;
 }
 
-memcached_return_t memcached_io_read(memcached_server_write_instance_st ptr,
-                                     void *buffer, size_t length, ssize_t *nread)
+static memcached_return_t io_wait(org::libmemcached::Instance* ptr,
+                                  const memc_read_or_write read_or_write)
 {
-  assert(ptr); // Programmer error
-  char *buffer_ptr= static_cast<char *>(buffer);
+  /*
+   ** We are going to block on write, but at least on Solaris we might block
+   ** on write if we haven't read anything from our input buffer..
+   ** Try to purge the input buffer if we don't do any flow control in the
+   ** application layer (just sending a lot of data etc)
+   ** The test is moved down in the purge function to avoid duplication of
+   ** the test.
+ */
+  if (read_or_write == MEM_WRITE)
+  {
+    if (memcached_purge(ptr) == false)
+    {
+      return MEMCACHED_FAILURE;
+    }
+  }
 
-  if (ptr->fd == INVALID_SOCKET)
+  struct pollfd fds;
+  fds.fd= ptr->fd;
+  fds.events= POLLIN;
+  fds.revents= 0;
+
+  if (read_or_write == MEM_WRITE) /* write */
   {
-    assert(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO));
-    return MEMCACHED_CONNECTION_FAILURE;
+    fds.events= POLLOUT;
+    ptr->io_wait_count.write++;
+  }
+  else
+  {
+    ptr->io_wait_count.read++;
   }
 
-  while (length)
+  if (ptr->root->poll_timeout == 0) // Mimic 0 causes timeout behavior (not all platforms do this)
   {
-    if (not ptr->read_buffer_length)
+    ptr->io_wait_count.timeouts++;
+    return memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
+  }
+
+  size_t loop_max= 5;
+  while (--loop_max) // While loop is for ERESTART or EINTR
+  {
+    int active_fd= poll(&fds, 1, ptr->root->poll_timeout);
+
+    if (active_fd >= 1)
     {
-      ssize_t data_read;
-      do
+      assert_msg(active_fd == 1 , "poll() returned an unexpected number of active file descriptors");
+      if (fds.revents & POLLIN or fds.revents & POLLOUT)
       {
-        data_read= recv(ptr->fd, ptr->read_buffer, MEMCACHED_MAX_BUFFER, MSG_DONTWAIT);
-        if (data_read == SOCKET_ERROR)
+        return MEMCACHED_SUCCESS;
+      }
+
+      if (fds.revents & POLLHUP)
+      {
+        return memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
+                                   memcached_literal_param("poll() detected hang up"));
+      }
+
+      if (fds.revents & POLLERR)
+      {
+        int local_errno= EINVAL;
+        int err;
+        socklen_t len= sizeof (err);
+        if (getsockopt(ptr->fd, SOL_SOCKET, SO_ERROR, &err, &len) == 0)
         {
-          switch (get_socket_errno())
+          if (err == 0) // treat this as EINTR
           {
-          case EINTR: // We just retry
             continue;
+          }
+          local_errno= err;
+        }
+        memcached_quit_server(ptr, true);
+        return memcached_set_errno(*ptr, local_errno, MEMCACHED_AT,
+                                   memcached_literal_param("poll() returned POLLHUP"));
+      }
+      
+      return memcached_set_error(*ptr, MEMCACHED_FAILURE, MEMCACHED_AT, memcached_literal_param("poll() returned a value that was not dealt with"));
+    }
 
-          case ETIMEDOUT: // OSX
-          case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-          case EAGAIN:
-#endif
+    if (active_fd == 0)
+    {
+      ptr->io_wait_count.timeouts++;
+      return memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
+    }
+
+    // Only an error should result in this code being called.
+    int local_errno= get_socket_errno(); // We cache in case memcached_quit_server() modifies errno
+    assert_msg(active_fd == -1 , "poll() returned an unexpected value");
+    switch (local_errno)
+    {
 #ifdef TARGET_OS_LINUX
-          case ERESTART:
+    case ERESTART:
 #endif
-            if (memcached_success(io_wait(ptr, MEM_READ)))
-            {
-              continue;
-            }
-            return MEMCACHED_IN_PROGRESS;
-
-            /* fall through */
-
-          case ENOTCONN: // Programmer Error
-            WATCHPOINT_ASSERT(0);
-          case ENOTSOCK:
-            WATCHPOINT_ASSERT(0);
-          case EBADF:
-            assert(ptr->fd != INVALID_SOCKET);
-          case EINVAL:
-          case EFAULT:
-          case ECONNREFUSED:
-          default:
-            {
-              memcached_quit_server(ptr, true);
-              *nread= -1;
-              return memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-            }
-          }
-        }
-        else if (data_read == 0)
+    case EINTR:
+      continue;
+
+    case EFAULT:
+    case ENOMEM:
+      memcached_set_error(*ptr, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT);
+
+    case EINVAL:
+      memcached_set_error(*ptr, MEMCACHED_MEMORY_ALLOCATION_FAILURE, MEMCACHED_AT, memcached_literal_param("RLIMIT_NOFILE exceeded, or if OSX the timeout value was invalid"));
+
+    default:
+      memcached_set_errno(*ptr, local_errno, MEMCACHED_AT, memcached_literal_param("poll"));
+    }
+
+    break;
+  }
+
+  memcached_quit_server(ptr, true);
+
+  if (memcached_has_error(ptr))
+  {
+    return memcached_instance_error_return(ptr);
+  }
+
+  return memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
+                             memcached_literal_param("number of attempts to call io_wait() failed"));
+}
+
+static bool io_flush(org::libmemcached::Instance* ptr,
+                     const bool with_flush,
+                     memcached_return_t& error)
+{
+  /*
+   ** We might want to purge the input buffer if we haven't consumed
+   ** any output yet... The test for the limits is the purge is inline
+   ** in the purge function to avoid duplicating the logic..
+ */
+  {
+    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+
+    if (memcached_purge(ptr) == false)
+    {
+      return false;
+    }
+  }
+  char *local_write_ptr= ptr->write_buffer;
+  size_t write_length= ptr->write_buffer_offset;
+
+  error= MEMCACHED_SUCCESS;
+
+  WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+
+  /* Looking for memory overflows */
+#if defined(DEBUG)
+  if (write_length == MEMCACHED_MAX_BUFFER)
+    WATCHPOINT_ASSERT(ptr->write_buffer == local_write_ptr);
+  WATCHPOINT_ASSERT((ptr->write_buffer + MEMCACHED_MAX_BUFFER) >= (local_write_ptr + write_length));
+#endif
+
+  while (write_length)
+  {
+    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+    WATCHPOINT_ASSERT(write_length > 0);
+
+    int flags= with_flush ? MSG_NOSIGNAL|MSG_DONTWAIT : MSG_NOSIGNAL|MSG_DONTWAIT|MSG_MORE;
+    ssize_t sent_length= ::send(ptr->fd, local_write_ptr, write_length, flags);
+
+    if (sent_length == SOCKET_ERROR)
+    {
+#if 0 // @todo I should look at why we hit this bit of code hard frequently
+      WATCHPOINT_ERRNO(get_socket_errno());
+      WATCHPOINT_NUMBER(get_socket_errno());
+#endif
+      switch (get_socket_errno())
+      {
+      case ENOBUFS:
+        continue;
+
+#if EWOULDBLOCK != EAGAIN
+      case EWOULDBLOCK:
+#endif
+      case EAGAIN:
         {
           /*
-            EOF. Any data received so far is incomplete
-            so discard it. This always reads by byte in case of TCP
-            and protocol enforcement happens at memcached_response()
-            looking for '\n'. We do not care for UDB which requests 8 bytes
-            at once. Generally, this means that connection went away. Since
-            for blocking I/O we do not return 0 and for non-blocking case
-            it will return EGAIN if data is not immediatly available.
-          */
-          WATCHPOINT_STRING("We had a zero length recv()");
-          assert(0);
+           * We may be blocked on write because the input buffer
+           * is full. Let's check if we have room in our input
+           * buffer for more data and retry the write before
+           * waiting..
+         */
+          if (repack_input_buffer(ptr) or process_input_buffer(ptr))
+          {
+            continue;
+          }
+
+          memcached_return_t rc= io_wait(ptr, MEM_WRITE);
+          if (memcached_success(rc))
+          {
+            continue;
+          }
+          else if (rc == MEMCACHED_TIMEOUT)
+          {
+            return false;
+          }
+
           memcached_quit_server(ptr, true);
-          *nread= -1;
-          return memcached_set_error(*ptr, MEMCACHED_UNKNOWN_READ_FAILURE, MEMCACHED_AT);
+          error= memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
+          return false;
         }
-      } while (data_read <= 0);
+      case ENOTCONN:
+      case EPIPE:
+      default:
+        memcached_quit_server(ptr, true);
+        error= memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
+        WATCHPOINT_ASSERT(ptr->fd == INVALID_SOCKET);
+        return false;
+      }
+    }
+
+    ptr->io_bytes_sent+= uint32_t(sent_length);
+
+    local_write_ptr+= sent_length;
+    write_length-= uint32_t(sent_length);
+  }
+
+  WATCHPOINT_ASSERT(write_length == 0);
+  ptr->write_buffer_offset= 0;
+
+  return true;
+}
+
+memcached_return_t memcached_io_wait_for_write(org::libmemcached::Instance* ptr)
+{
+  return io_wait(ptr, MEM_WRITE);
+}
+
+static memcached_return_t _io_fill(org::libmemcached::Instance* ptr)
+{
+  ssize_t data_read;
+  do
+  {
+    data_read= ::recv(ptr->fd, ptr->read_buffer, MEMCACHED_MAX_BUFFER, MSG_DONTWAIT);
+    if (data_read == SOCKET_ERROR)
+    {
+      switch (get_socket_errno())
+      {
+      case EINTR: // We just retry
+        continue;
+
+      case ETIMEDOUT: // OSX
+#if EWOULDBLOCK != EAGAIN
+      case EWOULDBLOCK:
+#endif
+      case EAGAIN:
+#ifdef TARGET_OS_LINUX
+      case ERESTART:
+#endif
+        {
+          memcached_return_t io_wait_ret;
+          if (memcached_success(io_wait_ret= io_wait(ptr, MEM_READ)))
+          {
+            continue;
+          }
+
+          return io_wait_ret;
+        }
+
+        /* fall through */
+
+      case ENOTCONN: // Programmer Error
+        WATCHPOINT_ASSERT(0);
+      case ENOTSOCK:
+        WATCHPOINT_ASSERT(0);
+      case EBADF:
+        assert_msg(ptr->fd != INVALID_SOCKET, "Programmer error, invalid socket");
+      case EINVAL:
+      case EFAULT:
+      case ECONNREFUSED:
+      default:
+        memcached_quit_server(ptr, true);
+        memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
+        break;
+      }
 
-      ptr->io_bytes_sent = 0;
-      ptr->read_data_length= (size_t) data_read;
-      ptr->read_buffer_length= (size_t) data_read;
-      ptr->read_ptr= ptr->read_buffer;
+      return memcached_instance_error_return(ptr);
     }
+    else if (data_read == 0)
+    {
+      /*
+        EOF. Any data received so far is incomplete
+        so discard it. This always reads by byte in case of TCP
+        and protocol enforcement happens at memcached_response()
+        looking for '\n'. We do not care for UDB which requests 8 bytes
+        at once. Generally, this means that connection went away. Since
+        for blocking I/O we do not return 0 and for non-blocking case
+        it will return EGAIN if data is not immediatly available.
+      */
+      memcached_quit_server(ptr, true);
+      return memcached_set_error(*ptr, MEMCACHED_CONNECTION_FAILURE, MEMCACHED_AT, 
+                                 memcached_literal_param("::rec() returned zero, server has disconnected"));
+    }
+    ptr->io_wait_count._bytes_read+= data_read;
+  } while (data_read <= 0);
 
-    if (length > 1)
+  ptr->io_bytes_sent= 0;
+  ptr->read_data_length= (size_t) data_read;
+  ptr->read_buffer_length= (size_t) data_read;
+  ptr->read_ptr= ptr->read_buffer;
+
+  return MEMCACHED_SUCCESS;
+}
+
+memcached_return_t memcached_io_read(org::libmemcached::Instance* ptr,
+                                     void *buffer, size_t length, ssize_t& nread)
+{
+  assert(memcached_is_udp(ptr->root) == false);
+  assert_msg(ptr, "Programmer error, memcached_io_read() recieved an invalid Instance"); // Programmer error
+  char *buffer_ptr= static_cast<char *>(buffer);
+
+  if (ptr->fd == INVALID_SOCKET)
+  {
+#if 0
+    assert_msg(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Programmer error, invalid socket state");
+#endif
+    return MEMCACHED_CONNECTION_FAILURE;
+  }
+
+  while (length)
+  {
+    if (ptr->read_buffer_length == 0)
     {
-      size_t difference;
+      memcached_return_t io_fill_ret;
+      if (memcached_fatal(io_fill_ret= _io_fill(ptr)))
+      {
+        nread= -1;
+        return io_fill_ret;
+      }
+    }
 
-      difference= (length > ptr->read_buffer_length) ? ptr->read_buffer_length : length;
+    if (length > 1)
+    {
+      size_t difference= (length > ptr->read_buffer_length) ? ptr->read_buffer_length : length;
 
       memcpy(buffer_ptr, ptr->read_ptr, difference);
       length -= difference;
@@ -381,18 +524,19 @@ memcached_return_t memcached_io_read(memcached_server_write_instance_st ptr,
     }
   }
 
-  ptr->server_failure_counter= 0;
-  *nread = (ssize_t)(buffer_ptr - (char*)buffer);
+  nread= ssize_t(buffer_ptr - (char*)buffer);
+
   return MEMCACHED_SUCCESS;
 }
 
-memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
+memcached_return_t memcached_io_slurp(org::libmemcached::Instance* ptr)
 {
-  assert(ptr); // Programmer error
+  assert_msg(ptr, "Programmer error, invalid Instance");
+  assert(memcached_is_udp(ptr->root) == false);
 
   if (ptr->fd == INVALID_SOCKET)
   {
-    assert(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO));
+    assert_msg(int(ptr->state) <= int(MEMCACHED_SERVER_STATE_ADDRINFO), "Invalid socket state");
     return MEMCACHED_CONNECTION_FAILURE;
   }
 
@@ -409,10 +553,10 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
         continue;
 
       case ETIMEDOUT: // OSX
+#if EWOULDBLOCK != EAGAIN
       case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-      case EAGAIN:
 #endif
+      case EAGAIN:
 #ifdef TARGET_OS_LINUX
       case ERESTART:
 #endif
@@ -425,11 +569,11 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
         /* fall through */
 
       case ENOTCONN: // Programmer Error
-        WATCHPOINT_ASSERT(0);
+        assert(0);
       case ENOTSOCK:
-        WATCHPOINT_ASSERT(0);
+        assert(0);
       case EBADF:
-        assert(ptr->fd != INVALID_SOCKET);
+        assert_msg(ptr->fd != INVALID_SOCKET, "Invalid socket state");
       case EINVAL:
       case EFAULT:
       case ECONNREFUSED:
@@ -442,39 +586,23 @@ memcached_return_t memcached_io_slurp(memcached_server_write_instance_st ptr)
   return MEMCACHED_CONNECTION_FAILURE;
 }
 
-static ssize_t _io_write(memcached_server_write_instance_st ptr,
-                         const void *buffer, size_t length, bool with_flush)
+static bool _io_write(org::libmemcached::Instance* ptr,
+                      const void *buffer, size_t length, bool with_flush,
+                      size_t& written)
 {
-  size_t original_length;
-  const char* buffer_ptr;
+  assert(ptr->fd != INVALID_SOCKET);
+  assert(memcached_is_udp(ptr->root) == false);
 
-  WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
+  const char *buffer_ptr= static_cast<const char *>(buffer);
 
-  original_length= length;
-  buffer_ptr= static_cast<const char *>(buffer);
+  const size_t original_length= length;
 
   while (length)
   {
     char *write_ptr;
-    size_t should_write;
-    size_t buffer_end;
-
-    if (ptr->type == MEMCACHED_CONNECTION_UDP)
-    {
-      //UDP does not support partial writes
-      buffer_end= MAX_UDP_DATAGRAM_LENGTH;
-      should_write= length;
-      if (ptr->write_buffer_offset + should_write > buffer_end)
-      {
-        return -1;
-      }
-    }
-    else
-    {
-      buffer_end= MEMCACHED_MAX_BUFFER;
-      should_write= buffer_end - ptr->write_buffer_offset;
-      should_write= (should_write < length) ? should_write : length;
-    }
+    size_t buffer_end= MEMCACHED_MAX_BUFFER;
+    size_t should_write= buffer_end -ptr->write_buffer_offset;
+    should_write= (should_write < length) ? should_write : length;
 
     write_ptr= ptr->write_buffer + ptr->write_buffer_offset;
     memcpy(write_ptr, buffer_ptr, should_write);
@@ -482,21 +610,15 @@ static ssize_t _io_write(memcached_server_write_instance_st ptr,
     buffer_ptr+= should_write;
     length-= should_write;
 
-    if (ptr->write_buffer_offset == buffer_end && ptr->type != MEMCACHED_CONNECTION_UDP)
+    if (ptr->write_buffer_offset == buffer_end)
     {
       WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
 
       memcached_return_t rc;
-      ssize_t sent_length= io_flush(ptr, with_flush, &rc);
-      if (sent_length == -1)
+      if (io_flush(ptr, with_flush, rc) == false)
       {
-        return -1;
-      }
-
-      /* If io_flush calls memcached_purge, sent_length may be 0 */
-      unlikely (sent_length != 0)
-      {
-        WATCHPOINT_ASSERT(sent_length == (ssize_t)buffer_end);
+        written= original_length -length;
+        return false;
       }
     }
   }
@@ -505,51 +627,71 @@ static ssize_t _io_write(memcached_server_write_instance_st ptr,
   {
     memcached_return_t rc;
     WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-    if (io_flush(ptr, with_flush, &rc) == -1)
+    if (io_flush(ptr, with_flush, rc) == false)
     {
-      return -1;
+      written= original_length -length;
+      return false;
     }
   }
 
-  return (ssize_t) original_length;
+  written= original_length -length;
+
+  return true;
 }
 
-ssize_t memcached_io_write(memcached_server_write_instance_st ptr,
-                           const void *buffer, size_t length, bool with_flush)
+bool memcached_io_write(org::libmemcached::Instance* ptr)
 {
-  return _io_write(ptr, buffer, length, with_flush);
+  size_t written;
+  return _io_write(ptr, NULL, 0, true, written);
 }
 
-ssize_t memcached_io_writev(memcached_server_write_instance_st ptr,
-                            const struct libmemcached_io_vector_st *vector,
-                            size_t number_of, bool with_flush)
+ssize_t memcached_io_write(org::libmemcached::Instance* ptr,
+                           const void *buffer, const size_t length, const bool with_flush)
 {
+  size_t written;
+
+  if (_io_write(ptr, buffer, length, with_flush, written) == false)
+  {
+    return -1;
+  }
+
+  return ssize_t(written);
+}
+
+bool memcached_io_writev(org::libmemcached::Instance* ptr,
+                         libmemcached_io_vector_st vector[],
+                         const size_t number_of, const bool with_flush)
+{
+  ssize_t complete_total= 0;
   ssize_t total= 0;
 
   for (size_t x= 0; x < number_of; x++, vector++)
   {
-    ssize_t returnable;
-
-    if ((returnable= _io_write(ptr, vector->buffer, vector->length, false)) == -1)
+    complete_total+= vector->length;
+    if (vector->length)
     {
-      return -1;
+      size_t written;
+      if ((_io_write(ptr, vector->buffer, vector->length, false, written)) == false)
+      {
+        return false;
+      }
+      total+= written;
     }
-    total+= returnable;
   }
 
   if (with_flush)
   {
-    if (memcached_io_write(ptr, NULL, 0, true) == -1)
+    if (memcached_io_write(ptr) == false)
     {
-      return -1;
+      return false;
     }
   }
 
-  return total;
+  return (complete_total == total);
 }
 
 
-void memcached_io_close(memcached_server_write_instance_st ptr)
+void memcached_io_close(org::libmemcached::Instance* ptr)
 {
   if (ptr->fd == INVALID_SOCKET)
   {
@@ -572,25 +714,26 @@ void memcached_io_close(memcached_server_write_instance_st ptr)
   ptr->fd= INVALID_SOCKET;
 }
 
-memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st *memc)
+org::libmemcached::Instance* memcached_io_get_readable_server(memcached_st *memc)
 {
 #define MAX_SERVERS_TO_POLL 100
   struct pollfd fds[MAX_SERVERS_TO_POLL];
-  unsigned int host_index= 0;
+  nfds_t host_index= 0;
 
-  for (uint32_t x= 0; x < memcached_server_count(memc) && host_index < MAX_SERVERS_TO_POLL; ++x)
+  for (uint32_t x= 0; x < memcached_server_count(memc) and host_index < MAX_SERVERS_TO_POLL; ++x)
   {
-    memcached_server_write_instance_st instance=
-      memcached_server_instance_fetch(memc, x);
+    org::libmemcached::Instance* instance= memcached_instance_fetch(memc, x);
 
     if (instance->read_buffer_length > 0) /* I have data in the buffer */
+    {
       return instance;
+    }
 
-    if (memcached_server_response_count(instance) > 0)
+    if (memcached_instance_response_count(instance) > 0)
     {
-      fds[host_index].events = POLLIN;
-      fds[host_index].revents = 0;
-      fds[host_index].fd = instance->fd;
+      fds[host_index].events= POLLIN;
+      fds[host_index].revents= 0;
+      fds[host_index].fd= instance->fd;
       ++host_index;
     }
   }
@@ -600,10 +743,9 @@ memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st
     /* We have 0 or 1 server with pending events.. */
     for (uint32_t x= 0; x< memcached_server_count(memc); ++x)
     {
-      memcached_server_write_instance_st instance=
-        memcached_server_instance_fetch(memc, x);
+      org::libmemcached::Instance* instance= memcached_instance_fetch(memc, x);
 
-      if (memcached_server_response_count(instance) > 0)
+      if (memcached_instance_response_count(instance) > 0)
       {
         return instance;
       }
@@ -622,178 +764,30 @@ memcached_server_write_instance_st memcached_io_get_readable_server(memcached_st
     break;
 
   default:
-    for (size_t x= 0; x < host_index; ++x)
+    for (nfds_t x= 0; x < host_index; ++x)
     {
       if (fds[x].revents & POLLIN)
       {
         for (uint32_t y= 0; y < memcached_server_count(memc); ++y)
         {
-          memcached_server_write_instance_st instance=
-            memcached_server_instance_fetch(memc, y);
+          org::libmemcached::Instance* instance= memcached_instance_fetch(memc, y);
 
           if (instance->fd == fds[x].fd)
-            return instance;
-        }
-      }
-    }
-  }
-
-  return NULL;
-}
-
-static ssize_t io_flush(memcached_server_write_instance_st ptr,
-                        const bool with_flush,
-                        memcached_return_t *error)
-{
-  /*
-   ** We might want to purge the input buffer if we haven't consumed
-   ** any output yet... The test for the limits is the purge is inline
-   ** in the purge function to avoid duplicating the logic..
- */
-  {
-    memcached_return_t rc;
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-    rc= memcached_purge(ptr);
-
-    if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
-    {
-      return -1;
-    }
-  }
-  ssize_t sent_length;
-  size_t return_length;
-  char *local_write_ptr= ptr->write_buffer;
-  size_t write_length= ptr->write_buffer_offset;
-
-  *error= MEMCACHED_SUCCESS;
-
-  WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-
-  // UDP Sanity check, make sure that we are not sending somthing too big
-  if (ptr->type == MEMCACHED_CONNECTION_UDP && write_length > MAX_UDP_DATAGRAM_LENGTH)
-  {
-    *error= MEMCACHED_WRITE_FAILURE;
-    return -1;
-  }
-
-  if (ptr->write_buffer_offset == 0 || (ptr->type == MEMCACHED_CONNECTION_UDP
-                                        && ptr->write_buffer_offset == UDP_DATAGRAM_HEADER_LENGTH))
-  {
-    return 0;
-  }
-
-  /* Looking for memory overflows */
-#if defined(DEBUG)
-  if (write_length == MEMCACHED_MAX_BUFFER)
-    WATCHPOINT_ASSERT(ptr->write_buffer == local_write_ptr);
-  WATCHPOINT_ASSERT((ptr->write_buffer + MEMCACHED_MAX_BUFFER) >= (local_write_ptr + write_length));
-#endif
-
-  return_length= 0;
-  while (write_length)
-  {
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-    WATCHPOINT_ASSERT(write_length > 0);
-    sent_length= 0;
-    if (ptr->type == MEMCACHED_CONNECTION_UDP)
-      increment_udp_message_id(ptr);
-
-    WATCHPOINT_ASSERT(ptr->fd != INVALID_SOCKET);
-    if (with_flush)
-    {
-      sent_length= send(ptr->fd, local_write_ptr, write_length, MSG_NOSIGNAL|MSG_DONTWAIT);
-    }
-    else
-    {
-      sent_length= send(ptr->fd, local_write_ptr, write_length, MSG_NOSIGNAL|MSG_DONTWAIT|MSG_MORE);
-    }
-
-    if (sent_length == SOCKET_ERROR)
-    {
-      memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-#if 0 // @todo I should look at why we hit this bit of code hard frequently
-      WATCHPOINT_ERRNO(get_socket_errno());
-      WATCHPOINT_NUMBER(get_socket_errno());
-#endif
-      switch (get_socket_errno())
-      {
-      case ENOBUFS:
-        continue;
-      case EWOULDBLOCK:
-#ifdef USE_EAGAIN
-      case EAGAIN:
-#endif
-        {
-          /*
-           * We may be blocked on write because the input buffer
-           * is full. Let's check if we have room in our input
-           * buffer for more data and retry the write before
-           * waiting..
-         */
-          if (repack_input_buffer(ptr) or
-              process_input_buffer(ptr))
-          {
-            continue;
-          }
-
-          memcached_return_t rc= io_wait(ptr, MEM_WRITE);
-          if (memcached_success(rc))
-          {
-            continue;
-          }
-          else if (rc == MEMCACHED_TIMEOUT)
           {
-            *error= memcached_set_error(*ptr, MEMCACHED_TIMEOUT, MEMCACHED_AT);
-            return -1;
+            return instance;
           }
-
-          memcached_quit_server(ptr, true);
-          *error= memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-          return -1;
         }
-      case ENOTCONN:
-      case EPIPE:
-      default:
-        memcached_quit_server(ptr, true);
-        *error= memcached_set_errno(*ptr, get_socket_errno(), MEMCACHED_AT);
-        WATCHPOINT_ASSERT(ptr->fd == -1);
-        return -1;
       }
     }
-
-    if (ptr->type == MEMCACHED_CONNECTION_UDP and
-        (size_t)sent_length != write_length)
-    {
-      memcached_quit_server(ptr, true);
-      *error= memcached_set_error(*ptr, MEMCACHED_WRITE_FAILURE, MEMCACHED_AT);
-      return -1;
-    }
-
-    ptr->io_bytes_sent += (uint32_t) sent_length;
-
-    local_write_ptr+= sent_length;
-    write_length-= (uint32_t) sent_length;
-    return_length+= (uint32_t) sent_length;
   }
 
-  WATCHPOINT_ASSERT(write_length == 0);
-  // Need to study this assert() WATCHPOINT_ASSERT(return_length ==
-  // ptr->write_buffer_offset);
-
-  // if we are a udp server, the begining of the buffer is reserverd for
-  // the upd frame header
-  if (ptr->type == MEMCACHED_CONNECTION_UDP)
-    ptr->write_buffer_offset= UDP_DATAGRAM_HEADER_LENGTH;
-  else
-    ptr->write_buffer_offset= 0;
-
-  return (ssize_t) return_length;
+  return NULL;
 }
 
 /*
   Eventually we will just kill off the server with the problem.
 */
-void memcached_io_reset(memcached_server_write_instance_st ptr)
+void memcached_io_reset(org::libmemcached::Instance* ptr)
 {
   memcached_quit_server(ptr, true);
 }
@@ -802,9 +796,9 @@ void memcached_io_reset(memcached_server_write_instance_st ptr)
  * Read a given number of bytes from the server and place it into a specific
  * buffer. Reset the IO channel on this server if an error occurs.
  */
-memcached_return_t memcached_safe_read(memcached_server_write_instance_st ptr,
+memcached_return_t memcached_safe_read(org::libmemcached::Instance* ptr,
                                        void *dta,
-                                       size_t size)
+                                       const size_t size)
 {
   size_t offset= 0;
   char *data= static_cast<char *>(dta);
@@ -814,27 +808,28 @@ memcached_return_t memcached_safe_read(memcached_server_write_instance_st ptr,
     ssize_t nread;
     memcached_return_t rc;
 
-    while (memcached_continue(rc= memcached_io_read(ptr, data + offset, size - offset, &nread))) { };
+    while (memcached_continue(rc= memcached_io_read(ptr, data + offset, size - offset, nread))) { };
 
     if (memcached_failed(rc))
     {
       return rc;
     }
 
-    offset+= (size_t) nread;
+    offset+= size_t(nread);
   }
 
   return MEMCACHED_SUCCESS;
 }
 
-memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
+memcached_return_t memcached_io_readline(org::libmemcached::Instance* ptr,
                                          char *buffer_ptr,
-                                         size_t size)
+                                         size_t size,
+                                         size_t& total_nr)
 {
+  total_nr= 0;
   bool line_complete= false;
-  size_t total_nr= 0;
 
-  while (not line_complete)
+  while (line_complete == false)
   {
     if (ptr->read_buffer_length == 0)
     {
@@ -844,7 +839,7 @@ memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
        * the logic.
      */
       ssize_t nread;
-      memcached_return_t rc= memcached_io_read(ptr, buffer_ptr, 1, &nread);
+      memcached_return_t rc= memcached_io_read(ptr, buffer_ptr, 1, nread);
       if (memcached_failed(rc) and rc == MEMCACHED_IN_PROGRESS)
       {
         memcached_quit_server(ptr, true);
@@ -856,18 +851,22 @@ memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
       }
 
       if (*buffer_ptr == '\n')
+      {
         line_complete= true;
+      }
 
       ++buffer_ptr;
       ++total_nr;
     }
 
     /* Now let's look in the buffer and copy as we go! */
-    while (ptr->read_buffer_length && total_nr < size && !line_complete)
+    while (ptr->read_buffer_length and total_nr < size and line_complete == false)
     {
       *buffer_ptr = *ptr->read_ptr;
       if (*buffer_ptr == '\n')
+      {
         line_complete = true;
+      }
       --ptr->read_buffer_length;
       ++ptr->read_ptr;
       ++total_nr;
@@ -875,45 +874,10 @@ memcached_return_t memcached_io_readline(memcached_server_write_instance_st ptr,
     }
 
     if (total_nr == size)
+    {
       return MEMCACHED_PROTOCOL_ERROR;
+    }
   }
 
   return MEMCACHED_SUCCESS;
 }
-
-/*
- * The udp request id consists of two seperate sections
- *   1) The thread id
- *   2) The message number
- * The thread id should only be set when the memcached_st struct is created
- * and should not be changed.
- *
- * The message num is incremented for each new message we send, this function
- * extracts the message number from message_id, increments it and then
- * writes the new value back into the header
- */
-static void increment_udp_message_id(memcached_server_write_instance_st ptr)
-{
-  struct udp_datagram_header_st *header= (struct udp_datagram_header_st *)ptr->write_buffer;
-  uint16_t cur_req= get_udp_datagram_request_id(header);
-  int msg_num= get_msg_num_from_request_id(cur_req);
-  int thread_id= get_thread_id_from_request_id(cur_req);
-
-  if (((++msg_num) & UDP_REQUEST_ID_THREAD_MASK) != 0)
-    msg_num= 0;
-
-  header->request_id= htons((uint16_t) (thread_id | msg_num));
-}
-
-memcached_return_t memcached_io_init_udp_header(memcached_server_write_instance_st ptr, uint16_t thread_id)
-{
-  if (thread_id > UDP_REQUEST_ID_MAX_THREAD_ID)
-    return MEMCACHED_FAILURE;
-
-  struct udp_datagram_header_st *header= (struct udp_datagram_header_st *)ptr->write_buffer;
-  header->request_id= htons((uint16_t) (generate_udp_request_thread_id(thread_id)));
-  header->num_datagrams= htons(1);
-  header->sequence_number= htons(0);
-
-  return MEMCACHED_SUCCESS;
-}