/*
Basic socket buffered IO
*/
#include "common.h"
#include "memcached_io.h"
#include <sys/select.h>
#include <poll.h>
typedef enum {
MEM_READ,
MEM_WRITE,
} memc_read_or_write;
static ssize_t io_flush(memcached_server_st *ptr, memcached_return *error);
static void increment_udp_message_id(memcached_server_st *ptr);
static memcached_return io_wait(memcached_server_st *ptr,
memc_read_or_write read_or_write)
{
struct pollfd fds[1];
short flags= 0;
int error;
if (read_or_write == MEM_WRITE) /* write */
flags= POLLOUT;
else
flags= POLLIN;
memset(&fds, 0, sizeof(struct pollfd));
fds[0].fd= ptr->fd;
fds[0].events= flags;
/*
** 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 rc=memcached_purge(ptr);
if (rc != MEMCACHED_SUCCESS && rc != MEMCACHED_STORED)
return MEMCACHED_FAILURE;
}
error= poll(fds, 1, ptr->root->poll_timeout);
if (error == 1)
return MEMCACHED_SUCCESS;
else if (error == 0)
{
return MEMCACHED_TIMEOUT;
}
/* Imposssible for anything other then -1 */
WATCHPOINT_ASSERT(error == -1);
memcached_quit_server(ptr, 1);
return MEMCACHED_FAILURE;
}
#ifdef UNUSED
void memcached_io_preread(memcached_st *ptr)
{
unsigned int x;
return;
for (x= 0; x < ptr->number_of_hosts; x++)
{
if (memcached_server_response_count(ptr, x) &&
ptr->hosts[x].read_data_length < MEMCACHED_MAX_BUFFER )
{
size_t data_read;
data_read= read(ptr->hosts[x].fd,
ptr->hosts[x].read_ptr + ptr->hosts[x].read_data_length,
MEMCACHED_MAX_BUFFER - ptr->hosts[x].read_data_length);
if (data_read == -1)
continue;
ptr->hosts[x].read_buffer_length+= data_read;
ptr->hosts[x].read_data_length+= data_read;
}
}
}
#endif
memcached_return memcached_io_read(memcached_server_st *ptr,
void *buffer, size_t length, ssize_t *nread)
{
char *buffer_ptr;
buffer_ptr= buffer;
while (length)
{
if (!ptr->read_buffer_length)
{
ssize_t data_read;
while (1)
{
data_read= read(ptr->fd, ptr->read_buffer, MEMCACHED_MAX_BUFFER);
if (data_read > 0)
break;
else if (data_read == -1)
{
ptr->cached_errno= errno;
memcached_return rc= MEMCACHED_UNKNOWN_READ_FAILURE;
switch (errno)
{
case EAGAIN:
case EINTR:
if ((rc= io_wait(ptr, MEM_READ)) == MEMCACHED_SUCCESS)
continue;
/* fall through */
default:
{
memcached_quit_server(ptr, 1);
*nread= -1;
return rc;
}
}
}
else
{
/*
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, 1);
*nread= -1;
return MEMCACHED_UNKNOWN_READ_FAILURE;
}
}
ptr->io_bytes_sent = 0;
ptr->read_data_length= data_read;
ptr->read_buffer_length= data_read;
ptr->read_ptr= ptr->read_buffer;
}
if (length > 1)
{
size_t difference;
difference= (length > ptr->read_buffer_length) ? ptr->read_buffer_length : length;
memcpy(buffer_ptr, ptr->read_ptr, difference);
length -= difference;
ptr->read_ptr+= difference;
ptr->read_buffer_length-= difference;
buffer_ptr+= difference;
}
else
{
*buffer_ptr= *ptr->read_ptr;
ptr->read_ptr++;
ptr->read_buffer_length--;
buffer_ptr++;
break;
}
}
ptr->server_failure_counter= 0;
*nread = (size_t)(buffer_ptr - (char*)buffer);
return MEMCACHED_SUCCESS;
}
ssize_t memcached_io_write(memcached_server_st *ptr,
const void *buffer, size_t length, char with_flush)
{
size_t original_length;
const char* buffer_ptr;
WATCHPOINT_ASSERT(ptr->fd != -1);
original_length= length;
buffer_ptr= buffer;
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;
}
write_ptr= ptr->write_buffer + ptr->write_buffer_offset;
memcpy(write_ptr, buffer_ptr, should_write);
ptr->write_buffer_offset+= should_write;
buffer_ptr+= should_write;
length-= should_write;
if (ptr->write_buffer_offset == buffer_end && ptr->type != MEMCACHED_CONNECTION_UDP)
{
memcached_return rc;
ssize_t sent_length;
WATCHPOINT_ASSERT(ptr->fd != -1);
sent_length= io_flush(ptr, &rc);
if (sent_length == -1)
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);
}
}
}
if (with_flush)
{
memcached_return rc;
WATCHPOINT_ASSERT(ptr->fd != -1);
if (io_flush(ptr, &rc) == -1)
return -1;
}
return original_length;
}
memcached_return memcached_io_close(memcached_server_st *ptr)
{
int r;
if (ptr->fd == -1)
return MEMCACHED_SUCCESS;
/* in case of death shutdown to avoid blocking at close() */
if (1)
{
r= shutdown(ptr->fd, SHUT_RDWR);
#ifdef DEBUG
if (r && errno != ENOTCONN)
{
WATCHPOINT_NUMBER(ptr->fd);
WATCHPOINT_ERRNO(errno);
WATCHPOINT_ASSERT(errno);
}
#endif
}
r= close(ptr->fd);
#ifdef DEBUG
if (r != 0)
WATCHPOINT_ERRNO(errno);
#endif
return MEMCACHED_SUCCESS;
}
memcached_server_st *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;
for (unsigned int x= 0;
x< memc->number_of_hosts && host_index < MAX_SERVERS_TO_POLL;
++x)
{
if (memc->hosts[x].read_buffer_length > 0) /* I have data in the buffer */
return &memc->hosts[x];
if (memcached_server_response_count(&memc->hosts[x]) > 0)
{
fds[host_index].events = POLLIN;
fds[host_index].revents = 0;
fds[host_index].fd = memc->hosts[x].fd;
++host_index;
}
}
if (host_index < 2)
{
/* We have 0 or 1 server with pending events.. */
for (unsigned int x= 0; x< memc->number_of_hosts; ++x)
if (memcached_server_response_count(&memc->hosts[x]) > 0)
return &memc->hosts[x];
return NULL;
}
int err= poll(fds, host_index, memc->poll_timeout);
switch (err) {
case -1:
memc->cached_errno = errno;
/* FALLTHROUGH */
case 0:
break;
default:
for (unsigned int x= 0; x < host_index; ++x)
if (fds[x].revents & POLLIN)
for (unsigned int y= 0; y < memc->number_of_hosts; ++y)
if (memc->hosts[y].fd == fds[x].fd)
return &memc->hosts[y];
}
return NULL;
}
static ssize_t io_flush(memcached_server_st *ptr,
memcached_return *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 rc;
WATCHPOINT_ASSERT(ptr->fd != -1);
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 != -1);
// 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)
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 != -1);
WATCHPOINT_ASSERT(write_length > 0);
sent_length= 0;
if (ptr->type == MEMCACHED_CONNECTION_UDP)
increment_udp_message_id(ptr);
sent_length= write(ptr->fd, local_write_ptr, write_length);
if (sent_length == -1)
{
ptr->cached_errno= errno;
switch (errno)
{
case ENOBUFS:
continue;
case EAGAIN:
{
memcached_return rc;
rc= io_wait(ptr, MEM_WRITE);
if (rc == MEMCACHED_SUCCESS || rc == MEMCACHED_TIMEOUT)
continue;
memcached_quit_server(ptr, 1);
return -1;
}
default:
memcached_quit_server(ptr, 1);
*error= MEMCACHED_ERRNO;
return -1;
}
}
if (ptr->type == MEMCACHED_CONNECTION_UDP &&
(size_t)sent_length != write_length)
{
memcached_quit_server(ptr, 1);
return -1;
}
ptr->io_bytes_sent += sent_length;
local_write_ptr+= sent_length;
write_length-= sent_length;
return_length+= 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 return_length;
}
/*
Eventually we will just kill off the server with the problem.
*/
void memcached_io_reset(memcached_server_st *ptr)
{
memcached_quit_server(ptr, 1);
}
/**
* 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 memcached_safe_read(memcached_server_st *ptr,
void *dta,
size_t size)
{
size_t offset= 0;
char *data= dta;
while (offset < size)
{
ssize_t nread;
memcached_return rc= memcached_io_read(ptr, data + offset, size - offset,
&nread);
if (rc != MEMCACHED_SUCCESS)
return rc;
offset+= nread;
}
return MEMCACHED_SUCCESS;
}
memcached_return memcached_io_readline(memcached_server_st *ptr,
char *buffer_ptr,
size_t size)
{
bool line_complete= false;
size_t total_nr= 0;
while (!line_complete)
{
if (ptr->read_buffer_length == 0)
{
/*
* We don't have any data in the buffer, so let's fill the read
* buffer. Call the standard read function to avoid duplicating
* the logic.
*/
ssize_t nread;
memcached_return rc= memcached_io_read(ptr, buffer_ptr, 1, &nread);
if (rc != MEMCACHED_SUCCESS)
return rc;
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)
{
*buffer_ptr = *ptr->read_ptr;
if (*buffer_ptr == '\n')
line_complete = true;
--ptr->read_buffer_length;
++ptr->read_ptr;
++total_nr;
++buffer_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_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);
uint16_t msg_num= get_msg_num_from_request_id(cur_req);
uint16_t 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(thread_id | msg_num);
}
memcached_return memcached_io_init_udp_header(memcached_server_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(generate_udp_request_thread_id(thread_id));
header->num_datagrams= htons(1);
header->sequence_number= htons(0);
return MEMCACHED_SUCCESS;
}