125 lines
4.1 KiB
C
125 lines
4.1 KiB
C
/* Synchronous socket and file I/O operations useful across the core.
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*
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* Copyright (c) 2009-Present, Redis Ltd.
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* All rights reserved.
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*
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* Licensed under your choice of the Redis Source Available License 2.0
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* (RSALv2) or the Server Side Public License v1 (SSPLv1).
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*/
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#include "server.h"
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/* ----------------- Blocking sockets I/O with timeouts --------------------- */
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/* Redis performs most of the I/O in a nonblocking way, with the exception
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* of the SYNC command where the slave does it in a blocking way, and
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* the MIGRATE command that must be blocking in order to be atomic from the
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* point of view of the two instances (one migrating the key and one receiving
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* the key). This is why need the following blocking I/O functions.
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*
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* All the functions take the timeout in milliseconds. */
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#define SYNCIO__RESOLUTION 10 /* Resolution in milliseconds */
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/* Write the specified payload to 'fd'. If writing the whole payload will be
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* done within 'timeout' milliseconds the operation succeeds and 'size' is
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* returned. Otherwise the operation fails, -1 is returned, and an unspecified
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* partial write could be performed against the file descriptor. */
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ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout) {
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ssize_t nwritten, ret = size;
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long long start = mstime();
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long long remaining = timeout;
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while(1) {
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long long wait = (remaining > SYNCIO__RESOLUTION) ?
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remaining : SYNCIO__RESOLUTION;
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long long elapsed;
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/* Optimistically try to write before checking if the file descriptor
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* is actually writable. At worst we get EAGAIN. */
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nwritten = write(fd,ptr,size);
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if (nwritten == -1) {
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if (errno != EAGAIN) return -1;
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} else {
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ptr += nwritten;
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size -= nwritten;
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}
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if (size == 0) return ret;
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/* Wait */
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aeWait(fd,AE_WRITABLE,wait);
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elapsed = mstime() - start;
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if (elapsed >= timeout) {
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errno = ETIMEDOUT;
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return -1;
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}
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remaining = timeout - elapsed;
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}
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}
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/* Read the specified amount of bytes from 'fd'. If all the bytes are read
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* within 'timeout' milliseconds the operation succeed and 'size' is returned.
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* Otherwise the operation fails, -1 is returned, and an unspecified amount of
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* data could be read from the file descriptor. */
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ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout) {
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ssize_t nread, totread = 0;
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long long start = mstime();
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long long remaining = timeout;
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if (size == 0) return 0;
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while(1) {
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long long wait = (remaining > SYNCIO__RESOLUTION) ?
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remaining : SYNCIO__RESOLUTION;
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long long elapsed;
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/* Optimistically try to read before checking if the file descriptor
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* is actually readable. At worst we get EAGAIN. */
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nread = read(fd,ptr,size);
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if (nread == 0) return -1; /* short read. */
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if (nread == -1) {
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if (errno != EAGAIN) return -1;
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} else {
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ptr += nread;
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size -= nread;
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totread += nread;
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}
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if (size == 0) return totread;
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/* Wait */
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aeWait(fd,AE_READABLE,wait);
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elapsed = mstime() - start;
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if (elapsed >= timeout) {
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errno = ETIMEDOUT;
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return -1;
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}
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remaining = timeout - elapsed;
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}
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}
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/* Read a line making sure that every char will not require more than 'timeout'
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* milliseconds to be read.
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*
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* On success the number of bytes read is returned, otherwise -1.
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* On success the string is always correctly terminated with a 0 byte. */
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ssize_t syncReadLine(int fd, char *ptr, ssize_t size, long long timeout) {
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ssize_t nread = 0;
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size--;
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while(size) {
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char c;
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if (syncRead(fd,&c,1,timeout) == -1) return -1;
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if (c == '\n') {
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*ptr = '\0';
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if (nread && *(ptr-1) == '\r') *(ptr-1) = '\0';
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return nread;
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} else {
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*ptr++ = c;
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*ptr = '\0';
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nread++;
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}
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size--;
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}
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return nread;
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}
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