1 | /* Synchronous socket and file I/O operations useful across the core. |
2 | * |
3 | * Copyright (c) 2009-2010, Salvatore Sanfilippo <antirez at gmail dot com> |
4 | * All rights reserved. |
5 | * |
6 | * Redistribution and use in source and binary forms, with or without |
7 | * modification, are permitted provided that the following conditions are met: |
8 | * |
9 | * * Redistributions of source code must retain the above copyright notice, |
10 | * this list of conditions and the following disclaimer. |
11 | * * Redistributions in binary form must reproduce the above copyright |
12 | * notice, this list of conditions and the following disclaimer in the |
13 | * documentation and/or other materials provided with the distribution. |
14 | * * Neither the name of Redis nor the names of its contributors may be used |
15 | * to endorse or promote products derived from this software without |
16 | * specific prior written permission. |
17 | * |
18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
19 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
20 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
21 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
22 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
23 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
24 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
25 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
26 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
27 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
28 | * POSSIBILITY OF SUCH DAMAGE. |
29 | */ |
30 | |
31 | #include "server.h" |
32 | |
33 | /* ----------------- Blocking sockets I/O with timeouts --------------------- */ |
34 | |
35 | /* Redis performs most of the I/O in a nonblocking way, with the exception |
36 | * of the SYNC command where the slave does it in a blocking way, and |
37 | * the MIGRATE command that must be blocking in order to be atomic from the |
38 | * point of view of the two instances (one migrating the key and one receiving |
39 | * the key). This is why need the following blocking I/O functions. |
40 | * |
41 | * All the functions take the timeout in milliseconds. */ |
42 | |
43 | #define SYNCIO__RESOLUTION 10 /* Resolution in milliseconds */ |
44 | |
45 | /* Write the specified payload to 'fd'. If writing the whole payload will be |
46 | * done within 'timeout' milliseconds the operation succeeds and 'size' is |
47 | * returned. Otherwise the operation fails, -1 is returned, and an unspecified |
48 | * partial write could be performed against the file descriptor. */ |
49 | ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout) { |
50 | ssize_t nwritten, ret = size; |
51 | long long start = mstime(); |
52 | long long remaining = timeout; |
53 | |
54 | while(1) { |
55 | long long wait = (remaining > SYNCIO__RESOLUTION) ? |
56 | remaining : SYNCIO__RESOLUTION; |
57 | long long elapsed; |
58 | |
59 | /* Optimistically try to write before checking if the file descriptor |
60 | * is actually writable. At worst we get EAGAIN. */ |
61 | nwritten = write(fd,ptr,size); |
62 | if (nwritten == -1) { |
63 | if (errno != EAGAIN) return -1; |
64 | } else { |
65 | ptr += nwritten; |
66 | size -= nwritten; |
67 | } |
68 | if (size == 0) return ret; |
69 | |
70 | /* Wait */ |
71 | aeWait(fd,AE_WRITABLE,wait); |
72 | elapsed = mstime() - start; |
73 | if (elapsed >= timeout) { |
74 | errno = ETIMEDOUT; |
75 | return -1; |
76 | } |
77 | remaining = timeout - elapsed; |
78 | } |
79 | } |
80 | |
81 | /* Read the specified amount of bytes from 'fd'. If all the bytes are read |
82 | * within 'timeout' milliseconds the operation succeed and 'size' is returned. |
83 | * Otherwise the operation fails, -1 is returned, and an unspecified amount of |
84 | * data could be read from the file descriptor. */ |
85 | ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout) { |
86 | ssize_t nread, totread = 0; |
87 | long long start = mstime(); |
88 | long long remaining = timeout; |
89 | |
90 | if (size == 0) return 0; |
91 | while(1) { |
92 | long long wait = (remaining > SYNCIO__RESOLUTION) ? |
93 | remaining : SYNCIO__RESOLUTION; |
94 | long long elapsed; |
95 | |
96 | /* Optimistically try to read before checking if the file descriptor |
97 | * is actually readable. At worst we get EAGAIN. */ |
98 | nread = read(fd,ptr,size); |
99 | if (nread == 0) return -1; /* short read. */ |
100 | if (nread == -1) { |
101 | if (errno != EAGAIN) return -1; |
102 | } else { |
103 | ptr += nread; |
104 | size -= nread; |
105 | totread += nread; |
106 | } |
107 | if (size == 0) return totread; |
108 | |
109 | /* Wait */ |
110 | aeWait(fd,AE_READABLE,wait); |
111 | elapsed = mstime() - start; |
112 | if (elapsed >= timeout) { |
113 | errno = ETIMEDOUT; |
114 | return -1; |
115 | } |
116 | remaining = timeout - elapsed; |
117 | } |
118 | } |
119 | |
120 | /* Read a line making sure that every char will not require more than 'timeout' |
121 | * milliseconds to be read. |
122 | * |
123 | * On success the number of bytes read is returned, otherwise -1. |
124 | * On success the string is always correctly terminated with a 0 byte. */ |
125 | ssize_t syncReadLine(int fd, char *ptr, ssize_t size, long long timeout) { |
126 | ssize_t nread = 0; |
127 | |
128 | size--; |
129 | while(size) { |
130 | char c; |
131 | |
132 | if (syncRead(fd,&c,1,timeout) == -1) return -1; |
133 | if (c == '\n') { |
134 | *ptr = '\0'; |
135 | if (nread && *(ptr-1) == '\r') *(ptr-1) = '\0'; |
136 | return nread; |
137 | } else { |
138 | *ptr++ = c; |
139 | *ptr = '\0'; |
140 | nread++; |
141 | } |
142 | size--; |
143 | } |
144 | return nread; |
145 | } |
146 | |