blob: aeee6026100f8bbe86f82e4e0357b4432c68980b [file] [log] [blame]
Willy Tarreaubaaee002006-06-26 02:48:02 +02001/*
2 * File descriptors management functions.
3 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +01004 * Copyright 2000-2014 Willy Tarreau <w@1wt.eu>
Willy Tarreaubaaee002006-06-26 02:48:02 +02005 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010011 * This code implements an events cache for file descriptors. It remembers the
12 * readiness of a file descriptor after a return from poll() and the fact that
13 * an I/O attempt failed on EAGAIN. Events in the cache which are still marked
14 * ready and active are processed just as if they were reported by poll().
Willy Tarreau7be79a42012-11-11 15:02:54 +010015 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010016 * This serves multiple purposes. First, it significantly improves performance
17 * by avoiding to subscribe to polling unless absolutely necessary, so most
18 * events are processed without polling at all, especially send() which
19 * benefits from the socket buffers. Second, it is the only way to support
20 * edge-triggered pollers (eg: EPOLL_ET). And third, it enables I/O operations
21 * that are backed by invisible buffers. For example, SSL is able to read a
22 * whole socket buffer and not deliver it to the application buffer because
23 * it's full. Unfortunately, it won't be reported by a poller anymore until
24 * some new activity happens. The only way to call it again thus is to keep
25 * this readiness information in the cache and to access it without polling
26 * once the FD is enabled again.
Willy Tarreau7be79a42012-11-11 15:02:54 +010027 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010028 * One interesting feature of the cache is that it maintains the principle
29 * of speculative I/O introduced in haproxy 1.3 : the first time an event is
30 * enabled, the FD is considered as ready so that the I/O attempt is performed
31 * via the cache without polling. And the polling happens only when EAGAIN is
32 * first met. This avoids polling for HTTP requests, especially when the
33 * defer-accept mode is used. It also avoids polling for sending short data
34 * such as requests to servers or short responses to clients.
35 *
36 * The cache consists in a list of active events and a list of updates.
37 * Active events are events that are expected to come and that we must report
38 * to the application until it asks to stop or asks to poll. Updates are new
39 * requests for changing an FD state. Updates are the only way to create new
40 * events. This is important because it means that the number of cached events
41 * cannot increase between updates and will only grow one at a time while
42 * processing updates. All updates must always be processed, though events
43 * might be processed by small batches if required.
Willy Tarreau7be79a42012-11-11 15:02:54 +010044 *
45 * There is no direct link between the FD and the updates list. There is only a
46 * bit in the fdtab[] to indicate than a file descriptor is already present in
47 * the updates list. Once an fd is present in the updates list, it will have to
48 * be considered even if its changes are reverted in the middle or if the fd is
49 * replaced.
50 *
51 * It is important to understand that as long as all expected events are
52 * processed, they might starve the polled events, especially because polled
Willy Tarreauf817e9f2014-01-10 16:58:45 +010053 * I/O starvation quickly induces more cached I/O. One solution to this
Willy Tarreau7be79a42012-11-11 15:02:54 +010054 * consists in only processing a part of the events at once, but one drawback
Willy Tarreauf817e9f2014-01-10 16:58:45 +010055 * is that unhandled events will still wake the poller up. Using an edge-
56 * triggered poller such as EPOLL_ET will solve this issue though.
Willy Tarreau7be79a42012-11-11 15:02:54 +010057 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010058 * Since we do not want to scan all the FD list to find cached I/O events,
59 * we store them in a list consisting in a linear array holding only the FD
60 * indexes right now. Note that a closed FD cannot exist in the cache, because
61 * it is closed by fd_delete() which in turn calls fd_release_cache_entry()
62 * which always removes it from the list.
Willy Tarreau7be79a42012-11-11 15:02:54 +010063 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010064 * The FD array has to hold a back reference to the cache. This reference is
65 * always valid unless the FD is not in the cache and is not updated, in which
66 * case the reference points to index 0.
Willy Tarreau7be79a42012-11-11 15:02:54 +010067 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010068 * The event state for an FD, as found in fdtab[].state, is maintained for each
69 * direction. The state field is built this way, with R bits in the low nibble
70 * and W bits in the high nibble for ease of access and debugging :
Willy Tarreau7be79a42012-11-11 15:02:54 +010071 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010072 * 7 6 5 4 3 2 1 0
73 * [ 0 | PW | RW | AW | 0 | PR | RR | AR ]
74 *
75 * A* = active *R = read
76 * P* = polled *W = write
77 * R* = ready
78 *
79 * An FD is marked "active" when there is a desire to use it.
80 * An FD is marked "polled" when it is registered in the polling.
81 * An FD is marked "ready" when it has not faced a new EAGAIN since last wake-up
82 * (it is a cache of the last EAGAIN regardless of polling changes).
Willy Tarreau7be79a42012-11-11 15:02:54 +010083 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010084 * We have 8 possible states for each direction based on these 3 flags :
Willy Tarreau7be79a42012-11-11 15:02:54 +010085 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010086 * +---+---+---+----------+---------------------------------------------+
87 * | P | R | A | State | Description |
88 * +---+---+---+----------+---------------------------------------------+
89 * | 0 | 0 | 0 | DISABLED | No activity desired, not ready. |
90 * | 0 | 0 | 1 | MUSTPOLL | Activity desired via polling. |
91 * | 0 | 1 | 0 | STOPPED | End of activity without polling. |
92 * | 0 | 1 | 1 | ACTIVE | Activity desired without polling. |
93 * | 1 | 0 | 0 | ABORT | Aborted poll(). Not frequently seen. |
94 * | 1 | 0 | 1 | POLLED | FD is being polled. |
95 * | 1 | 1 | 0 | PAUSED | FD was paused while ready (eg: buffer full) |
96 * | 1 | 1 | 1 | READY | FD was marked ready by poll() |
97 * +---+---+---+----------+---------------------------------------------+
Willy Tarreau7be79a42012-11-11 15:02:54 +010098 *
Willy Tarreauf817e9f2014-01-10 16:58:45 +010099 * The transitions are pretty simple :
100 * - fd_want_*() : set flag A
101 * - fd_stop_*() : clear flag A
102 * - fd_cant_*() : clear flag R (when facing EAGAIN)
103 * - fd_may_*() : set flag R (upon return from poll())
104 * - sync() : if (A) { if (!R) P := 1 } else { P := 0 }
105 *
106 * The PAUSED, ABORT and MUSTPOLL states are transient for level-trigerred
107 * pollers and are fixed by the sync() which happens at the beginning of the
108 * poller. For event-triggered pollers, only the MUSTPOLL state will be
109 * transient and ABORT will lead to PAUSED. The ACTIVE state is the only stable
110 * one which has P != A.
111 *
112 * The READY state is a bit special as activity on the FD might be notified
113 * both by the poller or by the cache. But it is needed for some multi-layer
114 * protocols (eg: SSL) where connection activity is not 100% linked to FD
115 * activity. Also some pollers might prefer to implement it as ACTIVE if
116 * enabling/disabling the FD is cheap. The READY and ACTIVE states are the
117 * two states for which a cache entry is allocated.
118 *
119 * The state transitions look like the diagram below. Only the 4 right states
120 * have polling enabled :
121 *
122 * (POLLED=0) (POLLED=1)
123 *
124 * +----------+ sync +-------+
125 * | DISABLED | <----- | ABORT | (READY=0, ACTIVE=0)
126 * +----------+ +-------+
127 * clr | ^ set | ^
128 * | | | |
129 * v | set v | clr
130 * +----------+ sync +--------+
131 * | MUSTPOLL | -----> | POLLED | (READY=0, ACTIVE=1)
132 * +----------+ +--------+
133 * ^ poll | ^
134 * | | |
135 * | EAGAIN v | EAGAIN
136 * +--------+ +-------+
137 * | ACTIVE | | READY | (READY=1, ACTIVE=1)
138 * +--------+ +-------+
139 * clr | ^ set | ^
140 * | | | |
141 * v | set v | clr
142 * +---------+ sync +--------+
143 * | STOPPED | <------ | PAUSED | (READY=1, ACTIVE=0)
144 * +---------+ +--------+
Willy Tarreaubaaee002006-06-26 02:48:02 +0200145 */
146
Willy Tarreau2ff76222007-04-09 19:29:56 +0200147#include <stdio.h>
Willy Tarreau4f60f162007-04-08 16:39:58 +0200148#include <string.h>
Willy Tarreaubaaee002006-06-26 02:48:02 +0200149#include <unistd.h>
Willy Tarreaubaaee002006-06-26 02:48:02 +0200150#include <sys/types.h>
151
Willy Tarreau2dd0d472006-06-29 17:53:05 +0200152#include <common/compat.h>
153#include <common/config.h>
Willy Tarreaubaaee002006-06-26 02:48:02 +0200154
Willy Tarreau7be79a42012-11-11 15:02:54 +0100155#include <types/global.h>
156
Willy Tarreau2a429502006-10-15 14:52:29 +0200157#include <proto/fd.h>
Willy Tarreauc6f4ce82009-06-10 11:09:37 +0200158#include <proto/port_range.h>
Willy Tarreaubaaee002006-06-26 02:48:02 +0200159
160struct fdtab *fdtab = NULL; /* array of all the file descriptors */
Willy Tarreau8d5d77e2009-10-18 07:25:52 +0200161struct fdinfo *fdinfo = NULL; /* less-often used infos for file descriptors */
Willy Tarreaubaaee002006-06-26 02:48:02 +0200162int maxfd; /* # of the highest fd + 1 */
163int totalconn; /* total # of terminated sessions */
164int actconn; /* # of active sessions */
165
Willy Tarreau4f60f162007-04-08 16:39:58 +0200166struct poller pollers[MAX_POLLERS];
167struct poller cur_poller;
168int nbpollers = 0;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200169
Willy Tarreau16f649c2014-01-25 19:10:48 +0100170unsigned int *fd_cache = NULL; // FD events cache
Willy Tarreau7be79a42012-11-11 15:02:54 +0100171unsigned int *fd_updt = NULL; // FD updates list
Willy Tarreau16f649c2014-01-25 19:10:48 +0100172int fd_cache_num = 0; // number of events in the cache
173int fd_nbupdt = 0; // number of updates in the list
Willy Tarreaubaaee002006-06-26 02:48:02 +0200174
Willy Tarreau4f60f162007-04-08 16:39:58 +0200175/* Deletes an FD from the fdsets, and recomputes the maxfd limit.
176 * The file descriptor is also closed.
177 */
178void fd_delete(int fd)
Willy Tarreaubaaee002006-06-26 02:48:02 +0200179{
Willy Tarreauad38ace2013-12-15 14:19:38 +0100180 if (fdtab[fd].linger_risk) {
181 /* this is generally set when connecting to servers */
182 setsockopt(fd, SOL_SOCKET, SO_LINGER,
183 (struct linger *) &nolinger, sizeof(struct linger));
184 }
Willy Tarreau6ea20b12012-11-11 16:05:19 +0100185 if (cur_poller.clo)
186 cur_poller.clo(fd);
187
Willy Tarreau899d9572014-01-25 19:20:35 +0100188 fd_release_cache_entry(fd);
Willy Tarreauf817e9f2014-01-10 16:58:45 +0100189 fdtab[fd].state = 0;
Willy Tarreau6ea20b12012-11-11 16:05:19 +0100190
Willy Tarreau8d5d77e2009-10-18 07:25:52 +0200191 port_range_release_port(fdinfo[fd].port_range, fdinfo[fd].local_port);
192 fdinfo[fd].port_range = NULL;
Willy Tarreau4f60f162007-04-08 16:39:58 +0200193 close(fd);
Willy Tarreaudb3b3262012-07-05 23:19:22 +0200194 fdtab[fd].owner = NULL;
Willy Tarreau1720abd2012-11-11 17:08:32 +0100195 fdtab[fd].new = 0;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200196
Willy Tarreaudb3b3262012-07-05 23:19:22 +0200197 while ((maxfd-1 >= 0) && !fdtab[maxfd-1].owner)
Willy Tarreau4f60f162007-04-08 16:39:58 +0200198 maxfd--;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200199}
Willy Tarreaubaaee002006-06-26 02:48:02 +0200200
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100201/* Scan and process the cached events. This should be called right after
Willy Tarreau5be2f352014-11-19 19:43:05 +0100202 * the poller. The loop may cause new entries to be created, for example
203 * if a listener causes an accept() to initiate a new incoming connection
204 * wanting to attempt an recv().
Willy Tarreau09f24562012-11-11 16:43:45 +0100205 */
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100206void fd_process_cached_events()
Willy Tarreau09f24562012-11-11 16:43:45 +0100207{
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100208 int fd, entry, e;
Willy Tarreau09f24562012-11-11 16:43:45 +0100209
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100210 for (entry = 0; entry < fd_cache_num; ) {
211 fd = fd_cache[entry];
Willy Tarreau69a41fa2014-01-20 11:02:59 +0100212 e = fdtab[fd].state;
Willy Tarreau09f24562012-11-11 16:43:45 +0100213
Willy Tarreau09f24562012-11-11 16:43:45 +0100214 fdtab[fd].ev &= FD_POLL_STICKY;
215
Willy Tarreauf817e9f2014-01-10 16:58:45 +0100216 if ((e & (FD_EV_READY_R | FD_EV_ACTIVE_R)) == (FD_EV_READY_R | FD_EV_ACTIVE_R))
Willy Tarreau09f24562012-11-11 16:43:45 +0100217 fdtab[fd].ev |= FD_POLL_IN;
218
Willy Tarreauf817e9f2014-01-10 16:58:45 +0100219 if ((e & (FD_EV_READY_W | FD_EV_ACTIVE_W)) == (FD_EV_READY_W | FD_EV_ACTIVE_W))
Willy Tarreau09f24562012-11-11 16:43:45 +0100220 fdtab[fd].ev |= FD_POLL_OUT;
221
222 if (fdtab[fd].iocb && fdtab[fd].owner && fdtab[fd].ev)
223 fdtab[fd].iocb(fd);
Willy Tarreaufa7fc952014-01-20 20:18:59 +0100224 else
Willy Tarreau5be2f352014-11-19 19:43:05 +0100225 fd_release_cache_entry(fd);
Willy Tarreau09f24562012-11-11 16:43:45 +0100226
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100227 /* If the fd was removed from the cache, it has been
Willy Tarreau09f24562012-11-11 16:43:45 +0100228 * replaced by the next one that we don't want to skip !
229 */
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100230 if (entry < fd_cache_num && fd_cache[entry] != fd)
Willy Tarreau09f24562012-11-11 16:43:45 +0100231 continue;
Willy Tarreau033cd9d2014-01-25 19:24:15 +0100232 entry++;
Willy Tarreau09f24562012-11-11 16:43:45 +0100233 }
234}
Willy Tarreaubaaee002006-06-26 02:48:02 +0200235
Willy Tarreau4f60f162007-04-08 16:39:58 +0200236/* disable the specified poller */
237void disable_poller(const char *poller_name)
238{
239 int p;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200240
Willy Tarreau4f60f162007-04-08 16:39:58 +0200241 for (p = 0; p < nbpollers; p++)
242 if (strcmp(pollers[p].name, poller_name) == 0)
243 pollers[p].pref = 0;
244}
Willy Tarreaubaaee002006-06-26 02:48:02 +0200245
246/*
Willy Tarreau4f60f162007-04-08 16:39:58 +0200247 * Initialize the pollers till the best one is found.
248 * If none works, returns 0, otherwise 1.
Willy Tarreaubaaee002006-06-26 02:48:02 +0200249 */
Willy Tarreau4f60f162007-04-08 16:39:58 +0200250int init_pollers()
Willy Tarreaubaaee002006-06-26 02:48:02 +0200251{
Willy Tarreau4f60f162007-04-08 16:39:58 +0200252 int p;
253 struct poller *bp;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200254
Vincent Bernat3c2f2f22016-04-03 13:48:42 +0200255 if ((fd_cache = calloc(1, sizeof(uint32_t) * global.maxsock)) == NULL)
Willy Tarreau16f649c2014-01-25 19:10:48 +0100256 goto fail_cache;
Willy Tarreau7be79a42012-11-11 15:02:54 +0100257
Vincent Bernat3c2f2f22016-04-03 13:48:42 +0200258 if ((fd_updt = calloc(1, sizeof(uint32_t) * global.maxsock)) == NULL)
Willy Tarreau7be79a42012-11-11 15:02:54 +0100259 goto fail_updt;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200260
Willy Tarreau4f60f162007-04-08 16:39:58 +0200261 do {
262 bp = NULL;
263 for (p = 0; p < nbpollers; p++)
264 if (!bp || (pollers[p].pref > bp->pref))
265 bp = &pollers[p];
Willy Tarreaubaaee002006-06-26 02:48:02 +0200266
Willy Tarreau4f60f162007-04-08 16:39:58 +0200267 if (!bp || bp->pref == 0)
Willy Tarreaubaaee002006-06-26 02:48:02 +0200268 break;
269
Willy Tarreau4f60f162007-04-08 16:39:58 +0200270 if (bp->init(bp)) {
271 memcpy(&cur_poller, bp, sizeof(*bp));
272 return 1;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200273 }
Willy Tarreau4f60f162007-04-08 16:39:58 +0200274 } while (!bp || bp->pref == 0);
275 return 0;
Willy Tarreau7be79a42012-11-11 15:02:54 +0100276
277 fail_updt:
Willy Tarreau16f649c2014-01-25 19:10:48 +0100278 free(fd_cache);
279 fail_cache:
Willy Tarreau7be79a42012-11-11 15:02:54 +0100280 return 0;
Willy Tarreaubaaee002006-06-26 02:48:02 +0200281}
282
Willy Tarreaubaaee002006-06-26 02:48:02 +0200283/*
Krzysztof Piotr Oledzkia643baf2008-05-29 23:53:44 +0200284 * Deinitialize the pollers.
285 */
286void deinit_pollers() {
287
288 struct poller *bp;
289 int p;
290
291 for (p = 0; p < nbpollers; p++) {
292 bp = &pollers[p];
293
294 if (bp && bp->pref)
295 bp->term(bp);
296 }
Willy Tarreau7be79a42012-11-11 15:02:54 +0100297
298 free(fd_updt);
Willy Tarreau16f649c2014-01-25 19:10:48 +0100299 free(fd_cache);
Willy Tarreau7be79a42012-11-11 15:02:54 +0100300 fd_updt = NULL;
Willy Tarreau16f649c2014-01-25 19:10:48 +0100301 fd_cache = NULL;
Krzysztof Piotr Oledzkia643baf2008-05-29 23:53:44 +0200302}
303
304/*
Willy Tarreau2ff76222007-04-09 19:29:56 +0200305 * Lists the known pollers on <out>.
306 * Should be performed only before initialization.
307 */
308int list_pollers(FILE *out)
309{
310 int p;
311 int last, next;
312 int usable;
313 struct poller *bp;
314
315 fprintf(out, "Available polling systems :\n");
316
317 usable = 0;
318 bp = NULL;
319 last = next = -1;
320 while (1) {
321 for (p = 0; p < nbpollers; p++) {
Willy Tarreau2ff76222007-04-09 19:29:56 +0200322 if ((next < 0 || pollers[p].pref > next)
Willy Tarreaue79c3b22010-11-19 10:20:36 +0100323 && (last < 0 || pollers[p].pref < last)) {
Willy Tarreau2ff76222007-04-09 19:29:56 +0200324 next = pollers[p].pref;
Willy Tarreaue79c3b22010-11-19 10:20:36 +0100325 if (!bp || (pollers[p].pref > bp->pref))
326 bp = &pollers[p];
327 }
Willy Tarreau2ff76222007-04-09 19:29:56 +0200328 }
329
330 if (next == -1)
331 break;
332
333 for (p = 0; p < nbpollers; p++) {
334 if (pollers[p].pref == next) {
335 fprintf(out, " %10s : ", pollers[p].name);
336 if (pollers[p].pref == 0)
337 fprintf(out, "disabled, ");
338 else
339 fprintf(out, "pref=%3d, ", pollers[p].pref);
340 if (pollers[p].test(&pollers[p])) {
341 fprintf(out, " test result OK");
342 if (next > 0)
343 usable++;
Willy Tarreaue79c3b22010-11-19 10:20:36 +0100344 } else {
Willy Tarreau2ff76222007-04-09 19:29:56 +0200345 fprintf(out, " test result FAILED");
Willy Tarreaue79c3b22010-11-19 10:20:36 +0100346 if (bp == &pollers[p])
347 bp = NULL;
348 }
Willy Tarreau2ff76222007-04-09 19:29:56 +0200349 fprintf(out, "\n");
350 }
351 }
352 last = next;
353 next = -1;
354 };
355 fprintf(out, "Total: %d (%d usable), will use %s.\n", nbpollers, usable, bp ? bp->name : "none");
356 return 0;
357}
358
359/*
360 * Some pollers may lose their connection after a fork(). It may be necessary
361 * to create initialize part of them again. Returns 0 in case of failure,
362 * otherwise 1. The fork() function may be NULL if unused. In case of error,
363 * the the current poller is destroyed and the caller is responsible for trying
364 * another one by calling init_pollers() again.
365 */
366int fork_poller()
367{
Conrad Hoffmann041751c2014-05-20 14:28:24 +0200368 int fd;
369 for (fd = 0; fd <= maxfd; fd++) {
370 if (fdtab[fd].owner) {
371 fdtab[fd].cloned = 1;
372 }
373 }
374
Willy Tarreau2ff76222007-04-09 19:29:56 +0200375 if (cur_poller.fork) {
376 if (cur_poller.fork(&cur_poller))
377 return 1;
378 cur_poller.term(&cur_poller);
379 return 0;
380 }
381 return 1;
382}
383
384/*
Willy Tarreaubaaee002006-06-26 02:48:02 +0200385 * Local variables:
386 * c-indent-level: 8
387 * c-basic-offset: 8
388 * End:
389 */