blob: 977b58e5aae7f21118130c64300d42c84e7f6541 [file] [log] [blame]
/*
* Ring buffer management
*
* Copyright (C) 2000-2019 Willy Tarreau - w@1wt.eu
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, version 2.1
* exclusively.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stdlib.h>
#include <haproxy/api.h>
#include <haproxy/applet.h>
#include <haproxy/buf.h>
#include <haproxy/cli.h>
#include <haproxy/ring.h>
#include <haproxy/stream_interface.h>
#include <haproxy/thread.h>
/* Initialize a pre-allocated ring with the buffer area
* of size */
void ring_init(struct ring *ring, void *area, size_t size)
{
HA_RWLOCK_INIT(&ring->lock);
LIST_INIT(&ring->waiters);
ring->readers_count = 0;
ring->ofs = 0;
ring->buf = b_make(area, size, 0, 0);
/* write the initial RC byte */
b_putchr(&ring->buf, 0);
}
/* Creates and returns a ring buffer of size <size> bytes. Returns NULL on
* allocation failure.
*/
struct ring *ring_new(size_t size)
{
struct ring *ring = NULL;
void *area = NULL;
if (size < 2)
goto fail;
ring = malloc(sizeof(*ring));
if (!ring)
goto fail;
area = malloc(size);
if (!area)
goto fail;
ring_init(ring, area, size);
return ring;
fail:
free(area);
free(ring);
return NULL;
}
/* Resizes existing ring <ring> to <size> which must be larger, without losing
* its contents. The new size must be at least as large as the previous one or
* no change will be performed. The pointer to the ring is returned on success,
* or NULL on allocation failure. This will lock the ring for writes.
*/
struct ring *ring_resize(struct ring *ring, size_t size)
{
void *area;
if (b_size(&ring->buf) >= size)
return ring;
area = malloc(size);
if (!area)
return NULL;
HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
/* recheck the buffer's size, it may have changed during the malloc */
if (b_size(&ring->buf) < size) {
/* copy old contents */
b_getblk(&ring->buf, area, ring->buf.data, 0);
area = HA_ATOMIC_XCHG(&ring->buf.area, area);
ring->buf.size = size;
}
HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
free(area);
return ring;
}
/* destroys and frees ring <ring> */
void ring_free(struct ring *ring)
{
if (!ring)
return;
free(ring->buf.area);
free(ring);
}
/* Tries to send <npfx> parts from <prefix> followed by <nmsg> parts from <msg>
* to ring <ring>. The message is sent atomically. It may be truncated to
* <maxlen> bytes if <maxlen> is non-null. There is no distinction between the
* two lists, it's just a convenience to help the caller prepend some prefixes
* when necessary. It takes the ring's write lock to make sure no other thread
* will touch the buffer during the update. Returns the number of bytes sent,
* or <=0 on failure.
*/
ssize_t ring_write(struct ring *ring, size_t maxlen, const struct ist pfx[], size_t npfx, const struct ist msg[], size_t nmsg)
{
struct buffer *buf = &ring->buf;
struct appctx *appctx;
size_t totlen = 0;
size_t lenlen;
uint64_t dellen;
int dellenlen;
ssize_t sent = 0;
int i;
/* we have to find some room to add our message (the buffer is
* never empty and at least contains the previous counter) and
* to update both the buffer contents and heads at the same
* time (it's doable using atomic ops but not worth the
* trouble, let's just lock). For this we first need to know
* the total message's length. We cannot measure it while
* copying due to the varint encoding of the length.
*/
for (i = 0; i < npfx; i++)
totlen += pfx[i].len;
for (i = 0; i < nmsg; i++)
totlen += msg[i].len;
if (totlen > maxlen)
totlen = maxlen;
lenlen = varint_bytes(totlen);
HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
if (lenlen + totlen + 1 + 1 > b_size(buf))
goto done_buf;
while (b_room(buf) < lenlen + totlen + 1) {
/* we need to delete the oldest message (from the end),
* and we have to stop if there's a reader stuck there.
* Unless there's corruption in the buffer it's guaranteed
* that we have enough data to find 1 counter byte, a
* varint-encoded length (1 byte min) and the message
* payload (0 bytes min).
*/
if (*b_head(buf))
goto done_buf;
dellenlen = b_peek_varint(buf, 1, &dellen);
if (!dellenlen)
goto done_buf;
BUG_ON(b_data(buf) < 1 + dellenlen + dellen);
b_del(buf, 1 + dellenlen + dellen);
ring->ofs += 1 + dellenlen + dellen;
}
/* OK now we do have room */
__b_put_varint(buf, totlen);
totlen = 0;
for (i = 0; i < npfx; i++) {
size_t len = pfx[i].len;
if (len + totlen > maxlen)
len = maxlen - totlen;
if (len)
__b_putblk(buf, pfx[i].ptr, len);
totlen += len;
}
for (i = 0; i < nmsg; i++) {
size_t len = msg[i].len;
if (len + totlen > maxlen)
len = maxlen - totlen;
if (len)
__b_putblk(buf, msg[i].ptr, len);
totlen += len;
}
*b_tail(buf) = 0; buf->data++; // new read counter
sent = lenlen + totlen + 1;
/* notify potential readers */
list_for_each_entry(appctx, &ring->waiters, wait_entry)
appctx_wakeup(appctx);
done_buf:
HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
return sent;
}
/* Tries to attach appctx <appctx> as a new reader on ring <ring>. This is
* meant to be used by low level appctx code such as CLI or ring forwarding.
* For higher level functions, please see the relevant parts in appctx or CLI.
* It returns non-zero on success or zero on failure if too many users are
* already attached. On success, the caller MUST call ring_detach_appctx()
* to detach itself, even if it was never woken up.
*/
int ring_attach(struct ring *ring)
{
int users = ring->readers_count;
do {
if (users >= 255)
return 0;
} while (!_HA_ATOMIC_CAS(&ring->readers_count, &users, users + 1));
return 1;
}
/* detach an appctx from a ring. The appctx is expected to be waiting at
* offset <ofs>. Nothing is done if <ring> is NULL.
*/
void ring_detach_appctx(struct ring *ring, struct appctx *appctx, size_t ofs)
{
if (!ring)
return;
HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
if (ofs != ~0) {
/* reader was still attached */
ofs -= ring->ofs;
BUG_ON(ofs >= b_size(&ring->buf));
LIST_DEL_INIT(&appctx->wait_entry);
HA_ATOMIC_DEC(b_peek(&ring->buf, ofs));
}
HA_ATOMIC_DEC(&ring->readers_count);
HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
}
/* Tries to attach CLI handler <appctx> as a new reader on ring <ring>. This is
* meant to be used when registering a CLI function to dump a buffer, so it
* returns zero on success, or non-zero on failure with a message in the appctx
* CLI context. It automatically sets the io_handler and io_release callbacks if
* they were not set.
*/
int ring_attach_cli(struct ring *ring, struct appctx *appctx)
{
if (!ring_attach(ring))
return cli_err(appctx,
"Sorry, too many watchers (255) on this ring buffer. "
"What could it have so interesting to attract so many watchers ?");
if (!appctx->io_handler)
appctx->io_handler = cli_io_handler_show_ring;
if (!appctx->io_release)
appctx->io_release = cli_io_release_show_ring;
appctx->ctx.cli.p0 = ring;
appctx->ctx.cli.o0 = ~0; // start from the oldest event
return 0;
}
/* This function dumps all events from the ring whose pointer is in <p0> into
* the appctx's output buffer, and takes from <o0> the seek offset into the
* buffer's history (0 for oldest known event). It looks at <i0> for boolean
* options: bit0 means it must wait for new data or any key to be pressed. Bit1
* means it must seek directly to the end to wait for new contents. It returns
* 0 if the output buffer or events are missing is full and it needs to be
* called again, otherwise non-zero. It is meant to be used with
* cli_release_show_ring() to clean up.
*/
int cli_io_handler_show_ring(struct appctx *appctx)
{
struct stream_interface *si = appctx->owner;
struct ring *ring = appctx->ctx.cli.p0;
struct buffer *buf = &ring->buf;
size_t ofs = appctx->ctx.cli.o0;
size_t last_ofs;
uint64_t msg_len;
size_t len, cnt;
int ret;
if (unlikely(si_ic(si)->flags & (CF_WRITE_ERROR|CF_SHUTW)))
return 1;
HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
LIST_DEL_INIT(&appctx->wait_entry);
HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
HA_RWLOCK_RDLOCK(LOGSRV_LOCK, &ring->lock);
/* explanation for the initialization below: it would be better to do
* this in the parsing function but this would occasionally result in
* dropped events because we'd take a reference on the oldest message
* and keep it while being scheduled. Thus instead let's take it the
* first time we enter here so that we have a chance to pass many
* existing messages before grabbing a reference to a location. This
* value cannot be produced after initialization.
*/
if (unlikely(ofs == ~0)) {
ofs = 0;
/* going to the end means looking at tail-1 */
if (appctx->ctx.cli.i0 & 2)
ofs += b_data(buf) - 1;
HA_ATOMIC_INC(b_peek(buf, ofs));
ofs += ring->ofs;
}
/* we were already there, adjust the offset to be relative to
* the buffer's head and remove us from the counter.
*/
ofs -= ring->ofs;
BUG_ON(ofs >= buf->size);
HA_ATOMIC_DEC(b_peek(buf, ofs));
/* in this loop, ofs always points to the counter byte that precedes
* the message so that we can take our reference there if we have to
* stop before the end (ret=0).
*/
ret = 1;
while (ofs + 1 < b_data(buf)) {
cnt = 1;
len = b_peek_varint(buf, ofs + cnt, &msg_len);
if (!len)
break;
cnt += len;
BUG_ON(msg_len + ofs + cnt + 1 > b_data(buf));
if (unlikely(msg_len + 1 > b_size(&trash))) {
/* too large a message to ever fit, let's skip it */
ofs += cnt + msg_len;
continue;
}
chunk_reset(&trash);
len = b_getblk(buf, trash.area, msg_len, ofs + cnt);
trash.data += len;
trash.area[trash.data++] = '\n';
if (ci_putchk(si_ic(si), &trash) == -1) {
si_rx_room_blk(si);
ret = 0;
break;
}
ofs += cnt + msg_len;
}
HA_ATOMIC_INC(b_peek(buf, ofs));
ofs += ring->ofs;
last_ofs = ring->ofs;
appctx->ctx.cli.o0 = ofs;
HA_RWLOCK_RDUNLOCK(LOGSRV_LOCK, &ring->lock);
if (ret && (appctx->ctx.cli.i0 & 1)) {
/* we've drained everything and are configured to wait for more
* data or an event (keypress, close)
*/
if (!si_oc(si)->output && !(si_oc(si)->flags & CF_SHUTW)) {
/* let's be woken up once new data arrive */
HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
LIST_APPEND(&ring->waiters, &appctx->wait_entry);
ofs = ring->ofs;
HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
if (ofs != last_ofs) {
/* more data was added into the ring between the
* unlock and the lock, and the writer might not
* have seen us. We need to reschedule a read.
*/
si_rx_endp_more(si);
} else
si_rx_endp_done(si);
ret = 0;
}
/* always drain all the request */
co_skip(si_oc(si), si_oc(si)->output);
}
return ret;
}
/* must be called after cli_io_handler_show_ring() above */
void cli_io_release_show_ring(struct appctx *appctx)
{
struct ring *ring = appctx->ctx.cli.p0;
size_t ofs = appctx->ctx.cli.o0;
ring_detach_appctx(ring, appctx, ofs);
}
/*
* Local variables:
* c-indent-level: 8
* c-basic-offset: 8
* End:
*/