trace2/tr2_dst.c
#include "git-compat-util.h"
#include "abspath.h"
#include "sigchain.h"
#include "strbuf.h"
#include "trace2/tr2_dst.h"
#include "trace2/tr2_sid.h"
#include "trace2/tr2_sysenv.h"
/*
* How many attempts we will make at creating an automatically-named trace file.
*/
#define MAX_AUTO_ATTEMPTS 10
/*
* Sentinel file used to detect when we should discard new traces to avoid
* writing too many trace files to a directory.
*/
#define DISCARD_SENTINEL_NAME "git-trace2-discard"
/*
* When set to zero, disables directory file count checks. Otherwise, controls
* how many files we can write to a directory before entering discard mode.
* This can be overridden via the TR2_SYSENV_MAX_FILES setting.
*/
static int tr2env_max_files = 0;
static int tr2_dst_want_warning(void)
{
static int tr2env_dst_debug = -1;
if (tr2env_dst_debug == -1) {
const char *env_value = tr2_sysenv_get(TR2_SYSENV_DST_DEBUG);
if (!env_value || !*env_value)
tr2env_dst_debug = 0;
else
tr2env_dst_debug = atoi(env_value) > 0;
}
return tr2env_dst_debug;
}
void tr2_dst_trace_disable(struct tr2_dst *dst)
{
if (dst->need_close)
close(dst->fd);
dst->fd = 0;
dst->initialized = 1;
dst->need_close = 0;
}
/*
* Check to make sure we're not overloading the target directory with too many
* files. First get the threshold (if present) from the config or envvar. If
* it's zero or unset, disable this check. Next check for the presence of a
* sentinel file, then check file count.
*
* Returns 0 if tracing should proceed as normal. Returns 1 if the sentinel file
* already exists, which means tracing should be disabled. Returns -1 if there
* are too many files but there was no sentinel file, which means we have
* created and should write traces to the sentinel file.
*
* We expect that some trace processing system is gradually collecting files
* from the target directory; after it removes the sentinel file we'll start
* writing traces again.
*/
static int tr2_dst_too_many_files(struct tr2_dst *dst, const char *tgt_prefix)
{
int file_count = 0, max_files = 0, ret = 0;
const char *max_files_var;
DIR *dirp;
struct strbuf path = STRBUF_INIT, sentinel_path = STRBUF_INIT;
struct stat statbuf;
/* Get the config or envvar and decide if we should continue this check */
max_files_var = tr2_sysenv_get(TR2_SYSENV_MAX_FILES);
if (max_files_var && *max_files_var && ((max_files = atoi(max_files_var)) >= 0))
tr2env_max_files = max_files;
if (!tr2env_max_files) {
ret = 0;
goto cleanup;
}
strbuf_addstr(&path, tgt_prefix);
if (!is_dir_sep(path.buf[path.len - 1])) {
strbuf_addch(&path, '/');
}
/* check sentinel */
strbuf_addbuf(&sentinel_path, &path);
strbuf_addstr(&sentinel_path, DISCARD_SENTINEL_NAME);
if (!stat(sentinel_path.buf, &statbuf)) {
ret = 1;
goto cleanup;
}
/* check file count */
dirp = opendir(path.buf);
while (file_count < tr2env_max_files && dirp && readdir(dirp))
file_count++;
if (dirp)
closedir(dirp);
if (file_count >= tr2env_max_files) {
dst->too_many_files = 1;
dst->fd = open(sentinel_path.buf, O_WRONLY | O_CREAT | O_EXCL, 0666);
ret = -1;
goto cleanup;
}
cleanup:
strbuf_release(&path);
strbuf_release(&sentinel_path);
return ret;
}
static int tr2_dst_try_auto_path(struct tr2_dst *dst, const char *tgt_prefix)
{
int too_many_files;
const char *last_slash, *sid = tr2_sid_get();
struct strbuf path = STRBUF_INIT;
size_t base_path_len;
unsigned attempt_count;
last_slash = strrchr(sid, '/');
if (last_slash)
sid = last_slash + 1;
strbuf_addstr(&path, tgt_prefix);
if (!is_dir_sep(path.buf[path.len - 1]))
strbuf_addch(&path, '/');
strbuf_addstr(&path, sid);
base_path_len = path.len;
too_many_files = tr2_dst_too_many_files(dst, tgt_prefix);
if (!too_many_files) {
for (attempt_count = 0; attempt_count < MAX_AUTO_ATTEMPTS; attempt_count++) {
if (attempt_count > 0) {
strbuf_setlen(&path, base_path_len);
strbuf_addf(&path, ".%d", attempt_count);
}
dst->fd = open(path.buf, O_WRONLY | O_CREAT | O_EXCL, 0666);
if (dst->fd != -1)
break;
}
} else if (too_many_files == 1) {
strbuf_release(&path);
if (tr2_dst_want_warning())
warning("trace2: not opening %s trace file due to too "
"many files in target directory %s",
tr2_sysenv_display_name(dst->sysenv_var),
tgt_prefix);
return 0;
}
if (dst->fd == -1) {
if (tr2_dst_want_warning())
warning("trace2: could not open '%.*s' for '%s' tracing: %s",
(int) base_path_len, path.buf,
tr2_sysenv_display_name(dst->sysenv_var),
strerror(errno));
tr2_dst_trace_disable(dst);
strbuf_release(&path);
return 0;
}
strbuf_release(&path);
dst->need_close = 1;
dst->initialized = 1;
return dst->fd;
}
static int tr2_dst_try_path(struct tr2_dst *dst, const char *tgt_value)
{
int fd = open(tgt_value, O_WRONLY | O_APPEND | O_CREAT, 0666);
if (fd == -1) {
if (tr2_dst_want_warning())
warning("trace2: could not open '%s' for '%s' tracing: %s",
tgt_value,
tr2_sysenv_display_name(dst->sysenv_var),
strerror(errno));
tr2_dst_trace_disable(dst);
return 0;
}
dst->fd = fd;
dst->need_close = 1;
dst->initialized = 1;
return dst->fd;
}
#ifndef NO_UNIX_SOCKETS
#define PREFIX_AF_UNIX "af_unix:"
#define PREFIX_AF_UNIX_STREAM "af_unix:stream:"
#define PREFIX_AF_UNIX_DGRAM "af_unix:dgram:"
static int tr2_dst_try_uds_connect(const char *path, int sock_type, int *out_fd)
{
int fd;
struct sockaddr_un sa;
fd = socket(AF_UNIX, sock_type, 0);
if (fd == -1)
return -1;
sa.sun_family = AF_UNIX;
strlcpy(sa.sun_path, path, sizeof(sa.sun_path));
if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
int saved_errno = errno;
close(fd);
errno = saved_errno;
return -1;
}
*out_fd = fd;
return 0;
}
#define TR2_DST_UDS_TRY_STREAM (1 << 0)
#define TR2_DST_UDS_TRY_DGRAM (1 << 1)
static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
const char *tgt_value)
{
unsigned int uds_try = 0;
int fd;
const char *path = NULL;
/*
* Allow "af_unix:[<type>:]<absolute_path>"
*
* Trace2 always writes complete individual messages (without
* chunking), so we can talk to either DGRAM or STREAM type sockets.
*
* Allow the user to explicitly request the socket type.
*
* If they omit the socket type, try one and then the other.
*/
if (skip_prefix(tgt_value, PREFIX_AF_UNIX_STREAM, &path))
uds_try |= TR2_DST_UDS_TRY_STREAM;
else if (skip_prefix(tgt_value, PREFIX_AF_UNIX_DGRAM, &path))
uds_try |= TR2_DST_UDS_TRY_DGRAM;
else if (skip_prefix(tgt_value, PREFIX_AF_UNIX, &path))
uds_try |= TR2_DST_UDS_TRY_STREAM | TR2_DST_UDS_TRY_DGRAM;
if (!path || !*path) {
if (tr2_dst_want_warning())
warning("trace2: invalid AF_UNIX value '%s' for '%s' tracing",
tgt_value,
tr2_sysenv_display_name(dst->sysenv_var));
tr2_dst_trace_disable(dst);
return 0;
}
if (!is_absolute_path(path) ||
strlen(path) >= sizeof(((struct sockaddr_un *)0)->sun_path)) {
if (tr2_dst_want_warning())
warning("trace2: invalid AF_UNIX path '%s' for '%s' tracing",
path, tr2_sysenv_display_name(dst->sysenv_var));
tr2_dst_trace_disable(dst);
return 0;
}
if (uds_try & TR2_DST_UDS_TRY_STREAM) {
if (!tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd))
goto connected;
if (errno != EPROTOTYPE)
goto error;
}
if (uds_try & TR2_DST_UDS_TRY_DGRAM) {
if (!tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd))
goto connected;
}
error:
if (tr2_dst_want_warning())
warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
path, tr2_sysenv_display_name(dst->sysenv_var),
strerror(errno));
tr2_dst_trace_disable(dst);
return 0;
connected:
dst->fd = fd;
dst->need_close = 1;
dst->initialized = 1;
return dst->fd;
}
#endif
static void tr2_dst_malformed_warning(struct tr2_dst *dst,
const char *tgt_value)
{
warning("trace2: unknown value for '%s': '%s'",
tr2_sysenv_display_name(dst->sysenv_var), tgt_value);
}
int tr2_dst_get_trace_fd(struct tr2_dst *dst)
{
const char *tgt_value;
/* don't open twice */
if (dst->initialized)
return dst->fd;
dst->initialized = 1;
tgt_value = tr2_sysenv_get(dst->sysenv_var);
if (!tgt_value || !strcmp(tgt_value, "") || !strcmp(tgt_value, "0") ||
!strcasecmp(tgt_value, "false")) {
dst->fd = 0;
return dst->fd;
}
if (!strcmp(tgt_value, "1") || !strcasecmp(tgt_value, "true")) {
dst->fd = STDERR_FILENO;
return dst->fd;
}
if (strlen(tgt_value) == 1 && isdigit(*tgt_value)) {
dst->fd = atoi(tgt_value);
return dst->fd;
}
if (is_absolute_path(tgt_value)) {
if (is_directory(tgt_value))
return tr2_dst_try_auto_path(dst, tgt_value);
else
return tr2_dst_try_path(dst, tgt_value);
}
#ifndef NO_UNIX_SOCKETS
if (starts_with(tgt_value, PREFIX_AF_UNIX))
return tr2_dst_try_unix_domain_socket(dst, tgt_value);
#endif
/* Always warn about malformed values. */
tr2_dst_malformed_warning(dst, tgt_value);
tr2_dst_trace_disable(dst);
return 0;
}
int tr2_dst_trace_want(struct tr2_dst *dst)
{
return !!tr2_dst_get_trace_fd(dst);
}
void tr2_dst_write_line(struct tr2_dst *dst, struct strbuf *buf_line)
{
int fd = tr2_dst_get_trace_fd(dst);
ssize_t bytes;
strbuf_complete_line(buf_line); /* ensure final NL on buffer */
/*
* We do not use write_in_full() because we do not want
* a short-write to try again. We are using O_APPEND mode
* files and the kernel handles the atomic seek+write. If
* another thread or git process is concurrently writing to
* this fd or file, our remainder-write may not be contiguous
* with our initial write of this message. And that will
* confuse readers. So just don't bother.
*
* It is assumed that TRACE2 messages are short enough that
* the system can write them in 1 attempt and we won't see
* a short-write.
*
* If we get an IO error, just close the trace dst.
*/
sigchain_push(SIGPIPE, SIG_IGN);
bytes = write(fd, buf_line->buf, buf_line->len);
sigchain_pop(SIGPIPE);
if (bytes >= 0)
return;
tr2_dst_trace_disable(dst);
if (tr2_dst_want_warning())
warning("unable to write trace to '%s': %s",
tr2_sysenv_display_name(dst->sysenv_var),
strerror(errno));
}