summaryrefslogtreecommitdiffstats
path: root/trace2/tr2_dst.c
diff options
context:
space:
mode:
Diffstat (limited to 'trace2/tr2_dst.c')
-rw-r--r--trace2/tr2_dst.c396
1 files changed, 396 insertions, 0 deletions
diff --git a/trace2/tr2_dst.c b/trace2/tr2_dst.c
new file mode 100644
index 0000000..5be892c
--- /dev/null
+++ b/trace2/tr2_dst.c
@@ -0,0 +1,396 @@
+#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));
+}