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authorJeff Hostetler <jeffhost@microsoft.com>2019-02-22 22:25:01 (GMT)
committerJunio C Hamano <gitster@pobox.com>2019-02-22 23:27:59 (GMT)
commitee4512ed481a126dadd33334186e0e759d7f2f47 (patch)
tree4bc0418115d44b1833c1d24d2ac1c92f067b7ad3 /trace2/tr2_dst.c
parente544221d97a57a9be7ba18a0df52a15b4cc76f97 (diff)
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trace2: create new combined trace facility
Create a new unified tracing facility for git. The eventual intent is to replace the current trace_printf* and trace_performance* routines with a unified set of git_trace2* routines. In addition to the usual printf-style API, trace2 provides higer-level event verbs with fixed-fields allowing structured data to be written. This makes post-processing and analysis easier for external tools. Trace2 defines 3 output targets. These are set using the environment variables "GIT_TR2", "GIT_TR2_PERF", and "GIT_TR2_EVENT". These may be set to "1" or to an absolute pathname (just like the current GIT_TRACE). * GIT_TR2 is intended to be a replacement for GIT_TRACE and logs command summary data. * GIT_TR2_PERF is intended as a replacement for GIT_TRACE_PERFORMANCE. It extends the output with columns for the command process, thread, repo, absolute and relative elapsed times. It reports events for child process start/stop, thread start/stop, and per-thread function nesting. * GIT_TR2_EVENT is a new structured format. It writes event data as a series of JSON records. Calls to trace2 functions log to any of the 3 output targets enabled without the need to call different trace_printf* or trace_performance* routines. Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'trace2/tr2_dst.c')
-rw-r--r--trace2/tr2_dst.c252
1 files changed, 252 insertions, 0 deletions
diff --git a/trace2/tr2_dst.c b/trace2/tr2_dst.c
new file mode 100644
index 0000000..fd490a4
--- /dev/null
+++ b/trace2/tr2_dst.c
@@ -0,0 +1,252 @@
+#include "cache.h"
+#include "trace2/tr2_dst.h"
+
+/*
+ * If a Trace2 target cannot be opened for writing, we should issue a
+ * warning to stderr, but this is very annoying if the target is a pipe
+ * or socket and beyond the user's control -- especially since every
+ * git command (and sub-command) will print the message. So we silently
+ * eat these warnings and just discard the trace data.
+ *
+ * Enable the following environment variable to see these warnings.
+ */
+#define TR2_ENVVAR_DST_DEBUG "GIT_TR2_DST_DEBUG"
+
+static int tr2_dst_want_warning(void)
+{
+ static int tr2env_dst_debug = -1;
+
+ if (tr2env_dst_debug == -1) {
+ const char *env_value = getenv(TR2_ENVVAR_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;
+}
+
+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, dst->env_var_name, 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 errno;
+
+ sa.sun_family = AF_UNIX;
+ strlcpy(sa.sun_path, path, sizeof(sa.sun_path));
+
+ if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
+ int e = errno;
+ close(fd);
+ return e;
+ }
+
+ *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;
+ int e;
+ 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, dst->env_var_name);
+
+ 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, dst->env_var_name);
+
+ tr2_dst_trace_disable(dst);
+ return 0;
+ }
+
+ if (uds_try & TR2_DST_UDS_TRY_STREAM) {
+ e = tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd);
+ if (!e)
+ goto connected;
+ if (e != EPROTOTYPE)
+ goto error;
+ }
+ if (uds_try & TR2_DST_UDS_TRY_DGRAM) {
+ e = tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd);
+ if (!e)
+ goto connected;
+ }
+
+error:
+ if (tr2_dst_want_warning())
+ warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
+ path, dst->env_var_name, strerror(e));
+
+ 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)
+{
+ struct strbuf buf = STRBUF_INIT;
+
+ strbuf_addf(&buf, "trace2: unknown value for '%s': '%s'",
+ dst->env_var_name, tgt_value);
+ warning("%s", buf.buf);
+
+ strbuf_release(&buf);
+}
+
+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 = getenv(dst->env_var_name);
+
+ 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))
+ 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);
+
+ 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.
+ */
+ if (write(fd, buf_line->buf, buf_line->len) >= 0)
+ return;
+
+ if (tr2_dst_want_warning())
+ warning("unable to write trace to '%s': %s", dst->env_var_name,
+ strerror(errno));
+ tr2_dst_trace_disable(dst);
+}