trace2: make SIDs more unique
Update SID component construction to use the current UTC datetime
and a portion of the SHA1 of the hostname.
Use an simplified date/time format to make it easier to use the
SID component as a logfile filename.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index cdc00bc..43adbf0 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -78,11 +78,11 @@
+
------------
$ cat ~/log.event
-{"event":"version","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"}
-{"event":"start","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]}
-{"event":"cmd_name","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"}
-{"event":"exit","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0}
-{"event":"atexit","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0}
+{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"}
+{"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]}
+{"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"}
+{"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0}
+{"event":"atexit","sid":"20190408T191610.507018Z-H9b68c35f-P028492","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0}
------------
== Enabling a Target
@@ -540,11 +540,11 @@
------------
{
"event":"version",
- "sid":"1547659722619736-11614",
+ "sid":"20190408T191827.272759Z-H9b68c35f-P011764",
"thread":"main",
- "time":"2019-01-16T17:28:42.620713Z",
+ "time":"2019-04-08T19:18:27.282761Z",
"file":"common-main.c",
- "line":38,
+ "line":42,
...
}
------------
diff --git a/trace2/tr2_sid.c b/trace2/tr2_sid.c
index 984524a..5047095 100644
--- a/trace2/tr2_sid.c
+++ b/trace2/tr2_sid.c
@@ -1,4 +1,5 @@
#include "cache.h"
+#include "trace2/tr2_tbuf.h"
#include "trace2/tr2_sid.h"
#define TR2_ENVVAR_PARENT_SID "GIT_TR2_PARENT_SID"
@@ -7,6 +8,53 @@
static int tr2sid_nr_git_parents;
/*
+ * Compute the final component of the SID representing the current process.
+ * This should uniquely identify the process and be a valid filename (to
+ * allow writing trace2 data to per-process files). It should also be fixed
+ * length for possible use as a database key.
+ *
+ * "<yyyymmdd>T<hhmmss>.<fraction>Z-<host>-<process>"
+ *
+ * where <host> is a 9 character string:
+ * "H<first_8_chars_of_sha1_of_hostname>"
+ * "Localhost" when no hostname.
+ *
+ * where <process> is a 9 character string containing the least signifcant
+ * 32 bits in the process-id.
+ * "P<pid>"
+ * (This is an abribrary choice. On most systems pid_t is a 32 bit value,
+ * so limit doesn't matter. On larger systems, a truncated value is fine
+ * for our purposes here.)
+ */
+static void tr2_sid_append_my_sid_component(void)
+{
+ const struct git_hash_algo *algo = &hash_algos[GIT_HASH_SHA1];
+ struct tr2_tbuf tb_now;
+ git_hash_ctx ctx;
+ pid_t pid = getpid();
+ unsigned char hash[GIT_MAX_RAWSZ + 1];
+ char hex[GIT_MAX_HEXSZ + 1];
+ char hostname[HOST_NAME_MAX + 1];
+
+ tr2_tbuf_utc_datetime(&tb_now);
+ strbuf_addstr(&tr2sid_buf, tb_now.buf);
+
+ strbuf_addch(&tr2sid_buf, '-');
+ if (xgethostname(hostname, sizeof(hostname)))
+ strbuf_add(&tr2sid_buf, "Localhost", 9);
+ else {
+ algo->init_fn(&ctx);
+ algo->update_fn(&ctx, hostname, strlen(hostname));
+ algo->final_fn(hash, &ctx);
+ hash_to_hex_algop_r(hex, hash, algo);
+ strbuf_addch(&tr2sid_buf, 'H');
+ strbuf_add(&tr2sid_buf, hex, 8);
+ }
+
+ strbuf_addf(&tr2sid_buf, "-P%08"PRIx32, (uint32_t)pid);
+}
+
+/*
* Compute a "unique" session id (SID) for the current process. This allows
* all events from this process to have a single label (much like a PID).
*
@@ -20,7 +68,6 @@
*/
static void tr2_sid_compute(void)
{
- uint64_t us_now;
const char *parent_sid;
if (tr2sid_buf.len)
@@ -38,9 +85,7 @@
tr2sid_nr_git_parents++;
}
- us_now = getnanotime() / 1000;
- strbuf_addf(&tr2sid_buf, "%" PRIuMAX "-%" PRIdMAX, (uintmax_t)us_now,
- (intmax_t)getpid());
+ tr2_sid_append_my_sid_component();
setenv(TR2_ENVVAR_PARENT_SID, tr2sid_buf.buf, 1);
}
diff --git a/trace2/tr2_tbuf.c b/trace2/tr2_tbuf.c
index eb1b240..2498482 100644
--- a/trace2/tr2_tbuf.c
+++ b/trace2/tr2_tbuf.c
@@ -30,3 +30,18 @@
tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec,
(long)tv.tv_usec);
}
+
+void tr2_tbuf_utc_datetime(struct tr2_tbuf *tb)
+{
+ struct timeval tv;
+ struct tm tm;
+ time_t secs;
+
+ gettimeofday(&tv, NULL);
+ secs = tv.tv_sec;
+ gmtime_r(&secs, &tm);
+
+ xsnprintf(tb->buf, sizeof(tb->buf), "%4d%02d%02dT%02d%02d%02d.%06ldZ",
+ tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
+ tm.tm_min, tm.tm_sec, (long)tv.tv_usec);
+}
diff --git a/trace2/tr2_tbuf.h b/trace2/tr2_tbuf.h
index 2a1d173..fa853d8 100644
--- a/trace2/tr2_tbuf.h
+++ b/trace2/tr2_tbuf.h
@@ -19,5 +19,6 @@
* Fill buffer with formatted UTC datatime string.
*/
void tr2_tbuf_utc_datetime_extended(struct tr2_tbuf *tb);
+void tr2_tbuf_utc_datetime(struct tr2_tbuf *tb);
#endif /* TR2_TBUF_H */
