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authorJeff Hostetler <jeffhost@microsoft.com>2019-04-15 20:39:49 (GMT)
committerJunio C Hamano <gitster@pobox.com>2019-04-16 04:37:07 (GMT)
commit08881b9a4c841b77bc2a4a17510ee33b98070b9e (patch)
treeda981a4a5c6ad307bc7dd3d682d3c06f6b03a1e7 /trace2/tr2_sid.c
parentbad229aef232256f3fb6e8ed9c09e26ff654399c (diff)
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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>
Diffstat (limited to 'trace2/tr2_sid.c')
-rw-r--r--trace2/tr2_sid.c53
1 files changed, 49 insertions, 4 deletions
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 struct strbuf tr2sid_buf = STRBUF_INIT;
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 int tr2sid_nr_git_parents;
*/
static void tr2_sid_compute(void)
{
- uint64_t us_now;
const char *parent_sid;
if (tr2sid_buf.len)
@@ -38,9 +85,7 @@ static void tr2_sid_compute(void)
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);
}