Merge branch 'js/t3404-typofix'
[git/git.git] / trace2 / tr2_sid.c
1 #include "cache.h"
2 #include "trace2/tr2_tbuf.h"
3 #include "trace2/tr2_sid.h"
4
5 #define TR2_ENVVAR_PARENT_SID "GIT_TRACE2_PARENT_SID"
6
7 static struct strbuf tr2sid_buf = STRBUF_INIT;
8 static int tr2sid_nr_git_parents;
9
10 /*
11 * Compute the final component of the SID representing the current process.
12 * This should uniquely identify the process and be a valid filename (to
13 * allow writing trace2 data to per-process files). It should also be fixed
14 * length for possible use as a database key.
15 *
16 * "<yyyymmdd>T<hhmmss>.<fraction>Z-<host>-<process>"
17 *
18 * where <host> is a 9 character string:
19 * "H<first_8_chars_of_sha1_of_hostname>"
20 * "Localhost" when no hostname.
21 *
22 * where <process> is a 9 character string containing the least signifcant
23 * 32 bits in the process-id.
24 * "P<pid>"
25 * (This is an abribrary choice. On most systems pid_t is a 32 bit value,
26 * so limit doesn't matter. On larger systems, a truncated value is fine
27 * for our purposes here.)
28 */
29 static void tr2_sid_append_my_sid_component(void)
30 {
31 const struct git_hash_algo *algo = &hash_algos[GIT_HASH_SHA1];
32 struct tr2_tbuf tb_now;
33 git_hash_ctx ctx;
34 pid_t pid = getpid();
35 unsigned char hash[GIT_MAX_RAWSZ + 1];
36 char hex[GIT_MAX_HEXSZ + 1];
37 char hostname[HOST_NAME_MAX + 1];
38
39 tr2_tbuf_utc_datetime(&tb_now);
40 strbuf_addstr(&tr2sid_buf, tb_now.buf);
41
42 strbuf_addch(&tr2sid_buf, '-');
43 if (xgethostname(hostname, sizeof(hostname)))
44 strbuf_add(&tr2sid_buf, "Localhost", 9);
45 else {
46 algo->init_fn(&ctx);
47 algo->update_fn(&ctx, hostname, strlen(hostname));
48 algo->final_fn(hash, &ctx);
49 hash_to_hex_algop_r(hex, hash, algo);
50 strbuf_addch(&tr2sid_buf, 'H');
51 strbuf_add(&tr2sid_buf, hex, 8);
52 }
53
54 strbuf_addf(&tr2sid_buf, "-P%08"PRIx32, (uint32_t)pid);
55 }
56
57 /*
58 * Compute a "unique" session id (SID) for the current process. This allows
59 * all events from this process to have a single label (much like a PID).
60 *
61 * Export this into our environment so that all child processes inherit it.
62 *
63 * If we were started by another git instance, use our parent's SID as a
64 * prefix. (This lets us track parent/child relationships even if there
65 * is an intermediate shell process.)
66 *
67 * Additionally, count the number of nested git processes.
68 */
69 static void tr2_sid_compute(void)
70 {
71 const char *parent_sid;
72
73 if (tr2sid_buf.len)
74 return;
75
76 parent_sid = getenv(TR2_ENVVAR_PARENT_SID);
77 if (parent_sid && *parent_sid) {
78 const char *p;
79 for (p = parent_sid; *p; p++)
80 if (*p == '/')
81 tr2sid_nr_git_parents++;
82
83 strbuf_addstr(&tr2sid_buf, parent_sid);
84 strbuf_addch(&tr2sid_buf, '/');
85 tr2sid_nr_git_parents++;
86 }
87
88 tr2_sid_append_my_sid_component();
89
90 setenv(TR2_ENVVAR_PARENT_SID, tr2sid_buf.buf, 1);
91 }
92
93 const char *tr2_sid_get(void)
94 {
95 if (!tr2sid_buf.len)
96 tr2_sid_compute();
97
98 return tr2sid_buf.buf;
99 }
100
101 int tr2_sid_depth(void)
102 {
103 if (!tr2sid_buf.len)
104 tr2_sid_compute();
105
106 return tr2sid_nr_git_parents;
107 }
108
109 void tr2_sid_release(void)
110 {
111 strbuf_release(&tr2sid_buf);
112 }