[PATCH 1/3] trace: implement %p placeholder for filenames
- From
Jeff King <peff@peff.net>
- Date
- Jun 16, 2015, 19:35 UTC
- Message-ID
- <20150616193531.GA15931@peff.net>
- In-Reply-To
- <20150616193102.GA15856@peff.net>
This lets you trace output on a per-process basis by naming the trace file after the PID. This is probably not all that useful for GIT_TRACE itself (which is about a global view of the process hierarchy anyway), but will be useful for traces which produce large amounts of data (e.g., whole packfiles).
Signed-off-by: Jeff King <peff@peff.net> --- This is the bare minimum to let you distinguish between the stdin of different processes. If we are going to use the trace subsystem to collect more long-term debugging logs, it would probably make sense to add placeholders for the program name and a timestamp. Then you could, for example, leave more verbose debugging enabled on your servers all the time.
Documentation/git.txt | 3 ++- trace.c | 19 +++++++++++++++++-- 2 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/Documentation/git.txt b/Documentation/git.txt index 3453669..80f6392 100644 --- a/Documentation/git.txt +++ b/Documentation/git.txt @@ -984,7 +984,8 @@ trace messages into this file descriptor. Alternatively, if the variable is set to an absolute path (starting with a '/' character), Git will interpret this as a file path and will try to write the trace messages -into it. +into it. If the filename contains the string `%p`, that string +will be replaced with the PID of the traced process. + Unsetting the variable, or setting it to empty, "0" or "false" (case insensitive) disables trace messages. diff --git a/trace.c b/trace.c index 7393926..e1d1360 100644 --- a/trace.c +++ b/trace.c @@ -25,6 +25,16 @@ #include "cache.h" #include "quote.h" +static size_t expand_trace_name(struct strbuf *out, const char *fmt, + void *data) +{ + if (*fmt == 'p') { + strbuf_addf(out, "%lu", (unsigned long)getpid()); + return 1; + } + return 0; +} + /* Get a trace file descriptor from "key" env variable. */ static int get_trace_fd(struct trace_key *key) { @@ -49,17 +59,22 @@ static int get_trace_fd(struct trace_key *key) else if (strlen(trace) == 1 && isdigit(*trace)) key->fd = atoi(trace); else if (is_absolute_path(trace)) { - int fd = open(trace, O_WRONLY | O_APPEND | O_CREAT, 0666); + struct strbuf name = STRBUF_INIT; + int fd; + + strbuf_expand(&name, trace, expand_trace_name, NULL); + fd = open(name.buf, O_WRONLY | O_APPEND | O_CREAT, 0666); if (fd == -1) { fprintf(stderr, "Could not open '%s' for tracing: %s\n" "Defaulting to tracing on stderr...\n", - trace, strerror(errno)); + name.buf, strerror(errno)); key->fd = STDERR_FILENO; } else { key->fd = fd; key->need_close = 1; } + strbuf_release(&name); } else { fprintf(stderr, "What does '%s' for %s mean?\n" "If you want to trace into a file, then please set "
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