WIP: JSON based telemetry

.gitignore

@@ -218,3 +218,4 @@
 *.pdb
 /Debug/
 /Release/
+*.so

Makefile

@@ -126,6 +126,8 @@ all::
 #
 # Define NEEDS_LIBGEN if your libgen needs -lgen when linking
 #
+# Define NEEDS_LIBDL if you need -ldl to get dlopen().
+#
 # Define NO_SYS_SELECT_H if you don't have sys/select.h.
 #
 # Define NO_SYMLINK_HEAD if you never want .git/HEAD to be a symbolic link.
@@ -662,6 +664,7 @@ TEST_PROGRAMS_NEED_X += test-fake-ssh
 TEST_PROGRAMS_NEED_X += test-genrandom
 TEST_PROGRAMS_NEED_X += test-hashmap
 TEST_PROGRAMS_NEED_X += test-index-version
+TEST_PROGRAMS_NEED_X += test-json-writer
 TEST_PROGRAMS_NEED_X += test-lazy-init-name-hash
 TEST_PROGRAMS_NEED_X += test-line-buffer
 TEST_PROGRAMS_NEED_X += test-match-trees
@@ -815,6 +818,7 @@ LIB_OBJS += hashmap.o
 LIB_OBJS += help.o
 LIB_OBJS += hex.o
 LIB_OBJS += ident.o
+LIB_OBJS += json-writer.o
 LIB_OBJS += kwset.o
 LIB_OBJS += levenshtein.o
 LIB_OBJS += line-log.o
@@ -899,6 +903,9 @@ LIB_OBJS += submodule-config.o
 LIB_OBJS += sub-process.o
 LIB_OBJS += symlinks.o
 LIB_OBJS += tag.o
+LIB_OBJS += telemetry.o
+LIB_OBJS += telemetry-perf.o
+LIB_OBJS += telemetry-plugin.o
 LIB_OBJS += tempfile.o
 LIB_OBJS += tmp-objdir.o
 LIB_OBJS += trace.o
@@ -1303,6 +1310,9 @@ endif
 ifdef NEEDS_LIBGEN
 	EXTLIBS += -lgen
 endif
+ifdef NEEDS_LIBDL
+	EXTLIBS += -ldl
+endif
 ifndef NO_GETTEXT
 ifndef LIBC_CONTAINS_LIBINTL
 	EXTLIBS += -lintl

cache.h

@@ -15,6 +15,9 @@
 #include "path.h"
 #include "sha1-array.h"
 #include "repository.h"
+#include "json-writer.h"
+#include "telemetry.h"
+#include "telemetry-perf.h"
 
 #ifndef platform_SHA_CTX
 /*

compat/mingw.h

@@ -145,7 +145,7 @@ static inline int fcntl(int fd, int cmd, ...)
 	return -1;
 }
 /* bash cannot reliably detect negative return codes as failure */
-#define exit(code) exit((code) & 0xff)
+#define exit(code) exit(telemetry_exit((code) & 0xff))
 #define sigemptyset(x) (void)0
 static inline int sigaddset(sigset_t *set, int signum)
 { return 0; }

config.mak.uname

@@ -34,6 +34,7 @@ ifeq ($(uname_S),Linux)
 	HAVE_CLOCK_MONOTONIC = YesPlease
 	# -lrt is needed for clock_gettime on glibc <= 2.16
 	NEEDS_LIBRT = YesPlease
+	NEEDS_LIBDL = YesPlease
 	HAVE_GETDELIM = YesPlease
 	SANE_TEXT_GREP=-a
 	FREAD_READS_DIRECTORIES = UnfortunatelyYes

contrib/telemetry-plugin-examples/README

@@ -0,0 +1,7 @@
+This directory contains some example telemetry plugins.
+These are built as shared libraries and installed in a
+known location.
+
+Users can set "telemetry.plugin" to the absolute path
+of the .so or .dll and have telemetry events routed to
+the plugin.

contrib/telemetry-plugin-examples/trivial-stderr/Makefile

@@ -0,0 +1,3 @@
+all:	Makefile *.c
+	gcc -c -Wall -Werror -fpic trivial-stderr.c
+	gcc -shared -o trivial-stderr.so trivial-stderr.o

contrib/telemetry-plugin-examples/trivial-stderr/trivial-stderr.c

@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+/*
+ * Initialize any private data.
+ *
+ * Return 1 if we can emit events and have a consumer.
+ */
+int plugin_initialize(void)
+{
+	return 1;
+}
+
+/*
+ * Emit the given json string as an event.
+ */
+void plugin_event(const char *json, int is_final_event)
+{
+	fprintf(stderr, "%s\n", json);
+	fflush(stderr);
+}

git-compat-util.h

@@ -1214,4 +1214,13 @@ extern void unleak_memory(const void *ptr, size_t len);
 #define UNLEAK(var) do {} while (0)
 #endif
 
+/*
+ * Intercept exit() so that we can catch the exit-code and generate
+ * telememtry data.
+ */
+#ifndef exit
+int telemetry_exit_event(int exit_code);
+#define exit(code) exit(telemetry_exit_event(code))
+#endif
+
 #endif

git.c

@@ -242,6 +242,7 @@ static int handle_alias(int *argcp, const char ***argv)
 			child.use_shell = 1;
 			argv_array_push(&child.args, alias_string + 1);
 			argv_array_pushv(&child.args, (*argv) + 1);
+			child.is_alias_expansion = 1;
 
 			ret = run_command(&child);
 			if (ret >= 0)   /* normal exit */
@@ -572,6 +573,7 @@ static void execv_dashed_external(const char **argv)
 	cmd.clean_on_exit = 1;
 	cmd.wait_after_clean = 1;
 	cmd.silent_exec_failure = 1;
+	cmd.is_alias_expansion = 1;
 
 	trace_argv_printf(cmd.args.argv, "trace: exec:");
 
@@ -636,6 +638,7 @@ int cmd_main(int argc, const char **argv)
 			cmd = slash + 1;
 	}
 
+	telemetry_start_event(argc, argv);
 	trace_command_performance(argv);
 
 	/*
@@ -699,5 +702,5 @@ int cmd_main(int argc, const char **argv)
 	fprintf(stderr, "Failed to run command '%s': %s\n",
 		cmd, strerror(errno));
 
-	return 1;
+	return telemetry_exit_event(1);
 }