trace2: use system/global config for default trace2 settings

Teach git to read the system and global config files for
default Trace2 settings.  This allows system-wide Trace2 settings to
be installed and inherited to make it easier to manage a collection of
systems.

The original GIT_TR2* environment variables are loaded afterwards and
can be used to override the system settings.

Only the system and global config files are used.  Repo and worktree
local config files are ignored.  Likewise, the "-c" command line
arguments are also ignored.  These limits are for performance reasons.

(1) For users not using Trace2, there should be minimal overhead to
detect that Trace2 is not enabled.  In particular, Trace2 should not
allocate lots of otherwise unused data strucutres.

(2) For accurate performance measurements, Trace2 should be initialized
as early in the git process as possible, and before most of the normal
git process initialization (which involves discovering the .git directory
and reading a hierarchy of config files).

Signed-off-by: Jeff Hostetler <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jeffhostetler

Makefile

@@ -1005,6 +1005,7 @@ LIB_OBJS += trace2/tr2_cfg.o
 LIB_OBJS += trace2/tr2_cmd_name.o
 LIB_OBJS += trace2/tr2_dst.o
 LIB_OBJS += trace2/tr2_sid.o
+LIB_OBJS += trace2/tr2_sysenv.o
 LIB_OBJS += trace2/tr2_tbuf.o
 LIB_OBJS += trace2/tr2_tgt_event.o
 LIB_OBJS += trace2/tr2_tgt_normal.o

t/t0210-trace2-normal.sh

@@ -3,6 +3,11 @@
 test_description='test trace2 facility (normal target)'
 . ./test-lib.sh
 
+# Turn off any inherited trace2 settings for this test.
+sane_unset GIT_TR2 GIT_TR2_PERF GIT_TR2_EVENT
+sane_unset GIT_TR2_BRIEF
+sane_unset GIT_TR2_CONFIG_PARAMS
+
 # Add t/helper directory to PATH so that we can use a relative
 # path to run nested instances of test-tool.exe (see 004child).
 # This helps with HEREDOC comparisons later.
@@ -15,11 +20,6 @@ PATH="$TTDIR:$PATH" && export PATH
 # Warning: So you may see extra lines in artifact files when
 # Warning: interactively debugging.
 
-# Turn off any inherited trace2 settings for this test.
-unset GIT_TR2 GIT_TR2_PERF GIT_TR2_EVENT
-unset GIT_TR2_BRIEF
-unset GIT_TR2_CONFIG_PARAMS
-
 V=$(git version | sed -e 's/^git version //') && export V
 
 # There are multiple trace2 targets: normal, perf, and event.
@@ -132,4 +132,43 @@ test_expect_success 'normal stream, error event' '
 	test_cmp expect actual
 '
 
+sane_unset GIT_TR2_BRIEF
+
+# Now test without environment variables and get all Trace2 settings
+# from the global config.
+
+test_expect_success 'using global config, normal stream, return code 0' '
+	test_when_finished "rm trace.normal actual expect" &&
+	test_config_global trace2.normalBrief 1 &&
+	test_config_global trace2.normalTarget "$(pwd)/trace.normal" &&
+	test-tool trace2 001return 0 &&
+	perl "$TEST_DIRECTORY/t0210/scrub_normal.perl" <trace.normal >actual &&
+	cat >expect <<-EOF &&
+		version $V
+		start _EXE_ trace2 001return 0
+		cmd_name trace2 (trace2)
+		exit elapsed:_TIME_ code:0
+		atexit elapsed:_TIME_ code:0
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'using global config with include' '
+	test_when_finished "rm trace.normal actual expect real.gitconfig" &&
+	test_config_global trace2.normalBrief 1 &&
+	test_config_global trace2.normalTarget "$(pwd)/trace.normal" &&
+	mv "$(pwd)/.gitconfig" "$(pwd)/real.gitconfig" &&
+	test_config_global include.path "$(pwd)/real.gitconfig" &&
+	test-tool trace2 001return 0 &&
+	perl "$TEST_DIRECTORY/t0210/scrub_normal.perl" <trace.normal >actual &&
+	cat >expect <<-EOF &&
+		version $V
+		start _EXE_ trace2 001return 0
+		cmd_name trace2 (trace2)
+		exit elapsed:_TIME_ code:0
+		atexit elapsed:_TIME_ code:0
+	EOF
+	test_cmp expect actual
+'
+
 test_done

t/t0211-trace2-perf.sh

@@ -3,6 +3,11 @@
 test_description='test trace2 facility (perf target)'
 . ./test-lib.sh
 
+# Turn off any inherited trace2 settings for this test.
+sane_unset GIT_TR2 GIT_TR2_PERF GIT_TR2_EVENT
+sane_unset GIT_TR2_PERF_BRIEF
+sane_unset GIT_TR2_CONFIG_PARAMS
+
 # Add t/helper directory to PATH so that we can use a relative
 # path to run nested instances of test-tool.exe (see 004child).
 # This helps with HEREDOC comparisons later.
@@ -15,11 +20,6 @@ PATH="$TTDIR:$PATH" && export PATH
 # Warning: So you may see extra lines in artifact files when
 # Warning: interactively debugging.
 
-# Turn off any inherited trace2 settings for this test.
-unset GIT_TR2 GIT_TR2_PERF GIT_TR2_EVENT
-unset GIT_TR2_PERF_BRIEF
-unset GIT_TR2_CONFIG_PARAMS
-
 V=$(git version | sed -e 's/^git version //') && export V
 
 # There are multiple trace2 targets: normal, perf, and event.
@@ -150,4 +150,25 @@ test_expect_success 'perf stream, child processes' '
 	test_cmp expect actual
 '
 
+sane_unset GIT_TR2_PERF_BRIEF
+
+# Now test without environment variables and get all Trace2 settings
+# from the global config.
+
+test_expect_success 'using global config, perf stream, return code 0' '
+	test_when_finished "rm trace.perf actual expect" &&
+	test_config_global trace2.perfBrief 1 &&
+	test_config_global trace2.perfTarget "$(pwd)/trace.perf" &&
+	test-tool trace2 001return 0 &&
+	perl "$TEST_DIRECTORY/t0211/scrub_perf.perl" <trace.perf >actual &&
+	cat >expect <<-EOF &&
+		d0|main|version|||||$V
+		d0|main|start||_T_ABS_|||_EXE_ trace2 001return 0
+		d0|main|cmd_name|||||trace2 (trace2)
+		d0|main|exit||_T_ABS_|||code:0
+		d0|main|atexit||_T_ABS_|||code:0
+	EOF
+	test_cmp expect actual
+'
+
 test_done

t/t0212-trace2-event.sh

@@ -3,6 +3,11 @@
 test_description='test trace2 facility'
 . ./test-lib.sh
 
+# Turn off any inherited trace2 settings for this test.
+sane_unset GIT_TR2 GIT_TR2_PERF GIT_TR2_EVENT
+sane_unset GIT_TR2_BARE
+sane_unset GIT_TR2_CONFIG_PARAMS
+
 perl -MJSON::PP -e 0 >/dev/null 2>&1 && test_set_prereq JSON_PP
 
 # Add t/helper directory to PATH so that we can use a relative
@@ -17,11 +22,6 @@ PATH="$TTDIR:$PATH" && export PATH
 # Warning: So you may see extra lines in artifact files when
 # Warning: interactively debugging.
 
-# Turn off any inherited trace2 settings for this test.
-unset GIT_TR2 GIT_TR2_PERF GIT_TR2_EVENT
-unset GIT_TR2_BARE
-unset GIT_TR2_CONFIG_PARAMS
-
 V=$(git version | sed -e 's/^git version //') && export V
 
 # There are multiple trace2 targets: normal, perf, and event.
@@ -233,4 +233,36 @@ test_expect_success JSON_PP 'basic trace2_data' '
 	test_cmp expect actual
 '
 
+# Now test without environment variables and get all Trace2 settings
+# from the global config.
+
+test_expect_success JSON_PP 'using global config, event stream, error event' '
+	test_when_finished "rm trace.event actual expect" &&
+	test_config_global trace2.eventTarget "$(pwd)/trace.event" &&
+	test-tool trace2 003error "hello world" "this is a test" &&
+	perl "$TEST_DIRECTORY/t0212/parse_events.perl" <trace.event >actual &&
+	sed -e "s/^|//" >expect <<-EOF &&
+	|VAR1 = {
+	|  "_SID0_":{
+	|    "argv":[
+	|      "_EXE_",
+	|      "trace2",
+	|      "003error",
+	|      "hello world",
+	|      "this is a test"
+	|    ],
+	|    "errors":[
+	|      "%s",
+	|      "%s"
+	|    ],
+	|    "exit_code":0,
+	|    "hierarchy":"trace2",
+	|    "name":"trace2",
+	|    "version":"$V"
+	|  }
+	|};
+	EOF
+	test_cmp expect actual
+'
+
 test_done

trace2.c

@@ -10,6 +10,7 @@
 #include "trace2/tr2_cmd_name.h"
 #include "trace2/tr2_dst.h"
 #include "trace2/tr2_sid.h"
+#include "trace2/tr2_sysenv.h"
 #include "trace2/tr2_tgt.h"
 #include "trace2/tr2_tls.h"
 
@@ -120,6 +121,7 @@ static void tr2main_atexit_handler(void)
 	tr2_sid_release();
 	tr2_cmd_name_release();
 	tr2_cfg_free_patterns();
+	tr2_sysenv_release();
 
 	trace2_enabled = 0;
 }
@@ -155,6 +157,8 @@ void trace2_initialize_fl(const char *file, int line)
 	if (trace2_enabled)
 		return;
 
+	tr2_sysenv_load();
+
 	if (!tr2_tgt_want_builtins())
 		return;
 	trace2_enabled = 1;

trace2.h

@@ -38,7 +38,8 @@ void trace2_initialize_clock(void);
 
 /*
  * Initialize TRACE2 tracing facility if any of the builtin TRACE2
- * targets are enabled in the environment.  Emits a 'version' event.
+ * targets are enabled in the system config or the environment.
+ * Emits a 'version' event.
  *
  * Cleanup/Termination is handled automatically by a registered
  * atexit() routine.
@@ -125,10 +126,11 @@ void trace2_cmd_alias_fl(const char *file, int line, const char *alias,
  * Emit one or more 'def_param' events for "interesting" configuration
  * settings.
  *
- * The environment variable "GIT_TR2_CONFIG_PARAMS" can be set to a
- * list of patterns considered important.  For example:
- *
- *    GIT_TR2_CONFIG_PARAMS="core.*,remote.*.url"
+ * Use the TR2_SYSENV_CFG_PARAM setting to register a comma-separated
+ * list of patterns configured important.  For example:
+ *     git config --system trace2.configParams 'core.*,remote.*.url'
+ * or:
+ *     GIT_TR2_CONFIG_PARAMS=core.*,remote.*.url"
  *
  * Note: this routine does a read-only iteration on the config data
  * (using read_early_config()), so it must not be called until enough

trace2/tr2_cfg.c

@@ -1,8 +1,7 @@
 #include "cache.h"
 #include "config.h"
-#include "tr2_cfg.h"
-
-#define TR2_ENVVAR_CFG_PARAM "GIT_TR2_CONFIG_PARAMS"
+#include "trace2/tr2_cfg.h"
+#include "trace2/tr2_sysenv.h"
 
 static struct strbuf **tr2_cfg_patterns;
 static int tr2_cfg_count_patterns;
@@ -21,7 +20,7 @@ static int tr2_cfg_load_patterns(void)
 		return tr2_cfg_count_patterns;
 	tr2_cfg_loaded = 1;
 
-	envvar = getenv(TR2_ENVVAR_CFG_PARAM);
+	envvar = tr2_sysenv_get(TR2_SYSENV_CFG_PARAM);
 	if (!envvar || !*envvar)
 		return tr2_cfg_count_patterns;
 

trace2/tr2_dst.c

@@ -1,23 +1,20 @@
 #include "cache.h"
 #include "trace2/tr2_dst.h"
+#include "trace2/tr2_sysenv.h"
 
 /*
  * If a Trace2 target cannot be opened for writing, we should issue a
  * warning to stderr, but this is very annoying if the target is a pipe
  * or socket and beyond the user's control -- especially since every
  * git command (and sub-command) will print the message.  So we silently
  * eat these warnings and just discard the trace data.
- *
- * Enable the following environment variable to see these warnings.
  */
-#define TR2_ENVVAR_DST_DEBUG "GIT_TR2_DST_DEBUG"
-
 static int tr2_dst_want_warning(void)
 {
 	static int tr2env_dst_debug = -1;
 
 	if (tr2env_dst_debug == -1) {
-		const char *env_value = getenv(TR2_ENVVAR_DST_DEBUG);
+		const char *env_value = tr2_sysenv_get(TR2_SYSENV_DST_DEBUG);
 		if (!env_value || !*env_value)
 			tr2env_dst_debug = 0;
 		else
@@ -42,7 +39,9 @@ static int tr2_dst_try_path(struct tr2_dst *dst, const char *tgt_value)
 	if (fd == -1) {
 		if (tr2_dst_want_warning())
 			warning("trace2: could not open '%s' for '%s' tracing: %s",
-				tgt_value, dst->env_var_name, strerror(errno));
+				tgt_value,
+				tr2_sysenv_display_name(dst->sysenv_var),
+				strerror(errno));
 
 		tr2_dst_trace_disable(dst);
 		return 0;
@@ -116,7 +115,8 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
 	if (!path || !*path) {
 		if (tr2_dst_want_warning())
 			warning("trace2: invalid AF_UNIX value '%s' for '%s' tracing",
-				tgt_value, dst->env_var_name);
+				tgt_value,
+				tr2_sysenv_display_name(dst->sysenv_var));
 
 		tr2_dst_trace_disable(dst);
 		return 0;
@@ -126,7 +126,7 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
 	    strlen(path) >= sizeof(((struct sockaddr_un *)0)->sun_path)) {
 		if (tr2_dst_want_warning())
 			warning("trace2: invalid AF_UNIX path '%s' for '%s' tracing",
-				path, dst->env_var_name);
+				path, tr2_sysenv_display_name(dst->sysenv_var));
 
 		tr2_dst_trace_disable(dst);
 		return 0;
@@ -148,7 +148,8 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
 error:
 	if (tr2_dst_want_warning())
 		warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
-			path, dst->env_var_name, strerror(e));
+			path, tr2_sysenv_display_name(dst->sysenv_var),
+			strerror(e));
 
 	tr2_dst_trace_disable(dst);
 	return 0;
@@ -168,7 +169,7 @@ static void tr2_dst_malformed_warning(struct tr2_dst *dst,
 	struct strbuf buf = STRBUF_INIT;
 
 	strbuf_addf(&buf, "trace2: unknown value for '%s': '%s'",
-		    dst->env_var_name, tgt_value);
+		    tr2_sysenv_display_name(dst->sysenv_var), tgt_value);
 	warning("%s", buf.buf);
 
 	strbuf_release(&buf);
@@ -184,7 +185,7 @@ int tr2_dst_get_trace_fd(struct tr2_dst *dst)
 
 	dst->initialized = 1;
 
-	tgt_value = getenv(dst->env_var_name);
+	tgt_value = tr2_sysenv_get(dst->sysenv_var);
 
 	if (!tgt_value || !strcmp(tgt_value, "") || !strcmp(tgt_value, "0") ||
 	    !strcasecmp(tgt_value, "false")) {
@@ -246,7 +247,8 @@ void tr2_dst_write_line(struct tr2_dst *dst, struct strbuf *buf_line)
 		return;
 
 	if (tr2_dst_want_warning())
-		warning("unable to write trace to '%s': %s", dst->env_var_name,
+		warning("unable to write trace to '%s': %s",
+			tr2_sysenv_display_name(dst->sysenv_var),
 			strerror(errno));
 	tr2_dst_trace_disable(dst);
 }

trace2/tr2_dst.h

@@ -2,9 +2,10 @@
 #define TR2_DST_H
 
 struct strbuf;
+#include "trace2/tr2_sysenv.h"
 
 struct tr2_dst {
-	const char *const env_var_name;
+	enum tr2_sysenv_variable sysenv_var;
 	int fd;
 	unsigned int initialized : 1;
 	unsigned int need_close : 1;