[Spice-devel] [PATCH spice-common 3/4] RFC: Add spice log categories
Marc-André Lureau
marcandre.lureau at redhat.com
Tue Jun 13 09:35:05 UTC 2017
Hi
----- Original Message -----
> This code assumes that there is only a single G_LOG_DOMAIN used within
> a particular project, but it's not stated explicity (as far as I can
> tell)
Kind of, you mean for the G_MESSAGES_DEBUG manipulation?
>
> On Mon, 2017-06-12 at 12:19 +0400, marcandre.lureau at redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau at redhat.com>
> >
> > A log category is defined with SPICE_LOG_CATEGORY(). The macro will
> > register a structure with a constructor (and unregister it on
> > unloading with a destructor).
> >
> > spice_log_init() must be called at initialization time, to set
> > enabled
> > categories and add the 'Spice' glib domain to G_MESSAGES_DEBUG (NB:
> > if
> > useful, we could have other log domains automatically associated with
> > categories and enable them too).
> >
> > A category can be enabled with SPICE_DEBUG="cat_name foo*" (*? are
> > accepted glob-like wildcards). All categories are enabled with
> > SPICE_DEBUG=1 or 'all'. To list available categories, you can run the
> > program with SPICE_DEBUG=help.
> >
> > spice_log() will log the debug message using structured logging if
> > available (or fallback on regular glog). The associated Spice log in
> > the journal will have the SPICE_LOG_CATEGORY field set accordingly.
> >
> > If deemed necessary, you can also avoid expensive log computation
> > with
> > SPICE_LOG_ENABLED() macro help.
> >
> > TODO: add tests
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau at redhat.com>
> > ---
> > common/log.c | 67
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> > common/log.h | 72
> > +++++++++++++++++++++++++++++++++++++++++++++++++++-
> > tests/test-logging.c | 1 +
> > 3 files changed, 139 insertions(+), 1 deletion(-)
> >
> > diff --git a/common/log.c b/common/log.c
> > index 6a15a30..029e279 100644
> > --- a/common/log.c
> > +++ b/common/log.c
> > @@ -18,3 +18,70 @@
> > #ifdef HAVE_CONFIG_H
> > #include <config.h>
> > #endif
> > +
> > +#include "log.h"
> > +
> > +static GSList *log_categories = NULL; /* all registered log
> > categories */
> > +
> > +void spice_log_category_register(SpiceLogCategory *cat)
> > +{
> > + if (!g_slist_find(log_categories, cat)) {
> > + log_categories = g_slist_prepend(log_categories, cat);
> > + }
> > +}
> > +
> > +void spice_log_category_unregister(SpiceLogCategory *cat)
> > +{
> > + log_categories = g_slist_remove(log_categories, cat);
> > +}
> > +
> > +void spice_log_init(void)
> > +{
> > + bool all = false;
> > + const char *env = g_getenv("SPICE_DEBUG");
> > + const char *genv = g_getenv("G_MESSAGES_DEBUG");
> > +
> > + if (g_strcmp0(env, "help") == 0) {
> > + g_printerr("SPICE_DEBUG=1 or 'all' to enable all debug\n");
> > + g_printerr("SPICE_DEBUG=\"cat1* cat2\" to enable specific
> > categories\n");
> > + g_printerr("Available Spice debug categories:\n");
> > + for (GSList *l = log_categories; l != NULL; l =
> > g_slist_next(l)) {
> > + SpiceLogCategory *cat = l->data;
> > + g_printerr("%-20s - %s\n", cat->name, cat->desc);
> > + }
> > + return;
> > + }
> > +
> > + /* Make sure GLib default log handler will show the debug
> > + * messages. Messing with environment variables like this is
> > + * rather ugly, but done for historical reasons.
> > + */
> > + if (env && *env != '\0') {
> > + if (genv == NULL) {
> > + g_setenv("G_MESSAGES_DEBUG", G_LOG_DOMAIN, TRUE);
> > + } else if (!g_str_equal(genv, "all")) {
> > + char *new_env = g_strconcat(genv, " ", G_LOG_DOMAIN,
> > NULL);
> > + g_setenv("G_MESSAGES_DEBUG", new_env, TRUE);
> > + g_free(new_env);
> > + }
> > + }
>
> One alternative to doing this env variable mangling may be to set our
> own log handler for this domain.
That can't be done with structured logging. I think the argument is that it's easier to let the application decide how and where to log, or have a single log handler to configure.
> > +
> > + all = g_strcmp0(env, "1") == 0 || g_strcmp0(env, "all") == 0;
> > + if (all) {
> > + for (GSList *l = log_categories; l != NULL; l =
> > g_slist_next(l)) {
> > + SpiceLogCategory *cat = l->data;
> > + cat->enabled = true;
> > + }
> > + } else if (env) {
> > + char **cat_sel = g_strsplit(env, " ", -1);
> > + for (char **strv = cat_sel; *strv != NULL; strv++) {
> > + GPatternSpec *pat = g_pattern_spec_new(*strv);
> > + for (GSList *l = log_categories; l != NULL; l =
> > g_slist_next(l)) {
> > + SpiceLogCategory *cat = l->data;
> > + cat->enabled = g_pattern_match_string(pat, cat-
> > >name);
> > + }
> > + g_pattern_spec_free(pat);
> > + }
> > + g_strfreev(cat_sel);
> > + }
> > +}
> > diff --git a/common/log.h b/common/log.h
> > index b86fd08..e202563 100644
> > --- a/common/log.h
> > +++ b/common/log.h
> > @@ -28,6 +28,63 @@
> >
> > G_BEGIN_DECLS
> >
> > +typedef struct SpiceLogCategory {
> > + const char *name;
> > + const char *desc;
> > + bool enabled;
> > +} SpiceLogCategory;
> > +
> > +/* This is only useful if the category is shared in several units.
> > */
> > +/* The code could probably be better organized instead. */
> > +#define SPICE_LOG_CATEGORY_DECLARE(Name) \
> > + extern SpiceLogCategory G_PASTE(spice_log_category_, Name);
> > +
> > +#define SPICE_LOG_CATEGORY(Name,
> > Desc) \
> > + SpiceLogCategory G_PASTE(spice_log_category_, Name) =
> > { \
> > + .name =
> > G_STRINGIFY(Name), \
> > + .desc =
> > Desc, \
> > + .enabled =
> > false, \
> > + };
> > \
> > + SPICE_CONSTRUCTOR_FUNC(G_PASTE(spice_log_category_ctor_, Name))
> > { \
> > + spice_log_category_register(&G_PASTE(spice_log_category_,
> > Name)); \
> > + }
> > \
> > + SPICE_DESTRUCTOR_FUNC(G_PASTE(spice_log_category_dtor_, Name))
> > { \
> > + spice_log_category_unregister(&G_PASTE(spice_log_category_,
> > Name)); \
> > + }
> > +
> > +#define SPICE_LOG_ENABLED(Name) \
> > + G_UNLIKELY(G_PASTE(spice_log_category_, Name).enabled)
> > +
> > +#if G_LOG_USE_STRUCTURED
> > +/* override future deprecation warning */
> > +#define g_log_structured(Domain, Level, ...) G_STMT_START { \
> > + G_GNUC_BEGIN_IGNORE_DEPRECATIONS \
> > + g_log_structured(Domain, Level, ## __VA_ARGS__); \
> > + G_GNUC_END_IGNORE_DEPRECATIONS \
> > +} G_STMT_END
>
> explain the deprecation bit?
I explained in the cover letter discussion, this is about glib versioning macros, it warns if we use symbols >2.28. We have similar tricks in spice-gtk.
>
> > +
> > +#define spice_log(Name, Msg, ...) G_STMT_START
> > { \
> > + if (SPICE_LOG_ENABLED(Name))
> > { \
> > + g_log_structured(G_LOG_DOMAIN,
> > G_LOG_LEVEL_DEBUG, \
> > + "CODE_FILE",
> > __FILE__, \
> > + "CODE_LINE",
> > G_STRINGIFY(__LINE__), \
> > + "CODE_FUNC",
> > G_STRFUNC, \
> > + "SPICE_LOG_CATEGORY",
> > G_STRINGIFY(Name), \
> > + "MESSAGE", G_STRINGIFY(Name)": " Msg, ##
> > __VA_ARGS__); \
> > + }
> > \
> > +} G_STMT_END
> > +#else /* !G_LOG_USE_STRUCTURED */
> > +#define spice_log(Name, Msg, ...) G_STMT_START { \
> > + if (SPICE_LOG_ENABLED(Name)) { \
> > + g_debug(G_STRINGIFY(Name)": " Msg, ## __VA_ARGS__); \
> > + } \
> > +} G_STMT_END
> > +#endif
> > +
> > +void spice_log_category_register(SpiceLogCategory *cat);
> > +void spice_log_category_unregister(SpiceLogCategory *cat);
> > +void spice_log_init(void);
> > +
> > /* deprecated, please use glib directly */
> > #define spice_return_if_fail(x) g_return_if_fail(x)
> > #define spice_return_val_if_fail(x, val) g_return_val_if_fail(x,
> > val)
> > @@ -36,7 +93,7 @@ G_BEGIN_DECLS
> > #define spice_assert(x) g_assert(x)
> > #define spice_static_assert(x) G_STATIC_ASSERT(x)
> >
> > -/* deprecated */
> > +/* deprecated, use spice_log() instead */
> > #ifndef SPICE_LOG_DOMAIN
> > #define SPICE_LOG_DOMAIN __FILE__
> > #endif
> > @@ -61,7 +118,20 @@ static inline void _spice_debug(const char
> > *domain, const char *file,
> > if (msg) {
> > g_string_append_vprintf(s, msg, args);
> > }
> > +#if G_LOG_USE_STRUCTURED
> > + G_GNUC_BEGIN_IGNORE_DEPRECATIONS
> > + const GLogField fields[] = {
> > + { "GLIB_DOMAIN", G_LOG_DOMAIN, -1 },
> > + { "MESSAGE", s->str, -1 },
> > + { "CODE_FILE", file, -1 },
> > + { "CODE_LINE", line, -1 },
> > + { "CODE_FUNC", func, -1 },
> > + };
>
> No SPICE_LOG_CATEGORY here?
This is compatibility code, it doesn't have categories.
All of the code marked as *deprecated* should in fact go away pretty quickly, once we replace existing spice_debug() with the new category API or straight g_debug().
>
> > + g_log_structured_array(G_LOG_LEVEL_DEBUG, fields,
> > G_N_ELEMENTS(fields));
> > + G_GNUC_END_IGNORE_DEPRECATIONS
> > +#else
> > g_debug("%s", s->str);
> > +#endif
> > va_end(args);
> > g_string_free(s, true);
> > }
>
> Up above, spice_log() checks to see whether the category is enabled
> before logging the message. But spice_debug() does not contain any
> categories so it doesn't check anything. So as far as I can tell, any
> message logged with spice_debug() will get printed if any other spice
> category is enabled. For instance, if I use the following
> configuration:
>
> SPICE_DEBUG=cat1 virt-viewer
>
> I will end up with a lot output that includes all messages printed via
> "spice_log(cat1, ...)" in addition to all messages printed with
> "spice_debug(...)". Is that correct?
>
>
True, a direct glog will be printed by default. That's why we introduce categories in the first place, to do the filtering.
> > diff --git a/tests/test-logging.c b/tests/test-logging.c
> > index 03f367a..cfe63e4 100644
> > --- a/tests/test-logging.c
> > +++ b/tests/test-logging.c
> > @@ -87,6 +87,7 @@ int main(int argc, char **argv)
> > fatal_mask =
> > (GLogLevelFlags)g_log_set_always_fatal((GLogLevelFlags)
> > G_LOG_FATAL_MASK);
> >
> > g_test_init(&argc, &argv, NULL);
> > + spice_log_init();
> >
> > /* Reset fatal mask set by g_test_init() as we don't want
> > * warnings/criticals to be fatal by default since this is what
> > some of the
>
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