log: Introduce PULSE_LOG_JOURNAL environment variable

By introducing such an environment variable, applications using the
PA client libraries can configure these libraries to send their logs
directly to the journal.

While client libraries journal logging can be indirectly achieved
using PULSE_LOG_SYSLOG, this pollutes the journal. Meta data gets
replicated twice: once in the journal meta fields and once in the
syslog(3) plain-text message itself.

For attaching any backtraces, also introduce the PA-specific journal
meta field PULSE_BACKTRACE. This is the recommend journal practice
instead of appending any furuther data to the logging message itself.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>

2 files changed, 15 insertions, 0 deletions

diff --git a/src/pulse/pulseaudio.h b/src/pulse/pulseaudio.h
index f5c5b0d13..5077e3b81 100644
--- a/src/pulse/pulseaudio.h
+++ b/src/pulse/pulseaudio.h
@@ -140,6 +140,14 @@
  *  - `PULSE_LOG_SYSLOG`: If defined, force all client libraries to log
  *     their output using the syslog(3) mechanism. Default behavior is to
  *     log all output to stderr.
+ *  - `PULSE_LOG_JOURNAL`: If defined, force all client libraries to log
+ *     their output using the systemd journal. If both `PULSE_LOG_JOURNAL`
+ *     and `PULSE_LOG_SYSLOG` are defined, logging to the systemd journal
+ *     takes a higher precedence. Each message originating library file name
+ *     and function are included by default through the journal fields
+ *     `CODE_FILE`, `CODE_FUNC`, and `CODE_LINE`. Any backtrace attached to
+ *     the logging message is sent through the PulseAudio-specific journal
+ *     field `PULSE_BACKTRACE`.
  *  - `PULSE_LOG_COLORS`: If defined, enables colored logging output.
  *  - `PULSE_LOG_TIME`: If defined, include timestamps with each message.
  *  - `PULSE_LOG_FILE`: If defined, include each message originating file
diff --git a/src/pulsecore/log.c b/src/pulsecore/log.c
index 552d41612..34ed0415f 100644
--- a/src/pulsecore/log.c
+++ b/src/pulsecore/log.c
@@ -60,6 +60,7 @@
 #include "log.h"
 
 #define ENV_LOG_SYSLOG "PULSE_LOG_SYSLOG"
+#define ENV_LOG_JOURNAL "PULSE_LOG_JOURNAL"
 #define ENV_LOG_LEVEL "PULSE_LOG"
 #define ENV_LOG_COLORS "PULSE_LOG_COLORS"
 #define ENV_LOG_PRINT_TIME "PULSE_LOG_TIME"
@@ -293,6 +294,11 @@ static void init_defaults(void) {
             target_override_set = true;
         }
 
+        if (getenv(ENV_LOG_JOURNAL)) {
+            target_override = PA_LOG_JOURNAL;
+            target_override_set = true;
+        }
+
         if ((e = getenv(ENV_LOG_LEVEL))) {
             maximum_level_override = (pa_log_level_t) atoi(e);
 
@@ -493,6 +499,7 @@ void pa_log_levelv_meta(
                                 "CODE_FILE=%s", file,
                                 "CODE_FUNC=%s", func,
                                 "CODE_LINE=%d", line,
+                                "PULSE_BACKTRACE=%s", pa_strempty(bt),
                                 NULL) < 0) {
 #ifdef HAVE_SYSLOG_H
                     pa_log_target new_target = { .type = PA_LOG_SYSLOG, .file = NULL };