support: add a journald logger implementation

Closes https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/358

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>

spa/plugins/support/journal.c

@@ -0,0 +1,276 @@
+/* Spa
+ *
+ * Copyright © 2020 Sergey Bugaev
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <stddef.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+#include <limits.h>
+#include <syslog.h>
+#include <sys/stat.h>
+
+#include <spa/support/log.h>
+#include <spa/support/plugin.h>
+#include <spa/utils/type.h>
+#include <spa/utils/names.h>
+
+#include <systemd/sd-journal.h>
+
+#define NAME "journal"
+
+#define DEFAULT_LOG_LEVEL SPA_LOG_LEVEL_INFO
+
+struct impl {
+	struct spa_handle handle;
+	struct spa_log log;
+
+	/* if non-null, we'll additionally forward all logging to there */
+	struct spa_log *chain_log;
+};
+
+static SPA_PRINTF_FUNC(6,0) void
+impl_log_logv(void *object,
+	      enum spa_log_level level,
+	      const char *file,
+	      int line,
+	      const char *func,
+	      const char *fmt,
+	      va_list args)
+{
+	struct impl *impl = object;
+	char line_buffer[32];
+	char file_buffer[strlen("CODE_FILE=") + strlen(file) + 1];
+	char message_buffer[LINE_MAX];
+	int priority;
+
+	if (impl->chain_log != NULL) {
+		va_list args_copy;
+		va_copy(args_copy, args);
+		spa_interface_call(&impl->chain_log->iface,
+				   struct spa_log_methods, logv, 0,
+				   level, file, line, func, fmt, args_copy);
+		va_end(args_copy);
+	}
+
+	/* convert SPA log level to syslog priority */
+	switch (level) {
+	case SPA_LOG_LEVEL_ERROR:
+		priority = LOG_ERR;
+		break;
+	case SPA_LOG_LEVEL_WARN:
+		priority = LOG_WARNING;
+		break;
+	case SPA_LOG_LEVEL_INFO:
+		priority = LOG_INFO;
+		break;
+	case SPA_LOG_LEVEL_DEBUG:
+	case SPA_LOG_LEVEL_TRACE:
+	default:
+		priority = LOG_DEBUG;
+		break;
+	}
+
+	/* we'll be using the low-level journal API, which expects us to provide
+	 * the location explicitly. line and file are to be passed as preformatted
+	 * entries, whereas the function name is passed as-is, and converted into
+	 * a field inside sd_journal_send_with_location(). */
+	snprintf(line_buffer, sizeof(line_buffer), "CODE_LINE=%d", line);
+	snprintf(file_buffer, sizeof(file_buffer), "CODE_FILE=%s", file);
+	vsnprintf(message_buffer, sizeof(message_buffer), fmt, args);
+
+	sd_journal_send_with_location(file_buffer, line_buffer, func,
+				      "MESSAGE=%s", message_buffer,
+				      "PRIORITY=%i", priority,
+				      NULL);
+}
+
+static SPA_PRINTF_FUNC(6,7) void
+impl_log_log(void *object,
+	     enum spa_log_level level,
+	     const char *file,
+	     int line,
+	     const char *func,
+	     const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	impl_log_logv(object, level, file, line, func, fmt, args);
+	va_end(args);
+}
+
+static const struct spa_log_methods impl_log = {
+	SPA_VERSION_LOG_METHODS,
+	.log = impl_log_log,
+	.logv = impl_log_logv,
+};
+
+static int impl_get_interface(struct spa_handle *handle, const char *type, void **interface)
+{
+	struct impl *this;
+
+	spa_return_val_if_fail(handle != NULL, -EINVAL);
+	spa_return_val_if_fail(interface != NULL, -EINVAL);
+
+	this = (struct impl *) handle;
+
+	if (strcmp(type, SPA_TYPE_INTERFACE_Log) == 0)
+		*interface = &this->log;
+	else
+		return -ENOENT;
+
+	return 0;
+}
+
+static int impl_clear(struct spa_handle *handle)
+{
+	spa_return_val_if_fail(handle != NULL, -EINVAL);
+
+	return 0;
+}
+
+static size_t
+impl_get_size(const struct spa_handle_factory *factory,
+	      const struct spa_dict *params)
+{
+	return sizeof(struct impl);
+}
+
+/** Determine if our stderr goes straight to the journal */
+static int
+stderr_is_connected_to_journal(void)
+{
+	const char *journal_stream;
+	unsigned long long journal_device, journal_inode;
+	struct stat stderr_stat;
+
+	/* when a service's stderr is connected to the journal, systemd sets
+	 * JOURNAL_STREAM in the environment of that service to device:inode
+	 * of its stderr. if the variable is not set, clearly our stderr is
+	 * not connected to the journal */
+	journal_stream = getenv("JOURNAL_STREAM");
+	if (journal_stream == NULL)
+		return 0;
+
+	/* if it *is* set, that doesn't immediately mean that *our* stderr
+	 * is (still) connected to the journal. to know for sure, we have to
+	 * compare our actual stderr to the stream systemd has created for
+	 * the service we're a part of */
+
+	if (sscanf(journal_stream, "%llu:%llu", &journal_device, &journal_inode) != 2)
+		return 0;
+
+	if (fstat(STDERR_FILENO, &stderr_stat) < 0)
+		return 0;
+
+	return stderr_stat.st_dev == journal_device && stderr_stat.st_ino == journal_inode;
+}
+
+static int
+impl_init(const struct spa_handle_factory *factory,
+	  struct spa_handle *handle,
+	  const struct spa_dict *info,
+	  const struct spa_support *support,
+	  uint32_t n_support)
+{
+	struct impl *impl;
+
+	spa_return_val_if_fail(factory != NULL, -EINVAL);
+	spa_return_val_if_fail(handle != NULL, -EINVAL);
+
+	handle->get_interface = impl_get_interface;
+	handle->clear = impl_clear;
+
+	impl = (struct impl *) handle;
+
+	impl->log.iface = SPA_INTERFACE_INIT(
+			SPA_TYPE_INTERFACE_Log,
+			SPA_VERSION_LOG,
+			&impl_log, impl);
+	impl->log.level = DEFAULT_LOG_LEVEL;
+
+	/* if our stderr goes to the journal, there's no point in logging both
+	 * via the native journal API and by printing to stderr, that would just
+	 * result in message duplication */
+	if (stderr_is_connected_to_journal())
+		impl->chain_log = NULL;
+	else
+		impl->chain_log = spa_support_find(support, n_support, SPA_TYPE_INTERFACE_Log);
+
+	spa_log_debug(&impl->log, NAME " %p: initialized", impl);
+
+	return 0;
+}
+
+static const struct spa_interface_info impl_interfaces[] = {
+	{SPA_TYPE_INTERFACE_Log,},
+};
+
+static int
+impl_enum_interface_info(const struct spa_handle_factory *factory,
+			 const struct spa_interface_info **info,
+			 uint32_t *index)
+{
+	spa_return_val_if_fail(factory != NULL, -EINVAL);
+	spa_return_val_if_fail(info != NULL, -EINVAL);
+	spa_return_val_if_fail(index != NULL, -EINVAL);
+
+	switch (*index) {
+	case 0:
+		*info = &impl_interfaces[*index];
+		break;
+	default:
+		return 0;
+	}
+	(*index)++;
+
+	return 1;
+}
+
+static const struct spa_handle_factory journal_factory = {
+	SPA_VERSION_HANDLE_FACTORY,
+	.name = SPA_NAME_SUPPORT_LOG,
+	.info = NULL,
+	.get_size = impl_get_size,
+	.init = impl_init,
+	.enum_interface_info = impl_enum_interface_info,
+};
+
+
+SPA_EXPORT
+int spa_handle_factory_enum(const struct spa_handle_factory **factory, uint32_t *index)
+{
+	spa_return_val_if_fail(factory != NULL, -EINVAL);
+	spa_return_val_if_fail(index != NULL, -EINVAL);
+
+	switch (*index) {
+	case 0:
+		*factory = &journal_factory;
+		break;
+	default:
+		return 0;
+	}
+	(*index)++;
+	return 1;
+}

spa/plugins/support/meson.build

@@ -40,3 +40,15 @@ spa_dbus_lib = shared_library('spa-dbus',
 			dependencies : [dbus_dep, ],
 			install : true,
 		        install_dir : join_paths(spa_plugindir, 'support'))
+
+
+if get_option('systemd') and systemd_dep.found()
+  spa_journal_sources = ['journal.c']
+
+  spa_journal_lib = shared_library('spa-journal',
+			  spa_journal_sources,
+			  include_directories : spa_inc,
+			  dependencies : systemd_dep,
+			  install : true,
+		          install_dir : join_paths(spa_plugindir, 'support'))
+endif