[Comb] Add syslog sink to be used with GLOG. (sonic-net#482)

Co-authored-by: rhalstea <[email protected]>
Co-authored-by: kishanps <[email protected]>

gutil/BUILD.bazel

@@ -316,3 +316,10 @@ cc_test(
         "@com_google_absl//absl/strings",
     ],
 )
+
+cc_library(
+    name = "syslog_sink",
+    srcs = ["syslog_sink.cc"],
+    hdrs = ["syslog_sink.h"],
+    deps = ["@com_github_google_glog//:glog"],
+)

gutil/syslog_sink.cc

@@ -0,0 +1,62 @@
+#include "gutil/syslog_sink.h"
+
+#include <sys/syscall.h>
+#include <sys/syslog.h>
+#include <sys/time.h>
+
+#include <array>
+
+#include "glog/logging.h"
+
+namespace gutil {
+namespace {
+
+// GLOG severity uses integers in the range [0-3]:
+//   https://github.com/google/glog/blob/master/src/glog/log_severity.h
+constexpr std::array<int, 4> kGlogSeverityToSyslog = {
+    LOG_INFO,
+    LOG_WARNING,
+    LOG_ERR,
+    LOG_EMERG,
+};
+constexpr std::array<char, 4> kGlogSeverityLetter = {
+    'I',
+    'W',
+    'E',
+    'F',
+};
+
+}  // namespace
+
+SyslogSink::SyslogSink(const char* process_name) {
+  openlog(process_name, LOG_NDELAY, LOG_USER);
+  google::AddLogSink(this);
+}
+
+SyslogSink::~SyslogSink() {
+  google::RemoveLogSink(this);
+  closelog();
+}
+
+void SyslogSink::send(google::LogSeverity severity, const char* full_filename,
+                      const char* base_filename, int line,
+                      const google::LogMessageTime& logmsgtime,
+                      const char* message, size_t message_len) {
+  // Create a timestamp with micosecond resolution.
+  struct timeval tv;
+  struct timezone tz;
+  struct tm time;
+  gettimeofday(&tv, &tz);
+  localtime_r(&tv.tv_sec, &time);
+
+  // Output format:
+  //   I0104 23:00:59.123456    71 filename.cc:100] Your Message Here!
+  syslog(kGlogSeverityToSyslog[severity],
+         "%c%02d%02d %02d:%02d:%02d.%06ld %5ld %s:%d] %.*s",
+         kGlogSeverityLetter[severity], 1 + time.tm_mon, time.tm_mday,
+         time.tm_hour, time.tm_min, time.tm_sec, static_cast<long>(tv.tv_usec),
+         syscall(SYS_gettid), base_filename, line,
+         static_cast<int>(message_len), message);
+}
+
+}  // namespace gutil

gutil/syslog_sink.h

@@ -0,0 +1,34 @@
+#ifndef PINS_GUTIL_SYSLOG_SINK_H_
+#define PINS_GUTIL_SYSLOG_SINK_H_
+
+#include <cstddef>
+
+#include "glog/logging.h"
+
+namespace gutil {
+
+// When constructed SyslogSink will automatically register with GLOG and begin
+// forwarding all LOG() messages to syslog. In the dtor we unregister with GLOG
+// so the SyslogSink should outlive the program. These messages are treated as
+// user-level (i.e. a LOG_USER facility), and serverities are mapped as follows:
+//   LOG(INFO)    -> LOG_INFO
+//   LOG(WARNING) -> LOG_WARNING
+//   LOG(ERROR)   -> LOG_ERR
+//   LOG(FATAL)   -> LOG_EMERG
+//
+// The syslog message will be formatted similar to a GLOG message with a
+// microsecond timestamp.
+class SyslogSink : google::LogSink {
+ public:
+  SyslogSink(const char* process_name);
+  ~SyslogSink();
+
+  void send(google::LogSeverity severity, const char* full_filename,
+            const char* base_filename, int line,
+            const google::LogMessageTime& logmsgtime, const char* message,
+            size_t message_len) override;
+};
+
+}  // namespace gutil
+
+#endif  // PINS_GUTIL_SYSLOG_SINK_H_

p4rt_app/BUILD.bazel

@@ -40,6 +40,7 @@ cc_binary(
         "@com_google_absl//absl/time",
         "@com_github_grpc_grpc//:grpc++_public_hdrs",
         "//gutil:status",
+        "//gutil:syslog_sink",
         "//p4rt_app/event_monitoring:app_state_db_port_table_event",
         "//p4rt_app/event_monitoring:app_state_db_send_to_ingress_port_table_event",
         "//p4rt_app/event_monitoring:config_db_cpu_queue_table_event",

p4rt_app/p4rt.cc

@@ -40,6 +40,7 @@
 #include "grpcpp/server.h"
 #include "grpcpp/server_builder.h"
 #include "gutil/status.h"
+#include "gutil/syslog_sink.h"
 #include "p4rt_app/event_monitoring/app_state_db_port_table_event.h"
 #include "p4rt_app/event_monitoring/app_state_db_send_to_ingress_port_table_event.h"
 #include "p4rt_app/event_monitoring/config_db_cpu_queue_table_event.h"
@@ -364,6 +365,7 @@ void ConfigDbEventLoop(P4RuntimeImpl* p4runtime_server,
 }  // namespace p4rt_app
 
 int main(int argc, char** argv) {
+  gutil::SyslogSink syslog_sink("p4rt");
   google::InitGoogleLogging(argv[0]);
   gflags::ParseCommandLineFlags(&argc, &argv, true);