From 91d8d4670924e04ba2a4155f17d556a55031d267 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Wed, 15 Jul 2015 15:54:49 +0300
Subject: [PATCH 1/2] logger: support for syslog()

Note that while syslog() may block, we still call it synchronously via
the reactor thread.  Anything else would make logging a nightmare.
---
 log.cc | 44 ++++++++++++++++++++++++++++++++++++++++----
 log.hh |  4 ++++
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/log.cc b/log.cc
index 0a849b8be2..4fd7e70ca1 100644
--- a/log.cc
+++ b/log.cc
@@ -3,10 +3,12 @@
  */
 
 #include "log.hh"
+#include "core/array_map.hh"
 #include <cxxabi.h>
 #include <system_error>
 #include <boost/range/adaptor/map.hpp>
 #include <map>
+#include <syslog.h>
 
 namespace logging {
 
@@ -46,6 +48,9 @@ std::istream& operator>>(std::istream& in, log_level& level) {
 
 namespace logging {
 
+std::atomic<bool> logger::_stdout = { true };
+std::atomic<bool> logger::_syslog = { false };
+
 logger::logger(sstring name) : _name(std::move(name)) {
     logger_registry().register_logger(this);
 }
@@ -60,21 +65,52 @@ logger::~logger() {
 
 void
 logger::really_do_log(log_level level, const char* fmt, stringer** s, size_t n) {
+    std::ostringstream out;
     const char* p = fmt;
     while (*p != '\0') {
         if (*p == '{' && *(p+1) == '}') {
             p += 2;
             if (n > 0) {
-                (*s++)->append(std::cout);
+                (*s++)->append(out);
                 --n;
             } else {
-                std::cout << "???";
+                out << "???";
             }
         } else {
-            std::cout << *p++;
+            out << *p++;
         }
     }
-    std::cout << "\n";
+    out << "\n";
+    auto msg = out.str();
+    if (_stdout.load(std::memory_order_relaxed)) {
+        std::cout << out;
+    }
+    if (_syslog.load(std::memory_order_relaxed)) {
+        static array_map<int, 20> level_map = {
+                { int(log_level::debug), LOG_DEBUG },
+                { int(log_level::info), LOG_INFO },
+                { int(log_level::trace), LOG_DEBUG },  // no LOG_TRACE
+                { int(log_level::warn), LOG_WARNING },
+                { int(log_level::error), LOG_ERR },
+        };
+        // NOTE: syslog() can block, which will stall the reactor thread.
+        //       this should be rare (will have to fill the pipe buffer
+        //       before syslogd can clear it) but can happen.  If it does,
+        //       we'll have to implement some internal buffering (which
+        //       still means the problem can happen, just less frequently).
+        // syslog() interprets % characters, so send msg as a parameter
+        syslog(level_map[int(level)], "%s", msg.c_str());
+    }
+}
+
+void
+logger::set_stdout_enabled(bool enabled) {
+    _stdout.store(enabled, std::memory_order_relaxed);
+}
+
+void
+logger::set_syslog_enabled(bool enabled) {
+    _syslog.store(enabled, std::memory_order_relaxed);
 }
 
 void
diff --git a/log.hh b/log.hh
index e49c788c34..34e71ca8c5 100644
--- a/log.hh
+++ b/log.hh
@@ -46,6 +46,8 @@ class registry;
 class logger {
     sstring _name;
     std::atomic<log_level> _level = { log_level::warn };
+    static std::atomic<bool> _stdout;
+    static std::atomic<bool> _syslog;
 private:
     struct stringer {
         // no need for virtual dtor, since not dynamically destroyed
@@ -104,6 +106,8 @@ public:
     void set_level(log_level level) {
         _level.store(level, std::memory_order_relaxed);
     }
+    static void set_stdout_enabled(bool enabled);
+    static void set_syslog_enabled(bool enabled);
 };
 
 class registry {

From f8a7c5bd2bd4271cead1d86bc568208a9798df0c Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Wed, 15 Jul 2015 16:18:10 +0300
Subject: [PATCH 2/2] main: allow configuring log destination (stdout and/or
 syslog)

---
 db/config.hh | 2 ++
 main.cc      | 8 ++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/db/config.hh b/db/config.hh
index 865cb95539..8cbcda246b 100644
--- a/db/config.hh
+++ b/db/config.hh
@@ -682,6 +682,8 @@ public:
     val(logger_log_level, string_map, /* none */, Used,\
             "map of logger name to log level.  Valid values are trace, debug, info, warn, error.  " \
             "Use --help-loggers for a list of logger names") \
+    val(log_to_stdout, bool, true, Used, "Send log output to stdout") \
+    val(log_to_syslog, bool, false, Used, "Send log output to syslog") \
     /* done! */
 
 #define _make_value_member(name, type, deflt, status, desc, ...)    \
diff --git a/main.cc b/main.cc
index da6662ae77..5e48af78ea 100644
--- a/main.cc
+++ b/main.cc
@@ -36,13 +36,16 @@ void do_help_loggers() {
     }
 }
 
-void apply_logger_settings(sstring default_level, db::config::string_map levels) {
+void apply_logger_settings(sstring default_level, db::config::string_map levels,
+        bool log_to_stdout, bool log_to_syslog) {
     logging::logger_registry().set_all_loggers_level(boost::lexical_cast<logging::log_level>(std::string(default_level)));
     for (auto&& kv: levels) {
         auto&& k = kv.first;
         auto&& v = kv.second;
         logging::logger_registry().set_logger_level(k, boost::lexical_cast<logging::log_level>(std::string(v)));
     }
+    logging::logger::set_stdout_enabled(log_to_stdout);
+    logging::logger::set_syslog_enabled(log_to_syslog);
 }
 
 int main(int ac, char** av) {
@@ -75,7 +78,8 @@ int main(int ac, char** av) {
         auto&& opts = app.configuration();
 
         return read_config(opts, *cfg).then([&cfg, &db, &qp, &proxy, &ctx, &opts]() {
-            apply_logger_settings(cfg->default_log_level(), cfg->logger_log_level());
+            apply_logger_settings(cfg->default_log_level(), cfg->logger_log_level(),
+                    cfg->log_to_stdout(), cfg->log_to_syslog());
             dht::set_global_partitioner(cfg->partitioner());
             uint16_t thrift_port = cfg->rpc_port();
             uint16_t cql_port = cfg->native_transport_port();