Move logging writes to separate thread

2 files changed, 72 insertions, 15 deletions

diff --git a/src/Log.cpp b/src/Log.cpp
index 55a4ebf..81f32a8 100644
--- a/src/Log.cpp
+++ b/src/Log.cpp
@@ -3,7 +3,7 @@
    Her Majesty the Queen in Right of Canada (Communications Research
    Center Canada)
 
-   Copyright (C), 2014, Matthias P. Braendli, matthias.braendli@mpb.li
+   Copyright (C), 2016, Matthias P. Braendli, matthias.braendli@mpb.li
  */
 /*
    This file is part of ODR-DabMod.
@@ -65,20 +65,44 @@ void Logger::log(log_level_t level, const char* fmt, ...)
 
 void Logger::logstr(log_level_t level, std::string message)
 {
-    /* Remove a potential trailing newline.
-     * It doesn't look good in syslog
-     */
-    if (message[message.length()-1] == '\n') {
-        message.resize(message.length()-1);
-    }
+    log_message_t m;
+    m.level = level;
+    m.message = message;
 
-    for (auto &backend : backends) {
-        backend->log(level, message);
-    }
+    m_message_queue.push(std::move(m));
+}
 
-    if (level != log_level_t::trace) {
-        std::lock_guard<std::mutex> guard(m_cerr_mutex);
-        std::cerr << levels_as_str[level] << " " << message << std::endl;
+void Logger::io_process()
+{
+    set_thread_name("logger");
+    while (1) {
+        log_message_t m;
+        while (m_message_queue.pop(m) == false) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(10));
+        }
+
+        auto message = m.message;
+
+        if (m.level == debug and m.message.empty()) {
+            // Special message to stop thread
+            break;
+        }
+
+        /* Remove a potential trailing newline.
+         * It doesn't look good in syslog
+         */
+        if (message[message.length()-1] == '\n') {
+            message.resize(message.length()-1);
+        }
+
+        for (auto &backend : backends) {
+            backend->log(m.level, message);
+        }
+
+        if (m.level != log_level_t::trace) {
+            std::lock_guard<std::mutex> guard(m_cerr_mutex);
+            std::cerr << levels_as_str[m.level] << " " << message << std::endl;
+        }
     }
 }
 
diff --git a/src/Log.h b/src/Log.h
index cbc3569..799ca85 100644
--- a/src/Log.h
+++ b/src/Log.h
@@ -3,7 +3,7 @@
    Her Majesty the Queen in Right of Canada (Communications Research
    Center Canada)
 
-   Copyright (C), 2014, Matthias P. Braendli, matthias.braendli@mpb.li
+   Copyright (C), 2016, Matthias P. Braendli, matthias.braendli@mpb.li
  */
 /*
    This file is part of ODR-DabMod.
@@ -40,6 +40,8 @@
 #include <string>
 #include <map>
 #include <mutex>
+#include <thread>
+#include <boost/lockfree/spsc_queue.hpp>
 
 #define SYSLOG_IDENT "ODR-DabMod"
 #define SYSLOG_FACILITY LOG_LOCAL0
@@ -148,9 +150,32 @@ class LogTracer : public LogBackend {
 
 class LogLine;
 
+struct log_message_t {
+    log_message_t(log_level_t _level, std::string _message) :
+        level(_level),
+        message(_message) {}
+
+    log_message_t() {}
+
+    log_level_t level;
+    std::string message;
+};
+
 class Logger {
     public:
-        Logger() {}
+        Logger() {
+            m_io_thread = std::thread(&Logger::io_process, this);
+        }
+
+        Logger(const Logger& other) = delete;
+        const Logger& operator=(const Logger& other) = delete;
+        ~Logger() {
+            // Special message to stop the thread
+            log_message_t m(debug, "");
+
+            m_message_queue.push(m);
+            m_io_thread.join();
+        }
 
         void register_backend(LogBackend* backend);
 
@@ -159,6 +184,9 @@ class Logger {
 
         void logstr(log_level_t level, std::string message);
 
+        /* All logging IO is done in another thread */
+        void io_process(void);
+
         /* Return a LogLine for the given level
          * so that you can write etiLog.level(info) << "stuff = " << 21 */
         LogLine level(log_level_t level);
@@ -166,6 +194,10 @@ class Logger {
     private:
         std::list<LogBackend*> backends;
 
+        boost::lockfree::spsc_queue<
+            log_message_t,
+            boost::lockfree::capacity<80> > m_message_queue;
+        std::thread m_io_thread;
         std::mutex m_cerr_mutex;
 };
 
@@ -176,6 +208,7 @@ extern Logger etiLog;
 class LogLine {
     public:
         LogLine(const LogLine& logline);
+        const LogLine& operator=(const LogLine& other) = delete;
         LogLine(Logger* logger, log_level_t level) :
             logger_(logger)
         {