Add support for logrotate in sairedis (sonic-net#192)

* Add support for logrotate in sairedis

* Fix attribute id access

* Fix logrotate variable name

* Address comments

Author: kcudnik

lib/inc/sai_redis.h

@@ -36,6 +36,7 @@ extern std::string joinFieldValues(
         _In_ const std::vector<swss::FieldValueTuple> &values);
 
 extern volatile bool                    g_useTempView;
+extern volatile bool                    g_logrotate;
 
 // other global declarations
 

lib/inc/sairedis.h

@@ -82,6 +82,25 @@ typedef enum _sai_redis_switch_attr_t
      */
     SAI_REDIS_SWITCH_ATTR_RECORDING_OUTPUT_DIR,
 
+    /**
+     * @brief Log rotate.
+     *
+     * This is action attribute. When set to true then at the next log line
+     * write it will close recording file and open it again. This is desired
+     * when doing log rotate, since sairedis holds handle to recording file for
+     * performance reasons. We are assuming logrotate will move recording file
+     * to ".n" suffix, and when we reopen file, we will actually create new
+     * one.
+     *
+     * This attribute is only setting variable in memroy, it's safe to call
+     * this from signal handler.
+     *
+     * @type bool
+     * @flags CREATE_AND_SET
+     * @default false
+     */
+    SAI_REDIS_SWITCH_ATTR_PERFORM_LOG_ROTATE,
+
 } sai_redis_switch_attr_t;
 
 /*

lib/src/sai_redis_record.cpp

@@ -22,10 +22,34 @@ std::string getTimestamp()
 
 // recording needs to be enabled explicitly
 volatile bool g_record = false;
+volatile bool g_logrotate = false;
 
 std::ofstream recording;
 std::mutex g_recordMutex;
 
+std::string recfile = "dummy.rec";
+
+void logfileReopen()
+{
+    SWSS_LOG_ENTER();
+
+    recording.close();
+
+    /*
+     * On log rotate we will use the same file name, we are assuming that
+     * logrotate deamon move filename to filename.1 and we will create new
+     * empty file here.
+     */
+
+    recording.open(recfile);
+
+    if (!recording.is_open())
+    {
+        SWSS_LOG_ERROR("failed to open recording file %s: %s", recfile.c_str(), strerror(errno));
+        return;
+    }
+}
+
 void recordLine(std::string s)
 {
     std::lock_guard<std::mutex> lock(g_recordMutex);
@@ -36,9 +60,21 @@ void recordLine(std::string s)
     {
         recording << getTimestamp() << "|" << s << std::endl;
     }
-}
 
-std::string recfile = "dummy.rec";
+    if (g_logrotate)
+    {
+        g_logrotate = false;
+
+        logfileReopen();
+
+        /* double check since reopen could fail */
+
+        if (recording.is_open())
+        {
+            recording << getTimestamp() << "|" << "#|logrotate on: " << recfile << std::endl;
+        }
+    }
+}
 
 void startRecording()
 {

lib/src/sai_redis_switch.cpp

@@ -361,6 +361,22 @@ sai_status_t sai_redis_notify_syncd(
 sai_status_t redis_set_switch_attribute(
         _In_ const sai_attribute_t *attr)
 {
+    if (attr != NULL && attr->id == SAI_REDIS_SWITCH_ATTR_PERFORM_LOG_ROTATE)
+    {
+        /*
+         * Let's avoid using mutexes, since this attribute could be used in
+         * signal handler, so check it's value here. If set this attribute will
+         * be performed from multiple threads there is possibility for race
+         * condition here, but this doesn't matter since we only set logrotate
+         * flag, and if that happens we will just reopen file less times then
+         * actual set operation was called.
+         */
+
+        g_logrotate = true;
+
+        return SAI_STATUS_SUCCESS;
+    }
+
     std::lock_guard<std::mutex> lock(g_apimutex);
 
     SWSS_LOG_ENTER();