Core: process remaining flow records on termination (SIGINT, SIGTERM)

Until now, when an external signal was received, the collector was quickly
terminated and the received but not yet processed flow records were discarded.

Now, when a signal is received, there is a gradual termination where the
reception of new flow records is terminated but all records received so far
are fully processed. Only if the termination signal arrives a second time
the processing of unprocessed records will be also interrupted.

Author: Lukas Hutak

src/core/configurator/configurator.cpp

@@ -73,17 +73,22 @@ termination_handler(int sig)
 
     // In case we change 'errno' (e.g. write())
     int errno_backup = errno;
+    enum ipx_cpipe_type request_type = IPX_CPIPE_TYPE_TERM_SLOW;
     static int cnt = 0;
 
-    if (cnt > 0) {
+    if (cnt == 1) {
+        static const char *msg = "Another termination signal detected. Skipping unprocess data...\n";
+        write(STDERR_FILENO, msg, strlen(msg));
+        request_type = IPX_CPIPE_TYPE_TERM_FAST;
+    } else if (cnt > 1) {
         static const char *msg = "Another termination signal detected. Quiting without cleanup...\n";
-        write(STDOUT_FILENO, msg, strlen(msg));
+        write(STDERR_FILENO, msg, strlen(msg));
         abort();
     }
     cnt++;
 
     // Send a termination request to the configurator
-    int rc = ipx_cpipe_send_term(NULL, IPX_CPIPE_TYPE_TERM_FAST);
+    int rc = ipx_cpipe_send_term(NULL, request_type);
     if (rc != IPX_OK) {
         static const char *msg = "ERROR: Signal handler: failed to send a termination request";
         write(STDOUT_FILENO, msg, strlen(msg));

src/core/configurator/cpipe.h

@@ -60,8 +60,7 @@ enum ipx_cpipe_type {
      * @brief Fast termination request
      *
      * Request to terminate the collector as fast as possible. Usually this request should be
-     * send in case of a fatal failure of any plugin instance (by a particular instance thread)
-     * or on a user request to terminate the collector (e.g. SIGINT/SIGTERM signals).
+     * send in case of a fatal failure of any plugin instance (by a particular instance thread).
      *
      * As a reaction to this request the configurator will force stop calling processing functions
      * of ALL plugin instances (i.e. ipx_plugin_get() and ipx_plugin_process() callbacks) and send