Core: add support for a PID file

Author: Lukas955

src/core/main.cpp

@@ -41,10 +41,12 @@
 #include <iostream>
 #include <string>
 #include <vector>
+#include <sys/types.h> // getpid()
 #include <unistd.h>
 
 #include <ipfixcol2.h>
 #include <iostream>
+#include <fstream>
 #include "configurator/config_file.hpp"
 #include "configurator/configurator.hpp"
 
@@ -53,6 +55,9 @@ extern "C" {
 #include <build_config.h>
 }
 
+/** Internal identification of the module */
+static const char *module = "Configurator";
+
 /**
  * \brief Print information about version of the collector to standard output
  */
@@ -77,17 +82,18 @@ print_help()
     std::cout
         << "IPFIX Collector daemon\n"
         << "Usage: ipfixcol [-c FILE] [-d PATH] [-vVh]\n"
-        << "  -c FILE   Path to the startup configuration file (default: "
-            << IPX_DEFAULT_STARTUP_CONFIG << ")\n"
-        << "  -p PATH   Add path to a directory with plugins or to a file (default: "
-            << IPX_DEFAULT_PLUGINS_DIR << ")\n"
-        << "  -e DIR    Path to a directory with definitions of IPFIX Information Elements "
-            << "(default: " << fds_api_cfg_dir() << ")\n"
+        << "  -c FILE   Path to the startup configuration file\n"
+        << "            (default: " << IPX_DEFAULT_STARTUP_CONFIG << ")\n"
+        << "  -p PATH   Add path to a directory with plugins or to a file\n"
+        << "            (default: " << IPX_DEFAULT_PLUGINS_DIR << ")\n"
+        << "  -e DIR    Path to a directory with definitions of IPFIX Information Elements\n"
+        << "            (default: " << fds_api_cfg_dir() << ")\n"
         << "  -h        Show this help message and exit\n"
         << "  -V        Show version information and exit\n"
         << "  -v        Be verbose (in addition, show warning messages)\n"
         << "  -vv       Be more verbose (like previous + info messages)\n"
-        << "  -vvv      Be even more verbose (like previous + debug messages)\n";
+        << "  -vvv      Be even more verbose (like previous + debug messages)\n"
+        << "  -P FILE   Path to a PID file (without this option, no PID file is created)\n";
 }
 
 /**
@@ -107,6 +113,47 @@ increase_verbosity()
     ipx_verb_level_set(level);
 }
 
+/**
+ * \brief Create a PID file (contains Process ID)
+ * \param[in] file PID file
+ * \return #IPX_OK on success
+ * \return #IPX_ERR_DENIED if it is not possible to create the file
+ */
+static int
+pid_create(const char *file)
+{
+    IPX_INFO(module, "Creating PID file '%s'", file);
+    std::ofstream pid_file(file, std::ofstream::out);
+    if (pid_file.fail()) {
+        IPX_WARNING(module, "Failed to create a PID file '%s'!", file);
+        return IPX_ERR_DENIED;
+    }
+
+    pid_file << getpid();
+    pid_file.close();
+    return IPX_OK;
+}
+
+/**
+ * \brief Remove a PID file (contains Process ID)
+ * \param[in] file PID file
+ * \return #IPX_OK on success
+ * \return #IPX_ERR_DENIED if it is not possible to remove the file
+ */
+static int
+pid_remove(const char *file)
+{
+    IPX_INFO(module, "Removing PID file '%s'", file);
+    if (unlink(file) == -1) {
+        const char *err_str;
+        ipx_strerror(errno, err_str);
+        IPX_WARNING(module, "Failed to remove a PID file '%s': %s", file, err_str);
+        return IPX_ERR_DENIED;
+    }
+
+    return IPX_OK;
+}
+
 /**
  * \brief Main function
  * \param[in] argc Number of arguments
@@ -117,12 +164,13 @@ int main(int argc, char *argv[])
 {
     const char *cfg_startup = nullptr;
     const char *cfg_iedir = nullptr;
+    const char *pid_file = nullptr;
     ipx_configurator conf;
 
     // Parse configuration
     int opt;
     opterr = 0; // Disable default error messages
-    while ((opt = getopt(argc, argv, "c:vVhp:e:")) != -1) {
+    while ((opt = getopt(argc, argv, "c:vVhp:e:P:")) != -1) {
         switch (opt) {
         case 'c': // Configuration file
             cfg_startup = optarg;
@@ -142,6 +190,9 @@ int main(int argc, char *argv[])
         case 'e':
             cfg_iedir = optarg;
             break;
+        case 'P':
+            pid_file = optarg;
+            break;
         default: // ?
             std::cerr << "Unknown parameter '" << static_cast<char>(optopt) << "'!" << std::endl;
             return EXIT_FAILURE;
@@ -162,6 +213,11 @@ int main(int argc, char *argv[])
     conf.finder.path_add(IPX_DEFAULT_PLUGINS_DIR);
     conf.iemgr_set_dir(cfg_iedir);
 
+    // Create a PID file
+    if (pid_file != nullptr && pid_create(pid_file) != IPX_OK) {
+        pid_file = nullptr; // Prevent removing the file
+    }
+
     // Pass control to the parser of the configuration file
     int rc;
     try {
@@ -174,6 +230,11 @@ int main(int argc, char *argv[])
         return EXIT_FAILURE;
     }
 
+    // Destroy a PID file
+    if (pid_file != nullptr) {
+        pid_remove(pid_file);
+    }
+
     // Destroy the pipeline configurator
     return rc;
 }