Process cassandra db configuration upon SIGUSR1 in control-node

During ISSU, V2 control-node needs to be notified to read the cassandra
db again as rabbitmq v2 which sends update notifications would not have
been up for a small time window.

Currently, DB is re-read only if the contrail-control.conf is modified
(wrt cassandra db server list, user name, password, etc.). We can do the
same re-read process upon SIGUSR1 signal as well. This can come in handy
in case control-node is stuck ever with stale config data as well. (as a
work around to restarting the control-node process itself)

This fix was verified by systest.

TODO: Unit tests for this entire config-db re-read is still a pending
action item.

Change-Id: Ib8b9e39a572cfb688d95e81756372a1f33964d8f
Closes-Bug: 1779186

src/control-node/main.cc

@@ -205,12 +205,14 @@ static void ControlNodeGetProcessStateCb(const BgpServer *bgp_server,
     }
 }
 
-void ReConfigSignalHandler(const boost::system::error_code &error, int sig) {
+void ReConfigSignalHandler(const boost::system::error_code &error, int sig,
+                           bool force_reinit) {
     if (error) {
         LOG(ERROR, "SIGHUP handler ERROR: " << error);
         return;
     }
-    options.ParseReConfig();
+    LOG(WARN, "Received signal " << sig << " inside ReConfigSignalHandler()");
+    options.ParseReConfig(force_reinit);
 }
 
 int main(int argc, char *argv[]) {
@@ -221,9 +223,13 @@ int main(int argc, char *argv[]) {
 
     srand(unsigned(time(NULL)));
     std::vector<Signal::SignalHandler> sighup_handlers = boost::assign::list_of
-        (boost::bind(&ReConfigSignalHandler, _1, _2));
+        (boost::bind(&ReConfigSignalHandler, _1, _2, false));
+    std::vector<Signal::SignalHandler> sigusr1_handlers = boost::assign::list_of
+        (boost::bind(&ReConfigSignalHandler, _1, _2, true));
     Signal::SignalCallbackMap smap = boost::assign::map_list_of
-        (SIGHUP, sighup_handlers);
+        (SIGHUP, sighup_handlers)
+        (SIGUSR1, sigusr1_handlers)
+    ;
     Signal signal(&evm, smap);
 
     ControlNode::SetProgramName(argv[0]);

src/control-node/options.cc

@@ -314,7 +314,7 @@ bool Options::Process(int argc, char *argv[],
     return true;
 }
 
-void Options::ParseReConfig() {
+void Options::ParseReConfig(bool force_reinit) {
     // ReParse the filtered config params
     opt::variables_map var_map;
     ifstream config_file_in;
@@ -343,7 +343,8 @@ void Options::ParseReConfig() {
 
     uint32_t old_config_chksum = configdb_chksum_;
     ParseConfigOptions(var_map);
-    if ((old_config_chksum != configdb_chksum_) && config_client_manager_) {
+    if ((force_reinit || old_config_chksum != configdb_chksum_) &&
+            config_client_manager_) {
         config_client_manager_->ReinitConfigClient(configdb_options());
     }
 }

src/control-node/options.h

@@ -81,7 +81,7 @@ class Options {
     }
     const SandeshConfig &sandesh_config() const { return sandesh_config_; }
 
-    void ParseReConfig();
+    void ParseReConfig(bool force_reinit);
 
     void set_config_client_manager(ConfigClientManager *mgr) {
         config_client_manager_ = mgr;