A new flag is introduced by the agent to permit syslogging

 of sessions that only obey SLO. Syslog is enabled if
either of use_syslog or use_session_syslog is enabled.
use_syslog to send sampled sessions to syslog;
use_session_syslog to send SLO sessions to syslog.
If use_syslog is enabled we dont send the session to
collector.
If only use_session_syslog is enabled, we send SLO
sessions to syslog but sampled sessions will continue
to go to collector.
Partial-Bug: 1729812

Change-Id: I02d6f3c3f369eb62343ee2f3237e3afdf2b4f002

sandesh/compiler/generate/t_cpp_generator.cc

@@ -1590,7 +1590,7 @@ void t_cpp_generator::generate_sandesh_flow_send_fn(ofstream &out,
     out << indent() << "return;" << endl;
     scope_down(out);
     out << indent() <<
-        "if (IsFlowLoggingEnabled() && LoggingUseSyslog()) {" << endl;
+        "if (IsFlowLoggingEnabled() && LoggingUseSyslog()) { " << endl;
     indent_up();
     out << indent() << "UpdateTxMsgFailStats(\"" << tsandesh->get_name() <<
         "\", 0, SandeshTxDropReason::SendingToSyslog);" << endl;
@@ -1599,12 +1599,16 @@ void t_cpp_generator::generate_sandesh_flow_send_fn(ofstream &out,
         out << indent() << "LogUnrolled" <<
             generate_sandesh_async_creator(tsandesh, false,
                 false, false, "", "", false, false, false) << ";" << endl;
+        out << indent() << "if (!IsSloSyslogEnabled()) {" << endl;
+        indent_up();
+        out << indent() << "return;" << endl;
+        scope_down(out);
     } else {
         out << indent() << "Log" <<
             generate_sandesh_async_creator(tsandesh, false,
                 false, false, "", "", false, false, false) << ";" << endl;
+        out << indent() << "return;" << endl;
     }
-    out << indent() << "return;" << endl;
     scope_down(out);
     out << indent() << "if (IsSendingAllMessagesDisabled() ||" <<
         " IsSendingFlowsDisabled()) {" << endl;

sandesh/library/cpp/sandesh.cc

@@ -45,6 +45,7 @@ using namespace contrail::sandesh::transport;
 Sandesh::SandeshRole::type Sandesh::role_ = SandeshRole::Invalid;
 bool Sandesh::enable_local_log_ = false;
 bool Sandesh::enable_flow_log_ = false;
+bool Sandesh::enable_session_syslog_ = false;
 int Sandesh::http_port_ = 0;
 bool Sandesh::enable_trace_print_ = false;
 bool Sandesh::send_queue_enabled_ = true;
@@ -349,12 +350,14 @@ void Sandesh::Uninit() {
 }
 
 void Sandesh::SetLoggingParams(bool enable_local_log, std::string category,
-        std::string level, bool enable_trace_print, bool enable_flow_log) {
+        std::string level, bool enable_trace_print, bool enable_flow_log,
+        bool enable_session_syslog) {
     SetLocalLogging(enable_local_log);
     SetLoggingCategory(category);
     SetLoggingLevel(level);
     SetTracePrint(enable_trace_print);
     SetFlowLogging(enable_flow_log);
+    SetSessionSyslogging(enable_session_syslog);
 }
 
 void Sandesh::SetLoggingParams(bool enable_local_log, std::string category,
@@ -451,6 +454,16 @@ void Sandesh::SetFlowLogging(bool enable_flow_log) {
     }
 }
 
+void Sandesh::SetSessionSyslogging(bool enable_session_syslog) {
+     if (enable_session_syslog_ != enable_session_syslog) {
+        SANDESH_LOG(INFO, "SANDESH: Flow Logging: " <<
+            (enable_session_syslog_ ? "ENABLED" : "DISABLED") << " -> " <<
+            (enable_session_syslog ? "ENABLED" : "DISABLED"));
+        enable_session_syslog_ = enable_session_syslog;
+    }
+
+}
+
 void Sandesh::DisableFlowCollection(bool disable) {
     if (disable_flow_collection_ != disable) {
         SANDESH_LOG(INFO, "SANDESH: Disable Flow Collection: " <<

sandesh/library/cpp/sandesh.h

@@ -212,7 +212,7 @@ class Sandesh {
     // Logging and category APIs
     static void SetLoggingParams(bool enable_local_log, std::string category,
             std::string level, bool enable_trace_print = false,
-            bool enable_flow_log = false);
+            bool enable_flow_log = false, bool enable_session_syslog = false);
     static void SetLoggingParams(bool enable_local_log, std::string category,
             SandeshLevel::type level, bool enable_trace_print = false,
             bool enable_flow_log = false);
@@ -223,7 +223,9 @@ class Sandesh {
     static bool IsLocalLoggingEnabled() { return enable_local_log_; }
     static void SetLocalLogging(bool enable);
     static bool IsFlowLoggingEnabled() { return enable_flow_log_; }
+    static bool IsSloSyslogEnabled() { return enable_session_syslog_; }
     static void SetFlowLogging(bool enable);
+    static void SetSessionSyslogging(bool enable_session_syslog);
     static bool IsTracePrintEnabled() { return enable_trace_print_; }
     static void SetTracePrint(bool enable);
     static void SetLoggingCategory(std::string category);
@@ -397,6 +399,7 @@ class Sandesh {
     static ModuleContextMap module_context_;
     static bool enable_local_log_;  // whether to just enable local logging
     static bool enable_flow_log_;  // whether to enable flow sandesh message logging
+    static bool enable_session_syslog_; // whether to enable syslog for SLO session messages
     static SandeshLevel::type logging_level_; // current logging level
     static SandeshLevel::type logging_ut_level_; // ut_debug logging level
     static std::string logging_category_; // current logging category