MXS-1734 Add possibility to instruct when to dump statements

With the configuration entry

dump_last_statements=[never|on_close|on_error]

you can now specify when and if to dump the last statements
of of a session.

include/maxscale/config.h

@@ -99,6 +99,7 @@ extern const char CN_AUTH_READ_TIMEOUT[];
 extern const char CN_AUTH_WRITE_TIMEOUT[];
 extern const char CN_AUTO[];
 extern const char CN_CONNECTION_TIMEOUT[];
+extern const char CN_DUMP_LAST_STATEMENTS[];
 extern const char CN_DATA[];
 extern const char CN_DEFAULT[];
 extern const char CN_DESCRIPTION[];

include/maxscale/session.h

@@ -83,6 +83,13 @@ typedef enum
     SESSION_TRX_READ_WRITE_ENDING = (SESSION_TRX_ENDING_BIT | SESSION_TRX_READ_WRITE),
 } mxs_session_trx_state_t;
 
+typedef enum
+{
+    SESSION_DUMP_STATEMENTS_NEVER,
+    SESSION_DUMP_STATEMENTS_ON_CLOSE,
+    SESSION_DUMP_STATEMENTS_ON_ERROR,
+} session_dump_statements_t;
+
 /**
  * The session statistics structure
  */
@@ -496,7 +503,7 @@ uint64_t session_get_current_id();
  *
  * @param n  The number of statements.
  */
-void session_retain_last_statements(uint32_t n);
+void session_set_retain_last_statements(uint32_t n);
 
 /**
  * @brief Retain provided statement, if configured to do so.
@@ -513,4 +520,18 @@ void session_retain_statement(MXS_SESSION* session, GWBUF* buffer);
  */
 void session_dump_statements(MXS_SESSION* pSession);
 
+/**
+ * @brief Specify whether statements should be dumped or not.
+ *
+ * @param value    Whether and when to dump statements.
+ */
+void session_set_dump_statements(session_dump_statements_t value);
+
+/**
+ * @brief Returns in what contexts statements should be dumped.
+ *
+ * @return Whether and when to dump statements.
+ */
+session_dump_statements_t session_get_dump_statements();
+
 MXS_END_DECLS

server/core/config.cc

@@ -80,6 +80,7 @@ const char CN_CONNECTION_TIMEOUT[]            = "connection_timeout";
 const char CN_DATA[]                          = "data";
 const char CN_DEFAULT[]                       = "default";
 const char CN_DESCRIPTION[]                   = "description";
+const char CN_DUMP_LAST_STATEMENTS[]          = "dump_last_statements";
 const char CN_ENABLE_ROOT_USER[]              = "enable_root_user";
 const char CN_FILTERS[]                       = "filters";
 const char CN_FILTER[]                        = "filter";
@@ -1740,13 +1741,33 @@ handle_global_item(const char *name, const char *value)
         int intval = strtol(value, &endptr, 0);
         if (*endptr == '\0' && intval >= 0)
         {
-            session_retain_last_statements(intval);
+            session_set_retain_last_statements(intval);
         }
         else
         {
             MXS_ERROR("Invalid value for '%s': %s", CN_RETAIN_LAST_STATEMENTS, value);
         }
     }
+    else if (strcmp(name, CN_DUMP_LAST_STATEMENTS) == 0)
+    {
+        if (strcmp(value, "on_close") == 0)
+        {
+            session_set_dump_statements(SESSION_DUMP_STATEMENTS_ON_CLOSE);
+        }
+        else if (strcmp(value, "on_error") == 0)
+        {
+            session_set_dump_statements(SESSION_DUMP_STATEMENTS_ON_ERROR);
+        }
+        else if (strcmp(value, "never") == 0)
+        {
+            session_set_dump_statements(SESSION_DUMP_STATEMENTS_NEVER);
+        }
+        else
+        {
+            MXS_ERROR("%s can have the values 'never', 'on_close' or 'on_error'.",
+                      CN_DUMP_LAST_STATEMENTS);
+        }
+    }
     else
     {
         for (i = 0; lognames[i].name; i++)

server/core/gateway.cc

@@ -3221,7 +3221,7 @@ static void retain_last_statements(const char* arg)
         n = 0;
     }
 
-    session_retain_last_statements(n);
+    session_set_retain_last_statements(n);
 }
 
 static void redirect_output_to_file(const char* arg)

server/core/session.cc

@@ -53,6 +53,7 @@ using std::stringstream;
 static uint64_t next_session_id = 1;
 
 static uint32_t retain_last_statements = 0;
+static session_dump_statements_t dump_statements = SESSION_DUMP_STATEMENTS_NEVER;
 
 static struct session session_dummy_struct;
 
@@ -392,6 +393,11 @@ static void session_free(MXS_SESSION *session)
 static void
 session_final_free(MXS_SESSION *session)
 {
+    if (dump_statements == SESSION_DUMP_STATEMENTS_ON_CLOSE)
+    {
+        session_dump_statements(session);
+    }
+
     gwbuf_free(session->stmt.buffer);
     delete session->last_statements;
     MXS_FREE(session);
@@ -1111,11 +1117,21 @@ uint64_t session_get_current_id()
     return session ? session->ses_id : 0;
 }
 
-void session_retain_last_statements(uint32_t n)
+void session_set_retain_last_statements(uint32_t n)
 {
     retain_last_statements = n;
 }
 
+void session_set_dump_statements(session_dump_statements_t value)
+{
+    dump_statements = value;
+}
+
+session_dump_statements_t session_get_dump_statements()
+{
+    return dump_statements;
+}
+
 void session_retain_statement(MXS_SESSION* pSession, GWBUF* pBuffer)
 {
     if (retain_last_statements)

server/modules/protocol/MySQL/mariadbclient/mysql_client.cc

@@ -1409,8 +1409,12 @@ static int gw_client_hangup_event(DCB *dcb)
     {
         CHK_SESSION(session);
         if (session->state != SESSION_STATE_DUMMY && !session_valid_for_pool(session))
+        {
+            if (session_get_dump_statements() == SESSION_DUMP_STATEMENTS_ON_ERROR)
             {
                 session_dump_statements(session);
+            }
+
             // The client did not send a COM_QUIT packet
             modutil_send_mysql_err_packet(dcb, 0, 0, 1927, "08S01", "Connection killed by MaxScale");
         }