MXS-1780 Make retain_last_statements service specific

Documentation/Getting-Started/Configuration-Guide.md

@@ -1230,6 +1230,22 @@ The following Server side config is needed too.
   session_track_transaction_info = CHARACTERISTICS
   ```
 
+#### `retain_last_statements`
+
+How many statements MaxScale should store for each session of this service.
+This overrides the value of the global setting with the same name. If
+`retain_last_statements` has been specified in the global section of the
+MaxScale configuration file, then if it has _not_ been explicitly specified
+for the service, the global value holds, otherwise the service specific
+value rules. That is, it is possible to enable the setting globally and
+turn it off for a specific service, or just enable it for specific services.
+
+The value of this parameter can be changed at runtime using `maxctrl` and the
+new value will take effect for sessions created thereafter.
+```
+maxctrl alter service MyService retain_last_statements 5
+```
+
 ### Server
 
 Server sections are used to define the backend database servers that can be

Documentation/Release-Notes/MaxScale-2.3.1-Release-Notes.md

@@ -51,6 +51,11 @@ feature can be used for debugging, if there is suspicion that MaxScale
 sends a particular statement to the wrong server (e.g. to a slave when it
 should be sent to the master).
 
+### Services
+
+The global configuration parameter `retain_last_statements` can now
+also be specified separately for individual services.
+
 ## Bug fixes
 
 [Here is a list of bugs fixed in MaxScale 2.3.1.](https://jira.mariadb.org/issues/?jql=project%20%3D%20MXS%20AND%20issuetype%20%3D%20Bug%20AND%20status%20%3D%20Closed%20AND%20fixVersion%20%3D%202.3.1)

include/maxscale/service.h

@@ -150,6 +150,8 @@ typedef struct service
                                                      * track mechanism */
     int active;                                     /**< Whether the service is still
                                                      * active */
+    int32_t retain_last_statements;                 /**< How many statements to retain per session,
+                                                     * -1 if not explicitly specified. */
 } SERVICE;
 
 typedef enum count_spec_t

maxctrl/lib/alter.js

@@ -26,7 +26,8 @@ const service_params = [
     'strip_db_esc',
     'localhost_match_wildcard_host',
     'max_slave_connections',
-    'max_slave_replication_lag'
+    'max_slave_replication_lag',
+    'retain_last_statements'
 ]
 
 // List of maxscale parameters that can be altered at runtime

server/core/config.cc

@@ -315,6 +315,7 @@ const MXS_MODULE_PARAM config_service_params[] =
     {CN_LOG_AUTH_WARNINGS,             MXS_MODULE_PARAM_BOOL,   "true"},
     {CN_RETRY_ON_FAILURE,              MXS_MODULE_PARAM_BOOL,   "true"},
     {CN_SESSION_TRACK_TRX_STATE,       MXS_MODULE_PARAM_BOOL,   "false"},
+    {CN_RETAIN_LAST_STATEMENTS,        MXS_MODULE_PARAM_COUNT,  "0"},
     {NULL}
 };
 

server/core/internal/session.hh

@@ -100,7 +100,7 @@ public:
 
     using FilterList = std::vector<SessionFilter>;
 
-    Session();
+    Session(SERVICE* service);
     ~Session();
 
     bool setup_filters(Service* service);
@@ -147,7 +147,7 @@ private:
     QueryInfos        m_last_queries;           /*< The N last queries by the client */
     int               m_current_query = -1;     /*< The index of the current query */
     DCBSet            m_dcb_set;                /*< Set of associated backend DCBs */
-    bool              m_retain_last_statements; /*< Should statement information be stored */
+    uint32_t          m_retain_last_statements; /*< How many statements be retained */
 };
 }
 

server/core/service.cc

@@ -200,6 +200,15 @@ Service::Service(const std::string& service_name,
     strip_db_esc = config_get_bool(params, CN_STRIP_DB_ESC);
     session_track_trx_state = config_get_bool(params, CN_SESSION_TRACK_TRX_STATE);
 
+    if (config_get_param(params, CN_RETAIN_LAST_STATEMENTS))
+    {
+        retain_last_statements = config_get_integer(params, CN_RETAIN_LAST_STATEMENTS);
+    }
+    else
+    {
+        retain_last_statements = -1; // Indicates that it has not been set.
+    }
+
     /**
      * At service start last update is set to config->users_refresh_time seconds earlier.
      * This way MaxScale could try reloading users just after startup. But only if user
@@ -2344,7 +2353,8 @@ bool Service::is_basic_parameter(const std::string& name)
         CN_USER,
         CN_VERSION_STRING,
         CN_WEIGHTBY,
-        CN_FILTERS
+        CN_FILTERS,
+        CN_RETAIN_LAST_STATEMENTS
     };
 
     return names.find(name) != names.end();
@@ -2415,4 +2425,8 @@ void Service::update_basic_parameter(const std::string& key, const std::string&
     {
         retry_start = config_truth_value(value.c_str());
     }
+    else if (key == CN_RETAIN_LAST_STATEMENTS)
+    {
+        retain_last_statements = std::stoi(value);
+    }
 }

server/core/session.cc

@@ -109,7 +109,7 @@ MXS_SESSION* session_alloc(SERVICE* service, DCB* client_dcb)
 
 MXS_SESSION* session_alloc_with_id(SERVICE* service, DCB* client_dcb, uint64_t id)
 {
-    Session* session = new(std::nothrow) Session;
+    Session* session = new (std::nothrow) Session(service);
 
     if (session == nullptr)
     {
@@ -1198,9 +1198,16 @@ const char* session_get_close_reason(const MXS_SESSION* session)
     }
 }
 
-Session::Session()
-    : m_retain_last_statements(this_unit.retain_last_statements)
+Session::Session(SERVICE* service)
 {
+    if (service->retain_last_statements != -1) // Explicitly set for the service
+    {
+        m_retain_last_statements = service->retain_last_statements;
+    }
+    else
+    {
+        m_retain_last_statements = this_unit.retain_last_statements;
+    }
 }
 
 Session::~Session()

server/modules/filter/test/mock_session.cc

@@ -13,6 +13,13 @@
 
 #include "maxscale/mock/session.hh"
 
+namespace
+{
+
+SERVICE dummy_service;
+
+}
+
 namespace maxscale
 {
 
@@ -20,7 +27,8 @@ namespace mock
 {
 
 Session::Session(Client* pClient)
-    : m_client(*pClient)
+    : mxs::Session(&dummy_service)
+    , m_client(*pClient)
     , m_client_dcb(this, pClient->user(), pClient->host(), pClient)
 {
     MXS_SESSION* pSession = this;