MXS-1356: Allow tee filter to be disabled at runtime

Disabling the tee filter at runtime is desirable for cases where the
branched service is not always needed. Migrations and pre-production
setups are one where changes to the branched service are expected and
splitting the queries would result in an error.

Documentation/Filters/Tee-Filter.md

@@ -99,6 +99,23 @@ sessions that are connected using this username are replicated.
 user=john
 ```
 
+## Module commands
+
+Read [Module Commands](../Reference/Module-Commands.md) documentation for
+details about module commands.
+
+The tee filter supports the following module commands.
+
+### `tee disable [FILTER]`
+
+This commmad disables a tee filter instance. A disabled tee filter will not send
+any queries to the target service.
+
+### `tee enable [FILTER]`
+
+Enable a disabled tee filter. This resumes the sending of queries to the target
+service.
+
 ## Examples
 
 ### Example 1 - Replicate all inserts into the orders table

Documentation/Release-Notes/MaxScale-2.2.0-Release-Notes.md

@@ -59,6 +59,13 @@ The `match` and `exclude` parameters were changed to use PCRE2 syntax for the
 regular expressions. The regular expression should be enclosed by slashes
 e.g. `match=/select.*from.*test/`.
 
+A tee filter instance can be disabled with the new `tee disable [FILTER]` and
+`tee enable [FILTER]` module commands. Refer to the
+[module command documentation](../Reference/Module-Commands.md) for more
+details on module commands and the
+[Tee Filter documentation](../Filters/Tee-Filter.md) for details on the tee
+filter specific commands.
+
 ### Dbfwfilter
 
 The `function` type rule will now match a query that does not use a function

server/modules/filter/tee/tee.cc

@@ -22,6 +22,7 @@
 #include <maxscale/alloc.h>
 #include <maxscale/modinfo.h>
 #include <maxscale/log_manager.h>
+#include <maxscale/modulecmd.h>
 
 #include "tee.hh"
 #include "local_client.hh"
@@ -44,7 +45,8 @@ Tee::Tee(SERVICE* service, std::string user, std::string remote,
     m_match_code(match),
     m_exclude_code(exclude),
     m_match(match_string),
-    m_exclude(exclude_string)
+    m_exclude(exclude_string),
+    m_enabled(true)
 {
 }
 
@@ -121,6 +123,7 @@ void Tee::diagnostics(DCB *dcb)
         dcb_printf(dcb, "\t\tExclude queries that match		%s\n",
                    m_exclude.c_str());
     }
+    dcb_printf(dcb, "\t\tFilter enabled: %s\n", m_enabled ? "yes" : "no");
 }
 
 /**
@@ -159,9 +162,25 @@ json_t* Tee::diagnostics_json() const
         json_object_set_new(rval, "exclude", json_string(m_exclude.c_str()));
     }
 
+    json_object_set_new(rval, "enabled", json_boolean(m_enabled));
+
     return rval;
 }
 
+static bool enable_tee(const MODULECMD_ARG *argv, json_t** output)
+{
+    Tee* instance = reinterpret_cast<Tee*>(filter_def_get_instance(argv->argv[0].value.filter));
+    instance->set_enabled(true);
+    return true;
+}
+
+static bool disable_tee(const MODULECMD_ARG *argv, json_t** output)
+{
+    Tee* instance = reinterpret_cast<Tee*>(filter_def_get_instance(argv->argv[0].value.filter));
+    instance->set_enabled(false);
+    return true;
+}
+
 MXS_BEGIN_DECLS
 
 /**
@@ -174,6 +193,18 @@ MXS_BEGIN_DECLS
  */
 MXS_MODULE* MXS_CREATE_MODULE()
 {
+    modulecmd_arg_type_t argv[] =
+    {
+        {
+            MODULECMD_ARG_FILTER | MODULECMD_ARG_NAME_MATCHES_DOMAIN,
+            "Filter to modify"
+        }
+    };
+
+    modulecmd_register_command(MXS_MODULE_NAME, "enable", MODULECMD_TYPE_ACTIVE,
+                               enable_tee, 1, argv, "Enable a tee filter instance");
+    modulecmd_register_command(MXS_MODULE_NAME, "disable", MODULECMD_TYPE_ACTIVE,
+                               disable_tee, 1, argv, "Disable a tee filter instance");
 
     static MXS_MODULE info =
     {

server/modules/filter/tee/tee.hh

@@ -67,6 +67,16 @@ public:
         return m_exclude_code;
     }
 
+    void set_enabled(bool value)
+    {
+        m_enabled = value;
+    }
+
+    bool is_enabled() const
+    {
+        return m_enabled;
+    }
+
 private:
     Tee(SERVICE* service, std::string user, std::string remote,
         pcre2_code* match, std::string match_string,
@@ -79,4 +89,5 @@ private:
     pcre2_code* m_exclude_code; /* Compiled exclude pattern*/
     std::string m_match;        /* Pattern for matching queries */
     std::string m_exclude;      /* Pattern for excluding queries */
+    bool        m_enabled;
 };

server/modules/filter/tee/teesession.cc

@@ -88,7 +88,8 @@ TeeSession* TeeSession::create(Tee* my_instance, MXS_SESSION* session)
     pcre2_match_data* md_match = NULL;
     pcre2_match_data* md_exclude = NULL;
 
-    if (my_instance->user_matches(session_get_user(session)) &&
+    if (my_instance->is_enabled() &&
+        my_instance->user_matches(session_get_user(session)) &&
         my_instance->remote_matches(session_get_remote(session)))
     {
         match = my_instance->get_match();