MXS-1929: Make services destroyable

Services can now be destroyed if they have no active listeners and they
are not linked to servers. When these conditions are met, the service will
be destroyed when the last session for the service is closed.

The closing of a service will close all listeners that were once assigned
to the service. This allows closing of the ports at runtime which
previously was done only on shutdown.

Exposed the command through the REST API but not through MaxAdmin as it is
deprecated.

server/core/service.cc

@@ -58,6 +58,7 @@
 #include "internal/filter.h"
 #include "internal/modules.h"
 #include "internal/service.h"
+#include "internal/routingworker.hh"
 
 /** This define is needed in CentOS 6 systems */
 #if !defined(UINT64_MAX)
@@ -114,6 +115,7 @@ SERVICE* service_alloc(const char *name, const char *router, MXS_CONFIG_PARAMETE
     service->stats.started = time(0);
     service->stats.n_failed_starts = 0;
     service->state = SERVICE_STATE_ALLOC;
+    service->active = true;
     spinlock_init(&service->spin);
 
     service->max_retry_interval = config_get_integer(params, CN_MAX_RETRY_INTERVAL);
@@ -183,6 +185,7 @@ SERVICE* service_alloc(const char *name, const char *router, MXS_CONFIG_PARAMETE
 void service_free(SERVICE* service)
 {
     ss_dassert(atomic_load_int(&service->client_count) == 0);
+    ss_dassert(!service->active);
 
     spinlock_acquire(&service_spin);
 
@@ -208,6 +211,7 @@ void service_free(SERVICE* service)
     {
         auto tmp = service->ports;
         service->ports = service->ports->next;
+        ss_dassert(!tmp->active);
         listener_free(tmp);
     }
 
@@ -219,6 +223,7 @@ void service_free(SERVICE* service)
     while (service->dbref)
     {
         SERVER_REF* tmp = service->dbref;
+        ss_dassert(!tmp->active);
         service->dbref = service->dbref->next;
         MXS_FREE(tmp);
     }
@@ -231,6 +236,34 @@ void service_free(SERVICE* service)
     MXS_FREE(service);
 }
 
+void service_destroy(SERVICE* service)
+{
+#ifdef SS_DEBUG
+    auto current = mxs::RoutingWorker::get_current();
+    auto main = mxs::RoutingWorker::get(mxs::RoutingWorker::MAIN);
+    ss_info_dassert(current == main, "Destruction of service must be done on the main worker");
+#endif
+
+    ss_dassert(service->active);
+    service->active = false;
+
+    char filename[PATH_MAX + 1];
+    snprintf(filename, sizeof(filename), "%s/%s.cnf", get_config_persistdir(),
+             service->name);
+
+    if (unlink(filename) == -1 && errno != ENOENT)
+    {
+        MXS_ERROR("Failed to remove persisted service configuration at '%s': %d, %s",
+                  filename, errno, mxs_strerror(errno));
+    }
+
+    if (atomic_load_int(&service->client_count) == 0)
+    {
+        // The service has no active sessions, it can be closed immediately
+        service_free(service);
+    }
+}
+
 /**
  * Check to see if a service pointer is valid
  *
@@ -841,6 +874,36 @@ bool service_has_named_listener(SERVICE *service, const char *name)
     return false;
 }
 
+bool service_can_be_destroyed(SERVICE *service)
+{
+    bool rval = true;
+    LISTENER_ITERATOR iter;
+
+    for (SERV_LISTENER *listener = listener_iterator_init(service, &iter);
+         listener; listener = listener_iterator_next(&iter))
+    {
+        if (listener_is_active(listener))
+        {
+            rval = false;
+            break;
+        }
+    }
+
+    if (rval)
+    {
+        for (auto s = service->dbref; s; s = s->next)
+        {
+            if (s->active)
+            {
+                rval = false;
+                break;
+            }
+        }
+    }
+
+    return rval;
+}
+
 /**
  * Allocate a new server reference
  *
@@ -1238,8 +1301,12 @@ service_find(const char *servname)
 
     spinlock_acquire(&service_spin);
     service = allServices;
-    while (service && strcmp(service->name, servname) != 0)
+    while (service)
     {
+        if (strcmp(service->name, servname) == 0 && service->active)
+        {
+            break;
+        }
         service = service->next;
     }
     spinlock_release(&service_spin);