Set database_application_name in workers and server.

Previously, pg_stat_activity would look like this:

```
vmdb_production=# select pid, application_name from pg_stat_activity;
 pid   | application_name
 ------+--------------------------------------------------
 13770 | /var/www/miq/vmdb/lib/workers/bin/evm_server.rb
 13950 | /var/www/miq/vmdb/lib/workers/bin/evm_server.rb
 13957 | /var/www/miq/vmdb/lib/workers/bin/evm_server.rb
 13969 | /var/www/miq/vmdb/lib/workers/bin/evm_server.rb
 13975 | /var/www/miq/vmdb/lib/workers/bin/evm_server.rb
 13984 | /var/www/miq/vmdb/lib/workers/bin/evm_server.rb
```

It now looks like this:

```
vmdb_development=# select pid, application_name from pg_stat_activity;
 pid  | application_name
------------------+------+-------------+----------------------
 5844 | MIQ 5835 Server[1r2], default[1r1]
 5888 | MIQ 5886 Generic[1r1111], s[1r2], default[1r1]
 5891 | MIQ 5889 Generic[1r1112], s[1r2], default[1r1]
 5894 | MIQ 5892 Priority[1r1113], s[1r2], default[1r1]
 5897 | MIQ 5895 Priority[1r1114], s[1r2], default[1r1]
 5900 | MIQ 5898 Schedule[1r1115], s[1r2], default[1r1]
 5928 | MIQ 5926 EventHandler[1r1116], s[1r2], default[1r1]
 5932 | MIQ 5929 Reporting[1r1117], s[1r2], default[1r1]
 5934 | MIQ 5931 Reporting[1r1118], s[1r2], default[1r1]
 5943 | MIQ 5941 Ui[1r1120], s[1r2], default[1r1]
 5940 | MIQ 5935 Websocket[1r1119], s[1r2], default[1r1]
 5946 | MIQ 5944 WebService[1r1121], s[1r2], default[1r1]
 5964 | MIQ 5935 Websocket[1r1119], s[1r2], default[1r1]
 5965 | MIQ 5941 Ui[1r1120], s[1r2], default[1r1]
 5966 | MIQ 5944 WebService[1r1121], s[1r2], default[1r1]
```

app/models/embedded_ansible_worker/runner.rb

@@ -63,6 +63,7 @@ def update_embedded_ansible_provider
 
   # Base class methods we override since we don't have a separate process.  We might want to make these opt-in features in the base class that this subclass can choose to opt-out.
   def set_process_title; end
+  def set_database_application_name; end
   def set_connection_pool_size; end
   def message_sync_active_roles(*_args); end
   def message_sync_config(*_args); end

app/models/miq_server.rb

@@ -455,6 +455,10 @@ def who_am_i
     @who_am_i ||= "#{name} #{my_zone} #{self.class.name} #{id}"
   end
 
+  def database_application_name
+    "MIQ #{Process.pid} Server[#{compressed_id}], #{zone.name}[#{zone.compressed_id}]".truncate(64)
+  end
+
   def is_local?
     guid == MiqServer.my_guid
   end

app/models/miq_worker.rb

@@ -478,6 +478,17 @@ def abbreviated_class_name
     type.sub(/^ManageIQ::Providers::/, "")
   end
 
+  def minimal_class_name
+    abbreviated_class_name
+      .sub(/Miq/, "")
+      .sub(/Worker/, "")
+  end
+
+  def database_application_name
+    zone = MiqServer.my_server.zone
+    "MIQ #{Process.pid} #{minimal_class_name}[#{compressed_id}], s[#{miq_server.compressed_id}], #{zone.name}[#{zone.compressed_id}]".truncate(64)
+  end
+
   def format_full_log_msg
     "Worker [#{self.class}] with ID: [#{id}], PID: [#{pid}], GUID: [#{guid}]"
   end

app/models/miq_worker/runner.rb

@@ -57,14 +57,18 @@ def initialize(cfg = {})
   def worker_initialization
     starting_worker_record
     set_process_title
-
     # Sync the config and roles early since heartbeats and logging require the configuration
     sync_active_roles
     sync_config
 
     set_connection_pool_size
   end
 
+  # More process specific stuff :-(
+  def set_database_application_name
+    ArApplicationName.name = @worker.database_application_name
+  end
+
   def set_connection_pool_size
     cur_size = ActiveRecord::Base.connection_pool.instance_variable_get(:@size)
     new_size = worker_settings[:connection_pool_size] || cur_size
@@ -144,6 +148,7 @@ def recover_from_temporary_failure
   end
 
   def prepare
+    set_database_application_name
     ObjectSpace.garbage_collect
     started_worker_record
     do_wait_for_worker_monitor if self.class.wait_for_worker_monitor?

lib/extensions/ar_application_name.rb

@@ -0,0 +1,16 @@
+module ArApplicationName
+  # We need to set the PGAPPNAME env variable and force the 'pg' gem objects to be
+  # recreated with this env variable set. This is done by disconnecting all of the
+  # connections in the pool.  We do this because reconnect! on an instance of the
+  # AR adapter created prior to our change to PGAPPNAME will have old connection
+  # options, which will reset our application_name.
+  #
+  # Because we fork workers from the server, if we don't disconnect the pool,
+  # any call to reconnect! on a connection will cause the worker's connection
+  # to have the server's application_name.
+  def self.name=(name)
+    # TODO: this is postgresql specific
+    ENV['PGAPPNAME'] = name
+    ActiveRecord::Base.connection_pool.disconnect!
+  end
+end

lib/workers/evm_server.rb

@@ -62,6 +62,7 @@ def start
 
     PidFile.create(MiqServer.pidfile)
     set_process_title
+    set_database_application_name
     MiqServer.start
   rescue Interrupt => e
     process_hard_signal(e.message)
@@ -77,6 +78,14 @@ def set_process_title
     Process.setproctitle(SERVER_PROCESS_TITLE) if Process.respond_to?(:setproctitle)
   end
 
+  def set_database_application_name
+    ArApplicationName.name = database_application_name
+  end
+
+  def database_application_name
+    MiqServer.my_server.database_application_name
+  end
+
   def self.start(*args)
     # Parse the args into the global config variable
     cfg = {}

spec/lib/workers/evm_server_spec.rb

@@ -6,6 +6,8 @@
 
     before do
       allow(MiqServer).to receive_messages(:running? => false)
+      allow(server).to receive(:set_database_application_name)
+      allow(server).to receive(:set_process_title)
       allow(PidFile).to receive(:create)
     end
 

spec/models/miq_schedule_worker/runner_spec.rb

@@ -26,7 +26,7 @@
         @worker1 = FactoryGirl.create(:miq_worker, :status => MiqWorker::STATUS_STOPPED)
         @dispatch1 = FactoryGirl.create(:miq_queue, {:zone => @zone1.name, :handler_type => @worker1.class.name, :handler_id => @worker1.id}.merge(@opts))
 
-        @zone2 = FactoryGirl.create(:zone, :name => 'zone2')
+        @zone2 = FactoryGirl.create(:zone)
         @worker2 = FactoryGirl.create(:miq_worker, :status => MiqWorker::STATUS_STOPPED)
 
         allow(MiqServer).to receive(:my_zone).and_return(@zone1.name)