Wait for migrations before starting scheduler

During bosh create-env, the scheduler process may start before the
director has completed running migrations, causing 'relation does not
exist' errors when the scheduler tries to query the director_attributes
table.

This adds migration waiting to the scheduler binary, following the same
pattern used by sync_dns_scheduler and metrics_collector. The scheduler
now:
1. Loads only config initially (not full director with models)
2. Calls DBMigrator.ensure_migrated! to wait for migrations
3. Then loads full director and starts the scheduler

Also adds scheduler_logger method to Config for consistent logging.

Author: rkoster

src/bosh-director/bin/bosh-director-scheduler

@@ -1,7 +1,8 @@
 #!/usr/bin/env ruby
 
-require 'bosh/director'
-require 'bosh/director/scheduler'
+require 'optparse'
+require 'bosh/director/config'
+require 'db_migrator'
 
 config_file = ::File.expand_path('../../config/bosh-director.yml', __FILE__)
 
@@ -14,6 +15,20 @@ end
 opts.parse!(ARGV.dup)
 
 config = Bosh::Director::Config.load_file(config_file)
+
+# Wait for migrations to complete before loading models and starting scheduler
+# This prevents race conditions during bosh create-env when director migrations
+# may still be running
+begin
+  DBMigrator.new(config.db).ensure_migrated!
+rescue DBMigrator::MigrationsNotCurrentError => e
+  config.scheduler_logger.error("Scheduler start failed: #{e.message}")
+  raise e
+end
+
+require 'bosh/director'
+require 'bosh/director/scheduler'
+
 Bosh::Director::App.new(config)
 
 scheduler = Bosh::Director::Scheduler.new(config.scheduled_jobs)

src/bosh-director/lib/bosh/director/config.rb

@@ -542,6 +542,14 @@ def sync_dns_scheduler_logger
       logger
     end
 
+    def scheduler_logger
+      logger = Logging::Logger.new('Scheduler')
+      logging_config = hash.fetch('logging', {})
+      logger.add_appenders(Logging.appenders.stdout('SchedulerIO', layout: ThreadFormatter.layout))
+      logger.level = Logging.levelify(logging_config.fetch('level', 'debug'))
+      logger
+    end
+
     def metrics_server_logger
       logger = Logging::Logger.new('MetricsServer')
       logging_config = hash.fetch('logging', {})