readiness-check-command: implemented.

The 'postgresql' service is a good example of how this is used in
practice.

services/postgresql.spec

@@ -2,6 +2,7 @@ name: postgresql
 user: postgres
 command: postgres -D ${SERVICE_ROOT}/db -k /tmp/postgresql-${ENVIRONMENT}
 #stop-command: kill -HUP ${PID}
+readiness-check-command: pg_isready -p ${POSTGRESQL_PORT}
 environment-variables:
 	- PGROOT=${SERVICE_ROOT}
 provides: postgresql

src/service/service.cr

@@ -179,6 +179,9 @@ class Service
 	def reload_command
 		@reference.reload_command
 	end
+	def readiness_check_command
+		@reference.readiness_check_command
+	end
 	def provides
 		@reference.provides
 	end
@@ -233,6 +236,12 @@ class Service
 
 		env["SERVICE_TOKENS"] = @providers.to_a.map(&.[0]).join ':'
 
+		@ports.each do |name, number|
+			name = name.upcase
+
+			env["PORT_#{name}"] = number.to_s
+		end
+
 		# FIXME: Parsing should probably be done… when parsing the file.
 		# FIXME: Parsing is probably a bit primitive. Maybe this isn’t the right way of defining this.
 		@reference.environment_variables.each do |string|
@@ -341,6 +350,26 @@ class Service
 		end
 
 		self.save_pid context.pid_directory, process.pid
+
+		# FIXME: At this point, let’s wait a few seconds for the service to be ready.
+		if command = readiness_check_command
+			context.info "Waiting for service to become ready…"
+
+			start_time = Time.local
+			now = Time.local
+
+			while (now - start_time).seconds < 5
+				r = Process.run "sh", ["-c", command]
+
+				if r.success?
+					break
+				end
+
+				sleep 0.05
+
+				now = Time.local
+			end
+		end
 	end
 
 	# TODO:

src/service/service_definition.cr

@@ -74,6 +74,7 @@ class ServiceDefinition
 	getter command : String
 	getter stop_command : String?
 	getter reload_command : String?
+	getter readiness_check_command : String?
 	getter directory : String?
 	getter user : String?
 	getter provides : String?
@@ -93,6 +94,7 @@ class ServiceDefinition
 		@non_runnable  = (@command == "none")
 		@stop_command  = specs["stop-command"]?.try &.as_s
 		@reload_command = specs["reload-command"]?.try &.as_s
+		@readiness_check_command = specs["readiness-check-command"]?.try &.as_s
 		@directory     = specs["directory"]?.try &.as_s
 		@user          = specs["user"]?.try &.as_s
 		@provides      = specs["provides"]?.try &.as_a_or_s.map { |x| Provides.new x } || Array(Provides).new