jAlarms includes a module, jalarms-protobuf, which allows you to run a service containing a configured AlarmSender implementation, which can be used remotely by a number of clients, via Protocol Buffers messaging.
There are also other protocols you can use, from the jalarms-remote module.
You need to set up a server application. It can be a JEE or JSE application; the protobuf module includes a Bootstrap class which will help you to run a JSE service without writing any code, you just need to configure the channels in a Spring application context. All you need to do is create a jalarms-protobuf.xml, containing a bean called "main" which is the ProtobufAlarmServer, and the AlarmSenderImpl itself, with all the channels you need:
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <context:annotation-config/> <bean id="alarmSender" class="com.solab.alarms.AlarmSenderImpl"> <property name="alarmChannels"><list> <bean class="com.solab.alarms.channels.TestChannel" /> </list></property> </bean> <bean id="main" class="com.solab.alarms.ProtobufAlarmServer"> <constructor-arg value="12345" /> </bean> </beans>
The ProtobufAlarmServer constructor parameter is the TCP port on which is must listen for incoming connections.
You start the application by running the com.solab.alarms.spring.ProtoBootstrap class. The classpath must contain the Spring libraries, jalarms-core, jalarms-channels if needed, SLF4J (the API and one runtime binding), and protobuf-2.4.1 or higher.
If you want to setup the service inside a JEE container, you must specify init-method="start" in the definition of the ProtobufAlarmServer, or it won't start listening. In this case it is recommended to also specify that the ProtobufAlarmServer depends on the AlarmSenderImpl bean, by adding depends-on="alarmSender" to the ProtobufAlarmServer definition.
Once you have setup the ProtobufAlarmServer, you can connect any number of clients to it. All you need is to use the ProtobufAlarmClient component instead of the AlarmSenderImpl. ProtobufAlarmClient implements the AlarmSender interface, so if you use that as a reference, you can inject the proper component into your components, without having to change any code. For example if you have a Spring application context in an application, with an AlarmSenderImpl defined, and you want to use the remote service instead, then all you have to do is change the bean:
<bean id="alarmSender" class="com.solab.alarms.ProtobufAlarmClient"> <constructor-arg value="127.0.0.1" /> <constructor-arg value="12345" /> </bean>
So if you have components with something like @Resource private AlarmSender sender; then the ProtobufAlarmClient will be injected into them, instead of the AlarmSenderImpl you had before. Any alarms will be sent through the remote alarm service.
You can download the alarm_protos.proto file from the Git repository, inside jalarms-protobuf/src/main/proto if you want to compile a protobuf client for another language, such as Objective-C, Python, Perl, Ruby, etc. This allows applications written in other languages to use the remote alarm service, although it's easier from a JVM language since the client already implements the AlarmSender interface and handles all the messaging.
If you want to implement a client in another language, remember to write a single byte before each message. Every connection received is processed in a loop which reads one byte, and then the protobuf Alarm message. The byte is read only to detect a read timeout after 5 seconds. The result is that you can use a connection to the service to send any number alarms, as long as no more than 5 seconds pass between each message sent. After 5 seconds, the server closes the connection, so if the client wants to send more alarms it needs to create a new connection. This frees the server from keeping many connections alive and inactive, but also allows for connection reuse in scenarios where many alarms are sent consecutively.