5.3.5. Web Service Client API

Client API is the name of the API offered to the end users of JQM: it allows to interact with running jobs, offering operations such as creating a new execution request, cancelling a request, viewing all currently running jobs, etc. Read client API before this chapter, as it gives the definition of many terms used here as well as the general way to use clients.

The main client API is the Hibernate Client API, which runs directly against the JQM central database. As JQM is database centric, finding jobs to run by polling the database, this is most efficient. However, this API has a serious drawback: it forces the user of the API to use Hibernate. This can be a huge problem in EE6 applications, as most containers (WebSphere, Glassfish, JBoss...) offer their own implementation of the JPA standard which is not compatible with Hibernate and cannot coexist with it (there must be only one JPA implementation at the same time, and a database created for Hibernate is very difficult to reuse in another JPA provider). Moreover, even outside the EE6 field, the client may already have chosen a JPA implementation that is not Hibernate. This is why JQM also offers an optional REST Web Service Client API.

5.3.5.1. Client side

There are two ways to use the WS Client API:

• Using the Java client
• Directly using the web service

5.3.5.1.1. Using the Java client

This is a standard client API implementing the JqmClient interface. Like all clients, it is used by putting its jar on your classpath. The client uses the JAX-RS 2 API, so it needs an implementation such as Jersey (obviously not provided, the one provided by the container will be used).

For Maven users:

<dependency>
        <groupId>com.enioka.jqm</groupId>
        <artifactId>jqm-api-client-jersey</artifactId>
        <version>${jqm.version}</version>
</dependency>

and then using the API:

JqmClient jqm = JqmClientFactory.getClient();

As with any client (see the JavaDoc) clients are cached by the API, so it is not necessary to cache them yourself.

Interrogating the API is then also exactly the same as with any other client. For example, to list all running jobs:

JqmClientFactory.getClient().getJobs()

The specific parameters are:

Name	Compulsory	Description	Example
com.enioka.ws.url	YES	The base URL of the web service	http://localhost:1789/api/ws
com.enioka.jqm.ws.login		If auth is used only.	mylogin
com.enioka.jqm.ws.password	if login		password
com.enioka.jqm.ws.keystoreFile	if CSA	Store for client certificates authentication	./conf/client.pfx
com.enioka.jqm.ws.keystoreType		Type of the previous store	PKCS12
com.enioka.jqm.ws.keystorePass		Password of the store	MyPassword
com.enioka.jqm.ws.truststoreFile	if SSL	Trust roots for server certificates	./conf/client.pfx
com.enioka.jqm.ws.truststorePass		Password of the store	NoPassword

and can be set:

• (specific to this client) with a jqm.properties file inside the META-INF directory

• (as for every other client) using Java code, before creating any client:

  Properties p = new Properties();
  p.put("com.enioka.ws.url", "http://localhost:9999/marsu/ws");
  JqmClientFactory.setProperties(p);
  

• through a system parameter (-Dcom.enioka.ws.url=http://...)

5.3.5.1.2. Interrogating the service directly

The previous client is only a use of the JAX-RS 2 API. You can also create your own web service proxy by interrogating the web service with the library of your choice (including the simple commons-http). See the Service reference for that.

Should that specific implementation need the interface objects, they are present in the jqm-api-client jar (the pure API jar without any implementation nor dependencies).

<dependency>
        <groupId>com.enioka.jqm</groupId>
        <artifactId>jqm-api-client</artifactId>
        <version>${jqm.version}</version>
</dependency>

5.3.5.1.3. Choosing between the two approaches

When using Java, the recommended approach is to use the provided client. This will allow you to:

• ignore completely all the plumbing needed to interrogate a web service
• change your client type at will, as all clients implement the same interface
• go faster with less code to write!

The only situations when it is recommended to build your own WS client are:

• when using another language
• when you don’t want or can’t place the WS client library Jersey on your classpath. For example, in an EE6 server that provides JAX-RS 1 and just don’t want to work with version 2.

5.3.5.2. Server side

The web service is not active on any engine by default. To activate it, see the administration guide.

It is not necessary to enable the service on all JQM nodes. It is actually recommended to dedicate a node that will not host jobs (or few) to the WS. Moreover, it is a standard web application with purely stateless sessions, so the standard mechanisms for load balancing or high availability apply if you want them.

5.3.5.3. Service reference

All objects are serialized to XML by default or to JSON if required. The service is a REST-style web service, so no need for SOAP and other bubbly things.

URL pattern	Method	Non-URL arguments	Return type	Return MIME	Interface equivalent	Description
/ji	GET		List<JobInstance>	application/xml	getJobs	List all known job instances
/ji	POST	JobRequest	JobInstance	application/xml	enqueue	New execution request
/ji/query	POST	Query	Query	application/xml	getJobs(Query)	Returns the executed query
/ji/{jobId}	GET		JobInstance	application/xml	getJob(int)	Details of a Job instance
/ji/{jobId}/messages	GET		List<String>	application/xml	getJobMessages(int)	Retrieve messages created by a Job Instance
/ji/{jobId}/files	GET		List<Deliverables>	application/xml	getJobDeliverables	Retrieve the description of all files created by a JI
/ji/{jobId}/stdout	GET		InputStream	application/os	getJobLogStdOut	Retrieve the stdout log file of the (ended) instance
/ji/{jobId}/stderr	GET		InputStream	application/os	getJobLogStdErr	Retrieve the stderr log file of the (ended) instance
/ji/{jobId}/position/{}	POST		void		setJobQueuePosition	Change the position of a waiting job instance inside a queue.
/ji/active	GET		List<JobInstance>	application/xml	getActiveJobs	List all waiting or running job instances
/ji/cancelled/{jobId}	POST		void		cancelJob(int)	Cancel a waiting Job Instance (leaves history)
/ji/killed/{jobId}	POST		void		killJob(int)	Stop (crashes) a running job instance if possible
/ji/paused/{jobId}	POST		void		pauseQueuedJob(int)	Pause a waiting job instance
/ji/paused/{jobId}	DELETE		void		resumeJob(int)	Resume a paused job instance
/ji/waiting/{jobId}	DELETE		void		deleteJob(int)	Completely cancel/remove a waiting Job Instance (even history)
/ji/crashed/{jobId}	DELETE		JobInstance	application/xml	restartCrashedJob	Restarts a crashed job instance (deletes failed history)
/q	GET		List<Queue>	application/xml	getQueues	List all queues defined in the JQM instance
/q/{qId}/{jobId}	POST		void		setJobQueue	Puts an existing waiting JI into a given queue.
/user/{uname}/ji	GET		List<JobInstance>	application/xml	getActiveJobs	List all waiting or running job instances for a user
/jd	GET		List<JobDef>	application/xml	getActiveJobs	List all job definitions
/jd/{appName}	GET		List<JobInstance>	application/xml	getActiveJobs	List all job definitions for a given application
/jr	GET		JobRequest	application/xml	N/A	Returns an empty JobRequest. Usefull for scripts.

Note: application/os = application/output-stream.

Used HTTP error codes are:

• 400 (bad request) when responsibility for the failure hangs on the user (trying to delete an already running instance, instance does not exist, etc)
• 500 when it hangs on the server (unexpected error)

On the full Java client side, these are respectively translated to JqmInvalidRequestException and JqmClientException.

The body of the response contains an XML or JSON item giving details on the error.:

1   404     GET on absent object
2   500
3   404     DELETE on absent object
4   400     Update user with absent role
5   500     Could not create certificate
6   400     Invalid enqueue parameters
7   400     Simple API  is only available when the application runs on top of JQM itself and not a web application server.
8   400     File does not exist
9   500     Generic internal exception
10  400     Generic bad request

5.3.5.4. Script sample

PowerShell script. Logics is the same in any language, script or compiled.:

# Note: we use JSON as a demonstration of how to use it over the default XML. Obviously, PowerShell deals with XML very well and does not need this.

# Authentication?
$cred = Get-Credential root

#################################
## Enqueue demonstration
#################################

$request = @{applicationName="DemoApi"; user=$env:USERNAME} | ConvertTo-Json
$jobInstance = Invoke-RestMethod http://localhost:62948/ws/client/ji -Method Post -Body $request -Credential $cred -ContentType "application/json" -Headers @{Accept="application/json"}
$jobInstance.id


#################################
## Query demonstration
#################################

$query = @{applicationName="DemoApi"} | ConvertTo-Json
$res = Invoke-RestMethod http://localhost:62948/ws/client/ji/query -Method Post -Body $query -Credential $cred -ContentType "application/json" -Headers @{Accept="application/json"}
$res.instances | Format-Table -AutoSize