Implementing Jobs
This information covers implementing jobs in Java. This includes how to write your own jobs, use parameterization and job result features, and how to set up your classpath to include your own job implementations. If you want to schedule execution of scripts, please see our Scripting Jobs topic.
SchedulableJob Interface
Note: If you need to set up a development environment to create Obsidian jobs, see the Classpath section.
Implementing jobs in Obsidian is very straightforward for most cases. At its most basic, implementing a job simply requires implementing the SchedulableJob interface which has a single method, as shown below.
public interface SchedulableJob {
public void execute(Context context) throws Exception;
}
In your implementation, the execute() method does any work required in the job and it can throw any type of Exception, which is handled automatically by Obsidian.
If you aren't using parameterization or saving job results, that's all you need to do. It's likely you'll just be calling some existing code through your job implementation. Here's an example:
import com.carfey.ops.job.Context;
import com.carfey.ops.job.SchedulableJob;
import com.carfey.ops.job.param.Description;
@Description("This helpful description will show in the job configuration screen.")
public class MyScheduledJob implements SchedulableJob {
public void execute(Context context) throws Exception {
CatalogExporter exporter = new CatalogExporter ();
exporter.export();
}
}
All executed jobs are supplied a Context object is used to expose configuration parameters and job results.
You can also access the scheduled runtime of the job using com.carfey.jdk.lang.DateTime Context.getScheduledTime(). If you wish to convert this to another Date type, such as java.util.Date, you can use the getMillis() method which provides UTC time in milliseconds from the epoch:
Date runTime = new java.util.Date(context.getScheduledTime().getMillis());
Note: You can annotate your job with the com.carfey.ops.job.param.Description annotation to provide a helpful job description which is shown in the job configuration screen. This can be useful for indicating how a job should be configured.
Dependency Injection via Spring
Obsidian supports executing jobs wired as components via Spring. See our dedicated page on Spring Integration for full details.
Parameterization
Obsidian offers flexibility and reuse in your jobs by supplying configurable parameters for each job schedule.
If you would like to parameterize jobs, you can define parameters on the job class itself, or use custom parameters which are only set when configuring a job. Defined parameters are automatically displayed in the Jobs screen to help guide configuration, but also to provide defaults and enforce data types and required values. Custom parameters can be set for any job, and lack additional validation.
Defined parameters are specified on the job class using the @Configuration annotation.
The following example shows a job using various parameters. Int includes a required url parameter, an optional set of names for saving the results and a Boolean value to determine whether compression should be used. It shows a fairly comprehensive usage of various data types and other parameter settings.
import com.carfey.ops.job.param.Configuration;
import com.carfey.ops.job.param.Parameter;
import com.carfey.ops.job.param.Type;
@Configuration(knownParameters={
@Parameter(name="url", required=true, type=Type.STRING),
@Parameter(name="saveResultsParam", required=false, allowMultiple=true, type=Type.STRING),
@Parameter(name="compressResults", required=false, defaultValue="false", type=Type.BOOLEAN)
})
public class MyScheduledJob implements SchedulableJob {
If you are running parameterized jobs, these parameters are very easy to access. Both defined and custom parameters are accessed in the same way. Example:
public void execute(Context context) throws Exception {
JobConfig config = context.getConfig();
MyExistingFunction function = new MyExistingFunction();
String url = config.getString("url");
function.setUrl(url);
boolean compress = config.getBoolean("compressResults"); // defaults to false
function.setCompress(compress);
String result = function.go();
for (String resultsName : config.getStringList("saveResultsParam")) {
context.saveJobResult(resultsName, result);
}
}
Here are all the available methods on JobConfig for retrieving your named parameters.
java.lang.Boolean getBoolean(java.lang.String name)java.util.List<java.lang.Boolean> getBooleanList(java.lang.String name)java.math.BigDecimal getDecimal(java.lang.String name)java.util.List<java.math.BigDecimal> getDecimalList(java.lang.String name)java.lang.Integer getInt(java.lang.String name)java.util.List<java.lang.Integer> getIntList(java.lang.String name)java.lang.Long getLong(java.lang.String name)java.util.List<java.lang.Long> getLongList(java.lang.String name)java.lang.String getString(java.lang.String name)java.util.List<java.lang.String> getStringList(java.lang.String name)
The following is the @Parameter source code, which helps illustrate attributes that can be configured:
public @interface Parameter {
public String name();
public boolean required();
public Type type() default Type.STRING;
public boolean allowMultiple() default false;
public String defaultValue() default "";
}
Ad Hoc & One-Time Run Parameters
In addition to defining parameters for at the job level, Obsidian supports accepting parameters for a specific run time (i.e. job history) through the Jobs screen, or via the REST or Embedded APIs.
These parameters are treated the same as those at the job level, and are exposed to the job in the same manner as parameters at the job level. Note that parameters must have the same data type as any already configured for the job, and must conform to restrictions defined by the @Configuration annotation if applicable.
Config Validating Job
In addition to providing simple validation mechanisms through the @Parameter annotation, Obsidian gives you a way to add custom parameter validation to a job.
The interface <ccode>com.carfey.ops.job.ConfigValidatingJob extends SchedulableJob and allows you to provide additional parameter validation that goes beyond type validity and mandatory values. Below is its definition:
public interface ConfigValidatingJob extends SchedulableJob {
public void validateConfig(JobConfig config) throws ValidationException, ParameterException;
}
When a job implementing this interface is configured or executed, the <code>validateConfig()</code> method is called. All configured parameters are available in the same <code>JobConfig</code> object that is provided to the <code>execute()</code> method. You can perform any validation you require within this method. If validation fails, the job will not be created, modified or executed (depending on when validation fails), and the messages you added to the <code>ValidationException</code> are displayed to the user. Consider this example:
<pre>
public void validateConfig(JobConfig config) throws ValidationException, ParameterException {
List<String> hosts = config.getStringList("hosts");
ValidationException ve = new ValidationException();
if (hosts.size() < 2) {
ve.add("Host syncronization job requires at least two hosts to synchronize.");
}
int timeout = config.getInt("timeout");
if (timeout < 0) {
ve.add(String.format("Timeout must be 0 indicating no timeout or greater than 0 to indicate timeout duration. Timeout provided was %s.", timeout));
}
if (!ve.getMessages().isEmpty()) {
throw ve;
}
}
Job Results
Obsidian also allows for storing information about your job execution. This information is then available in chained/resubmitted jobs. In addition, as of release 1.4, jobs can be conditionally chained based on the saved results of a completed trigger job.
Job Results can be viewed after a job completes in the Job History screen.
Note this example that both evaluates source job information and saves state from its own execution:
public void execute(Context context) throws Exception {
String resultsParamName = context.getConfig().getString("saveResultsParam");
Map<String, List<Object>> sourceJobResults = context.getSourceJobResults();
List<Object> oldResultsList = sourceJobResults.get(resultsParamName);
String oldResults = (String) oldResultsList.get(0);
... job execution ...
context.saveJobResult(resultsParamName, oldResults + " Updated");
// As of 2.2, you can save multiple results at a time as a convenience.
context.saveMultipleJobResults("file", Arrays.asList("first", "second"));
}
The signatures for the three methods used for retrieving and storing results:
java.util.Map<java.lang.String,java.util.List<java.lang.Object>> getSourceJobResults()void saveJobResult(java.lang.String name, java.lang.Object value)void saveMultipleJobResults(java.lang.String name, Collection<?> values)(from 2.2 onward)
Schedulable/ScheduledRun Annotations
Obsidian jobs can also be classes with declared annotations when all you need to do is mark a class and method(s) for execution. com.carfey.ops.job.SchedulableJob.Schedulable is a class level marker annotation indicating that methods are annotated for scheduled execution. com.carfey.ops.job.SchedulableJob.ScheduledRun is a method level annotation to indicated which method(s) to execute at runtime. It has an int executionOrder() method that defaults to 0. Duplication of execution order is not permitted. Method(s) must have no arguments.
Using these annotations precludes you from storing job results or parameterizing your job.
Interruptable Jobs
As of Obsidian 1.5.1, it is possible to forcibly terminate a running job.
In some exceptional cases, it may be necessary or desired to force termination of a job. Since exposing this functionality for all jobs could result in unexpected and even dangerous results, Obsidian provides an additional job interface that is used specifically for this function.
com.carfey.ops.job.InterruptableJob extends SchedulableJob and flags a job as interruptable. Technically speaking, this means that the main job thread will be interrupted by Thread.interrupt(), when an interrupt request is received via the UI or REST API.
The InterruptableJob interface mandates implementation of a void beforeInterrupt() method. This method allows for you to perform house-cleaning before Obsidian interrupts the job. For example, you may have additional threads to shut down, or other resources to release. You should attempt to have your beforeInterrupt() execute in a timely fashion, though it will not interrupt other job scheduling/execution functionality if it takes some time.
It is possible that the job completes either successfully or with failure before the interrupt can proceed. If the interrupt proceeds, the job will be marked as Error and the interruption details will be made available for review in both the Job History and Log views.
Note: After invoking void beforeInterrupt(), Obsidian will invoke Thread.interrupt() on the job to force it to abort. This necessitates acquiring and releasing resources in a way that is more defensive than is normally used. Specifically, resources must be acquired within a try block, so that an interrupt does not happen after a resource is acquired, but before a try block is entered. For example:
public void execute(Context context) throws Exception {
// This is not safe!
/*
java.sql.Connection conn = acquireConnection();
try {
// ...
} finally {
conn.close();
}
*/
// Instead, do this:
java.sql.Connection conn = null;
try {
conn = acquireConnection();
// ...
} finally {
if (conn != null) {
conn.close();
}
}
}
Classpath for Building and Deploying
To implement jobs in Java, you will need to reference Obsidian base classes in your Java project. In addition, your built code and any 3rd party libraries it requires must be included in the Obsidian servlet container (e.g. Tomcat) under /WEB-INF/lib. This could be a plain installation of Obsidian, or a web app bundled with your application.
The base libraries to build Java jobs are found in the zip file you downloaded under the /standalone directory:
obsidian.jar
Prior to Obsidian 2.1.1, the following libraries were also included.
jdk.jarjdk-gen.jarsuite.jarsuite-gen.jarobsidian-gen.jarcarfey-date-1.2.jarorcarfey-date-1.1.jar
These libraries should not conflict with your existing build classpath since they are internal Obsidian libraries.
To build a custom WAR, you can use the provided WAR artifacts in the Obsidian zip package you downloaded, and customize it in your desired build technology (e.g. Ant, Maven, Gradle, etc.).
Maven users: Note that we do not publish Maven artifacts for Obsidian, so you will not be able to include them by referencing a public repository.
Classpath Scanning
As of Obsidian 2.0, Obsidian supports classpath scanning to find your jobs, whether they are implementations of com.carfey.ops.job.SchedulableJob or use the com.carfey.ops.job.SchedulableJob.Schedulable and com.carfey.ops.job.SchedulableJob.ScheduledRun annotations.
You must specify one or more package prefixes using the Admin System. Select the "Job" category, "packageScannerPrefix" parameter. Specify your comma delimited list of package prefixes.
