Understanding Configuration Configuring Declaratively

It is also possible to configure Jet through XML files when a JetInstance is created without any explicit JetConfig file. Jet will look for a configuration file in the following order:

1. Check the system property hazelcast.jet.config. If the value is set, and starts with classpath:, then it will be treated as a classpath resource. Otherwise, it will be treated as a file reference.
2. Check for the presence of hazelcast-jet.xml in the working directory.
3. Check for the presence of hazelcast-jet.xml in the classpath.
4. If all the above checks fail, then the default XML configuration will be loaded.

An example configuration looks like the following:

<hazelcast-jet xsi:schemaLocation="http://www.hazelcast.com/schema/jet-config hazelcast-jet-config-0.3.xsd"
               xmlns="http://www.hazelcast.com/schema/jet-config"
               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <instance>
        <!-- number of threads to use for DAG execution -->
       <cooperative-thread-count>8</cooperative-thread-count>
        <!-- frequency of flow control packets, in milliseconds -->
       <flow-control-period>100</flow-control-period>
        <!-- working directory to use for placing temporary files -->
       <temp-dir>/var/tmp/jet</temp-dir>
    </instance>
    <properties>
       <property name="custom.property">custom property</property>
    </properties>
    <edge-defaults>
        <!-- number of available slots for each concurrent queue between two vertices -->
       <queue-size>1024</queue-size>

        <!-- number of slots before high water is triggered for the outbox -->
       <high-water-mark>2048</high-water-mark>

        <!-- maximum packet size in bytes, only applies to distributed edges -->
       <packet-size-limit>16384</packet-size-limit>

        <!-- target receive window size multiplier, only applies to distributed edges -->
       <receive-window-multiplier>3</receive-window-multiplier>
    </edge-defaults>
    <!-- custom properties which can be read within a ProcessorSupplier -->
</hazelcast-jet>

The following table lists the configuration elements for Hazelcast Jet: