Category: WSO2

Introduction

Many times we need to store data for short period of time, like access token or some time stamp. Some times we need to share data between processing messages in sequences. Or maybe we need to store some configuration information for API. That sort of problem we can resolve by use WSO2 Enterprise Integrator registry. In this post I will show you how to play with registry on two type manner.

In this post I won’t describe all ways, how to add new content / elements to registry. Adding in the old fashioned way could be done by WSO2 carbon panel, described here . Other way is by using Integration Studio and deploy in Carbon Application, which is described here.

Problem

Is how to read, modify and store some data content stored as XML file and more. First I create simple XML file configuration, with access token and its refresh time stamp. In conclusion, I point some problem while using registry approach.

Solution

I assume that we have already stored our configuration as XML file in registry. And it should looks like below:

<SomeConfiguration>      
    <token>urn:uuid:00000000-0000-0000-0000-000000000000</token>
    <time>1600000000000</time>
</SomeConfiguration>

Our solution is straight forward. First we store time to calculate difference between token refresh. Next we read our configuration from registry, using property mediator as sample like below:

<property name="sample" scope="default"
expression="get-property('registry', 'conf:/Testing/Sample.xml')" type="OM"/>

For that, we use: get-property(‘registry’, ‘conf:/Testing/Sample.xml’) with type=”OM”, and naming it sample. We calculate the time stamp difference, and check in filter mediator, is there need to refresh the token. If yes we get new token. In my example i just use get-property(‘Message ID’) as token for maximal simplicity. In realistic environment, you probably will call some API endpoint to receive new token. Next we want to modify our content. In my opinion, for property like XML, the easiest way is to use enrich mediator. Therefore we use it for setting new token and time stamp. After that, we store modified property, using property mediator like belowe.

<property name="conf:/Testing/Sample.xml" scope="registry"
expression="$ctx:sample" type="OM"/>

Above all, this is the secret thing. But there is one downside to doing in that way, which is covered later. Certainly most important is set proper name of property, pointing to registry configuration file: conf:/Testing/Sample.xml. Another thing is set scope to registry, and use type OM. After that we can go to registry and checkout how our Sample.xml configuration looks like. For me it looks like below.

In the same vein, you can manipulate the governance registry. As you see, we use “conf” for configuration. Similarly, to modify governance registry just use “gov“. This steps are quite easy, and also described in documentation.

Known downside

This solution has a one drawback, which i must told you. That is to say, when you will read this property from registry, the entry will be cached for 15 seconds. In short, every time you will update this entry, the old value stays in cache. Therefore, you read will read old, not new value by property mediator- you will get cached value. However i find out how to “fix” this, and got solution for you., in the form of a script mediator, listed below:

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<script language="js"><![CDATA[
var regUrl = mc.getProperty('regUrl');
mc.getConfiguration()
   .getRegistry()
   .updateResource(regUrl ,mc.getProperty('sample'));
var regEntry = mc.getConfiguration()
    .getRegistry().getRegistryEntry(regUrl);
regEntry.setCachableDuration(0);
mc.getConfiguration()
   .getRegistry()
   .updateRegistryEntry(regEntry);
]]></script>

In conclusion, we need change manually cache duration for our registry entry.

Summary

To sum up, my example sequence solution, with ten minutes validity token time, looks like below.

<sequence name="sample" xmlns="http://ws.apache.org/ns/synapse">
    <property name="regUrl" scope="default" type="STRING" value="conf:/Testing/Sample.xml"/>    
    <property expression="get-property('SYSTEM_TIME')" name="actualTime"
        scope="default" type="STRING" xmlns:ns="http://org.apache.synapse/xsd"/>
    <property
        expression="get-property('registry', $ctx:regUrl)"
        name="sample" scope="default" type="OM" xmlns:ns="http://org.apache.synapse/xsd"/>
    <property expression="get-property('SYSTEM_TIME')-$ctx:sample//time"
        name="timeDiff" scope="default" type="STRING" xmlns:ns="http://org.apache.synapse/xsd"/>
    <filter xmlns:ns="http://org.apache.synapse/xsd" xpath="$ctx:timeDiff >= 600000.0 or $ctx:timeDiff='NaN'">
        <then>
            <property expression="get-property('MessageID')"
                name="someNewToken" scope="default" type="STRING"/>
            <log level="custom">
                <property expression="$ctx:someNewToken" name="NewToken"/>
            </log>
            <enrich>
                <source clone="false" type="custom" xpath="$ctx:someNewToken"/>
                <target action="replace" type="custom" xpath="$ctx:sample//token"/>
            </enrich>
            <enrich>
                <source clone="false" type="custom" xpath="$ctx:actualTime"/>
                <target action="replace" type="custom" xpath="$ctx:sample//time"/>
            </enrich>
            <script language="js"><![CDATA[var regUrl = mc.getProperty('regUrl');
mc.getConfiguration().getRegistry().updateResource(regUrl ,mc.getProperty('sample'));
var regEntry = mc.getConfiguration().getRegistry().getRegistryEntry(regUrl);
regEntry.setCachableDuration(0);
mc.getConfiguration().getRegistry().updateRegistryEntry(regEntry);]]></script>
        </then>
        <else>
            <log level="custom">
                <property expression="$ctx:sample//token" name="Token"/>
                <property
                    expression="600000.0-number($ctx:timeDiff)" name="Valid for"/>
            </log>
        </else>
    </filter>
    <enrich>
        <source clone="true" property="sample" type="property"/>
        <target action="replace" type="body"/>
    </enrich>
    <respond/>
</sequence>

In conclusion, storing the file in registry from sequence is quite easy. For read only, we can use just property mediator, but for often changes better way is to use script mediator with manually set cache duration.