Saturday, September 29, 2012

Unix timestamp vs Java timestamp

A recent incident which occurred to me and a colleague of mine made me write this little post. We were setting a property in a hive script and was trying to retrieve some data comparing with the value we set. In other words, this is what we did.
  1. We set a property named max_ts to hive context within a Java class. We used the Timestamp.getTime() method to get the time.
  2. In the hive script, we were doing something like:
    1. Select my_columns from my_table where unix_timestamp(a_string) > ${hiveconf:max_ts}
 But this was not seem to be working. Even when we had records which has a timestamp greater than the max_ts, query was not returning them. Then we added some debug logs and realized what was going wrong.

Unix timestamp gives the number of seconds which has passed since the epoch.
Java timestamp gives the number of milliseconds since the epoch.

Although both of these uses the same epoch (midnight of January 1st 1970), they provide two different values. Thats why the query was not behaving as intended. Although I had read/learned about this difference, it took some time to kick it into the mind.

Saturday, September 15, 2012

Now you can send the SoapFaults to the Fault Sequence in WSO2 ESB

WSO2 ESB 4.5.0 was released recently. There are many new features, enhancements and performance gains in this new release. I wanted to highlight one new cool feature which I couldn't wait anymore. That is the title of this post.

In the previous releases of WSO2 ESB fault sequence was hit only when there was a fault during the mediation process taking place inside the WSO2 ESB. If a soap fault was received from a backend service it was sent to the out sequence because the WSO2 ESB considered it as a response from the backend. It was fair from ESB's point of view and unfair from developer's point of view. But with the 4.5.0 release, now you can send the soap faults to the fault sequence and do the fault handling.

To do that, you need to set the FORCE_ERROR_ON_SOAP_FAULT property before you send the message to the backend. This is a newly introduced property and following sample proxy service will show you how to do it.


Hope this property will help many integration developers during their use of WSO2 ESB.


Above proxy configuration was taken from a resource which was emailed to me by Kasun Indrasiri who is an ESB expert in WSO2.

Happy Integration.... :)

Sunday, May 20, 2012

Getting ActiveMQ Redelivery to work with WSO2 ESB

Recently I wanted to use the redelivery mechanism available in Apache ActiveMQ while using it with WSO2 ESB. My scenario was like this.
  1. Retrieve a message from a JMS queue
  2. Write the message to a file URI (in your case you may want to send it to a given endpoint)
  3. If writing to the file is not successful due to some failure, I wanted the message to be in the queue and ActiveMQ to try repeatedly writing to the file.
Following are the properties/parameters I had to put in the axis2.xml of WSO2 ESB (under JMS transport receiver). Remember that you need to put the other parameters such as initial context factory, provider url, connection factory and connection factory type etc.
<parameter name="transport.Transactionality" locked="true">jta</parameter>
<parameter name="transport.jms.SessionTransacted" locked="true">true</parameter>
<parameter name="redeliveryPolicy.maximumRedeliveries" locked="true">-1</parameter>
<parameter name="redeliveryPolicy.redeliveryDelay" locked="true">2000</parameter>
<parameter name="transport.jms.CacheLevel" locked="true">consumer</parameter>

I will explain some of the above parameters.

  1. transport.Transactionality - This is the desired mode of transactionality. I was using distributed transactions. Therefore the value was jta. If you are using local transactions you can put it as local.
  2. transport.jms.SessionTransacted - Whether the JMS session should be transacted or not.
  3. redeliveryPolicy.maximumRedeliveries - Maximum number of retries you wish. If set to -1, ActiveMQ will infinitely retry.
  4. redeliveryPolicy.redeliveryDelay - Delay between retries. I have set it to 2 seconds (i.e. 2000 milliseconds).
  5. transport.jms.CacheLevel - This is the most important property to get the redelivery mechanism to work properly. This has to be set to "consumer". Reason for this is ActiveMQ  RedeliveryPolicy is dictated by CONSUMER, not PRODUCER.
With above configurations, you are able to get the redelivery mechanism in ActiveMQ to work when used with WSO2 ESB.

You will also need to set the SET_ROLLBACK_ONLY property in the fault sequence of your proxy service. Otherwise the transaction will not get rollbacked.
<property name="SET_ROLLBACK_ONLY" value="true" scope="axis2"/> 

Following links will provide further help.
1. WSO2 ESB documentation's JMS transport section
2. ActiveMQ redeliverPolicy configuration parameters