Friday, August 17, 2018

How to Increase the Timeout for Generating the Alfresco PDF Preview

The Formtek EDM Module for Alfresco provides custom transformers to convert several CAD file formats (such as AutoCAD DWG) to PDF for previewing in Alfresco Share. The default time allowed for this transformation to complete is 120,000 milliseconds or 2 minutes. For most drawings, this is more than enough time to create the preview PDF. However, some complex drawings may need a little more time. You can change the timeout period on the transformer itself, but there are a few other timeout settings you'll to change as well to make it all work properly.

Here are the steps for increasing the time allowed for transforming DWG to PDF using the custom transformer provided by the Formek EDM Module. In this example, the time is being increased to 3.5 minutes (210,000 ms):

1) Add the following properties to the file to change both the specific transformer timeout and the system-wide timeout and error time values:

# ==========================================================================
# DWG to PDF transformer timeout defaults to 180000 ms in Formtek EDM Module 
# and 120000 ms in previous releases
# ==========================================================================

# =======================================================
# System-wide timeout and error time default to 120000 ms
# =======================================================

Although these settings (after an Alfresco restart) do provide a DWG file more time to complete its transformation, the following odd behavior is observed:

  • If the transformation continues beyond 2 minutes, a second transformation attempt is surprisingly triggered. Sometimes, but not always, that second attempt is started before the first one finishes.
  • So now there may be two transformation processes running at the same time for the same file, and competing for same system resources until the first transformation completes.
  • Furthermore, the "busy" indicator in the Alfresco Share preview window does not go away until the second 2-minute period (or a total of 4 minutes) elapses, thus making you wait longer than necessary to see the PDF preview.
  • But wait. Instead of loading the newly generated PDF preview, the following message is displayed leading you to believe that the transformation attempt may have failed:
  • A manual window refresh does load the PDF preview (once the second transformation attempt completes), but that's a not-so-obvious detail.

Here's an example of the two transformation attempts for doc2.dwg when the logger property, org.alfresco.repo.content.transform.TransformerDebug, is set to DEBUG. In this example, the second attempts starts one second after the first one completes:

2018-08-14 09:38:39,171 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 11             dwg  pdf  doc2.dwg 2.5 MB -- pdf -- ContentService.transform(...)
2018-08-14 09:38:39,177 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 11             workspace://SpacesStore/28a8aa18-9681-417e-83ec-0fa8de0efbd1
2018-08-14 09:38:39,178 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 11             **a)  [50] dwg2pdf1<<Runtime>>           140,966 ms
2018-08-14 09:38:39,178 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 11.1           dwg  pdf  doc2.dwg 2.5 MB dwg2pdf1<<Runtime>>
2018-08-14 09:41:02,873 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 11             Finished in 143,702 ms

2018-08-14 09:41:03,455 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 12             dwg  pdf  doc2.dwg 2.5 MB -- pdf -- ContentService.transform(...)
2018-08-14 09:41:03,455 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 12             workspace://SpacesStore/28a8aa18-9681-417e-83ec-0fa8de0efbd1
2018-08-14 09:41:03,455 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 12             **a)  [50] dwg2pdf1<<Runtime>>           141,512 ms
2018-08-14 09:41:03,455 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 12.1           dwg  pdf  doc2.dwg 2.5 MB dwg2pdf1<<Runtime>>
2018-08-14 09:43:22,587 DEBUG [org.alfresco.repo.content.transform.TransformerDebug] [pool-13-thread-2] 12             Finished in 139,133 ms

Even though the first transformation attempt completed in about 2 minutes 23 seconds (143,702 ms), I don't see the PDF preview in Share for about 4 minutes 43 seconds (after the second attempt completes). 

To avoid this second transformation attempt, you need to change the read timeout for the HTTP socket connection, which defaults to 120,000 ms. So, in addition to Step 1 above, you'll also need to complete Step 2 as follows:

2) Create the tomcat\shared\classes\alfresco\web-extension\custom-slingshot-application-context.xml file with the following content, setting the readTimeout value accordingly (in my case, 210,000 ms).

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="" 
  <bean id="connector.remoteclient" parent="connector.remoteclient.abstract" 
  class="org.alfresco.web.scripts.SlingshotRemoteClient" scope="prototype" > 
<!-- the http.connection.timeout value in milliseconds to apply to HTTP connections --> 
    <property name="connectTimeout"><value>10000</value></property> 
<!-- the http.socket.timeout value in milliseconds to apply to HTTP connections --> 
    <property name="readTimeout"><value>210000</value></property> 

3) Finally, restart Alfresco so the changes take effect.

Now, when you preview a newly upload drawing that takes more than 2 minutes to convert to PDF, only a single transformation attempt occurs and you will see the drawing preview sooner and without having to manually refresh the window.

Also note that this same configuration can be applied to other content transformers. However, you will need to configure the property that corresponds to that specific transformer in Step 1 above.