FAQ & Future Work

Frequently Asked Questions

For more questions, you may

  • Ask a question, and keep up to date on the library development by joining the discussion group / forum: Google Group.
  • Submit a Github Issue for any questions and suggestions too.

Import and Setup

Q: Why Eclipse has an error related to the "@Override" annotation ?

A: Please set the compiler level 1.6+ in pom.xml


Q: What JDK has you tested Parallec with ?

A: We tested it with JDK 6 7 8.


Q: How to view logs ?

A: Yes.

  • Parallec Log: we use slf4j + logback with rotation. Location is in "parallec_logs"
  • ParallelTask result log: can be turned on with ParallelTaskBuilder.setAutoSaveLogToLocal(), by default this is turned off.

Q: Do you support retries ?


  1. Async Http Client supports retry with config.
  2. From our experience, retrying on a ParallelTask is insufficient as 1% of the failed hosts will keep on retrying, slowing the whole task down. The right way would be 1 time try on all host, then collect those failed one, and then try again on these failed ones.

Q: Do you have plans to update the versions of Async Http Client?

A: We have not been able to use AHC version 1.9.x due to an issue with client auth. Last year with some performance testing, we found more CPU usage and less speed after upgrade from AHC 1.65 to AHC 1.8.14 . We need to do more performance testing before the upgrade.

Updated 09/2016:

Parallec with async-http-client 2.x The version with more up-to-date async-http-client (currently using AHC version 2.0.15) is 0.20.0-SNAPSHOT. This version has passed comprehensive unit tests but has not been used yet in production. This version requires JDK8 due to AHC 2.x and can be used with the parallec-plugins with the same version 0.20.0-SNAPSHOT, details please check #37.

Q: The logs are too chatty/verbose, can I disable or reduce them?

A: Please refer to the configuration section on "Reduce Verbose Logs"

Q: The task ends prematurely around 10 minutes with response count less than original?

A: Please refer to the configurations section on "Long Running Jobs"

Future Work

Extension to Other Protocols

With the framework and design, Expanding to other new protocols are fairly simple, with changes mostly to add a worker for this new protocol.

  • Add support for HTTP/2 or gPRC if needed.
  • Add support for SNMP protocols for network devices.
  • Evaluate more performant implementations than JSch for SSH.