These are the highlights of new features or additions to existing features in v5.0.x and 5.1.x. For the complete list of all changes see this JIRA Release Notes.

General changes

  • We do no longer require the Boost library to build!

Jira: TS-3068

New configuration options

  • You can now force unsatisfiable Range: requests to go to origin even when read-while-writer is in effect. This can help avoid significant latency on large objects. The setting is overloaded on the existing proxy.config.cache.enable_read_while_writer configuration.
  • The option to specify configuration location, proxy.config.config_dir, is now actually implemented.
  • Add option to support SO_LINGER to origin server, via

Jira: TS-2314, TS-3192, TS-3119


 We continue to improve our TLS (HTTPS) features and support. Noteworthy in 5.2.x is:

  • SSLv3 is now disabled by default!
  • Dynamic TLS record size tuning. According to Ilya, this makes us the first server that is all Green. (smile)
  • Add forward secrecy support with DHE.
  • Add ssl_pre_handshake hook for better plugin access to SSL handling.
  • Improved session cache, for better performance and scalability.
  • New configuration for OpenSSL session cache, proxy.config.ssl.session_cache.auto_clear.


Jira: TS-3153TS-2503TS-2417TS-2956TS-3080TS-3127


  • traffic_line -m is now using an unachored regular expression, similar to how diagnostic tracers work.
  • traffic_line --backtrace will produce a stack backtrace for all running threads.

Jira: TS-3034, TS-3145


A new command line utility, traffic_layout, is now available. This will show the layout and configuration option for the ATS build tree.

Jira: TS-3041


This is a new command line tool, to parse and decipher the Via: header that Traffic Server can produce. This is useful for debugging e.g. cache results etc.

Jira: TS-3149


This is the helper application around the new crash logging feature. For more information, see the documentation.

Jira: TS-3195

Plugin Improvements

The following plugins have new features and improvements.


  • We now support variable expansion in the set-redirect operator.
  • You can now do matching operators on the port.
  • We do not need Boost.

Jira: TS-2955, TS-3108, TS-3068


This plugin will now emit JSON numbers.

Jira: TS-3071


  • The plugin behavior and activation can now be controlled per remap-rule.
  • You an control the behavior based on content type.

Jira: TS-2682, TS-2683

Plugin APIs

The following additions were made to the plugin APIs:

  • TSMutexDestroy() was added, for symmetry with the TSMutexCreate() API.
  • TSTextLogObjectRollingSizeMbSet() was added, it as simply missing.
  • TSHttpHdrHostGet() was added.


Jira: TS-1432, TS-3059, TS-3101


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