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These are the highlights of new features or additions to existing features in v5.0.x, 5.1.x, and 5.2.x. For the complete list of all changes see this JIRA Release Notes.

General changes

  • Allow traffic_server to validate config at the command line - TS-3364
  • TLS ticket rotation - TS-3301


Basic support for HTTP/2 (aka "H2") over TLS is now supported. This is still work in progress, and not everything from the H2 specifications is supported. In particular

  • Priorities
  • Server PUSH
  • HTTP/2 over non-TLS

are not supported. In addition, HTTP/2 is only supported on the client side, outbound HTTP/2 is not supported yet (i.e. we only support proxying H2 to an HTTP/1.1 backend server (origin)). For some details on the implementation, see the TS-2729 Jira.

The following records.config settings are needed to enable HTTP/2 on trafficserver in 5.3.x.

       CONFIG proxy.config.http2.enabled INT 1

Additionally, there should be at least one TLS port configured in proxy.config.http.server_ports.

For example, 

       CONFIG proxy.config.http.server_ports STRING 80 443:ssl

New command line tool: traffic_ctl

The new traffic_ctl command is intended to replace the old traffic_line command. We're keeping both around for the duration of 6.0.0, but expect traffic_line to be deprecated and removed for 7.0.0. As such, please update any tools and utilities you have around the old traffic_line, and use traffic_ctl instead. For details on this new tool, see TS-3367.

"Dynamic" keep-alive timeouts

In old versions of ATS, you had to manually configure how long to keep connections in HTTP Keep-Alive state. This turns out to be really difficult, and a new feature was added to simplify this. Using these new configurations, you can now specify a max number of connections to keep in Keep-Alive. The new configuration for this is See the JIRA (TS-153) for more details.

New configuration options

  • A new configuration to disallow POST with Expect: 100-continue - TS-3459

  • Have HostDB use /etc/hosts - proxy.config.hostdb.host_file.pathTS-3088


  • Add metrics to represent configuration freshness - TS-3231
  • Add stat to count cache wrap - proxy.process.cache.wrap_count - TS-2515 
  • Add new metric to count the number of SSL connections from ATS to origin - TS-3409

Plugin Improvements



  • Add milestone and  DSCP API support - TS-3454
  • Other API support - TS-3225


  • Add support for modifying the SCHEME - TS-3211
  • Add support for METHOD as condition - TS-3398



This new plugin allows ATS to act as a content generator, typically useful for setting up test environments. For details, see the docs.

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