Varnish 2.1.3 was just released, and keeping with the traditions of the 2.0 releases, it contains a sensible mixture of bug fixes, performance improvements and features.
We are happy to see that the reports of performance degradation on the 2.1 series now seems to be solved. The critbit hasing algorithm has been adjusted to scale better, which will allow lock-free lookups of large datasets. In short: Better performance with multiple millions of objects being requested frequently.
For those who use varnishncsa to parse Varnish log-data with tools designed for Apache-logs, you'll be happy to hear that an issue where certain log entries would be missing has been resolved.
We also added a "log" command to VCL, which will allow you to add custom log-data to the normal Varnish log, all from VCL.
The upgrade from previous 2.1 releases to 2.1.3 should not require any adjustments in configuration.