The beta is out. Varnish Cache 4.0 is just around the corner and we need a bit of help to cross the finishing line. The beta seems to be pretty solid, we've given it a fair beating in out testing facilities as well as some pretty rough production workload. The final production tests last week where done in cooperation with A-Media andRedpill Linpro and where quite encouraging. Varnish 4.0 ran stable on their workload happily chugging away 1300 requests a second.
If you have the option of giving Varnish Cache 4.0 a spin on your website, or giving it parts of your traffic we would be grateful. Crashes are very unlikely at this point, but just to be safe, we would recommend having a load balancer in front of the beta so you can gradually increase the load. If you need any help with converting the VCL, please let us know.
The changes, on a high level, from the 3.0 version are:
- Frontend and backend threads are now separated
- Brand new logging framework, with a query language for log filtering
- Directors are now modules
- Lots of VCL changes
- Significant documentation update
Most of the changes are architectural, paving the way for future enhancements like parallell ESI, HTTP 2.0 support and Proxy protocol support (for better SSL integration). Since tech preview 2 there have been a few additions, in addition to myriads of bugfixes.
- Timestamping in the log, giving you detailed information on where Varnish spends it's time
- Accouting. Accurate accounts of bandwidth consumed by Varnish
The bundled documentation should give you a pretty good idea of how to test this and unless your VCL is really complicated it shoudn't take much time to upgrade. By far, the most significant change is that vcl_fetch is now gone, replaced by vcl_backend_response and the logic previously in vcl_miss now resides in vcl_backend_fetch. Have a look at the VCL section of the user guide to get an idea.