Archive for 2017

People who have upgraded to macOS High Sierra and who are using a preforking app server such as Puma or Unicorn (with the right settings), may have noticed this error:

objc[81924]: +[__NSPlaceholderDictionary initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.

This cryptic error is triggered under the following conditions:

1. You are using Unicorn with preload_app, or Puma in cluster mode, or iodine in prefork mode, or Passenger in smart spawning mode.
2. And you are using MRI.
3. And your application uses a gem that is either directly or indirectly linked to the macOS Foundation framework.

This error is caused by changes in how fork() behaves in High Sierra. This article covers:

• What is this and why did Apple change it?
• How are the Puma, Unicorn and Passenger authors responding to this?
• What can you do about it, and do you need to do anything at all?
• What should the wider Ruby ecosystem do?

Update August 9: urikanegun has kindly contributed a Japanese translation of this article.

Developers love speed, so developers love benchmarks. Benchmarks on programming language performance, app server performance, JavaScript engine performance, etc. have always attracted a lot of attention. However, there are lots of caveats involved in running a good benchmark. One of those caveats is benchmark stability: if you run a benchmark multiple times then the timings usually differ a bit. A a lot of people have the tendency to hand-wave this caveat by just shutting down all apps, rerunning the benchmark a few times and averaging the results. Is that truly good enough?

Lately, I have been researching the topic of benchmark stability because I am interested in creating reliable benchmarks that are reproducible by third parties, so that they can verify benchmark results by themselves — e.g. allowing users of my software to verify that my benchmarks are reliable. Such research has led me to Victor Stinner, a Python core developer who has been focusing on improving Python 3 performance for several years.

Red Hat and New Relic are some of the most interesting companies out there. We all know how big Red Hat is. New Relic is an application monitoring tool company that sped past all its competitors in its early days and achieved IPO. In 2015 the company had a monthly revenue of $29 million, with a year-on-year revenue growth of 69%. What do these tech giants have in common? Their marketing strategy.