Gentoo linux, Apache web server.

might be related to php gettext caching.
this also happens after the apache webserver is restarted, right ?

At http://zabbix.org/wiki/Translating_Zabbix is an instruction where very last step is "restart your web server"
I may recall similar behavior (not partial translation, but randomly changed locales current-previous) if web server was started before current .mo file was created.
That's why there is such a step.

Try to restart your web server.

It doesn't help.

Interesting. I have no idea how to troubleshoot it.
Maybe some specific modules for Apache/PHP are used, like for caching etc, and they cause such a behavior ...

https://www.zabbix.com/forum/showthread.php?t=41840
That guy had same problem

zalex had a good point - are you using any other caching, like apc ?

I was reading gettext documentation when working on locale-related server issues and I've also seen bits of locale-related frontend code. I can't claim that I am 100% confident, but here is my understanding of the problem.

Gettext uses environment variables to determine which language is desired. Environment variables can be set per process.

Usual workflow to generate a page:

• set appropriate locale for the user (web server sets environment variables for its process)
• call gettext multiple times (web server channels the call to gettext library)

Imagine web server process generating pages for two users with different language settings:

• (is for user A)
  • (is for user B)
• set locale to A
• gettext calls return strings in language A
  • set locale to B
• gettext calls return strings in language B
  • gettext calls return strings in language B

As a result for user A upper part of the page is in his language, but bottom part is in the language of user B. I imagine that situation is getting worse when there are more users per web server process and problem appears more frequently on the pages which take longer time to generate.

Dear zalex_ua, have you tried to reproduce?

Now we need PHP developers to come and share their thoughts.

richlv, nope.

Interesting. I've changed all users 'lang: to 'ru_RU' in DB, restarted apache, but still have problem.

Cross linking - ZBX-11982

Got the same problem after upgrade to 3.4.4

Actually ZBX-13005

Have this problem since 2.0...

Dear _Andrey, could you provide more information about your setup?

Thanks for reply I had submitted a bug report (ZBX-15288) but already closed it as duplicate since found this one. All basic info about versions, environment and also some screenshots that demonstrate the problem you can find there.
Also there is a zabbix forum thread, where i discussed this problem when first time faced with it (in 2013, when i just upgraded from v1.8 to 2.0, where gettext usage were first implemented) Unfortunately whole thread on Russian but maybe it will be helpful...
If there anything else that i can provide (info/tests/access) - feel free to ask.

I have an excellent news because, as i think, i have found the solution of the problem! The problem that is gettext itself, on which is zabbix translation is related, is not support safe multithreading, so disabling multithreading in php and apache (USE="-threads" APACHE2_MPMS="prefork" - for gentoo users) solve this problem. Another workaround, for saving multithreading abilities, is to integrate some framework such Zend_Translate into zabbix frontend but unfortunately i cannot complete such difficult task at the moment... so multithreading, unfortunately, is a necessary sacrifice.

Great news, _Andrey!

My guess was close, but you killed the issue. Now it's time to share the solution in that forum thread and community portal.

Dear martins-v, do you think it's worth adding this information to official documentation?

Added to the known issue listing for the currently supported versions: 2.2, 3.0, 4.0, 4.2.

Are you sure "flipping" is a good alternative for "flapping"?

In this case "flipping" is just a form of the verb "flip" that seemed like a common word to use for something changing places randomly. "Flapping" implies a subject - something or somebody that does the "flapping" which in this case is, at least originally, very obscure.

But I'm sure that a case could be made for "flapping" as the better way.