Long Polling with Ajax and PHP - Apache freezes -


we try implement long-polling based notification service in our company's erp. similar facebook notifications.

technologies used:

  • php timeout set 60 seconds , 1 second sleep in each iteration of loop.
  • jquery ajax handling.
  • apache web server.

after month of coding, went production. few minutes after deployment had rollback everything. turned out our server (8 cores) couldn't handle long requests 20 employees, using ~5 browser tabs each. example: user opened 3 tabs our erp, 1 long-polling ajax on each tab. opening 4th tab impossible - hangs until 1 of previous 3 killed (and therefore ajax stopped).

'apache limitations', thought. went googling. found info apache's mpm modules , configs, gave try. our server use prefork mpm, apachectl -l shown us. changed few lines in config this:

<ifmodule mpm_prefork_module>     startservers          1     minspareservers       16     maxspareservers      32     serverlimit          50%     maxclients          150     maxclients           50%     maxrequestsperchild   0 </ifmodule>

funny thing is, works on local machine similar config. on server, looks apache ignores config, because minspareservers set 16, lauches 8 after restart. whe have no idea do.

passerby in first comment of previous post gave me direction check out if hit max browser connections 1 server.

as turns out, each browser has limit , can't change them (as far know). made workaround make work.

let's assume getting ajax data 

http://domain.com/ajax

to avoid hitting max browser connections, each long-polling ajax connects random subdomain, like:

http://31289.domain.com/ajax http://43289.domain.com/ajax

and on. there's wildcard on dns server pointing *.domain.com domain.com, , subdomain unique random number, generated js on each tab.

for more information, check out this thread.

there's been problems ajax same origin security, managed work out, using appropriate headers on both js , php sides.

if want know more headers, check out here on stackoverflow, , here on mozilla developer's page. thanks!


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