multithreading - Nodejs synchronicity between requests -

-

i understand asynchronous nature of node , async programming concepts, have been doing long time. in situation need simultaneous requests check "in sync" if will. let me explain:

  • usera requests resource doesn't exist.
  • set flag "isprocessing" let others know resource being created.
  • userb requests same resource, sees it's processing, , waits ready (using polling - don't focus on this, part works way want)
  • [a bunch of heavy async stuff happens generate resource]
  • resource ready, polling notified (like said, part works)

the part has me in pickle "step 2" set "isprocessing" flag. asynchronous database operation (mongo) not yet complete when 2+ requests come in at same time. result, multiple requests attempting create same resource. problem goes away if requests separated enough time database write happen (~5ms), not "simultaneous" requests.

can offer advice solve this. seems need set "isprocessing" flag in synchronous (thread-blocking) way. know file system has synchronous operations - way go? using node on multi-core machine scale cloud day. using pm2 distribute our app across multiple cores. advice appreciated.

you need database access right. when say

update mylocktable set isprocessing = 1 isprocessing = 0

you 0 rows modified if isprocessing set 1. otherwise, 1 row. how can tell 2 cases apart , start heavy work once.


Comments

Post a Comment

Popular posts from this blog

database - VFP Grid + SQL server 2008 - grid not showing correctly -

-
i having problem, have grid called "gridbasica" , this: thisform.gridbase.recordsource = "sgviemp" sgviemp cursor made executing select sqlserver command sqlexec. when want modify registry, go form , the update there. so, when come form grid, grid isnt grid anymore, big white rectangle. reading around said: delete recordsource , asingt again. thisform.gridbase.recordsource = "" *--i sqlexe here thisform.gridbase.recordsource = "sgviemp" i , works, but, when click button modify again cursos updated modify form doesnt load fields did first time. could me out that? thanks in advance. --------------- edit ------------------ i have been doing recommended: lnselect = select(0) n = sqlexec(thisform.conexion,"select emp_ccodigo codigo, emp_cnombre 'nombre o razon social', emp_cnumrif 'r.i.f' sgviempr","sgviemp1") set echo on suspend select sgviemp zap in sgviemp *-- browse *--zaps correct
Read more

jquery - Set jPicker field to empty value -

-
im using jpicker color selector in form. have clear value set window/icon 'no color selected' state. i've tried following: $(':input[name="color"]').val(''); //access value directly. (does not affect jpicker) 2: $.jpicker.list[0].color.active.val('hex', '', this); //set color black , input value 000000, instead of empty string 3: $.jpicker.list[0].color.active.val(null, '', this); //does nothing none of 3 methods seems behave properly. in advance. this works me :) $.jpicker.list[0].color.active.val('v', null); here example: http://jsfiddle.net/3up7n/
Read more

.htaccess - htaccess convert request to clean url and add slash at the end of the url -

-
ok , searched more 4 days , more 20 posts here in stach or in websites without kind of success first here htaccess file rewriteengine on rewriterule ^([a-za-z0-9_]+)/?$ index.php?page=$1 [nc] rewriterule ^([a-za-z0-9_]+)\/([a-za-z0-9_]+)\/?$ index.php?page=$1&action=$2 [nc] i tried many codes 1 worked me can call request , works me www.example.com/pagename => www.example.com/index.php?page=pagename here questions , please provide me information "in detail" understand code well 1- how convert request automatically www.example.com/index.php?page=pagename www.example.com/pagename 2- if tried add slash @ end shows me page without images or styling mean www.example.com/pagename => works www.example.com/pagename/ => doesn't work that's :) for first part need 301 rule this: rewritecond %{the_request} /index\.php\?page=([^\s&]+) [nc] rewriterule ^ /%1? [r=301,l] for second part use absolute path in css, js, images files r
Read more