concurrency - Running multiple concurrent Python programs accessing the same database table -


is there in python allows run multiple concurrent python programs potentially access same database table , prevent each program using full cpu , thereby allow server have additional capacity left over?

several issues:

  1. multiple concurrent python programs - see http://wiki.python.org/moin/concurrency, start try builtin module multiprocessing (http://docs.python.org/2/library/multiprocessing.html)
  2. access same database table - each process should create own db connection - after concurrency managed by/or configured within rdbms and/or connection/query options. if need sync between processes - using locks/semaphores help.
  3. prevent each program using full cpu - depends processes should do, go with:
    • having 1 main program runs time (master process), pauses (time.sleep, gevent.sleep or similar) , spawns , controls spawned processes (workers)
    • spawned processes job (workers) - open new connection, db actions , quit

i'm sure of workflows/systems provided multiprocessing (or other) modules fit needs (workers, pools, queues, pipes, shared states, synchronization, ...).


Comments

Post a Comment

Popular posts from this blog

linux - xterm copying to CLIPBOARD using copy-selection causes automatic updating of CLIPBOARD upon mouse selection -

i've tried various ways coerce xterm (versions 285 , 292) copy selection clipboard clipboard whenever press ctrl-shift-c. promising way far has been, in ~/.xresources, put this: xterm*vt100.translations: #override \ ctrl shift <keypress> c: copy-selection(clipboard) \n\ ctrl shift <keypress> v: insert-selection(clipboard) ctrl-shift-v works perfectly, copying has nuance... if restart xterm, highlighting text puts things in primary clipboard; expected, proper, default behavior. if hit ctrl-shift-c, copies current selection clipboard clipboard. the bug, however, if highlight text after first time pressed ctrl-shift-c, you'll see highlighting copies both primary and clipboard. cannot figure out how stop xterm updating clipboard upon selection... , doesn't make sense me in first place. i said, @ specific point in time, copy selection clipboard... yet starts updating automatically upon selection after doing once... anyone have workaround...
Read more

c++ - qgraphicsview horizontal scrolling always has a vertical delta -

Image
i've subclassed qgraphicsview custom canvas used in cad application. i've reimplemented qgraphicsview::wheelevent check keyboard modifiers control key and, if control key pressed, zoom. i'm trying implement horizontal scroll when user holds shift , uses wheel. the problem i'm having horizontal scrolling always scrolls 0.279. not huge problem, hugely annoying , points else being wrong. so, here questions: is right way implement horizontal scrolling? if not, is? how eliminate delta of 0.279? thanks in advance. code , sample output below void myview::zoom(int delta) { double factor = pow(1.2, delta/abs(delta)); this->scale(factor, factor); } void myview::scrollhorizontal(int level) { qpointf center = maptoscene(viewport()->rect().center()); qdebug() << "center: " << center.x() << ", " << center.y(); centeron(qpointf(center.x() - level, center.y())); } void myview::wheelevent(qwheeleve...
Read more