Created
November 11, 2011 23:44
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Software watchdog in Javascript
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| // Use a watchdog to control functions that may take too long. | |
| // You might use a watchdog to update the UI if your JSONP script fails to load | |
| // in a timely manner. | |
| function may_fail(n, slot) { | |
| setTimeout(function(){ | |
| //stop processing if the watchdog fired | |
| if (dog[slot] == "FIRED") { | |
| console.log("<may_fail slot='"+slot+"'> FAILED"); | |
| return; | |
| } | |
| //we're ok so processing can continue | |
| dog[slot]="SAFE"; | |
| console.log("<may_fail slot='"+slot+"'> OK"); | |
| //process http response or whatever | |
| }, n); | |
| } | |
| var dog = {} | |
| gscount=function(){ | |
| var n = 0; | |
| return function(){return n++} | |
| }(); | |
| function gensym(){return "sym"+gscount()} | |
| function watchdog(func, time_allowed) { | |
| var slot = gensym(); | |
| dog[slot] = "ARMED"; | |
| function watcher(captured) {return function() { | |
| console.log(new Date()); | |
| console.log(slot+" is "+dog[slot]); | |
| if (dog[slot] == captured) { | |
| console.log("***watchdog fired: bow-wow!"); | |
| dog[slot]="FIRED"; | |
| } | |
| else {console.log("watchdog is sleeping.") } | |
| }} | |
| //Set the watcher to fire after the time_allowed | |
| setTimeout(watcher(dog[slot]), time_allowed); | |
| //Run the target function | |
| func(slot); | |
| } | |
| console.log("Starting watchdogs..."); | |
| //watchdog does not fire | |
| watchdog(function(f){may_fail(100, f)}, 120); | |
| //watchdog fires | |
| watchdog(function(f){may_fail(200, f)}, 120); | |
| watchdog(function(f){may_fail(300, f)}, 301); | |
| watchdog(function(f){may_fail(320, f)}, 301); |
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