How to sleep the thread in node js without affecting other threads

Question

As per Understanding the node js event loop  node js supports a single thread model  That means if I make multiple requests to a node js server  it won t spawn a new thread for each request but will execute each request one by one   It means if I do the following for the first request in my node js code  and meanwhile a new request comes in on node  the second request has to wait until the first request completes  including 5 second sleep time   Right   var sleep   require  sleep        sleep sleep 5   sleep for 5 seconds   Is there a way that node js can spawn a new thread for each request so that the second request does not have to wait for the first request to complete  or can I call sleep on specific thread only

User · Answer

Please consider the deasync module  personally I don t like the Promise way to make all functions async  and keyword async await anythere  And I think the official node js should consider to expose the event loop API  this will solve the callback hell simply  Node js is a framework not a language   var node   require  deasync    node loop   node runLoopOnce   var done   0     async call here db query  select   from ticket    error  results  fields   gt       done   1       while   done      node loop        Now  here you go

User · Answer

In case you have a loop with an async request in each one and you want a certain time between each request you can use this code      var startTimeout   function timeout  i           setTimeout function                 myAsyncFunc i  then function data                   console log data                             timeout            var myFunc   function            timeout   0          i   0          while i  lt  10                  By calling a function  the i-value is going to be 1   10 and not always 10             startTimeout timeout  i                  Increase timeout by 1 sec after each call             timeout    1000              i                      This examples waits 1 second after each request before sending the next one

User · Answer

When working with async functions or observables provided by 3rd party libraries  for example Cloud firestore  I ve found functions the waitFor method shown below  TypeScript  but you get the idea     to be helpful when you need to wait on some process to complete  but you don t want to have to embed callbacks within callbacks within callbacks nor risk an infinite loop   This method is sort of similar to a while   condition  sleep loop  but yields asynchronously and performs a test on the completion condition at regular intervals till true or timeout    export const sleep    ms  number    gt        return new Promise resolve   gt  setTimeout resolve  ms            Wait until the condition tested in a function returns true  or until     a timeout is exceeded      param interval The frenequency with which the boolean function contained in condition is called      param timeout  The maximum time to allow for booleanFunction to return true     param booleanFunction   A completion function to evaluate after each interval  waitFor will return true as soon as the completion function returns true         export const waitFor   async function  interval  number  timeout  number      booleanFunction  Function   Promise lt boolean gt        let elapsed   1      if  booleanFunction    return true      while  elapsed  lt  timeout            elapsed    interval          await sleep interval           if  booleanFunction                  return true                      return false      The say you have a long running process on your backend you want to complete before some other task is undertaken   For example if you have a function that totals a list of accounts  but you want to refresh the accounts from the backend before you calculate  you can do something like this   async recalcAccountTotals     number        this accountService refresh        start the async process       if  this accounts dirty               let updateResult   await waitFor 100 2000     gt   return   this accounts dirty            if  updateResult           console error  Account refresh timed out  recalc aborted          return NaN         return       calculate the account total

User · Answer

If you are referring to the npm module sleep  it notes in the readme that sleep will block execution  So you are right - it isn t what you want  Instead you want to use setTimeout which is non-blocking  Here is an example   setTimeout function       console log  hello world        5000       For anyone looking to do this using es7 async await  this example should help   const snooze   ms   gt  new Promise resolve   gt  setTimeout resolve  ms     const example   async      gt      console log  About to snooze without halting the event loop         await snooze 1000     console log  done         example

[multithreading] How to sleep the thread in node.js without affecting other threads?

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