memjs: timeout but failed to retry until restarting program

Hi, I am using memjs 1.2.0 with memcache. However it sometimes go into fail state for every request until I restart program:

error: socket timed out connecting to server.
 at Socket.<anonymous> (/path/node_modules/memjs/lib/memjs/server.js:169:20)
 at Object.onceWrapper (events.js:272:13)
 at Socket.emit (events.js:180:13)
 at Socket.emit (domain.js:421:20)
 at Socket._onTimeout (net.js:396:8)
 at ontimeout (timers.js:466:11)
 at tryOnTimeout (timers.js:304:5)
 at Timer.listOnTimeout (timers.js:267:5)

Node v9.9.0

About this issue

Original URL
State: closed
Created 6 years ago
Reactions: 5
Comments: 28 (12 by maintainers)

Most upvoted comments

@UmanShahzad any help is appreciated. I have been unable to reproduce this issue so also a pointer on how to reproduce this error would help a lot.

saschat on Oct 25, 2019

@tengattack I finally understand what you mean 😃

This would be an option (we actually use event emitters internally) but I don’t think this would be ideal since it would remove choice for the user. For example lets consider a get request. It can return a hit, a miss, or an error. If I use an event emitter for errors a get only returns a hit or a miss. This means as a library developer I need to decide for you how to treat this error. Now in a get request this might be easy (I would treat it as a miss), but what about a set or an incr command.

So to summarize, an event emitter would basically mean that as the library developer I would have to decide how to treat all errors for the different commands and as a user you only get to react to errors in one way, independently which command they occurred with. The second might not be too mad but the former I am not comfortable doing.

saschat on Sep 24, 2020

This looks as follows with callbacks:

var mc = memjs.Client.create(/* ... */);
mc.get("test-key", function (err, val) {
  if (err != null) {
    // Error (e.g., the one you see) -> get value from source
  } else {
    if (val == null) {
      // Miss -> get value from source
    } else {
      // Return value
    }
  }
});

And with promises:

var mc = memjs.Client.create(/* ... */);
mc.get("test-key")
  .then(function (val) {
    if (val == null) {
      // Miss -> get value from source
    } else {
      // Return value
    }
  })
  .catch(function (err) {
    // Error (e.g., the one you see) -> get value from source
  });

saschat on Sep 21, 2020

I tried to reproduce this error again and finally realized that the posted error is an exception that was not caught. Our examples are with callbacks where errors are implicitly handled so I missed that. If you do not use callbacks you need to catch this error with .catch for promises or a try/catch block for async/await and handle the error by getting the info from the ground truth. This is normal caching behavior.

saschat on Sep 21, 2020