Node-redis: TypeError: Cannot assign to read only property 'callback' of decr

Created on 23 Jun 2016 · 6Comments · Source: NodeRedis/node-redis

Version: node redis 2.6.2
Platform: Node 4.4.5 on Ubuntu 14.04
Description:
I keep getting this error while trying to decrement a simple online counter in redis:

    TypeError: Cannot assign to read only property 'callback' of decr
    at RedisClient.internalSendCommandWrapper (/home/alex/node_modules/newrelic/lib/instrumentation/redis.js:76:22)
    at RedisClient.wrappedFunction [as internal_send_command] (/home/alex/node_modules/newrelic/lib/transaction/tracer/index.js:354:24)
    at RedisClient.(anonymous function).RedisClient.(anonymous function) (/home/alex/node_modules/redis/lib/commands.js:45:25)
    at Socket.eval (eval at <anonymous> (/home/alex/server2.js:2:52), <anonymous>:2456:12)
    at emitOne (events.js:77:13)
    at Socket.emit (events.js:169:7)
    at Socket.emit (/home/alex/node_modules/socket.io/lib/socket.js:128:10)
    at Socket.onclose (/home/alex/node_modules/socket.io/lib/socket.js:425:8)
    at Client.onclose (/home/alex/node_modules/socket.io/lib/client.js:232:24)
    at Client.onerror (/home/alex/node_modules/socket.io/lib/client.js:213:8)

The code is:

    db.decr('online',function(err){
        if(err){
            console.log('DECREMENTING ONLINE NUMBER FAILED:');
            console.log(err);
        }
        console.log('DECREMENTING ONLINE NUMBER WAS SUCCESSFUL!');
    });

I can't seem to replicate it, but it only happens when lots of people are on the site. When it's only me and a couple of friends testing it it seems to do the job just fine incrementing and decrementing the value.

By the way it happens even without the callback function (just db.decr('online')), I only added the callback to see if it would throw any errors.

I repeat, the code works fine until more people start using it. Maybe it's trying to do .decr at the same time and it can't handle that or?

question

Source

Alchemystic

Most helpful comment

I just hit this problem with [email protected] and [email protected]. Setting newrelic back to 1.28.0 removed the issue.

However, using redis 2.6.2 and newrelic 1.28.3 works fine.

landau on 21 Jul 2016

👍3

All 6 comments

Just noticed it in the logs that db.get() calls also throw a similar error sometimes:

    TypeError: Cannot assign to read only property 'callback' of get
    at RedisClient.internalSendCommandWrapper (/home/alex/node_modules/newrelic/lib/instrumentation/redis.js:76:22)
    at RedisClient.wrappedFunction [as internal_send_command] (/home/alex/node_modules/newrelic/lib/transaction/tracer/index.js:354:24)
    at RedisClient.(anonymous function).RedisClient.(anonymous function) (/home/alex/node_modules/redis/lib/commands.js:45:25)
    at eval (eval at <anonymous> (/home/alex/server2.js:2:52), <anonymous>:2384:16)
    at checkLogin (eval at <anonymous> (/home/alex/server2.js:2:52), <anonymous>:572:13)
    at Socket.eval (eval at <anonymous> (/home/alex/server2.js:2:52), <anonymous>:2001:9)
    at emitOne (events.js:77:13)
    at Socket.emit (events.js:169:7)
    at Socket.onevent (/home/alex/node_modules/socket.io/lib/socket.js:335:8)
    at Socket.onpacket (/home/alex/node_modules/socket.io/lib/socket.js:295:12)

Code:

            db.get('triviaAnswer',function(err,dbAnswer){
                if(err){
                    console.log('Error getting triviaAnswer from redis: '+err);
                    return;
                }

Also, the 'online' and 'triviaAnswer' fields are already set, and the code above works until.. Well until it doesn't. It's not "new" code either, it's been working on a different server for weeks now, so I doubt there's a problem with that.

Alchemystic on 23 Jun 2016

This seems to be a issue with newrelic, so I recommend to contact them about this. I'm sorry that I can't help you any more, as I do not use newrelic on my own.

BridgeAR on 23 Jun 2016

🎉1

That was it, thank you.

Alchemystic on 23 Jun 2016

@Alchemystic would you mind going into detail about the fix? I've found this locally too with NR, but upgrading to 2.6.2 (from 2.6.0-1) seemed to fix it for me, so want to make sure that's not just a red herring.