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onebeyond / rascal

A config driven wrapper for amqp.node supporting multi-host connections, automatic error recovery, redelivery flood protection, transparent encryption / decryption and channel pooling.

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MaxListenersExceededWarning

nico3dfx opened this issue · comments

commented

Hi,
I have the MaxListenersExeededWarning warning with my configuration.

(node:23904) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 newListener listeners added to [Broker]. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:390:17)
    at Broker.addListener (events.js:406:10)
    at forwardEmitter (c:\laragon\www\rascal-mc\node_modules\forward-emitter\index.js:18:8)
    at c:\laragon\www\rascal-mc\node_modules\rascal\lib\amqp\tasks\initVhosts.js:15:9
    at c:\laragon\www\rascal-mc\node_modules\rascal\lib\amqp\Vhost.js:70:14
    at c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:2022:31
    at wrapper (c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:271:20)
    at c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:1963:19
    at wrapper (c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:271:20)
    at replenish (c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:441:29)
(node:23904) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 removeListener listeners added to [Broker]. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:390:17)
    at Broker.addListener (events.js:406:10)
    at forwardEmitter (c:\laragon\www\rascal-mc\node_modules\forward-emitter\index.js:22:8)
    at c:\laragon\www\rascal-mc\node_modules\rascal\lib\amqp\tasks\initVhosts.js:15:9
    at c:\laragon\www\rascal-mc\node_modules\rascal\lib\amqp\Vhost.js:70:14
    at c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:2022:31
    at wrapper (c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:271:20)
    at c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:1963:19
    at wrapper (c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:271:20)
    at replenish (c:\laragon\www\rascal-mc\node_modules\async\dist\async.js:441:29)

Environment

My config (today, the number will increase) has 32 vhosts each with:

  • 1 connection (same URL for all vhosts)
  • 100 queues
  • 100 bindings
  • 100 subscriptions

No problem when the warmup process complete: Rabbit has all the queues with the relative consumer.

Thanks,
Nico.

commented

Hi @nico3dfx,

I will try to reproduce. Can you confirm your node.js and rascal version please?

commented

Hi @nico3dfx,

I will try to reproduce. Can you confirm your node.js and rascal version please?

Node @ 14.16.1
Rascal @ 15.0.0

Thank you @cressie176

commented

I've been able to reproduce. The warning is caused because Rascal uses the forward-emitter package to forward events from each vhost to the broker object, so that when an "error" event is emitted from a vhost (which isn't exposed by Rascal), it is re-emitted on the broker, where it can be handled.

Confusingly forward-events library doesn't work by forwarding events at all. Instead it registers a newListener event handler on the broker, then when an event handler is added, duplicates it on the vhost.

This means that each new vhost adds an "newListener" handler, and after the 10th vhost, node reports the MaxListenersExceededWarning.

I'll increase the threshold to Math.max(10, numberOfVhosts)

commented

Published as rascal@15.0.1