Error On Using PubSub in Node.js

[beingmohit]

Type: Bug

Severity: Critical

Description: Error on using pubsub in nodejs

TypeError: Cannot read property 'listenerCount' of undefined
    at subscribe (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:90:11)
    at Promise (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:23:11)
    at Promise (<anonymous>)
    at Object.subscribe (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:22:16)    at IPFSPubsub.subscribe (/home/mohit/projects/iptv/node_modules/orbit-db-pubsub/src/ipfs-pubsub.js:23:27)
    at OrbitDB._createStore (/home/mohit/projects/iptv/node_modules/orbit-db/src/OrbitDB.js:71:20)
    at OrbitDB.eventlog (/home/mohit/projects/iptv/node_modules/orbit-db/src/OrbitDB.js:29:17)
    at IPFS.ipfs.on (/home/mohit/projects/iptv/src/api/index.js:12:24)
    at emitNone (events.js:105:13)
    at IPFS.emit (events.js:207:7) Promise {
  <rejected> TypeError: Cannot read property 'listenerCount' of undefined
    at subscribe (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:90:11)
    at Promise (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:23:11)
    at Promise (<anonymous>)
    at Object.subscribe (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:22:16)
    at IPFSPubsub.subscribe (/home/mohit/projects/iptv/node_modules/orbit-db-pubsub/src/ipfs-pubsub.js:23:27)
    at OrbitDB._createStore (/home/mohit/projects/iptv/node_modules/orbit-db/src/OrbitDB.js:71:20)
    at OrbitDB.eventlog (/home/mohit/projects/iptv/node_modules/orbit-db/src/OrbitDB.js:29:17)
    at IPFS.ipfs.on (/home/mohit/projects/iptv/src/api/index.js:12:24)
    at emitNone (events.js:105:13)
    at IPFS.emit (events.js:207:7) }
TypeError: Cannot read property 'publish' of undefined
    at Function.publish.promisify (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:54:19)
    at /home/mohit/projects/iptv/node_modules/promisify-es6/index.js:41:20
    at Promise (<anonymous>)
    at Object.publish (/home/mohit/projects/iptv/node_modules/promisify-es6/index.js:35:16)
    at IPFSPubsub.publish (/home/mohit/projects/iptv/node_modules/orbit-db-pubsub/src/ipfs-pubsub.js:37:25)
    at Immediate.setImmediate [as _onImmediate] (/home/mohit/projects/iptv/node_modules/orbit-db/src/OrbitDB.js:88:54)
    at runCallback (timers.js:781:20)
    at tryOnImmediate (timers.js:743:5)
    at processImmediate [as _immediateCallback] (timers.js:714:5) Promise {
  <rejected> TypeError: Cannot read property 'publish' of undefined
    at Function.publish.promisify (/home/mohit/projects/iptv/node_modules/ipfs/src/core/components/pubsub.js:54:19)
    at /home/mohit/projects/iptv/node_modules/promisify-es6/index.js:41:20
    at Promise (<anonymous>)
    at Object.publish (/home/mohit/projects/iptv/node_modules/promisify-es6/index.js:35:16)
    at IPFSPubsub.publish (/home/mohit/projects/iptv/node_modules/orbit-db-pubsub/src/ipfs-pubsub.js:37:25)
    at Immediate.setImmediate [as _onImmediate] (/home/mohit/projects/iptv/node_modules/orbit-db/src/OrbitDB.js:88:54)
    at runCallback (timers.js:781:20)
    at tryOnImmediate (timers.js:743:5)
    at processImmediate [as _immediateCallback] (timers.js:714:5) }

On digging up in ipfs code, found
this._pubsub = undefined
on src/core/index.js:74

Where is pubsub module code?

• Version: 0.26.0
• Platform: Linux workstation 4.13.3-1-ARCH Add to cli: ipfs pin [-r] <ipfs-path> #1 SMP PREEMPT Thu Sep 21 20:33:16 CEST 2017 x86_64 GNU/Linux
• Subsystem: pubsub

Steps to reproduce the error:

const IPFS = require('ipfs')
const IpfsApi = require('ipfs-api')
const OrbitDB = require('orbit-db')

const ipfs = new IPFS()
const orbitdb = new OrbitDB(ipfs)

process.on('unhandledRejection', (e, p) => console.error(e,p));
ipfs.on('error', (e) => console.error(e));

ipfs.on('ready', (e) => {
    const db = orbitdb.eventlog('iptv')
    db.add(0);
})

[victorb]

You need to use EXPERIMENTAL.pubsub option when instantiating IPFS. Code will end up being:

const ipfs = new IPFS({
  EXPERIMENTAL: {
    pubsub: true
  }
})

[thisconnect]

Could/should ipfs-api check if EXPERIMENTAL.pubsub is true or throw a descriptive error?

[victorb]

@thisconnect I was thinking about how we could make this error more descriptive to avoid these issues from being created but would involve either 1) having this._pubsub being a getter that we can throw if undefined with better error or 2) libraries checking if node.pubsub is actually defined before using it.

1. would solve most cases but not sure about support in nodejs versions + browsers yet

2. would require every library using js-ipfs to implement basically the same logic