MaxListenersExceededWarning in Kibana

[wolframhaussig]

**Kibana version:**6.5.4

**Elasticsearch version:**6.5.4

**Server OS version:**RedHat Enterprise Linux 7

**Browser version:**Chrome 72

**Browser OS version:**Windows 10

Original install method (e.g. download page, yum, from source, etc.): download page

Describe the bug:
While working with Kibana(modifying visualizations, logstash pipelines,...) I got a lot of timeouts today so I looked into the error log of Kibana to see if I could find an error message. This is what I found:
MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 message listeners added. Use emitter.setMaxListeners() to increase limit
at _addListener (events.js:280:19)
at ChildProcess.addListener (events.js:297:10)
at resolve (/logserver/applications/kibana-6.5.4-linux-x86_64/node_modules/x-pack/plugins/canvas/server/lib/route_expression/thread/index.js:57:12)
at new Promise ()
at exports.thread (/logserver/applications/kibana-6.5.4-linux-x86_64/node_modules/x-pack/plugins/canvas/server/lib/route_expression/thread/index.js:54:30)
at Namespace.io.on (/logserver/applications/kibana-6.5.4-linux-x86_64/node_modules/x-pack/plugins/canvas/server/routes/socket.js:51:7)
at
at process._tickDomainCallback (internal/process/next_tick.js:229:7)

After restarting Kibana the error is gone.

Steps to reproduce:
Not yet known

Expected behavior:
The error should not occur

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 message listeners added. Use emitter.setMaxListeners() to increase limit
at _addListener (events.js:280:19)
at ChildProcess.addListener (events.js:297:10)
at resolve (/logserver/applications/kibana-6.5.4-linux-x86_64/node_modules/x-pack/plugins/canvas/server/lib/route_expression/thread/index.js:57:12)
at new Promise ()
at exports.thread (/logserver/applications/kibana-6.5.4-linux-x86_64/node_modules/x-pack/plugins/canvas/server/lib/route_expression/thread/index.js:54:30)
at Namespace.io.on (/logserver/applications/kibana-6.5.4-linux-x86_64/node_modules/x-pack/plugins/canvas/server/routes/socket.js:51:7)
at
at process._tickDomainCallback (internal/process/next_tick.js:229:7)

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-canvas

[monfera]

Likely duplicate of #28227

[cqliu1]

Fixed by #31779. Fix is available in Kibana 6.7+