Bluemix error: Module version mismatch - node.js

Question

I am trying to run a node.js application that uses PouchDB (a local CouchDB implementation). I can run this successfully locally and even upload it and build it on my Bluemix instance. However, whenever I send a request to my app, I do not get a response and I see the following error in my Bluemix console:
[Error: Module version mismatch. Expected 46, got 14. This generally implies that leveldown was built with a different version of node than that which is running now. You may try fully removing and reinstalling PouchDB or leveldown to resolve.]
I have tried to add npm rebuild into my build pipeline above the npm install, which I can see does indeed do a rebuild. However, I still get the previous error.
A bit about my app: It is a bot for the Slack platform. A user sends a command and my Bluemix app then responds. My Bluemix app has multiple documents that PouchDB stores. As I say, all this runs and responds correctly on my development machine.
Here is my package.js for reference:
{
"name": "XXXXXXXXXXX",
"version": "0.x.0",
"description": "XXXXXXXXXXXX",
"main": "app.js",
"scripts": {
"start": "node app.js"
},
"repository": {
"type": "git",
"url": "XXXXXXXXXXX"
},
"keywords": [
"slack",
"bot",
"nodejs"
],
"author": "xxxxxxxxx",
"license": "MIT",
"dependencies": {
"bluebird": "^3.1.1",
"body-parser": "^1.14.2",
"cfenv": "^1.0.3",
"cheerio": "^0.19.0",
"express": "^4.13.3",
"pouchdb": "^5.1.0",
"request-promise": "^1.0.2"
},
"engines": {
"node": "^4.2.x",
"npm": "^2.14.x"
}
}
Also some additional history: I ran a prior version of my app on Bluemix when I was using MongoDB instead of PouchDB. My node version at the time was the default that Bluemix gave me when I started, which was version 0.12.x. However, this version didn't support arrow functions, which I make heavy use of now. Hence, the bump to node 4.2.x.
Thanks!
Edit: After some digging I found out that 'leveldown' (a dependency of PouchDB) makes use of npm prebuilds where available. What this means is that if a prebuild is available on their GitHub it will be downloaded instead of the source, as a convenience. Looking through the logs I notice that version 1.4.2 is being downloaded as the prebuild version through Bluemix. However, there is a version 1.4.3 available that looks like it solves my 'Expected 46, got 14` issue. So the new question is why is Bluemix doing this and how can I rectify it?

Answer 1

I tried to push on Bluemix the same version that you are using ("^5.1.0") in your package.json and it is working fine, even using node engine "4.0.x".
Moreover according to CF infrastructure, the runtime is build during application staging step, so the pouchdb module should be built with the right dependencies and references.
Have you tried to push your application again in order to force a full application restage?
If yes, the first step to understand what is going on is to get the application logs during the staging process and also as soon as this error message is returned.
So, on your terminal, run the following commands:
1 - cd into your source directory
2 - connect to Bluemix API
cf api https://api.[REGION].bluemix.net

where [REGION] is one of
eu-gb for United Kingdom
ng for US South
au-syd for Sydney
3 - Login to Bluemix and choose the right ORG and SPACE
cf login -u [BLUEMIX USERNAME]
cf target -o [BLUEMIX ORG] -s [BLUEMIX SPACE]
4 - push your application and, as soon as it has been staged, run
cf logs [app-name] --recent > staging_output.txt
5 - tail the application logs, running
cf logs [app-name]
and without closing it make the request that is generating the error message
6 - check the output generated at step #5 for details on where in the code your application is failing and on the failing module

Answer 2

After a lot of debugging the answer, as ever, was to delete my Bluemix application first and then push a new version via the build system. The leveldown prebuilt npm package that was causing the error was cached somewhere. I could only get rid of this by deleting my app. Nothing special there.