andrewlocatelliwoodcock

Thoughts on Software

Posts Tagged ‘Erlang

Unable to replicate from local CouchDB to Cloudant – a quick resolution for the {“error”:”shutdown”} message

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Just in case anyone else hits an issue whereby you are unable to replicate a local CouchDB database to Cloudant … I was using Curl on Windows (which never helps of course 🙂 ) and found that I was unable to replicate from a local instance to Cloudant even though my passwords, ca cert bundle, etc. were all correct. Naturally, it took a couple of goes to get the curl escaping on Windows right but even once I’d figured that out it was still failing with the uninformative

{"error":"shutdown"}

I eventually found some posts that pointed to my (very) out-of-date CouchDB instance being the issue: you need to be running CouchDB 1.2.0 preferably on Erlang R15 for this to work correctly.

I upgraded everything and key presto! It works!

Written by andrewlocatelliwoodcock

June 15, 2012 at 18:13

Posted in CouchDb, Databases, Erlang

Tagged with , ,

Connecting to Cloudant from Erlang: a quick example of using HTTPS from httpc:request

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Wiser heads than me will no doubt already know this but I for one struggled with working out how to do this so I thought I’d put the example up in the hope it will help others. So, what I was trying to do was get and put to a Cloudant database from Erlang. Cloudant requires both HTTPS and a username and password and I struggled to find an Erlang example online.

First, make sure that you can connect to Cloudant over curl and fetch at least the _all_dbs resource. If you can’t, Erlang isn’t going to work either. I found that to get curl working correctly, I needed to update the ca cert bundle that came with it.

Here’s how to retrive _all_dbs for your Cloudant account using curl:

curl https://username:password@username.cloudant.com/_all_dbs

where username is your Cloudant username and password is the password associated with your username. For example, if your username were ‘foo’ and your password ‘bar’, here’s the command you would use:

curl https://foo:bar@foo.cloudant.com/_all_dbs

If this doesn’t work, the most likely explanation is that your ca cert bundle is out of date: follow the instructions on the curl website for how to update them.
Assuming this worked, your now in a position to try the same with Erlang. I’m going to use the httpc library here:

inets:start(),

ssl:start(),

httpc:request (get, {“https://foo:bar@foo.cloudant.com/_all_dbs”, []}, [{ssl,[{verify,0}]}], []).

It is important to remember to start inets and ssl before attempting to use httpc:request. A put to Cloudant is similar, here’s an example that assumes the existance of a database barfoo and a resource widget on your Cloudant instance and also that you have a suitably initialized variable Update which contains the data which you are writing to the widget resource:

inets:start(),

ssl:start(),

httpc:request (put, {“https://foo:bar@foo.cloudant.com/barfoo/widget”, [], [], Update}, [], []).

And there you have it

Written by andrewlocatelliwoodcock

June 12, 2012 at 11:40