Couchbase views and JSHint
Gets rid of this.
Debugging Erlang NIF with LLDB
Earlier today I ran across a segfault while trying something with
cberl so I figured it’s time to startup
gdb and see what is going on, but how to actually do that? Luckily
I found a post on the erlang programming
with the exact same problem. Since I’m on a Mac I wanted to use
lldb instead so a quick modification to the
startup script did the trick.
./rebar skip_deps=true eunit runs erland via lldb and ready to
Couchbase Lite on the Raspberry Pi using JRuby
After having my Raspberry Pi sitting quietly in the corner for quite some time
I recently heard Dave Starling talk about
running Couchbase Lite on it and just had to
try it out. After all having a small embedded database sounds perfect to the
Pi and I can think of a couple fun projects with it, from dashboards to home
automation, to the intelligent fridge ;). Also with DevoxxUK
coming up, this sounded like a perfect talk subject for a quick 15min session.
So what is Couchbase Lite?
Couchbase Lite is a NoSQL database, for mobile and embedded devices. Similar to
using SQLite you add a library to your project and now you have a database
available to you, but unlike SQLite it provides additional syncing
capabilities, and stores JSON documents instead of Rows. So what does that give
you? Basically it means that you can use JSON APIs directly and store the
results in the database, which makes building such apps much easier. Also
having syncing done for you means that you can just work with your data locally
like you always were, but have it available on every device connected, be it
Android / iOS / Windows Phone and of course the Raspberry Pi, even if you are
offline. This works via the so called
sync_gateway which takes care of
the nitty-gritty details of sync and managing conflicts as well as the
connection to Couchbase to keep the data available on
Couchbase Lite + JRuby on MacOS from Philipp Fehre on Vimeo.
OK let’s build something!
Since there is a full Linux, in my case Raspbian, running on the Pi you can
develop in any language you like, but Couchbase lites portable version is
written in Java, so the way to go for me was using JRuby. JRuby lends itself
quite nicely to trying stuff quickly without the overhead of setting up a big
project, and since it provides great interoperability with
Java, using any of
the Java libs is very easy.
So what are building?
As shown in the video we will create a small messaging app, which works cross
platform and even if you are offline. The idea is to store all the messages in
the local Couchbase Lite database and have it sync with a server somewhere on
EC2, which in turn all clients subscribe to. The full final code is available
on github. Just to quickly
review what you need to follow along:
- JRuby (http://jruby.org)
- Raspberry Pi running with Raspbian or a Mac running OSX
- A sync gateway instance, you can get one by signing up to
Let’s get started!
Loading in all the dependencies
Couchbase Lite has some dependencies, and we first of all need to make sure all
the needed jars are loaded, for the most part those are plain java jars so
there is no need to do anything platform specific, so simply loading the whole
directory works fine.
There is one natively compiled dependency so which needs some special attention to be loaded
depending which platform you are on. In this case detecting the OS as well as
the CPU platform let’s us get the right jar loaded. I compiled the
in for Raspbian and the linux-arm platform, as well as for MacOS so
the application runs on either and load depending on which platform the app currently runs on.
Compiling for additional platforms is simple as well, just checkout the code
$ gradle jar, in case of the Raspberry Pi you might need
to adjust the
build.gradle file according to the
crosscompile-build.gradle and include the paths for the compiler
as well as the path to
jni.h. Take a look the compiler settings
in this case
And make sure it finds the required JNI header
With this out of the way we can start using Couchbase Lite in our application.
Initialize the application
Using the database from within the application requires some setup during the initialization.
We need to get access to a
JavaContext first, which is similar to
an Android Application Context, and is needed to provide a basic information for
the whole application. This contains elements like the directory for data
storage and alike. We also need to make sure to get the java String object from a URL string
used as the location of the Sync Gateway, which we will talk about shortly.
Lastly the manager is used to acquire the actual database instances, and handle
access to them. Getting access to the Database via the manager is done by
simply getting the database with a given name, in case the database is not
present already it will be created for you and stored on disk in the data
directory, which defaults to the current application directory.
Setting up the sync
The ease of sync is one of the big advantages Couchbase Lite has, so let’s set
it up. First we need some backend to sync with. If you just want to try it out
take a look at Couchbase Cloud which
let’s you setup a sync_gateway with just a few clicks, or just run it locally,
by downloading form Couchbase Mobile, soon
sync_gateway will also be available in
homebrew for MacOS. After
this is done just grab the URL and point the app to it.
Now all is left is to create two replications one to pull data from the remote
whenever there is a change, and one to push our own changes up.
And finally we need to handle any changes which get passed along, this is done
by implementing a so called
ChangeListener Interface which just
needs to implement one method
void change(ChangeEvent event) which
gets called for every change being replicated. I our case we just log the
change and update the UI as needed. Since this class is implementing a
Java Interface we also need to include some annotations for JRuby to handle the
interfacing with Java correctly, mainly annotating the method with the type
And with this we are now ready to create and read the data.
Reading and writing data
When writing to couchbase lite we need to create a document first and than save
the data to it.
In this case we create a document in the given database with the provided text.
The type of the document is set to message. The type is no special property but it
is common to set it because it allows us to filter more easily later as there
are more different types of documents stored in the database. Now to read the
data out we could either do so via the document id which is assigned on
creation or by creating a query. Since we want to display all the documents it
makes sense to create a query which reads all the documents and stores them in
Couchbase Lite allows for more advanced queries using Map Reduce and also for
live updating queries, but for this simple application this approach will be
Displaying the results in the UI
Now that everything is in place we can create a UI using Swing to actually
provide us with the needed interactions. This is rather simple so I’m not going
to walk through all the code, the important part is to setup a listener to
actually create new messages as the user presses
And adding rows to the created table as the new data rolls in
Thats it a quick and simple messaging app, runnable on a Raspberry
Pi, MacOSX and basically anywhere there is Java.
Getting up and running with JRuby and Couchbase Lite on the Raspberry Pi is
really simple, the JVM comes pre-installed and JRuby is just a download away,
this opens up the Raspberry Pi to a nice set of applications with the ability
to operate on the data locally without having to worry about the syncing
yourself. I’m already looking forward to some home automation, dashboards and
alike interfacing with my iPhone or Android Tablet, maybe I finally get my
intelligent fridge? ;).
chruby homebrew and native extensions fail…
I always try to run the latest version of ruby, via chruby and ruby-build.
Recently I ran into a wierd issue, and I’m not really sure how to resolve it,
yet, but managed to work around it. When installing gems with native extensions
via bundler, ruby seems to not find libraries installed via homebrew, it works
fine just running
gem install so. Also all extensions installed
seem to stop working between ruby 2.1.0 and 2.1.1. Even though I don’t know
what’s going on, the work around seems to be installing all gems which have
native extensions via
gem install GEM and running
install after the fact. Now everything works again…
Using CouchbaseLite from RubyMotion
Recently Couchbase Lite 1.0 got released, and you can find anything about it at
the Couchbase Mobile Developer Portal.
As I’ve been quite interested in RubyMotion since some time, I decided to check
how easy it would be to take CouchbaseLite for a spin on RubyMotion, and I have
to say it is quite easy. Besides some small problems with RubyMotion handling
of blocks everything worked as expected. The full project is up on
github for you to checkout,
but I’d like to walk through some of the parts worth noting here.
Getting the database ready
First things first, opening a database file for CouchbaseLite works as expected
simply porting over what is presented in the examples.
This database object can now be passed down to wherever it is needed. So now is
the time to get onto one of the big features of CouchbaseLite, which is sync. To
get this working we authenticate against Facebook using ACAccountStore
and feed the credentials back to CouchbaseLite to authenticate any replications,
which are setup.
And with those little pieces of code we actually have a working sync setup.
A syncing database is nice, but without data in it also kind of useless ;), so
let’s get something in there. CouchbaseLite actually provides a nice layer on
top here, letting you define models for your data which you can then read and
write like you would with any ORM. And it’s more than that, you can actually use
those as well to directly bind to a view, but more about that later. First let’s
get some data in there, by first creating a model to represent this.
So all there is left to do is creating a new object of this kind and save it.
And that’s it, we can now store items in our database fairly simple.
… and data out
With this we can take advantage of one of the other big features of
CouchbasLite, at least to me, which is using CouchbaseLite as an
TableViewDataSource. This cuts out huge amounts of boilerplate code, so
will get everything setup, and make sure that the display is always up to date.
One more (sad) thing…
Sadly right now, due to a bug in the handling of Procs in RubyMotion, it does
not allow you to setup map and reduce blocks via Ruby. This will probably be
resolved by Rubymotion soon, but for now it means you have to setup the blocks
from Objective-C. But don’t worry it’s not hard, basically it’s just the code
for the block itself which is pretty easy to grasp.
In TodoLite-Motion I set it
up to be a vendored Xcode project, so it can easily be compiled and changed when
And that’s it, a basic project up and running with everything needed to have a
synced and shared database in RubyMotion.
Building Couchbase from Source
Thanks to @trondn it is easier than ever to build
couchbase from source. So I decided to take the new
build system for a spin on my Macbook based on the
Getting all the dependencies
First of all if you are not yet using homebrew already, start
doing so it will make your live a lot easier throughout the world of open source
tool chains. Ok let’s get started, by installing all the needed dependencies
Ok now let’s see what all this is
- repo is a tool which ties together
multiple git repositories so we can use them as one big project. It it also
reponsible for the whole code review process when used in conjuction with
- snappy is a compression library optimized
for speed. This is used internally to compress the data written to disk.
- icu4c unicode library to handle all
the unicode needs.
- google-perftools provides
TCMalloc a faster
malloc implementation which is used whereever malloc is needed.
- erlang a programming language build for highly
concurrent systems. In Couchbase this is used in multiple places but
especially the cluster managing.
- libevent event library used internally in couchbase.
- cmake cross platform build system to make it easy to
build on multiple platforms native build systems. Couchbase uses this now to
generate the build files needed on either Windows / Mac and Linux.
- git Version control system.
This covers the basics now it’s time to get the source and start building!
Getting the source Couchbase
As metioned before Couchbase relies on repo to manage all the interdepended
repositories. So to get the source in the right versions you need to get the
manifest for the version of Couchbase you want to build so repo can get all the
right source for you. This is easy enough, simply create a folder for the source
and setup repo in there in this case with the master branch.
And finally we get the source by telling repo to sync our local copy
That’s it time to build
Building the software itself is now as simple as running
Afterwards couchbase should be ready to run
and you can visit the webinterface for all your
And there you have it, that’s all you need todo to get your locally build
version of couchbase up and Running, to maybe tryout all the new features
currently in development.
Setting up Couchbase PHP-SDK with XAMPP on Windows
Getting up and running with PHP on Windows has always been quite easy due to
XAMPP. It provides everything needed
to get started quickly and build something using a default stack available
everywhere. A lot of people get (or got) started this way, including me. But now
that MySQL, PHP, and Apache are setup maybe it’s time to try something new. For
me it’s been a while since I ran a setup like this and so I thought it’s worth
documenting the process.
Getting all the pieces
First of all you’ll need:
- XAMPP for all your PHP and
Apache needs, so install at least PHP and Apache
- Couchbase, remember that you can try
out the Enterprise version for development for free.
XAMPP uses thread safe PHP so make sure you download the correct version
(either x86 or x64 Thread Safe) for your environment.
Getting everything installed
For Couchbase and XAMPP you basically follow the instructions on the screen to
get it up and running, and make sure you configure Couchbase as well at the end
by visiting the web interface. Now all there is left is
moving the PHP stuff into place, which is probably the most complicated part of
a really easy setup. The zip downloaded from the windows PECL
page contains 2 dll files,
libcouchbase.dll and php_couchbase.dll which need to be moved in the right
place. First to make php find libcouchbase it’s needs to be present c:\\apache\bin\libcouchbase.dll and to make sure you can also use
php from the command line also copy it to c:\xampp\php\libcouchbase.dll and
add the XAMPP PHP to your PATH by going to Control Panel -> System and Security
-> Advanced System Settings -> Environment Variables and edit the PATH
variable by appending c:\YOUR XAMPP DIRECTORY\php. And that’s it you are
now ready to use Couchbase in XAMPP, by adding the extension to php.ini, so just add
Try it out!
Create a new PHP file at c:\YOUR XAMPP DIRECTORY\htdocs\cb-test.php containing
and open it in your browser to make apache run
it you should now see the result in your browser.
you can also use the command line of course.
OK so you are now ready to use Couchbase from PHP, and if you need any help and
are in London this week stop by the Couchbase Developer Day as part of Big Data
or even if you don’t still you should still stop by.
You should also checkout Trond Norbye’s Blog basically describing the same setup.
Setting up Couchbase views with Rake
If you are like me, you like your code and at best everything else about your
app to be versioned. This makes setting up a new development environment quick,
and even more important reproducible. So one thing which always bothered me was
setting up external code outside of the application to generate Couchbase views,
web interface, far away from my application code. If you want to know more about
them watch the Couchbase 103 - Views and
Map-Reduce by the way.
like to keep it inside as well, and provide a task to actually set them up for
the given environments. The following quick gist provides a rake task to do
this, adding all views in
config/couchbase_views to Couchbase.
This works great together with dotenv to provide the connection details via
environment variables, but can also depend on any other way to
set up the database connection easily.
Installing Couchbase sync_gateway via Homebrew
Homebrew is my favorite package manager on the Mac, sadly
there is no package to setup and install the Couchbase
sync_gateway which is used for
interaction between a Couchbase
Server and a Couchbase Lite
mobile database. Since
this is easily fixed, I created a formula for sync_gateway. Currently the
Pull-Request is still open so
if you like to have this in homebrew make sure to let the homebrew maintainers
know. For the time being you can install it by referencing my fork of homebrew
directly in the brew install.
brew install https://raw.github.com/sideshowcoder/homebrew/sync-gateway-add-formula/Library/Formula/sync_gateway.rb
Quick Erlang Snippet: Run EUnit Tests from the shell
While working through the code samples for Learn you some Erlang I found it helpful to quickly define and run some EUnit test cases. So far all the Erlang I did involved using rebar, but that didn’t make sense for code snippets so here is a simple command line for recompiling and running the unit tests for a module.