#Avro-Nodejs

A wrapper for the c++ implemenation of Avro.

#The Why

Javascript is a async callback world so the avro library should play in that world. I've also seen far too many partially completed avro javascript projects on github.

#API

###Avro sync

avro.encodeDatum(value, schema);

avro.decodeDatum([/array of bytes/], schema);

#####Example var addon = require('../build/Release/avro'); var avro = new addon.Avro(); var bytes = avro.encodeDatum(12345.89, '"double"'); var result = avro.decodeDatum(bytes, '"double"'); avro.close();

The result will contain the value that we encoded.

###Avro async

avro.queueSchema(schema, onSuccess, onError);

avro.push([/array of bytes/]);

Currently there is only async support for decoding avro. The implementation is designed for the ability to queue multiple avro schemas to be decoded with queueSchema(). The push() function pushes bytes to the stream being parsed in a none blocking manor. On the completion the call backs are called.

#####Example var addon = require('../build/Release/avro'); var avro = new addon.Avro(); avro.queueSchema('{"type": "map", "values": "bytes"', function(datum){ console.log("datum: ", datum); }, function(error){ console.log(error); });

avro.push(message.binarydata);//message as defined by some stream or websocket. 
avro.close();

###Closing

The currently implementation is defined to keep getting input from queueSchema and push. So to close out the Avro object call.

	avro.close();

To run the tests you'll need to install mocha.

npm install mocha -g

Once that is done just run the specified test.

mocha tests/AvroSync.js

#Build and run

Install Node.js. There are various methods to install Node.js that vary from system to system. Information on installing using package managers can be found at: https://github.com/joyent/node/wiki/Installing-Node.js-via-package-manager Other installation options can be found at: http://nodejs.org/download/

Install and build the Avro C++ project found here: https://github.com/apache/avro

The Avro C++ library is dependent on one or more Boost libraries, so you may need to install Boost before compiling Avro. On Ubuntu, installing the package "libboost-all-dev" is known to work, though it may be possible to install with a smaller subset of the Boost libraries.

Specific build instructions for the C++ Avro library may be found in the "PATH_TO_AVRO_CHECKOUT/lang/c++/README" file. However, it seems that currently the documentation there is a little off. The following has been known to work:

Execute the following from within the "PATH_TO_AVRO_CHECKOUT/lang/c++" folder:

./build.sh test

If all of the required dependencies are installed, that should configure and build the Node C++ libs and run the included tests. This should be all that is needed for this step, and you should now have a shiny new shared lib in the "PATH_TO_AVRO_CHECKOUT/lang/c++/build" folder (and a symlink named "libavrocpp.so" pointing to it).

If desired, you can easily create a Debian package (or RPM if its your preferred package manager) using checkinstall by executing the following:

sudo checkinstall \
            --install=no \
            --pkgname="avro-cpp" \
            --pkgrelease="_avro version here_" \
            --maintainer="_maintainer email here_" \
            --addso=yes

Then simply use dpkg to install the generated .deb package.

dpkg -i avro-cpp_VERSION_ARCH.deb

Next, it may be necessary to update the paths in the "binding.gyp" file. Simply edit the file and replace paths in the following lines with appropriate paths:

'include_dirs': ['/usr/local/include'],

'ldflags': ['-Lavrocpp/lib'],
'libraries': ['avrocpp/lib/libavrocpp.so']

For example, if you built the Avro C++ libraries and installed under the prefix "/usr/local", you would update the lines to the following:

'include_dirs': ['/usr/local/include'],

'ldflags': ['-L/usr/local/lib'],
'libraries': ['/usr/local/lib/libavrocpp.so']

If you don't already have them installed, there are several npm packages that are required to build, install and use the library.

The library its self does not require websockets but it is recommended for the async use case using a websocket implementation (https://github.com/Worlize/WebSocket-Node), which can be installed via npm by running the following from the root folder of your avro-nodejs folder:

npm install websocket

To build, you need the node package node-gyp:

sudo npm install -g node-gyp

After you have all of the prerequisite packages installed, you can build avro-nodejs.

node-gyp configure build

Tests under the "tests" subfolder can then be run:

cd tests
node AvroSync.js

Copyright (c) 2013 Gensler ben@metzger.cc

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.