Avalanche Dispatcher Library

As in, a lot of SNO(+) coming your way at alarming speed.

The SNO+ network dispatch client library.

Versions

This is the main version of avalanche, which listens for dispatched records using libratzdab and is capable of listening to a CouchDB changes feed.

Other versions, maintained on branches in this repository, include:

• zmq: Client and server libraries for sending ROOT objects around with ZeroMQ PUB/SUB sockets
• zmq-couchdb: zmq features, plus can listen to a CouchDB changes feed

Documentation

Generate doxygen documentation by running

cd src && doxygen Doxyfile

HTML output is located at doc/html/index.html.

Building

To build the default, RAT-enabled libavalanche, you will need a few things in your environment:

$RATZDAB_ROOT  Path to ratzdab (rat-tools/ratzdab)
$ROOTSYS       Path to ROOT installation
$RATROOT       Path to RAT installation

With these set, just run

make

This will create a shared library libavalanche.so which you may link into your application, as well as the ROOT library avalanche_rat.so.

If you wish to disable the RAT features (namely the built-in RAT-ification of CouchDB changes), ignore $RATROOT and run make norat. This produces libavalanche.so and avalanche_root.so.

Source Code

Avalanche is open source software; code is available on github.

Issues

Report any issues at http://github.com/mastbaum/avalanche/issues.

API Overview

avalanche::client

Creating a Client

avalanche::client()

Example:

avalanche::client client;
c.addDispatcher("localhost");
c.addDB("http://localhost:5984", "mydb", doc_object_map);

This will connect to a ZDAB dispatcher running on localhost and to the changes feed of a CouchDB database at http://localhost:5984/mydb.

Talking to CouchDB

The avalanche client always returns a TObject, so when connecting to a database you must give it a functor that will convert CouchDB documents. This is the doc_object_map in the above example.

The functor looks like this:

class myMap : public avalanche::docObjectMap {
    public:
        TObject* operator()(const Json::Value& v) {
            // ... convert and return a TObject ...
        }
};

Then, to use this to decode a changes feed:

myMap map;
client.addDB("http://localhost:5984", "mydb", map);

For SNO+ users, the mapping function is provided. Include avalanche_rat.hpp and use:

avalanche::ratDocObjectMap map;
client.addDB("http://localhost:5984", "mydb", map);

Receiving Objects

void* avalanche::client::recv(bool blocking=false)

Example:

TObject* o = client->recv();
if (o->IsA()->Class() == TH1F::Class()) {
    TH1F* h = dynamic_cast<TH1F*>(o);
    std::cout << "Mean: " << h->GetMean() << std::endl;
}

By default, recv is non-blocking; blocking=true will cause it to wait until data is available before returning.

recv always returns a TObject*, which must be cast appropriately, likely using TObject::IsA().