Graph Procedures

A Graph Procedure is much like a regular Procedure, with the only difference coming in how you structure code in the body. As its mame implies, the body of a Graph Procedure will be structured as a graph of operations. Specifically it is a DAG (directed-acyclic-graph) where each node in the DAG represents some isolated unit of work which may depend on data produced by one or more other nodes and will produce its own resulting data. This structure is inherently parallelizable as Claro can analyze the provided DAG to schedule nodes to run as soon as possible once all of the data depended on by that node is ready. If any two nodes happen to have all of their dependent data ready at the same time, then Claro may schedule those nodes to run concurrently.

In fact, not only does Claro enable concurrency, it actually is able to create the optimal schedule to run your nodes. You don't need to think about scheduling at all, simply encode the data relationships between your operations, and Claro does the rest.

All of this is achieved by scheduling nodes to run cooperatively on a threadpool currently configured to have a single thread per CPU core (as of this writing, this default is the only option, but it will become configurable in the future (i.e. Google Java services default to 50 request threads)). This allows you to trivially achieve significantly better utilization of your available hardware resources than single threaded code, and much more safely and more easily than can generally be achieved with a handcrafted threaded program.

The example below shows syntax vs DAG visualization:

Fig 1:

graph function getWatchlist(userId: UserId) -> future<Watchlist> {
    root recWatchlist <- mergeTopTen(@movies, @shows);
    node movies <- getTopMovies(@profile);
    node shows <- getTopShows(@profile);
    node profile <- getUserFromDB(userId);
}

As you can see clearly in the diagram below, profile must run first but movies and shows may be computed concurrently:

    graph TD
    profile(profile) --> movies
    profile --> shows
    movies(movies) --> recWatchList
    shows(shows) --> recWatchList