cf_worker

Cuneiform worker implementation

The Cuneiform worker is a worker implementation for the common runtime environment (CRE). The worker uses the Erlang foreign function interface (Effi) to execute tasks and interacts with the (distributed) filesystem via a Posix interface.

Integration and Build

Adding the Worker to a Project

Although the Cuneiform worker application can be imported also directly from GitHub, we recommend adding a dependency via hex.pm. Here, we show how this can be done using the build tools rebar3 or mix.

rebar3

To integrate the Cuneiform worker application into a rebar3-managed project change the deps entry in your application's rebar.config file to include the tuple {cf_worker, "0.1.8"}.

{deps, [{cf_worker, "0.1.8"}]}.

mix

To integrate effi into a mix-managed project include the following

{:cf_worker, "~> 0.1.8"}

Compiling

Having rebar3 available on your system, compile the project as an Erlang project by entering

rebar3 compile

If you want to drive the project from the command line please compile the project by entering

rebar3 escriptize

Command Line Synopsis

Compiling the Cuneiform client using escriptize creates an Erlang script file cf_worker which allows starting the Cuneiform client via the command line.

To display a help text enter

./cf_worker --help

This will show the command line synopsis, which looks like the following:

Usage: cf_worker [-v] [-h] [-s <suppl_file>] [-c <cre_node>] [-n <n_wrk>]
                 [-w <wrk_dir>] [-r <repo_dir>] [-d <data_dir>]

  -v, --version     Show cf_worker version.
  -h, --help        Show command line options.
  -s, --suppl_file  Supplementary configuration file.
  -c, --cre_node    Erlang node running the CRE application (must be 
                    specified).
  -n, --n_wrk       Number of worker processes to start. 0 means 
                    auto-detect available processors.
  -w, --wrk_dir     Working directory in which workers store temporary 
                    files.
  -r, --repo_dir    Repository directory for intermediate and output data.
  -d, --data_dir    Data directory where input data is located.

To start the worker application from the command line and connect with a running CRE instance enter

./cf_worker -c cre@my_node

Here, we assume that the CRE runs on an Erlang node identified as cre@my_node.

Erlang API

If a CRE instance is already running on the same Erlang node you can start the Cuneiform worker application by calling

cf_worker:start().

Which is exactly the same as calling

application:start( cf_worker ).

Starting Under the Default Supervisor

To start the Cuneiform worker default supervisor under a custom supervision tree enter

CreNode = node().
NWrk    = 4.
WrkDir  = "./_cuneiform/wrk".
RepoDir = "./_cuneiform/repo".
DataDir = "./".

cf_client_sup:start_link( CreNode, NWrk, WrkDir, RepoDir, DataDir ).

This starts a worker supervisor with four workers using WrkDir to store temporal data, RepoDir for intermediate and output data, and DataDir to look up input data. Also, we expect a CRE to be running on the same node.

Starting Directly

The Cuneiform client process can be started directly. There are several ways to do this. The first is to start the process with a function that allows it to locate the CRE:

CreNode = node().
F = fun() -> cre:pid( CreNode ) end.

WrkDir  = "./_cuneiform/wrk".
RepoDir = "./_cuneiform/repo".
DataDir = "./".

{ok, WorkerPid} = cf_worker_process:start_link( F, WrkDir, RepoDir, DataDir ).

Giving a function instead of a plain CRE process identifier has the advantage, that if the CRE crashes, taking the Cuneiform worker with it, the restarted worker instance uses the output of the function, which offers the possibility of locating the CRE under its new process identifier.

If this is too tedious, one can start it giving the CRE process identifier directly:

CrePid = cre:pid( node() ).

WrkDir  = "./_cuneiform/wrk".
RepoDir = "./_cuneiform/repo".
DataDir = "./".

{ok, WorkerPid} = cf_worker_process:start_link( CrePid ).

Both previous direct starting methods do not register the Cuneiform client with any registry service.

System Requirements

• Erlang OTP 19.0 or higher
• Rebar3 3.0.0 or higher

Resources

• joergen7/cre. A common runtime environment (CRE) for distributed workflow languages.
• joergen7/cuneiform. A functional language for large-scale data analysis whose distributed execution environment is implemented on top of the CRE.
• joergen7/effi. Erlang foreign function interface.

Authors

• Jörgen Brandt (@joergen7) joergen.brandt@onlinehome.de

License

Apache 2.0