Node configuration

SnowFox nodes are configured through an extensible LUA interface. This is the core set of options and values provided.

The core object

A snow-fox node requres a few options to be set and allows many other to be tuned.

The core object collects all configuration options that relate to the fundamental functioning of a node rather than a specific feature of snow-fox.

This section provides a list of options provided in the official snow-fox distribution. Remember that components can extend these options so check the documentation of any additional or modified component you use.

core.event_manager

As SnowFox is an event-based system with an asynchronous run loop (similar to how node.js works) it needs a way to know if any of its configured sources has received an event.

The event manager is what looks after all the sources and determines when one of them has an event that needs to be handled.

The default value of event_managers.epoll should work for most cases and should only be changed by users that understand the implementation of the event managers in the code.

core.logger

By default SnowFox logs to standard output and standard error. The logging configuration can be changed by creating a new logger with the desired options.

Allowed values for this options are picked from the loggers collection and the options of each logger is documented there.

core.events_from(source)

Register an event source for use by the new configuration. An event source is one of the sources with their configuration.

See the definition of each of the availale of sources for what they do and what options are available.

The connectors object

Connectors are SnowFox way to interface with processes. This means how processes start, stop, restart, etc … Different connectors’ configurations are stored in the connectors object.

See individual connectors for details of the available options.

connectors["local"]

The local connector is the interface to the local host processes. Uses fork and execve to create new processes and signals to interact with them.

Global functions

Not all configuration options can be described with one value or a list of values so components can define extra interfaces to the user by means of LUA functions.

Below is the list of functions that are registered by core components.

Available event_managers

Below is a list of available event manager.

event_managers.epoll

This uses the epoll kernel feature to watch for events on the configured event sources.

Available loggers

Different loggers target different backends. By default SnowFox uses the console logger to output events to stdout and stderr to ensure that early messages reach the user.

The following special values are used to configure the logging level:

• DEBUG
• INFO
• WARNING
• ERROR

loggers.console

Writes DEBUG and INFO messages to standard output and WARNING and ERROR messages to standard error.

loggers.null

Drop all log messages.

Available sources

Sources are the starting point of all activity in SnowFox. Different features either register their own sources or register events with either the ManualSource or the ScheduledSource which are always available.

sources.scheduler

Configure the SchedulerSource.

Events are enqueued with a delay after which the event should be handled. Delays are expressed as multiple of ticks so that speeding up or down instances can be acieved easly. This avoids implementation guessing a delay that does not overload the system and let the user tune delays.

The following options can be passed to configure the source: