Apama EPL Plug-ins¶

Contains classes used to define EPL plug-ins written in Python that run inside the Apama correlator.

EPL plug-ins must inherit from EPLPluginBase and have methods on them decorated with the EPLAction decorator to declare the EPL type of the methods.

There are also several classes defined to pass custom EPL types from EPL to Python.

Event¶

class apama.eplplugin.Event(type, fields)¶

Bases: tuple

Event is a class containing type and fields.

Create new instance of Event(type, fields)

_asdict()¶: Return a new dict which maps field names to their values.

classmethod _make(iterable)¶: Make a new Event object from a sequence or iterable

_replace(**kwds)¶: Return a new Event object replacing specified fields with new values

fields¶: A dictionary containing key-value pairs of field name and value.

type¶: A string containing the fully-qualified name of this Event instance. For example: apama.tests.myEvent

Location¶

class apama.eplplugin.Location(x1, y1, x2, y2)¶

Bases: tuple

Location class defines a position in Apama using 2 coordinates.

Create new instance of Location(x1, y1, x2, y2)

_asdict()¶: Return a new dict which maps field names to their values.

classmethod _make(iterable)¶: Make a new Location object from a sequence or iterable

_replace(**kwds)¶: Return a new Location object replacing specified fields with new values

x1¶: Float defining the x position of the first coordinate pair.

x2¶: Float defining the x position of the second coordinate pair.

y1¶: Float defining the y position of the first coordinate pair.

y2¶: Float defining the y position of the second coordinate pair.

Context¶

class apama.eplplugin.Context(name, contextId)[source]¶

Bases: object

Context class represents an Apama EPL context.

Parameters

name – The string name of the context.
contextId – The integer id of the context.

getName()[source]¶

Retrieve the name of this context.

Returns: The string name of the context.

str()[source]¶

Stringify the context.

Returns: A string representation of the context, containing the context name.

repr()[source]¶

Stringify this context.

Returns: A string representation of the contexts, containing the context name and ID.

_getContextId()[source]¶

Get the id of this context.

Returns: The integer ID of this context.

Channel¶

class apama.eplplugin.Channel(channel, context)¶

Bases: tuple

Channel class represents an Apama channel.

Create new instance of Channel(channel, context)

_asdict()¶: Return a new dict which maps field names to their values.

classmethod _make(iterable)¶: Make a new Channel object from a sequence or iterable

_replace(**kwds)¶: Return a new Channel object replacing specified fields with new values

channel¶: A string representing the name for the channel.

context¶: A context object for the channel.

Any¶

class apama.eplplugin.Any(type, value)¶

Bases: tuple

Any class representing the any variant type in EPL.

Create new instance of Any(type, value)

_asdict()¶: Return a new dict which maps field names to their values.

classmethod _make(iterable)¶: Make a new Any object from a sequence or iterable

_replace(**kwds)¶: Return a new Any object replacing specified fields with new values

type¶: String name of the EPL type contained in the any, may be None if empty. Uses EPL-format type names, for example: dictionary<string, sequence<integer> >

value¶: Contents of the any. Will be of the equivalent Python type to the EPL type named in type, or None if empty.

Correlator¶

class apama.eplplugin.Correlator[source]¶

Bases: object

Contains static methods to interact with the correlator directly from an EPL plug-in, such as by sending events.

static sendTo(destination, event, type=None)[source]¶

Send an event from Python to a destination within the correlator.

sendTo takes two or three arguments, but can only be invoked with positional arguments, not named arguments. For example:

Correlator.sendTo("channelname", "MyEvent(123, 456)")
Correlator.sendTo(Channel("channelname"), {"i":123, "j":456}, type="MyEvent")
Correlator.sentTo(Correlator.getCurrentContext(), Event("MyEvent", {"i":123, "j":456}))

This method may block if sending to a context with a full queue.

You may not call this method from the plugin module (static) code or from the plugin constructor.

Parameters

destination – Either a string representing a channel name, a Context object or a Channel object containing either a string channel name or a Context object. The event will be sent to the specified context, or any context subscribed to the specified channel. (required)
event – Either a string in Apama event string format; a dictionary of string field names to values (in which case type must be specified); an Event object. (required)
type (str) – The fully-qualified name of an EPL event type. (optional)

static getCurrentContext()[source]¶

Get the current context we are running in.

Returns: A Context object representing the current execution context, or None if called on a background thread.

EPLPluginBase¶

class apama.eplplugin.EPLPluginBase(init)[source]¶

Bases: object

This is the base class which all Python EPL plug-in instances should inherit from, and therefore defines all the ways in which the plug-in can interact with the correlator.

Methods on a Python EPL plug-in class must be decorated with the EPLAction decorator in order to be exposed to EPL.

Parameters: init – An opaque structure which must be passed up from the plug-in constructor verbatim.

getLogger()[source]¶

Get a reference to the system logger.

Returns: A logging.Logger object which can be used to log to the correlator log file.

getConfig()[source]¶

Get the plug-in instance configuration.

Returns: A dictionary with string keys as specified in the configuration file for this plug-in instance.

EPLAction¶

apama.eplplugin.EPLAction(actionsig, actionname=None)[source]¶

EPLAction is the available decorator that can be set on a method to allow access to the method from EPL. For example:

@EPLAction("action<> returns string", actionname="eplaction")

Parameters

actionsig (str) – The EPL action signature used to access the decorated method. Uses the same syntax as declaring action variables, for example: action<integer> returns string.
actionname (str) – The action name to use in EPL to access the decorated method. Optional, defaults to the name of the method in Python.