Lightstreamer SDK for Python Adapters
Project description
A Python library to write Data Adapters and Metadata Adapters for Lightstreamer Server. The adapters will run in a separate process, communicating with the Server through the Adapter Remoting Infrastructure.
Use
Install the package:
$ pip install --pre lightstreamer-adapter
Configure Lightstreamer
Download and install Lightstreamer
Go to the adapters folder of your Lightstreamer Server installation. Create a new folder to deploy the remote adapters in, let’s call it PythonAdapter
Create an adapters.xml file inside the PythonAdapter folder and use the following contents (this is an example configuration, you can modify it to your liking by using the generic template, DOCS-SDKs/adapter_remoting_infrastructure/doc/adapter_conf_template/adapters.xml or DOCS-SDKs/adapter_remoting_infrastructure/doc/adapter_robust_conf_template/adapters.xml, as a reference):
<?xml version="1.0"?> <adapters_conf id=
"PROXY_PYTHON"> <metadata_provider> <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class> <classloader>log-enabled</classloader> <param name="request_reply_port">8003</param> <param name="timeout">36000000</param> </metadata_provider> <data_provider> <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class> <classloader>log-enabled</classloader> <param name="request_reply_port">8001</param> <param name="notify_port">8002</param> <param name="timeout">36000000</param> </data_provider> </adapters_conf>Take note of the ports configured in the adapters.xml file as those are needed to write the remote part of the adapters.
Write the Adapters
Create a new python module, let’s call it adapters.py, where we will put the minimal logic required to write a basic Adapter Set.
Import the sever classes needed to setup the connection to the Lightstreamer server, and the adapter classes to be extended to write your own Remote Adapters:
from lightstreamer_adapter.server import (DataProviderServer, MetadataProviderServer) from lightstreamer_adapter.interfaces.data import DataProvider from lightstreamer_adapter.interfaces.metadata import MetadataProvider
Create a new Remote Data Adapter by subclassing the DataProvider abstract class:
class MyDataAdapter(DataProvider): """This Remote Data Adapter sample class shows a simple implementation of the DataProvider abstract class.""" def __init__(self): # Reference to the provided ItemEventListener instance self._listener = None def issnapshot_available(self, item_name): """Returns True if Snapshot information will be sent for the item_name item before the updates.""" snapshot = False # May be based on the item_name item return snapshot def set_listener(self, event_listener): """Caches the reference to the provided ItemEventListener instance.""" self._listener = event_listener def subscribe(self, item_name): """Invoked to request data for an item. From now on you can start sending real time updates for item_name item, through invocations like the following: self._listener.update(item_name, {'field1': valField1, 'field2': valField2}, False) """ def unsubscribe(self, item_name): """Invoked to end a previous request of data for an item. From now on, you should stop sending updates for item_name item."""
Create a new Remote Metadata Adapter by subclassing the MetadataProvider class, if the latter’s default behaviour does not meet your requirements, and override the methods for which you want to supply a custom implementation:
class MyMetadataAdapter(MetadataProvider): """This Remote Metadata Adapter sample class shows a minimal custom implementation of the notify_user_message method. """ def notify_user_message(self, user, session_id, message): """Invoked to forward a message received by a User""" print("Message {} arrived for user {} in the session {}" .format(user, session_id, message))
Run the adapters, by creating, configuring and starting the server class instances:
if __name__ == "__main__": # The host of the Lightstreamer server, to be changed as required. LS_SERVER_HOST = 'localhost' # Creates a new MetadataProviderServer instance, passing a new # MyMetadataAdpater object and the remote address. metadata_provider_server = MetadataProviderServer(MyMetadataAdapter(), (LS_SERVER_HOST, 8003)) # Starts the server instance. metadata_provider_server.start() # Creates a new DataProviderServer instance, passing a new MyDataAdpater # object and the remote address data_provider_sever = DataProviderServer(MyDataAdapter(), (LS_SERVER_HOST, 8001, 8002)) # Starts the server instance. data_provider_sever.start()
Run
From the command line, execute:
$ python adapters.py
Connect a Client
var lsClient = new LightstreamerClient(LS_SERVER_HOST, "PROXY_PYTHON");
lsClient.connect();
// To be completed with other client side activities, like registration of subscriptions and handling of
// real time updates.
// ...
where LS_SERVER_HOST is the host of the Lightstreamer Server, and "PROXY_PYTHON" is the Adapter Set ID as specified in the adapters.xml file.
API Reference
API Reference is available at http://pythonhosted.org/lightstreamer_adapter.
You can generate it by executing the following command from the doc folder:
$ make html
The generated documentation will be available under the doc\_build\html folder.
See Also
Adapter Remoting Infrastructure Network Protocol Specification
Lightstreamer Chat Demo adapter for Python
Lightstreamer Compatibility Notes
Compatible with Adapter Remoting Infrastructure since 1.7
Release History
1.0.0a1 (2016-04-08)
Initial release
Lightstreamer Compatibility Notes
Compatible with Adapter Remoting Infrastructure since 1.7
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