lightstreamer-adapter
Advanced tools
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.
.. _Lightstreamer Server: http://www.lightstreamer.com
Install the package:
.. code-block:: bash
$ pip install lightstreamer-adapter
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, https://lightstreamer.com/docs/ls-server/latest/remote_adapter_conf_template/adapters.xml or https://lightstreamer.com/docs/ls-server/latest/remote_adapter_robust_conf_template/adapters.xml, as a reference):
.. code-block:: xml
<adapters_conf id="PROXY_PYTHON"> <metadata_provider> <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class> log-enabled 8003 36000000 </metadata_provider> <data_provider> <adapter_class>ROBUST_PROXY_FOR_REMOTE_ADAPTER</adapter_class> log-enabled 8001 36000000 </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.
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 server classes needed to setup the connection to the Lightstreamer server, and the adapter classes to be extended to write your own Remote Adapters:
.. code-block:: python
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:
.. code-block:: python
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:
.. code-block:: python
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:
.. code-block:: python
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))
# Starts the server instance.
data_provider_sever.start()
Ensure that the main thread stays alive. This is needed, since Python 3.9, to allow the SDK library to take advantage of the system's ThreadPoolExecutor class. Here we show a simple way to do so:
.. code-block:: python
from threading import Event
.....
shutdown_event = Event() shutdown_event.wait()
From the command line, execute:
.. code-block:: bash
$ python adapters.py
.. code-block:: javascript
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 is available at <https://lightstreamer.com/api/ls-python-adapter/1.3.1/>_.
You can generate it by executing the following command from the doc folder:
.. code-block:: bash
$ make html
The generated documentation will be available under the doc\_build\html folder.
Adapter Remoting Infrastructure Network Protocol Specification_Lightstreamer Chat Demo adapter for Python_.. _Adapter Remoting Infrastructure Network Protocol Specification: https://lightstreamer.com/api/ls-generic-adapter/latest/ARI%20Protocol.pdf .. _Lightstreamer Chat Demo adapter for Python: https://github.com/Lightstreamer/Lightstreamer-example-Chat-adapter-python
Compatible with Adapter Remoting Infrastructure since Server version 7.4.
this tag_.this older tag_... _this tag: https://github.com/Lightstreamer/Lightstreamer-lib-python-adapter/tree/version-1.2.3 .. _this older tag: https://github.com/Lightstreamer/Lightstreamer-lib-python-adapter/tree/version-1.0.0post1-27
.. :changelog:
1.3.1 (2023-12-11) ++++++++++++++++++
Improvements
Lightstreamer Compatibility Notes
1.3.0 (2023-07-17) ++++++++++++++++++
New Features
Introduced the support for a single connection instead of two for the communication of the Remote Data Adapters. In fact, since Server version 7.4, the Proxy Data Adapter can (and should) be configured to use a single connection for the communication. Hence, the "address" argument of init for the DataProviderServer class, which is a tuple, can now have only 2 values (including one port); a tuple with 3-values will now be refused. As a consequence, if an existing Remote Server based on the previous version of this SDK launches a Remote Data Adapter, it cannot be upgraded to this new SDK version seamlessly. The upgrade will require a change in the code to supply a single port for the connection to the Proxy Data Adapter. This, in turn, will require the configuration of a single port on the Proxy Data Adapter, which is only possible with Lightstreamer Server 7.4 or later. However, if a Remote Server only launches Remote Metadata Adapters, the compatibility with Server version 7.3 is kept.
Thoroughly modified the supplied unit tests to implement the single-connection behavior and the new compatibility rules.
Improvements
Revised the supplied unit tests to clarifiy dequeueing from the sockets and expected messages.
Clarified the meaning of a None or missing value for a "userMsg" argument supplied in a CreditsError: an empty string should be sent to the client. Note that, previously, the Server used to send the "null" string as a placeholder. Hence, Adapters relying on this behavior should now supply "null" explicitly.*
Lightstreamer Compatibility Notes
1.2.3 (2023-03-21) ++++++++++++++++++
Improvements
Added handling of runtime exceptions in the internal threads, by submitting them to the exception handlers and extended the default handling of runtime exceptions by always showing the stack trace.
Added a unit test on keepalive packets for the notify connection. Also improved unit tests log to better identify the current test.
Added documentation notes regarding the compatibility with Python 3.9 and later. See "start" in MetadataProviderServer and DataProviderServer.
Bug Fixes
Fixed a race condition which could have caused the RAC message to be sent too late and break the protocol. However, this could only happen when the Proxy Adapter had no credential check configured.
Addressed possible race conditions in the unit tests.
Lightstreamer Compatibility Notes
1.2.2 (2021-08-30) ++++++++++++++++++
Improvements
Introduced full support for Server version 7.2. Now the library can log any message sent by the Proxy Adapter when forcibly closing the connection.
Modified the behavior when incomplete credentials are configured: now they are sent to the Proxy Adapter, whereas previously they were not sent. Note that, if the Proxy Adapter has credentials configured, they cannot be incomplete; hence the Proxy Adapter is expected to refuse the connection in all cases.
Bug Fixes
Lightstreamer Compatibility Notes
1.2.1 (2021-05-25) +++++++++++++++++++
Improvements
Lightstreamer Compatibility Notes
1.2.0 (2020-01-24) +++++++++++++++++++
Improvements
Extended DataProviderServer and MetadataProviderServer (through the Server superclass) with settings of credentials, to be sent to the Proxy Adapter upon each connection. Credential check is an optional configuration of the Proxy Adapter; if not leveraged, the credentials will be ignored.
Modified the handling of the keepalives when connected to a Proxy Adapter (i.e. Adapter Remoting Infrastructure) version 1.9 (corresponding to Server 7.1) or higher: the preferred keepalive interval requested by the Proxy Adapter, when stricter than the configured one, is now obeyed (with a safety minimun of 1 second). Moreover, in that case, the default interval configuration is now 10 seconds instead of
Added full support for ARI Protocol extensions introduced in Adapter Remoting Infrastructure version 1.9 (corresponding to Server 7.1).
Added full support for TLS/SSL encrypted connections the Proxy Adapters.
Added clarifications in the documentation of the exception handlers and fix a few obsolete notes.
Added clarifications in the documentation of MetadataProviderServer and DataProviderServer classes.
Improved code layout as per pylint/pycodestyle outputs.
Remove useless "pass" statement from classes of the interfaces package.
Updated unit tests according to new features
Bug Fixes
Removed useless optional client_principal parameter from the MetadataProvider.notify_user method.
Fixed documentation of the DataProvider class, where "Lightstreamer Kernel" was erroneously referred as "Lightstreamer1".
Fixed broken links in the documentation of the DataProviderServer class.
Lightstreamer Compatibility Notes
1.1.4 (2019-03-29) +++++++++++++++++++
Bug Fixes
Lightstreamer Compatibility Notes
1.1.3 (2019-03-28) +++++++++++++++++++
Bug Fixes
Lightstreamer Compatibility Notes
1.1.2 (2018-02-22) +++++++++++++++++++
Improvements
Bug Fixes
Lightstreamer Compatibility Notes
1.1.1 (2017-12-22) +++++++++++++++++++
Improvements
Moved API documentation to <http://lightstreamer-lib-python-adapter.readthedocs.io/en/latest/>_.
Fixed few source code fragments to make them PEP 8 compliant.
Bug Fixes
Lightstreamer Compatibility Notes
1.1.0 (2017-12-19) +++++++++++++++++++
Improvements
Modified the signature of the notify_mpn_device_access and notify_mpn_device_token_change methods of the MetadataProvider class, to add a session ID argument. Existing Remote Metadata Adapters leveraging notify_mpn_device_access and/or notify_mpn_device_token_change have to be ported to the new signature.
Revised the public constants defined in the MpnPlatformType class. The constants referring to the supported platforms have got new names, whereas the constants for platforms not yet supported have been removed. Existing Remote Metadata Adapters explicitly referring to the constants have to be aligned.
Removed the subclasses of MpnSubscriptionInfo (namely MpnApnsSubscriptionInfo and MpnGcmSubscriptionInfo) that were used by the SDK library to supply the attributes of the MPN subscriptions in notify_mpn_subscription_activation. Now, simple instances of MpnSubscriptionInfo will be supplied and attribute information can be obtained through the new "notification_format" property. See the MPN chapter on the General Concepts document for details on the characteristics of the Notification Format. Existing Remote Metadata Adapters leveraging notify_mpn_subscription_activation and inspecting the supplied MpnSubscriptionInfo have to be ported to the new class contract.
Improved the interface documentation of MPN-related methods.
Clarified in the docs for notifySessionClose which race conditions with other methods can be expected.
Aligned the documentation to comply with current licensing policies.
Lightstreamer Compatibility Notes
1.0.0.post1 (2016-11-22) ++++++++++++++++++++++++
1.0.0 (2016-11-22) +++++++++++++++++++
Improvements
Bug Fixes
Fixed notification of End Of Snaphsot in case of not availability of the snapshot.
Fixed docstrings in modules lightstreamer_adapter/server.py and lightstreamer_adapter/subscription.py.
Fixed unit tests.
Lightstreamer Compatibility Notes
1.0.0b1 (2016-04-15) +++++++++++++++++++++
Bug Fixes
Fixed docstrings.
Fixed typo in some Exceptions' message.
Fixed unit tests.
Lightstreamer Compatibility Notes
1.0.0a2 (2016-04-08) +++++++++++++++++++++
Bug Fixes
Fixed return values in lightstreamer_adapter.interfaces.metadata.MetadataProvider class.
Fixed default handling of I/O related errors.
Fixed docstrings in modules lightstreamer_adapter/data_protocol.py and lightstreamer_adapter/metadata_protocol.py.
Lightstreamer Compatibility Notes
1.0.0a1 (2016-04-08) +++++++++++++++++++++
Initial release
Lightstreamer Compatibility Notes
FAQs
Lightstreamer SDK for Python Adapters
We found that lightstreamer-adapter demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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