Dripline v3 Release

Dripline v3 introduces some new features and make a number of changes that should make life easier in building a controls system relative to v2.

Note that some features from project8/dragonfly were imported into dripline-python.

New Features and Changes

• The core features of the Dripline standard are now all implemented in dripline-cpp, and dripline-python wraps and extends the C++ code.

• The C++ code is multithreaded, allowing services to process messages and listen for new messages simultaneously (in both C++ and Python).

• dripline-python is organized to enable easy extension of the dripline namespace with plugins.

• Several classes are imported from project8/dragonfly as official dripline-python implementations.

• dripline-cpp includes executables dl-agent (for sending messages), and dl-mon (for monitoring message traffic).

• dripline-python includes executable dl-serve (for running services).

• Large requests can be split into multiple individual messages.

• An automatic heartbeat (in the form of an alert message) has been added to each service.

• Exceptions raised in Python or thrown in C++ result in reply messages being sent using ThrowReply and throw_reply in Python and C++, respectively.

Moving from Dripline v2 to v3

The message structure and overall API (especially in Python) changed very little, so hopefully the effort to upgrade a system to the new version will be minimal.

That said, the two versions are not compatible, so you cannot run a mixed-version system. It’s possible to have parallel v2 and v3 meshes, though not recommended, even using the same broker. However, the components on one mesh will not be able to talk to the components on the other mesh. You would also need to ensure that endpoint names are unique between the two meshes.

You’ll need to make at least the following changes:

Command Line Interface

Description	Dripline v2 / Dragonfly	Dripline v3
Starting a service	dragonfly serve (dragonfly)	dl-serve
Sending a request	dragonfly [get/set/cmd] (dragonfly)	dl-agent [get/set/cmd]
Monitoring message traffic	dragonfly monitor (dragonfly)	dl-mon

Python Classes

Description	Dripline v2 / Dragonfly	Dripline v3
The aspect of a service that communicates with an instrument	Provider	Service
The main type of service used to interact with instruments	Spimescape	Service
A service that listens on the alerts queue for broadcasts from other services	Gogol	AlertConsumer
An endpoint that logs at regular intervals	Spime	Entity
SCPI communication with an instrument over ethernet	EthernetProvider (dragonfly)	EthernetSCPIService
Endpoints for SCPI communication	SimpleSCPI*Spime, FormatSpime (dragonfly)	SimpleSCPI*Entity, FormatEntity
Communication with a PostgresQL database	PostgresQLInterface (dragonfly)	PostgresQLInterface
Logging to a PostgresQL database	SensorLogger (dragonfly)	PostgresSensorLogger
Example service that stores values in a dictionary	kv_store (dragonfly)	KeyValueStore

Python API

Description	Dripline v2 / Dragonfly	Dripline v3
Sending a reply by raising an exception	raise exceptions.Dripline[ErrorType]('[message]')	raise ThrowReply('error_type', '[message]')