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]')