BaseTopic¶

class lsst.ts.salobj.topics.BaseTopic(*, salinfo: SalInfo, name: str, sal_prefix: str)¶

Bases: abc.ABC

Base class for topics.

Parameters

salinfoSalInfo: SAL component information
namestr: Topic name, without a “command_” or “logevent_” prefix.
sal_prefixstr: SAL topic prefix: one of “command_”, “logevent_” or “”

Raises

RuntimeError: If the topic cannot be constructed.

Attributes

salinfoSalInfo: The salinfo constructor argument.
namestr: The name constructor argument.
sal_namestr: The topic name used by SAL. For example: “logevent_summaryState”.
loglogging.Logger: A logger.
qos_setsalobj.QosSet: Quality of service set.
volatilebool: Does this topic have volatile durability?
attr_namestr: Name of topic attribute in Controller and Remote. For example: “evt_summaryState”.
rev_codestr: Revision hash code for the topic. This code changes whenever the schema for the topic changes, and it is part of the DDS topic name. For example: “90255bf1”
dds_namestr: Name of topic seen by DDS. For example: “Test_logevent_summaryState_90255bf1”.

Attributes Summary

`DataType`	The type (class) for a message of this topic.
`metadata`	Get topic metadata as a `TopicMetadata`, if available,else None.
`volatile`	Does this topic have volatile durability?

Attributes Documentation

DataType¶

The type (class) for a message of this topic.

When you read or write a message for this topic you are reading or writing an instance of DataType.

Notes

The preferred way to write a message for a topic is:

RemoteCommand.set_start to start a command.
CommandEvent.set_put to write an event.
CommandTelemetry.set_put to write a telemetry message.

However, it is also possible to use DataType to create a message, then write, it as separate operations. For example, assuming we have a Remote for SAL component “Test”:

# The preferred way to issue a command:
await = remote.cmd_wait.set_put(duration=2, timeout=5)

# But an alternative is to first create the command,
# then send it, as two separate operations:
message = remote.cmd_wait.DataType(duration=2)
await remote.cmd_wait.start(message, timeout=5)

# Or, even more verbosely:
message = remote.cmd_wait.DataType()
message.duration = 2
await remote.cmd_wait.start(message, timeout=5)

metadata¶: Get topic metadata as a TopicMetadata, if available,else None.

volatile¶: Does this topic have volatile durability?

Navigation

BaseTopic¶