RemoteCommand

class lsst.ts.salobj.topics.RemoteCommand(salinfo, name)

Bases: lsst.ts.salobj.topics.WriteTopic

Issue a specific command topic and wait for acknowldgement.

Parameters:
salinfo : SalInfo

SAL component information

name : str

Command name

Attributes Summary

DataType The type (class) for a message of this topic.
data Internally cached message.
has_data Has data ever been set?
metadata Get topic metadata as a TopicMetadata, if available, else None.
volatile Does this topic have volatile durability?

Methods Summary

basic_close() A synchronous and possibly less thorough version of close.
close() Shut down and release resources.
next_ackcmd(ackcmd[, timeout, wait_done]) Wait for the next acknowledement for the command
put([data, priority]) Output this topic.
set(**kwargs) Create a new self.data and set one or more fields.
set_start([timeout, wait_done]) Create a new self.data, set zero or more fields, and start the command.
start([data, timeout, wait_done]) Start a command.

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)
data

Internally cached message.

Raises:
TypeError

If data is not an instance of DataType

Notes

Do not assume the data will be constant. You can make a copy using copy.copy(data).

has_data

Has data ever been set?

metadata

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

volatile

Does this topic have volatile durability?

Methods Documentation

basic_close()

A synchronous and possibly less thorough version of close.

Intended for exit handlers and constructor error handlers.

close()

Shut down and release resources.

Intended to be called by SalInfo.close(), since that tracks all topics.

next_ackcmd(ackcmd, timeout=3600, wait_done=True)

Wait for the next acknowledement for the command

Parameters:
ackcmd : SalInfo.AckCmdType

The command acknowledgement returned by the previous wait (e.g. from start).

timeout : float, optional

Time limit, in seconds. If None then use DEFAULT_TIMEOUT. This time limit is for the entire command if wait_done is true, else it is for the first acknowledgement after the initial “CMD_ACK”.

wait_done : bool, optional

If True then wait for final command acknowledgement. If False then wait until the next command acknowledgement; if that acknowledgement is not final (the ack code is not in done_ack_codes), then you will almost certainly want to await next_ackcmd again.

Returns:
ackcmd : SalInfo.AckCmdType

Command acknowledgement.

Raises:
salobj.AckError

If the command fails or times out.

RuntimeError

If the command specified by seq_num is unknown or has already finished.

put(data=None, priority=0)

Output this topic.

Parameters:
data : self.DataType or None

New message data to replace self.data, if any.

priority : int, optional

Priority; used to set the priority field of events. Ignored for commands and telemetry.

Raises:
TypeError

If data is not None and not an instance of DataType.

set(**kwargs)

Create a new self.data and set one or more fields.

Parameters:
**kwargs : dict [str, any]

Dict of field name: new value for that field:

  • Any key whose value is None is checked for existence, but the value of the field is not changed.
  • If the field being set is an array then the value must either be an array of the same length or a scalar (which replaces every element of the array).
Returns:
did_change : bool

True if self.data was changed, or if this was the first call to set.

Raises:
AttributeError

If the topic does not have the specified field.

ValueError

If the field cannot be set to the specified value.

Notes

If one or more fields cannot be set, the data may be partially updated.

set_start(timeout=3600, wait_done=True, **kwargs)

Create a new self.data, set zero or more fields, and start the command.

Parameters:
timeout : float, optional

Time limit, in seconds. If None then use DEFAULT_TIMEOUT. This time limit is for the entire command if wait_done is true, else it is for the first acknowledgement after the initial CMD_ACK. If the command is acknowledged with CMD_INPROGRESS then the timeout is extended by the timeout value in the acknowledgement. Thus a slow command will not need a long timeout, so long as the command issues a CMD_INPROGRESS acknowledgement with a reasonable timeout value.

wait_done : bool, optional

If True then wait for final command acknowledgement. If False then wait for the first acknowledgement after the initial “CMD_ACK”; if that acknowledgement is not final (the ack code is not in done_ack_codes), then you will almost certainly want to await next_ackcmd.

**kwargs : dict [str, any]

The remaining keyword arguments are field name = new value for that field. See set for more information about values.

Returns:
ackcmd : SalInfo.AckCmdType

Command acknowledgement.

Raises:
salobj.AckError

If the command fails.

salobj.AckTimeoutError

If the command times out.

TypeError

If data is not None and not an instance of DataType.

start(data=None, timeout=3600, wait_done=True)

Start a command.

Parameters:
data : self.DataType, optional

Command message. If None then send the current self.data.

timeout : float, optional

Time limit, in seconds. If None then use DEFAULT_TIMEOUT. This time limit is for the entire command if wait_done is true, else it is for the first acknowledgement after the initial CMD_ACK. If the command is acknowledged with CMD_INPROGRESS then the timeout is extended by the timeout value in the acknowledgement. Thus a slow command will not need a long timeout, so long as the command issues a CMD_INPROGRESS acknowledgement with a reasonable timeout value.

wait_done : bool, optional

If True then wait for final command acknowledgement. If False then wait for the first acknowledgement after the initial “CMD_ACK”; if that acknowledgement is not final (the ack code is not in done_ack_codes), then you will almost certainly want to await next_ackcmd.

Returns:
ackcmd : SalInfo.AckCmdType

Command acknowledgement.

Raises:
salobj.AckError

If the command fails.

salobj.AckTimeoutError

If the command times out.

RuntimeError

If the salinfo has not started reading.

TypeError

If data is not None and not an instance of DataType.