# Clock¶

class lsst.ts.watcher.Clock(config)

Monitor the system clock of a SAL component using the heartbeat event.

Set alarm severity WARNING if the absolute value of the clock error is above the configured threshold for min_errors sequential heartbeat events. The clock error is computed as the difference between the time the heartbeat event was sent and received; thus some delay is inevitable.

Parameters: config : types.SimpleNamespace Rule configuration, as validated by the schema.

Notes

The alarm name is f”Clock.{name}:{index}”, where name and index are derived from config.name.

Attributes Summary

 min_errors Number of sequential errors required for a failure name Get the rule name.

Methods Summary

 __call__(topic_callback) Run the rule and return the severity and reason. get_schema() Return a jsonschema to validate configuration, as a dict. is_usable(disabled_sal_components) Return True if rule can be used, despite disabled SAL components. start() Start any background tasks, such as a polling loop. stop() Stop all background tasks.

Attributes Documentation

min_errors = 3

Number of sequential errors required for a failure

name

Get the rule name.

Methods Documentation

__call__(topic_callback)

Run the rule and return the severity and reason.

Parameters: topic_callback : TopicCallback Topic callback wrapper. A tuple of two values: severity: lsst.ts.idl.enums.Watcher.AlarmSeverity The new alarm severity. reason : str Detailed reason for the severity, e.g. a string describing what value is out of range, and what the range is. If severity is NONE then this value is ignored (but still required) and the old reason is retained until the alarm is reset to nominal state.

Notes

You may return NoneNoReason if the alarm states is NONE.

To defer setting the alarm state, start a task that calls self.alarm.set_severity later. For example the heartbeat rule’s __call__ method is called when the heartbeat event is seen, and this restarts a timer and returns NoneNoReason. If the timer finishes, meaning the next heartbeat event was not seen in time, the timer sets alarm severity > NONE.

classmethod get_schema()

Return a jsonschema to validate configuration, as a dict.

Notes

Please provide default values for all fields for which defaults make sense. This makes watcher configuration files easier to write.

If your rule has no configuration then return None.

We recommend that you write the schema as yaml, for compactness, then use yaml.safe_load to convert it to a dict. For example:

schema_yaml = """
$schema: http://json-schema.org/draft-07/schema#$id: https://github.com/lsst-ts/ts_watcher/MyRule.yaml
description: Configuration for MyRule
type: object
properties:
...
required: [...]
"""

is_usable(disabled_sal_components)

Return True if rule can be used, despite disabled SAL components.

The attributes config, name and remote_info_list will all be available when this is called:

Parameters: disabled_sal_components : List of disabled SAL components. Each element is a tuple of: SAL component name (e.g. “ATPtg”) SAL index
start()

Start any background tasks, such as a polling loop.

This is called when the watcher goes into the enabled state.

Notes

Do not assume that start is called before stop; the order depends on the initial state of the Watcher.

Immediate subclasses need not call super().start()

stop()

Do not assume that start is called before stop; the order depends on the initial state of the Watcher.
This base implementation does nothing, so immediate subclasses need not call super().stop().