Events

Events are the most basic type of asynchronous notification in TMT when an activity occurs somewhere in the TMT system and other components need to be notified. Each type of event has a unique purpose and unique information, but they all share the same structural features. All events have EventInfo and a ParameterSet.

Type definition for Event can be found here

EventTime

Each event includes its time of creation in UTC format. You can access that eventTime as follows:

Typescript

copysourceconst source = new Prefix('IRIS', 'filter.wheel')
const eventName = new EventName('temperatures')
const event = SystemEvent.make(source, eventName)

// accessing eventTime
const eventTime = event.eventTime

System Event

SystemEvent is the type used to describe the majority of events in the system. An example is a demand that is the output of an algorithm in one component that is used as an input to another. SystemEvent is also used to publish internal state or status values of a component that may be of interest to other components in the system.

Example snippets for creation of System Event

Typescript

copysource//keys
const k1 = intKey('encoder')
const k2 = intKey('speed')
const k3 = stringKey('filter')
const k4 = intKey('notUsed')

//prefixes
const ck1 = Prefix.fromString('wfos.red.filter')
const name1 = new EventName('filterWheel')
const ck3 = Prefix.fromString('iris.imager.filter')
const name3 = new EventName('status')

//parameters
const p1: Parameter<IntKey> = k1.set([22])
const p2: Parameter<IntKey> = k2.set([44])
const p3: Parameter<StringKey> = k3.set(['A', 'B', 'C', 'D'])

//Create SystemEvent using madd
const se1: SystemEvent = SystemEvent.make(ck1, name1).madd([p1, p2])
//Create SystemEvent using make
const se2: SystemEvent = SystemEvent.make(ck3, name3, [p1, p2])
//Create SystemEvent and use add
const se3: SystemEvent = SystemEvent.make(ck3, name3).add(p1).add(p2).add(p3)

//access keys
const k1Exists: Boolean = se1.exists(k1) //true

//access Parameters
const p4: Option<Parameter<IntKey>> = se1.get(k1)

//access values
const v1: Option<number[]> = se1.get(k1)?.values
const v2: Option<number[]> = se2.get(k2)?.values

//remove keys
const se4: SystemEvent = se3.remove(k3)

//add more than one parameters, using madd
const se5: SystemEvent = se4.madd([k3.set(['X', 'Y', 'Z']), k4.set([99, 100])])
const paramSize: number = se5.size()

//update existing key with set
const se6: SystemEvent = se5.add(k2.set([5, 6, 7, 8]))

Observe Event

ObserveEvent are standardized events used to describe the activities within the data acquisition process. These events are typically published by Science Detector Assemblies, which emit ObserveEvents during their exposures to signal the occurrence of specific activities/actions during the acquisition of data.

Example snippets for creation of Observe Event

Typescript

copysource
//keys
const k1 = intKey('readoutsCompleted')
const k2 = intKey('coaddsCompleted')
const k3 = stringKey('fileID')
const k4 = intKey('notUsed')

//prefixes
const ck1 = Prefix.fromString('iris.ifu.detectorAssembly')
const name1 = new EventName('readoutEnd')
const ck3 = Prefix.fromString('wfos.red.detector')
const name3 = new EventName('exposureStarted')

//parameters
const p1: Parameter<IntKey> = k1.set([4])
const p2: Parameter<IntKey> = k2.set([2])
const p3: Parameter<StringKey> = k3.set(['WFOS-RED-0001'])

//Create ObserveEvent using madd
const se1: ObserveEvent = ObserveEvent.make(ck1, name1).madd([p1, p2])
//Create ObserveEvent using apply
const se2: ObserveEvent = ObserveEvent.make(ck3, name3, [p1, p2])
//Create ObserveEvent and use add
const se3: ObserveEvent = ObserveEvent.make(ck3, name3).add(p1).add(p2).add(p3)

//access keys
const k1Exists: Boolean = se1.exists(k1) //true

//access Parameters
const p4: Option<Parameter<IntKey>> = se1.get(k1)

//access values
const v1: Option<number[]> = se1.get(k1)?.values
const v2: Option<number[]> = se2.get(k2)?.values

//remove keys
const se4: ObserveEvent = se3.remove(k3)

Unique Key Constraint

By choice, a ParameterSet in either ObserveEvent or SystemEvent event will be optimized to store only unique keys. When using add or madd methods on events to add new parameters, if the parameter being added has a key which is already present in the paramSet, the already stored parameter will be replaced by the given parameter.

Here are some examples that illustrate this point

Typescript

copysource//keys
const encoderKey = intKey('encoder')
const filterKey = intKey('filter')
const miscKey = intKey('misc')

//prefix
const prefix = Prefix.fromString('wfos.blue.filter')

const name1 = new EventName('filterWheel')

//params
const encParam1 = encoderKey.set([1])
const encParam2 = encoderKey.set([2])

const encParam3 = encoderKey.set([3])
const filterParam1 = filterKey.set([1])
const filterParam2 = filterKey.set([2])

const filterParam3 = filterKey.set([3])

const miscParam1 = miscKey.set([100])
//StatusEvent with duplicate key via constructor
const systemEvent = SystemEvent.make(prefix, name1, [
  encParam1,
  encParam2,
  encParam3,
  filterParam1,
  filterParam2,
  filterParam3
])

//try adding duplicate keys via add + madd
const changedStatusEvent = systemEvent.add(encParam3).madd([filterParam1, filterParam2, filterParam3])
//duplicate keys will not be added. Should contain one Encoder and one Filter key
const uniqueKeys2 = changedStatusEvent.paramSet.map((x) => x.keyName)

//miscKey(unique) will be added; encoderKey(duplicate) will not be added
const finalStatusEvent = systemEvent.madd([miscParam1, encParam1])
//now contains encoderKey, filterKey, miscKey
const uniqueKeys3 = finalStatusEvent.paramSet.map((x) => x.keyName)