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Triggers defines a dependency for a task or family . There can be only one trigger dependency per node , but that can be a complex boolean expression of the status of several nodes. Triggers can not be added to the suite node. A node with a trigger can only be activated when its trigger has expired. A trigger holds the node as long as the trigger’s expression evaluation returns false.

Trigger evaluation occurs when ever the child command communicates with the server. i.e. whenever there is a state change in the suite definition and at least once every 60 seconds. The keywords in trigger expressions are: unknown , suspended , complete , queued , submitted , active , aborted and clear and set for event status. Triggers can also reference Node attributes like event , meter , variable , repeat and generated variables and limits. Triggers can also reference the late flag on a node. Trigger evaluation for node attributes uses integer arithmetic. See Glossary

from ecflow import Defs,Suite,Task,Trigger,Complete
defs = Defs( 
        Suite("s1",
           Task("t1"),
           Task("t2",
             Trigger("t1 == active and t3 == aborted"),
             Complete("t3 == complete")),
           Task("t3")))

The following examples show alternative styles that produce the same definition:

defs = Defs()
s1 = defs.add_suite("s1") 
t1 = s1.add_task("t1")
t2 = s1.add_task("t2")
t2.add_trigger( "t1 == active and t3 == aborted" )
t2.add_complete( "t3 == complete" )
t3 = s1.add_task("t3")
defs = Defs().add(
         Suite("s1").add(
           Task("t1"),
           Task("t2").add(
              Trigger("t1 == active and t3 == aborted"),
              Complete("t3 == complete")),
           Task("t3")))
defs = Defs(Suite("s1"))
defs.s1 += [ Task("t{}".format(i)) for i in range(1,4) ]
defs.s1.t2 += [ Trigger("t1 == active and t3 == aborted"),
                        Complete("t3 == complete") ]

Adding triggers like '<nodepath> == complete' is extremely common. Hence there are a few short cuts;

Short cut for <node> == complete
task = Task("task")
# Using a trigger with a 'list' argument, each string/node element converted to <name> == complete
t = Trigger(["a","b",task])  # because Task("task") does *NOT* have a parent, we will use the name
assert str(t) == "a == complete AND b == complete AND task == complete","Trigger not as expected: " + str(t))

defs = Defs()
task = defs.add_suite("s").add_family("f").add_task("task")
t = Trigger(["a","b",task])      # Task('task') has a parent hierarchy, hence we use full path in trigger expression
assert str(t) == "a == complete AND b == complete AND /s/f/task == complete", "Trigger not as expected: " + str(t))

Chaining Tasks

There are many times where we want to add a chain of task, i,e where task must be run sequentially one after the other. The following examples show different styles of chaining tasks which are identical:

from ecflow import *
defs = Defs(
        Suite("s1",
            Task("t1"),
            Task("t2",Trigger( "t1 == complete" )),
            Task("t3",Trigger( "t2 == complete" )),
            Task("t4",Trigger( "t3 == complete" )))) 
from ecflow import *
defs = Defs() + Suite("s1")
defs.s1 += [ Task("t1"),Task("t2"),
             Task("t3"),Task("t4") ]
defs.s1.t2 += Trigger( ["t1"] ) 
defs.s1.t3 += Trigger( ["t2"] )
defs.s1.t4 += Trigger( ["t3"] )
from ecflow import *
defs = Defs() + Suite("s1")
defs.s1 >> Task("t1") >> Task("t2") >> Task("t3") >> Task("t4")
# >> relies on the leading node to be a Family or Suite

Reverse Chaining

It is also possible to << to reverse chain task.

The following suites are identical:

defs = Defs() + Suite("s1")
defs.s1 += [ Task("t1"),Task("t2"),Task("t3"),Task("t4") ]
defs.s1.t1 += Trigger( "t2 == complete" )
defs.s1.t2 += Trigger( "t3 == complete" )
defs.s1.t3 += Trigger( "t4 == complete" )
defs = Defs() + Suite("s1")
defs.s1 << Task("t1") << Task("t2") << Task("t3") << Task("t4")
# << relies on the leading node to be a Suite or Family

In the examples above we use 'defs.s1.*' to reference a node by name. This is useful in small designs but will produce maintenance issues in large designs IF the node names are changed.

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