Adding Triggers and Complete

Triggers define a dependency on 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 whenever the child task 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 the Glossary for more details.

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;

Listing 101 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 tasks, i.e. where tasks 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

Warning

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.