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In the previous exercise we saw that the two tasks were running simultaneously.
We would like now to make sure that t2 only runs once t1 is complete.
For this we have to define a trigger

...

  • A family is complete when all its tasks are complete
  • A task will be started if its triggers and the triggers of all its parent families evaluate to true

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A node can only have one trigger expression, but very complex expressions can be built (and keep in mind that the triggers of the parent nodes are also implicit triggers).

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Triggers can be very complex, and ecFlow supports all kinds of conditions
(not, and, or, ...), in addition they can also reference Node attributes like
event, meter, variable, repeat, limits and generated variables. 

Text

Code Block
languagebash
# Definition of the suite test.
suite test
   edit ECF_INCLUDE "$HOME/course"   # replace '$HOME' with the path to your home directory
   edit ECF_HOME    "$HOME/course"
   family f1
     edit SLEEP 20
     task t1
     task t2
         trigger t1 eq complete
   endfamily
endsuite
 


Python

The trigger expression can be checked,  this is especially important when dealing with very large suites and complex triggers.

Code Block
languagepy
title$HOME/course/test.py
import os
from ecflow import Defs,Suite,Family,Task,Edit,Trigger

def create_family_f1():
    return Family("f1",
                Edit(SLEEP=20),
                Task("t1"),
                Task("t2",Trigger("t1 == complete")))
             
print("Creating suite definition")
home = os.path.join(os.getenv("HOME"), "course")
defs = Defs( 
        Suite("test",
            Edit(ECF_INCLUDE=home,ECF_HOME=home),
            create_family_f1()))
print(defs) 

print("check trigger expressions")
check = defs.check()
assert len(check) == 0, check 
 
print("Checking job creation: .ecf -> .job0")  
print(defs.check_job_creation())

print("Saving definition to file 'test.def'")
defs.save_as_defs("test.def")

What to do

  1. Edit the suite definition file to add the trigger.
  2. Replace the suite
    python:   python python3 test.py ;  python python3 client.py
    text:        ecflow_client --suspend=/test ; ecflow_client --replace=/test  test.def
  3. Observe the tasks in ecflow_ui .
  4. See the triggers by selecting t1 or t2.
  5. See the trigger relation by clicking on the trigger tab.
  6. Search any reference to t1 by using the search menu.
  7. Introduce an error in the trigger expression and ensure that this error is trapped. i.e. change trigger to.

    Code Block
    languagepy
    titleCheck trigger expressions
    Trigger("t == complete")  # there is no node with name t, this should be reported as an error


     

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