Example query parallel handler.

Workflow defined in this example runs tasks in a multiple distinctive workflow execution stages: init, stage_1, stage_2, wait_async, cleanup and finalize. Workflow execution is queried every second with <<"get_progress">> query. When workflow execution is in open state, progress query parallel handler responds with workflow state "open" and current workflow execution stage. When workflow execution is closed, conventional query handle callback function responds with workflow state "closed" and last workflow history event type. Query responses are echoed to the terminal.

Example run:

Elixir

iex(1)> QueryParallelHandler.start()
progress after 0 sec: ["open", "init"]
progress after 1 sec: ["open", "init"]
progress after 2 sec: ["open", "stage_1"]
progress after 3 sec: ["open", "stage_1"]
progress after 4 sec: ["open", "stage_2"]
progress after 5 sec: ["open", "stage_2"]
progress after 6 sec: ["open", "wait_async"]
progress after 7 sec: ["open", "wait_async"]
progress after 8 sec: ["open", "cleanup"]
progress after 9 sec: ["open", "cleanup"]
progress after 10 sec: ["open", "finalize"]
progress after 11 sec: ["open", "finalize"]
progress after 12 sec: ["closed", "EVENT_TYPE_WORKFLOW_EXECUTION_COMPLETED"]
closed WF query: ["closed", "EVENT_TYPE_WORKFLOW_EXECUTION_COMPLETED"]
:ok

Sample source: lib/query_parallel_handler

Erlang

1> query_parallel_handler:start().
progress after 0 sec: ["open",<<"init">>]
progress after 1 sec: ["open",<<"init">>]
progress after 2 sec: ["open",<<"stage_1">>]
progress after 3 sec: ["open",<<"stage_1">>]
progress after 4 sec: ["open",<<"stage_2">>]
progress after 5 sec: ["open",<<"stage_2">>]
progress after 6 sec: ["open",<<"wait_async">>]
progress after 7 sec: ["open",<<"wait_async">>]
progress after 8 sec: ["open",<<"cleanup">>]
progress after 9 sec: ["open",<<"cleanup">>]
progress after 10 sec: ["open",<<"finalize">>]
progress after 11 sec: ["open",<<"finalize">>]
progress after 12 sec: ["closed",
                        <<"EVENT_TYPE_WORKFLOW_EXECUTION_COMPLETED">>]
closed WF query: ["closed",<<"EVENT_TYPE_WORKFLOW_EXECUTION_COMPLETED">>]
ok

Sample source: src/query_parallel_handler

REMAINDER: Temporal query requests are not persisted in the workflow history hence they are nondeterministic and cannot be used in a workflow execution branching. Following example commands will fail workflow execution or behave unexpectedly:

Elixir

await({:query_request, "test_query"}, 10_000)

await_one([{:query_request, "test_query"}, {:marker, :uuid4, :test_marker}])

case await({:query, "test_query"}) do
 {:ok, _} -> start_timer(1_000)
 _ -> start_activity(:echo_activity, [])
end

Erlang

await({query_request, "test_query"}, 10_000)

await_one([{query_request, "test_query"}, {marker, uuid4, test_marker}])

case await({query, "test_query"}) of
 {ok, _} -> start_timer(1_000);
 _ -> start_activity(echo_activity, [])
end