Activity heartbeating and selective cancelation example.

In this example workflow starts a single activity that can be canceled. Activity execution has three stages s1, s2 and s3. Each activity stage takes some time to execute. Activity execution can be canceled in stages s1 and s3 but not in stage s2. Activity heartbeating provides a detailed history of activity stage execution, which can be considered activity mini-metrics in the Temporal web UI. Consecutive heartbeats sent to the Temporal server are echoed to the terminal.

Workflow execution can be started with start/1 which takes a cancellation stage number as an argument. To skip activity cancelation step, cancelation stage number should be any integer greater than 3.

Example run output for activity cancelation request in stage 2 (HB heartbeats echoed every second):

Elixir

iex(1)> ActivityHeartbeat.start(2)
HB: %{cancel_requested: false, current_stage: :s1, s1: 1}
HB: %{cancel_requested: false, current_stage: :s1, s1: 2}
HB: %{cancel_requested: false, current_stage: :s1, s1: 3}
HB: %{cancel_requested: false, current_stage: :s2, s1: 3, s2: 1}
HB: %{cancel_requested: false, current_stage: :s2, s1: 3, s2: 2}
HB: %{cancel_requested: false, current_stage: :s2, s1: 3, s2: 3}
HB: %{cancel_requested: false, current_stage: :s2, s1: 3, s2: 4}
cancelation: Ignore cancelation in stage s2.
HB: %{cancel_requested: true, current_stage: :s2, s1: 3, s2: 5}
cancelation: Ignore cancelation in stage s2.
HB: %{cancel_requested: true, current_stage: :s3, s1: 3, s2: 5, s3: 1}
cancelation: Cleanup and cancelation in stage s3.
{%{
   started: true,
   request_id: ~c"cluster_1-Elixir.ActivityHeartbeat.Workflow-f7a69412-2537-468e-9a54-12372f2de997",
   workflow_execution: %{
     workflow_id: ~c"Elixir.ActivityHeartbeat.Workflow/f920b769-0446-416c-951a-327931d52e49",
     run_id: "019a91ea-c4d3-7e97-b74a-4f0f81de4441"
   }
 },
 {:completed,
  %{
    result: ["stage s3 cancelation"],
    workflow_task_completed_event_id: 16,
    new_execution_run_id: ""
  }}}

Sample source: lib/activity_heartbeat

Erlang

1> activity_heartbeat:start(2).
HB: #{cancel_requested => false,current_stage => s1,s1 => 1}
HB: #{cancel_requested => false,current_stage => s1,s1 => 2}
HB: #{cancel_requested => false,current_stage => s1,s1 => 3}
HB: #{cancel_requested => false,current_stage => s2,s1 => 3,s2 => 1}
HB: #{cancel_requested => false,current_stage => s2,s1 => 3,s2 => 2}
HB: #{cancel_requested => false,current_stage => s2,s1 => 3,s2 => 3}
HB: #{cancel_requested => false,current_stage => s2,s1 => 3,s2 => 4}
cancelation: Ignore cancelation in stage s2.
HB: #{cancel_requested => true,current_stage => s2,s1 => 3,s2 => 5}
cancelation: Ignore cancelation in stage s2.
HB: #{cancel_requested => true,current_stage => s3,s1 => 3,s2 => 5,s3 => 1}
cancelation: Cleanup and cancelation in stage s3.
{#{started => true,
   request_id =>
       "cluster_1-activity_heartbeat_workflow-88914644-d406-4c9c-9e76-3521d3720539",
   workflow_execution =>
       #{workflow_id =>
             "activity_heartbeat_workflow/d02fa362-9bea-4508-896c-b1ae9d86e56a",
         run_id => <<"019a1fc0-6924-726a-a456-f9999fc9acfb">>}},
 {completed,#{result => ["stage s3 cancelation"],
              workflow_task_completed_event_id => 16,
              new_execution_run_id => <<>>}}}

Sample source: src/activity_heartbeat

REMAINDER: Activity can only be canceled if it has a heartbeat_timeout option set, otherwise workflow execution will fail.