3.1.8: A Tale of Two Features

What's Changed

Runner Heartbeats for Flow Run Monitoring

Flow runs can now emit heartbeat events to detect infrastructure failures (crashed machines, evicted containers, etc). When enabled, an automation can automatically mark flows as crashed when heartbeats stop, preventing stuck "zombie" flows in the running state.

Enable with:

• Set PREFECT_RUNNER_HEARTBEAT_FREQUENCY (requires Prefect 3.1.8+)
• Deploy the provided automation script to update flow states when heartbeats stop

from prefect.automations import Automation
from prefect.client.schemas.objects import StateType
from prefect.events.actions import ChangeFlowRunState
from prefect.events.schemas.automations import EventTrigger, Posture

my_automation = Automation(
    name="Crash zombie flows",
    trigger=EventTrigger(
        after={"prefect.flow-run.heartbeat"},
        expect={
            "prefect.flow-run.heartbeat",
            "prefect.flow-run.Completed",
            "prefect.flow-run.Failed",
            "prefect.flow-run.Cancelled",
            "prefect.flow-run.Crashed",
        },
        match={"prefect.resource.id": ["prefect.flow-run.*"]},
        for_each={"prefect.resource.id"},
        posture=Posture.Proactive,
        threshold=1,
        within=90,
    ),
    actions=[
        ChangeFlowRunState(
            state=StateType.CRASHED,
            message="Flow run marked as crashed due to missing heartbeats.",
        )
    ],
)

my_automation.create()

Basic Authentication

We have also added a long requested feature: basic authentication support for the Prefect API. Enable by setting an auth string:

Start a protected server:

PREFECT_SERVER_API_AUTH_STRING="admin:admin" prefect server start

Authenticate client operations:

PREFECT_API_AUTH_STRING="admin:admin" python flow_script.py

Enhancements ➕➕

• Add working implementation of basic auth to server and client by @cicdw in #16408
• Add basic auth UI by @aaazzam in #16411
• Enhance Runner to send heartbeat events for flow runs by @desertaxle in #16410

Integrations & Dependencies 🤝

• add async redis client utils to prefect-redis by @zzstoatzz in #16417

Documentation 📓

• Add state change diagram by @mthatt in #16421

Full Changelog: 3.1.7...3.1.8