healthchecks/templates/docs/measuring_script_run_time.md

# Measuring Script Run Time

 Append `/start` to a ping URL and use it to signal when a job starts.
 After receiving a start signal, Healthchecks.io will show the check as "Started."
 It will store the "start" events and display the job execution times. SITE_NAME
 calculates the job execution times as the time gaps between adjacent "start" and
 "success" events.

## Alerting Logic

SITE_NAME applies an additional alerting rule for jobs that  use the `/start` signal.

If a job sends a "start" signal, but then does not send a "success"
signal within its configured grace time, SITE_NAME will assume the job
has failed. It will mark the job as "down" and send out alerts.

## Usage Example

Below is a code example in Python:

```python
import requests
URL = "PING_URL"


# "/start" kicks off a timer: if the job takes longer than
# the configured grace time, the check will be marked as "down"
try:
    requests.get(URL + "/start", timeout=5)
except requests.exceptions.RequestException:
    # If the network request fails for any reason, we don't want
    # it to prevent the main job from running
    pass


# TODO: run the job here
fib = lambda n: n if n < 2 else fib(n - 1) + fib(n - 2)
print("F(42) = %d" % fib(42))

# Signal success:
requests.get(URL)
```

## Viewing Measured Run Times

When SITE_NAME receives a "start" signal followed by a regular ping or a "fail"
signal, and the two events are less than 24 hours apart,
you will see the time delta displayed in the list of checks. If the two events are
more than 24 hours apart, they are assumed to be unrelated, and the time delta is
not displayed.

![List of checks with durations](IMG_URL/checks_durations.png)

You can also see durations of the previous runs when viewing an individual check:

![Log of received pings with durations](IMG_URL/details_durations.png)