`Poll`¶

Refresh a fragment at a bounded interval while it remains in the DOM.


Import	`from hedron import Poll`
Distribution	`hedron`
Backend activity	On every interval
Normal render mode	`RenderMode.FRAGMENT`

Live demo¶

DemoCode

Docs simulation — not a running Hedron server. Interactive demos show a “Simulated HTMX” trace when applicable.

QueuedWaiting for a worker

Auto-polls up to four steps in this docs sim, then stops.

Minimal runnable app.py that reproduces this demo (real Hedron, not the docs simulator):

app.py

import os

from hedron import ComponentRef, Hedron, Page, Poll, html, swap

app = Hedron(
    title="Poll demo",
    security="standard",
    explorer="off",
    session_secret=os.environ.get("HEDRON_SESSION_SECRET", "dev-only"),
)

box = app.region("poll-box")
ref = ComponentRef(
    logical_id="job-42",
    path="/jobs/42",
    target=box.selector,
    swap="innerHTML",
)

_STEPS = [
    ("Queued", "Waiting for a worker"),
    ("Running", "Step 1 of 2"),
    ("Running", "Step 2 of 2"),
    ("Complete", "84 records imported; polling stopped"),
]
_tick = 0


def panel(state: str, detail: str):
    return html.div(
        html.strong(state),
        html.span(detail),
        id=box.id,
        role="status",
    )


@app.page("/")
def home() -> Page:
    return Page(
        Poll(
            ref=ref,
            interval_ms=700,
            target_id=box.id,
            content=panel(*_STEPS[0]),
        ),
        title="Poll",
    )


@app.fragment("/jobs/42", region=box)
def tick():
    global _tick
    state, detail = _STEPS[min(_tick, len(_STEPS) - 1)]
    _tick = min(_tick + 1, len(_STEPS) - 1)
    return swap(panel(state, detail))

Basic use¶

from hedron import Poll, Status

component = Poll(ref=app.ref('job-status', job_id=job.id), interval_ms=2000, content=Status('Queued'))

Compose under Page for full documents, or return from a fragment route for HTMX swaps.

How it works¶

HTMX's every Nms trigger refreshes the component into its collision-free self-target. Repeated instances can share one ComponentRef safely. Stop polling by returning replacement markup without the polling attributes once the terminal state is reached.

This component can initiate or represent a backend interaction. The live documentation intercepts that interaction with JavaScript and shows the same pending, success, or replacement states without making a real request. In an application, keep the URL, authorization, validation, and returned fragment on the server; JavaScript is only progressive enhancement.

Constructor and parameters¶

Poll(*, ref, interval_ms=5000, target_id=None, content=None)

Parameter	Type	Meaning
`ref`	`ComponentRef`	Typed polling endpoint.
`interval_ms`	`int`	Interval, clamped to at least 250 ms.
`target_id`	`str \| None`	Explicit self-target ID; generated collision-free by default.
`content`	`NodeLike \| None`	Initial content.

Composition and backend behavior¶

Keep Poll at the smallest semantic boundary. Fragment routes should return only the replaced region and preserve stable target IDs across success, validation, empty, loading, and error responses.

Mutating flows must use POST, validate CSRF, authorize on the server, re-validate typed input, and return a bounded fragment. GET remains safe and repeatable; native submit should still work without HTMX.

Accessibility¶

Announce only meaningful state transitions; announcing every timer tick overwhelms screen-reader users.

Security¶

Escaping and SafeUrl / TrustedHtml are framework concerns; authorization and data exposure remain application code. Redact secrets before rendering.

Common mistakes¶

Use conservative intervals, private caching where appropriate, and a terminal response that stops server load.
Do not copy docs-preview JavaScript into an application server.

Testing¶

from hedron import RenderMode, render

result = render(component, mode=RenderMode.FRAGMENT)
assert result.html
assert not result.diagnostics

All component demos · Built-in API · Testing

Poll¶