v3.12.0

Highlights

Built-in Prometheus metrics. One parameter, zero dependencies:

api = responder.API(metrics_route="/metrics")

Request counters (responder_requests_total{method,path,status}) and latency histograms (responder_request_duration_seconds) in Prometheus text format. Labels use route patterns (/users/{id}) so cardinality stays bounded, and errors are recorded with their real status codes.

Server-side sessions. Cookie-payload sessions cap out at ~4KB and can't be revoked. Move the data server-side — only an opaque ID travels in the cookie, and handler code is unchanged:

from responder.ext.sessions import MemorySessionBackend, RedisSessionBackend

api = responder.API(session_backend=RedisSessionBackend(url="redis://localhost"))

Custom backends need just get/set/delete.

Query-parameter validation. params_model completes the Pydantic story:

class SearchParams(BaseModel):
    q: str
    limit: int = 10

@api.route("/search", params_model=SearchParams)
async def search(req, resp):
    params = req.state.validated_params  # coerced & validated

Invalid queries get a 422, repeated keys map to list fields, and the parameters appear in your OpenAPI spec automatically.

resp.render(). resp.render("hello.html", name=name) — one call to render a template as the HTML body.

Full changelog: https://github.com/kennethreitz/responder/blob/main/CHANGELOG.md

PyPI: https://pypi.org/project/responder/3.12.0/