Middleware

The page_views service matches every URL ('/**') and bumps total in its after hook. The number below reads the live state; every page you visit on this site, including this refresh, adds one.

# main.rat
> service [page_views]
match: '/**'
total: 0

after[req]
    total << total + 1

# any page
> page
<p> This site has been viewed [page_views.total] times.

A before hook runs before the page handler. Assign to redirect or abort to bail out: the page handler never runs and the user sees the alternative response. Pair with match to scope the gate to a subtree.

> service [admin_gate]
match: '/admin/**'

before[req]
    (is not session.user_id)
        redirect << '/login'

# or for an API endpoint:
> service [api_auth]
match: '/api/**'

before[req]
    (is not session.user_id)
        abort << {status: 401, body: 'unauthorized'}

on_start[] runs once when the server boots; on_shutdown[] runs once at SIGINT/SIGTERM (the framework calls http.Server.Shutdown after the hook returns). Use them for warming caches, opening pools, registering metrics, or draining connections. They take no parameters and run only for their side effects.

> service [warmup]
ready: false

on_start[]
    log('booting')
    ready << true

on_shutdown[]
    log('draining connections')

When you don't need URL matching but want a hook on every request (request tracing, structured access logs, request-scoped resources), declare on_request_start[] and on_request_end[]. They fire on every URL regardless of match:.

> service [tracer]

on_request_start[]
    log('begin')

on_request_end[]
    log('end')

match is a glob over the request path. '/**' matches every route; '/api/**' matches every API call; '/admin' matches only the literal path; '/users/*/posts' uses single-segment wildcards. Multiple middlewares can match the same request; they fire in alphabetic-name order for before, and reverse for after.

> service [api_log]
match: '/api/**'
hits: 0

after[req]
    hits << hits + 1
    log(req.method, req.url)

> service [request_log]
match: '/**'

after[req]
    log('served:', req.url)