Dev profiler bar

gebweb.useProfilerBar(app) mounts a collapsible profiler toolbar that injects itself into the bottom of every HTML response. It is a development aid: at a glance you see how long a request took, where the time went, how much memory it used, and the basic request facts. It is enabled in non-prod environments and turns into a no-op in production.

Mounting

One call after building the app wires it up:

import gebweb;

class HomeController {
    @Get("/")
    func index(): string {
        return gebweb.html("<html><body><h1>Home</h1></body></html>");
    }
}

let app = gebweb.app([HomeController()]);
gebweb.useProfilerBar(app);
gebweb.serve(app, ":8080");

Open any HTML page and the bar appears pinned to the bottom of the viewport. Click a segment to expand its panel.

When it runs

By default the bar is gated on the environment: it is enabled whenever GEBWEB_ENV is not prod (and GEBWEB_ENV defaults to prod when unset). That means it is off in production with no cost, since mounting registers no middleware at all when disabled.

Override the gate explicitly with the enabled option:

gebweb.useProfilerBar(app, {"enabled": true});   /* force on  */
gebweb.useProfilerBar(app, {"enabled": false});  /* force off */

The bar only ever touches HTML responses. A response whose Content-Type does not start with text/html (JSON, files, streams, redirects) passes through untouched, so it never corrupts an API response or a download.

The panels

The bar shows three panels, each summarised in the bar itself and expandable for detail:

• Time - total request time in milliseconds, plus a table of every recorded timeline entry (label and duration).
• Memory - heap delta for the request and the process peak heap, plus CPU time and GC cycles.
• Request - method, path, status code, and response content-type.

Recording timeline entries

The Time panel's table is fed by timings your handlers record. Call gebweb.recordTiming with the request, a label, and a duration in milliseconds:

class ReportController {
    @Get("/report")
    func report(dict<string, any> request): string {
        gebweb.recordTiming(request, "query", 18);
        gebweb.recordTiming(request, "render", 4);
        return gebweb.html("<html><body>Report</body></html>");
    }
}

Each recorded entry becomes a row in the Time panel. The bar works fine with no recorded timings: the table is simply empty and only the total request time is shown.

Requirements

The profiler bar relies on the language runtime's monotonic clock and the profiler module, so it requires geblang >= 1.14.0.

Reference

• gebweb.useProfilerBar(GebwebApp app, dict<string, any> opts = {}) - mount the bar. opts["enabled"] (bool) overrides the environment gate. Returns the app.
• gebweb.recordTiming(dict<string, any> request, string label, int durationMs) - record one timeline entry for the current request.