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stream_handlers customizable #32

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e9f2d2c
Allow other handlers and an example using telemetry
IciaCarroBarallobre Oct 2, 2025
3770d03
fixing dialyzer problems
IciaCarroBarallobre Oct 23, 2025
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1 change: 1 addition & 0 deletions examples/index/priv/web/static/index.html
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Expand Up @@ -18,6 +18,7 @@ <h2>Apps</h2>
<li><a href="http://localhost:8093">Chat</a></li>
<li><a href="http://localhost:8094">REST API</a></li>
<li><a href="http://localhost:8095">TODO</a></li>
<li><a href="http://localhost:8096">REST with Telemetry</a></li>
</ul>
</p>

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12 changes: 12 additions & 0 deletions examples/rest_with_telemetry/README.md
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# Kraft REST API with Telemetry Example

This example is about how to build a REST API using the Kraft web framework,
while integrating telemetry monitoring through
[Cowboy Telemetry](https://github.com/beam-telemetry/cowboy_telemetry).

> [!TIP]
> [Cowboy Telemetry](https://github.com/beam-telemetry/cowboy_telemetry) is a
> prerequisite for using
> [opentelemetry_cowboy](https://hexdocs.pm/opentelemetry_cowboy/readme.html),
> a Telemetry handler that translates Cowboy events into OpenTelemetry spans,
> enabling HTTP request/response instrumentation.
1 change: 1 addition & 0 deletions examples/rest_with_telemetry/priv/web/static/assets/scripts/htmx@1.4.1.min.js
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37 changes: 37 additions & 0 deletions ...est_with_telemetry/priv/web/static/assets/scripts/htmx@1.4.1/ext/client-side-templates.js
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htmx.defineExtension('client-side-templates', {
transformResponse : function(text, xhr, elt) {

var mustacheTemplate = htmx.closest(elt, "[mustache-template]");
if (mustacheTemplate) {
var data = JSON.parse(text);
var templateId = mustacheTemplate.getAttribute('mustache-template');
var template = htmx.find("#" + templateId);
if (template) {
return Mustache.render(template.innerHTML, data);
} else {
throw "Unknown mustache template: " + templateId;
}
}

var handlebarsTemplate = htmx.closest(elt, "[handlebars-template]");
if (handlebarsTemplate) {
var data = JSON.parse(text);
var templateName = handlebarsTemplate.getAttribute('handlebars-template');
return Handlebars.partials[templateName](data);
}

var nunjucksTemplate = htmx.closest(elt, "[nunjucks-template]");
if (nunjucksTemplate) {
var data = JSON.parse(text);
var templateName = nunjucksTemplate.getAttribute('nunjucks-template');
var template = htmx.find('#' + templateName);
if (template) {
return nunjucks.renderString(template.innerHTML, data);
} else {
return nunjucks.render(templateName, data);
}
}

return text;
}
});
1 change: 1 addition & 0 deletions examples/rest_with_telemetry/priv/web/static/assets/scripts/mustache@4.2.0.min.js
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57 changes: 57 additions & 0 deletions examples/rest_with_telemetry/priv/web/static/index.html
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<!doctype html>
<html>
<head>
<title>Kraft REST API with Telemetry</title>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<script src="/assets/scripts/htmx@1.4.1.min.js"></script>
<script src="/assets/scripts/htmx@1.4.1/ext/client-side-templates.js"></script>
<script src="/assets/scripts/mustache@4.2.0.min.js"></script>

</head>
<body style="margin: 0; padding: 0;">


<h1>Kraft REST API with Telemetry</h1>

<div style="text-align: left; margin-bottom: 30px;">
<a href="/telemetry.html" style="background-color: #007bff; color: white; margin: 10px; padding: 10px 20px;">
Telemetry Dashboard
</a>
</div>

<div style="text-align: center; " hx-ext="client-side-templates">
<h2>API Testing</h2>

<button hx-get="/api/v1/example/endpoint" hx-target="#content" mustache-template="content-template" >
Click Me (Get request)
</button>

<button hx-get="/api/v1/error">
Click Me (Generate an error for telemetry)
</button>

<div id="content"></div>

<template id="content-template">
<div style="text-align: left; margin-left: 20px;">
<h3>Response</h3>
<dl>
<dt>User</dt>
<dd>{{user}}</dd>

<dt>ID</dt>
<dd>{{id}}</dd>

<dt>Role</dt>
<dd>{{role}}</dd>

<dt>Last Accessed</dt>
<dd>{{access}}</dd>
</dl>
</div>
</template>
</div>

</body>
</html>
80 changes: 80 additions & 0 deletions examples/rest_with_telemetry/priv/web/static/telemetry.html
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<!DOCTYPE html>
<html lang="en">
<head>
<title>Telemetry</title>
<script src="/assets/scripts/htmx@1.4.1.min.js"></script>
<script src="/assets/scripts/htmx@1.4.1/ext/client-side-templates.js"></script>
<script src="/assets/scripts/mustache@4.2.0.min.js"></script>
</head>
<body>
<h1>Kraft REST API with Telemetry</h1>

<a href="/"> &lt; Back to main page</a>

<div hx-ext="client-side-templates" style="padding: 10px 10px 10px 0;">
<button id="clear-btn"
hx-delete="/api/v1/telemetry/events"
hx-swap="none"
hx-confirm="Are you sure you want to clear all events?">
Clear All Events
</button>

<script>
document.body.addEventListener('htmx:afterRequest', function(evt) {
if (evt.detail.elt.id === 'clear-btn') {
document.getElementById('refresh-btn').click();
}
});
</script>

<button id="refresh-btn"
hx-get="/api/v1/telemetry/events"
hx-target="#events"
mustache-template="events-template">
Refresh Events
</button>

<div id="events"></div>

<template id="events-template">
<h2>Events ({{count}})</h2>
<p>Last updated: {{timestamp}}</p>

{{#events}}
<div style="border: 1px solid #ccc; margin: 10px 0; padding: 10px;">
<p><strong>Request ID (Connection PID + Stream ID):</strong> {{request_id}}</p>
<p><strong>Type:</strong> {{event_type}}</p>
<p><strong>Path:</strong> {{method}} {{path}}</p>

{{#measurements}}
<div style="margin-top: 10px; padding: 5px; background-color: #f5f5f5;">
<strong>Measurements:</strong>
{{#duration}}
<p>&bull; <strong>Duration:</strong> {{duration}}&micro;s</p>
{{/duration}}
{{#resp_body_length}}
<p>&bull; <strong>Response Size:</strong> {{resp_body_length}} bytes</p>
{{/resp_body_length}}
</div>
{{/measurements}}

{{#meta}}
<div style="margin-top: 10px; padding: 5px; background-color: #f0f8ff; border-left: 3px solid #007acc;">
<strong>Meta (Raw Telemetry Data):</strong>
<pre style="white-space: pre-wrap; word-wrap: break-word; font-size: 12px; background-color: #f9f9f9; padding: 5px; margin: 5px 0;">
{{meta}}
</pre>
</div>
{{/meta}}

</div>
{{/events}}

{{^events}}
<p>No events captured yet.</p>
<p>Go to <a href="/">main page</a> and click "Click Me" to generate events.</p>
{{/events}}
</template>
</div>
</body>
</html>
7 changes: 7 additions & 0 deletions examples/rest_with_telemetry/rebar.config
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{erl_opts, [debug_info]}.

{deps, [
kraft,
cowboy_telemetry,
telemetry
]}.
18 changes: 18 additions & 0 deletions examples/rest_with_telemetry/src/rest_with_telemetry.app.src
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{application, rest_with_telemetry, [
{description, "A REST API example in Kraft"},
{vsn, "0.1.0"},
{registered, []},
{mod, {rest_with_telemetry, []}},
{applications, [
kernel,
stdlib,
telemetry,
cowboy_telemetry,
kraft
]},
{env, []},
{modules, []},

{licenses, ["Apache 2.0"]},
{links, []}
]}.
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