x/debug/debug.go

// Copyright (c) 2021 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package debug

import (
	"html/template"
	"io"
	"net/http"
	"runtime/debug"

	"go.uber.org/yarpc"
	"go.uber.org/yarpc/internal/introspection"
	"go.uber.org/zap"
)

var (
	// _defaultTmpl is the default template used.
	_defaultTmpl = template.Must(template.New("tmpl").Parse(`
<html>
	<head>
	<title>/debug/yarpc</title>
	<style type="text/css">
		body {
			font-family: "Courier New", Courier, monospace;
		}
		table {
			color:#333333;
			border-width: 1px;
			border-color: #3A3A3A;
			border-collapse: collapse;
		}
		table th {
			border-width: 1px;
			padding: 8px;
			border-style: solid;
			border-color: #3A3A3A;
			background-color: #B3B3B3;
		}
		table td {
			border-width: 1px;
			padding: 8px;
			border-style: solid;
			border-color: #3A3A3A;
			background-color: #ffffff;
		}
		header::after {
			content: "";
			clear: both;
			display: table;
		}
		h1 {
			width: 40%;
			float: left;
			margin: 0;
		}
		div.dependencies {
			width: 60%;
			float: left;
			font-size: small;
			text-align: right;
		}
	</style>
	</head>
	<body>

<header>
<h1>/debug/yarpc</h1>
<div class="dependencies">
	{{range .PackageVersions}}
	<span>{{.Name}}={{.Version}}</span>
	{{end}}
</div>
</header>

{{range .Dispatchers}}
	<hr />
	<h2>Dispatcher "{{.Name}}" <small>({{.ID}})</small></h2>
	<table>
		<tr>
			<th>Procedure</th>
			<th>Encoding</th>
			<th>Signature</th>
			<th>RPC Type</th>
		</tr>
		{{range .Procedures}}
		<tr>
			<td>{{.ProcedureName}}</td>
			<td>{{.Encoding}}</td>
			<td>{{.Signature}}</td>
			<td>{{.RPCType}}</td>
		</tr>
		{{end}}
	</table>
	<h3>Inbounds</h3>
	<table>
		<tr>
			<th>Transport</th>
			<th>Endpoint</th>
			<th>State</th>
		</tr>
		{{range .Inbounds}}
		<tr>
			<td>{{.Transport}}</td>
			<td>{{.Endpoint}}</td>
			<td>{{.State}}</td>
		</tr>
		{{end}}
	</table>
	<h3>Outbounds</h3>
	<table>
		<thead>
		<tr>
			<th>Outbound Key</th>
			<th>Service</th>
			<th>Transport</th>
			<th>RPC Type</th>
			<th>Endpoint</th>
			<th>State</th>
			<th colspan="3">Chooser</th>
		</tr>
		<tr>
			<th></th>
			<th></th>
			<th></th>
			<th></th>
			<th></th>
			<th>Name</th>
			<th>State</th>
			<th>Peers</th>
		</tr>
		</thead>
		<tbody>
		{{range .Outbounds}}
		<tr>
			<td>{{.OutboundKey}}</td>
			<td>{{.Service}}</td>
			<td>{{.Transport}}</td>
			<td>{{.RPCType}}</td>
			<td>{{.Endpoint}}</td>
			<td>{{.State}}</td>
			<td>{{.Chooser.Name}}</td>
			<td>{{.Chooser.State}}</td>
			<td>
				<ul>
				{{range .Chooser.Peers}}
					<li>{{.Identifier}} ({{.State}})</li>
				{{end}}
				</ul>
			</td>
		</tr>
		</tbody>
		{{end}}
	</table>
{{end}}
	</body>
</html>
`))
)

// NewHandler returns a http.HandlerFunc to expose dispatcher status and package versions.
func NewHandler(dispatcher *yarpc.Dispatcher, opts ...Option) http.HandlerFunc {
	return newHandler(dispatcher, opts...).handle
}

type handler struct {
	dispatcher *yarpc.Dispatcher
	logger     *zap.Logger
	tmpl       templateIface
}

func newHandler(dispatcher *yarpc.Dispatcher, options ...Option) *handler {
	opts := applyOptions(options...)
	return &handler{
		dispatcher: dispatcher,
		logger:     opts.logger,
		tmpl:       opts.tmpl,
	}
}

func (h *handler) handle(responseWriter http.ResponseWriter, _ *http.Request) {
	defer func() {
		if r := recover(); r != nil {
			responseWriter.WriteHeader(http.StatusInternalServerError)
			h.logger.Error("Unary handler panicked:", zap.Any("recover", r), zap.ByteString("stacktrace", debug.Stack()))
		}
	}()
	responseWriter.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := h.tmpl.Execute(responseWriter, newTmplData(h.dispatcher.Introspect())); err != nil {
		// TODO: does this work, since we already tried a write?
		responseWriter.WriteHeader(http.StatusInternalServerError)
		h.logger.Error("yarpc/debug: failed executing template", zap.Error(err))
	}
}

type tmplData struct {
	Dispatchers     []introspection.DispatcherStatus
	PackageVersions []introspection.PackageVersion
}

func newTmplData(dispatcherStatus introspection.DispatcherStatus) *tmplData {
	// TODO: Why don't we just use dispatcherStatus as the data directly, it has
	// PackageVersions on it already, do we want to use multiple dispatchers in the future?
	return &tmplData{
		Dispatchers: []introspection.DispatcherStatus{
			dispatcherStatus,
		},
		PackageVersions: yarpc.PackageVersions,
	}
}

// templateIface represents a template created from either the html/template
// or text/template packages.
type templateIface interface {
	Execute(io.Writer, interface{}) error
}