debug.go

/*
Copyright (c) 2015 VMware, Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package soap

import (
	"fmt"
	"io"
	"net/http"
	"net/http/httputil"
	"sync/atomic"

	"github.com/vmware/govmomi/vim25/debug"
)

var (
	// Trace reads an http request or response from rc and writes to w.
	// The content type (kind) should be one of "xml" or "json".
	Trace = func(rc io.ReadCloser, w io.Writer, kind string) io.ReadCloser {
		return debug.NewTeeReader(rc, w)
	}
)

// debugRoundTrip contains state and logic needed to debug a single round trip.
type debugRoundTrip struct {
	cn uint64      // Client number
	rn uint64      // Request number
	cs []io.Closer // Files that need closing when done
}

func (d *debugRoundTrip) enabled() bool {
	return d != nil
}

func (d *debugRoundTrip) done() {
	for _, c := range d.cs {
		c.Close()
	}
}

func (d *debugRoundTrip) newFile(suffix string) io.WriteCloser {
	return debug.NewFile(fmt.Sprintf("%d-%04d.%s", d.cn, d.rn, suffix))
}

func (d *debugRoundTrip) ext(h http.Header) string {
	const json = "application/json"
	ext := "xml"
	if h.Get("Accept") == json || h.Get("Content-Type") == json {
		ext = "json"
	}
	return ext
}

func (d *debugRoundTrip) debugRequest(req *http.Request) string {
	if d == nil {
		return ""
	}

	// Capture headers
	var wc io.WriteCloser = d.newFile("req.headers")
	b, _ := httputil.DumpRequest(req, false)
	wc.Write(b)
	wc.Close()

	ext := d.ext(req.Header)
	// Capture body
	wc = d.newFile("req." + ext)
	if req.Body != nil {
		req.Body = Trace(req.Body, wc, ext)
	}

	// Delay closing until marked done
	d.cs = append(d.cs, wc)

	return ext
}

func (d *debugRoundTrip) debugResponse(res *http.Response, ext string) {
	if d == nil {
		return
	}

	// Capture headers
	var wc io.WriteCloser = d.newFile("res.headers")
	b, _ := httputil.DumpResponse(res, false)
	wc.Write(b)
	wc.Close()

	// Capture body
	wc = d.newFile("res." + ext)
	res.Body = Trace(res.Body, wc, ext)

	// Delay closing until marked done
	d.cs = append(d.cs, wc)
}

var cn uint64 // Client counter

// debugContainer wraps the debugging state for a single client.
type debugContainer struct {
	cn uint64 // Client number
	rn uint64 // Request counter
}

func newDebug() *debugContainer {
	d := debugContainer{
		cn: atomic.AddUint64(&cn, 1),
		rn: 0,
	}

	if !debug.Enabled() {
		return nil
	}
	return &d
}

func (d *debugContainer) newRoundTrip() *debugRoundTrip {
	if d == nil {
		return nil
	}

	drt := debugRoundTrip{
		cn: d.cn,
		rn: atomic.AddUint64(&d.rn, 1),
	}

	return &drt
}