weave-scope/app/router.go

package app

import (
	"compress/gzip"
	"encoding/gob"
	"net/http"
	"net/url"
	"strings"

	"github.com/PuerkitoBio/ghost/handlers"
	"github.com/gorilla/mux"
	"github.com/ugorji/go/codec"
	"golang.org/x/net/context"

	"github.com/weaveworks/scope/common/hostname"
	"github.com/weaveworks/scope/common/xfer"
	"github.com/weaveworks/scope/report"
)

var (
	// Version - set at buildtime.
	Version = "dev"

	// UniqueID - set at runtime.
	UniqueID = "0"
)

// RequestCtxKey is key used for request entry in context
const RequestCtxKey = "request"

// CtxHandlerFunc is a http.HandlerFunc, with added contexts
type CtxHandlerFunc func(context.Context, http.ResponseWriter, *http.Request)

func requestContextDecorator(f CtxHandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		ctx := context.WithValue(context.Background(), RequestCtxKey, r)
		f(ctx, w, r)
	}
}

// URLMatcher uses request.RequestURI (the raw, unparsed request) to attempt
// to match pattern.  It does this as go's URL.Parse method is broken, and
// mistakenly unescapes the Path before parsing it.  This breaks %2F (encoded
// forward slashes) in the paths.
func URLMatcher(pattern string) mux.MatcherFunc {
	return func(r *http.Request, rm *mux.RouteMatch) bool {
		vars, match := matchURL(r, pattern)
		if match {
			rm.Vars = vars
		}
		return match
	}
}

func matchURL(r *http.Request, pattern string) (map[string]string, bool) {
	matchParts := strings.Split(pattern, "/")
	path := strings.SplitN(r.RequestURI, "?", 2)[0]
	parts := strings.Split(path, "/")
	if len(parts) != len(matchParts) {
		return nil, false
	}

	vars := map[string]string{}
	for i, part := range parts {
		unescaped, err := url.QueryUnescape(part)
		if err != nil {
			return nil, false
		}
		match := matchParts[i]
		if strings.HasPrefix(match, "{") && strings.HasSuffix(match, "}") {
			vars[strings.Trim(match, "{}")] = unescaped
		} else if matchParts[i] != unescaped {
			return nil, false
		}
	}
	return vars, true
}

func gzipHandler(h http.HandlerFunc) http.HandlerFunc {
	return handlers.GZIPHandlerFunc(h, nil)
}

// TopologyHandler registers the various topology routes with a http mux.
//
// The returned http.Handler has to be passed directly to http.ListenAndServe,
// and cannot be nested inside another gorrilla.mux.
//
// Routes which should be matched before the topology routes should be added
// to a router and passed in preRoutes.  Routes to be matches after topology
// routes should be added to a router and passed to postRoutes.
func TopologyHandler(c Reporter, preRoutes *mux.Router, postRoutes http.Handler) http.Handler {
	get := preRoutes.Methods("GET").Subrouter()
	get.HandleFunc("/api", gzipHandler(requestContextDecorator(apiHandler)))
	get.HandleFunc("/api/topology", gzipHandler(requestContextDecorator(topologyRegistry.makeTopologyList(c))))
	get.HandleFunc("/api/topology/{topology}",
		gzipHandler(requestContextDecorator(topologyRegistry.captureRenderer(c, handleTopology))))
	get.HandleFunc("/api/topology/{topology}/ws",
		requestContextDecorator(topologyRegistry.captureRenderer(c, handleWs))) // NB not gzip!
	get.HandleFunc("/api/report", gzipHandler(requestContextDecorator(makeRawReportHandler(c))))

	// We pull in the http.DefaultServeMux to get the pprof routes
	preRoutes.PathPrefix("/debug/pprof").Handler(http.DefaultServeMux)

	if postRoutes != nil {
		preRoutes.PathPrefix("/").Handler(postRoutes)
	}

	// We have to handle the node details path manually due to
	// various bugs in gorilla.mux and Go URL parsing.  See #804.
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		vars, match := matchURL(r, "/api/topology/{topology}/{id}")
		if !match {
			preRoutes.ServeHTTP(w, r)
			return
		}

		topologyID := vars["topology"]
		nodeID := vars["id"]
		if nodeID == "ws" {
			preRoutes.ServeHTTP(w, r)
			return
		}

		handler := gzipHandler(requestContextDecorator(topologyRegistry.captureRendererWithoutFilters(
			c, topologyID, handleNode(topologyID, nodeID),
		)))
		handler.ServeHTTP(w, r)
	})
}

// RegisterReportPostHandler registers the handler for report submission
func RegisterReportPostHandler(a Adder, router *mux.Router) {
	post := router.Methods("POST").Subrouter()
	post.HandleFunc("/api/report", requestContextDecorator(func(ctx context.Context, w http.ResponseWriter, r *http.Request) {
		var (
			rpt    report.Report
			reader = r.Body
			err    error
		)
		if strings.Contains(r.Header.Get("Content-Encoding"), "gzip") {
			reader, err = gzip.NewReader(r.Body)
			if err != nil {
				http.Error(w, err.Error(), http.StatusBadRequest)
				return
			}
		}

		decoder := gob.NewDecoder(reader).Decode
		if strings.HasPrefix(r.Header.Get("Content-Type"), "application/json") {
			decoder = codec.NewDecoder(reader, &codec.JsonHandle{}).Decode
		} else if strings.HasPrefix(r.Header.Get("Content-Type"), "application/msgpack") {
			decoder = codec.NewDecoder(reader, &codec.MsgpackHandle{}).Decode
		}

		if err := decoder(&rpt); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		a.Add(ctx, rpt)
		w.WriteHeader(http.StatusOK)
	}))
}

func apiHandler(_ context.Context, w http.ResponseWriter, r *http.Request) {
	respondWith(w, http.StatusOK, xfer.Details{
		ID:       UniqueID,
		Version:  Version,
		Hostname: hostname.Get(),
	})
}