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caddy/modules/caddyhttp/reverseproxy/reverseproxy.go

685 lines
22 KiB
Go

// Copyright 2015 Matthew Holt and The Caddy Authors
//
// 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 reverseproxy
import (
"context"
"encoding/json"
"fmt"
"net"
"net/http"
"regexp"
"strconv"
"strings"
"time"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"github.com/caddyserver/caddy/v2/modules/caddyhttp/headers"
"go.uber.org/zap"
"golang.org/x/net/http/httpguts"
)
func init() {
caddy.RegisterModule(Handler{})
}
// Handler implements a highly configurable and production-ready reverse proxy.
type Handler struct {
TransportRaw json.RawMessage `json:"transport,omitempty"`
CBRaw json.RawMessage `json:"circuit_breaker,omitempty"`
LoadBalancing *LoadBalancing `json:"load_balancing,omitempty"`
HealthChecks *HealthChecks `json:"health_checks,omitempty"`
Upstreams UpstreamPool `json:"upstreams,omitempty"`
FlushInterval caddy.Duration `json:"flush_interval,omitempty"`
Headers *headers.Handler `json:"headers,omitempty"`
Transport http.RoundTripper `json:"-"`
CB CircuitBreaker `json:"-"`
logger *zap.Logger
}
// CaddyModule returns the Caddy module information.
func (Handler) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
Name: "http.handlers.reverse_proxy",
New: func() caddy.Module { return new(Handler) },
}
}
// Provision ensures that h is set up properly before use.
func (h *Handler) Provision(ctx caddy.Context) error {
h.logger = ctx.Logger(h)
// start by loading modules
if h.TransportRaw != nil {
val, err := ctx.LoadModuleInline("protocol", "http.handlers.reverse_proxy.transport", h.TransportRaw)
if err != nil {
return fmt.Errorf("loading transport module: %s", err)
}
h.Transport = val.(http.RoundTripper)
h.TransportRaw = nil // allow GC to deallocate
}
if h.LoadBalancing != nil && h.LoadBalancing.SelectionPolicyRaw != nil {
val, err := ctx.LoadModuleInline("policy",
"http.handlers.reverse_proxy.selection_policies",
h.LoadBalancing.SelectionPolicyRaw)
if err != nil {
return fmt.Errorf("loading load balancing selection module: %s", err)
}
h.LoadBalancing.SelectionPolicy = val.(Selector)
h.LoadBalancing.SelectionPolicyRaw = nil // allow GC to deallocate
}
if h.CBRaw != nil {
val, err := ctx.LoadModuleInline("type", "http.handlers.reverse_proxy.circuit_breakers", h.CBRaw)
if err != nil {
return fmt.Errorf("loading circuit breaker module: %s", err)
}
h.CB = val.(CircuitBreaker)
h.CBRaw = nil // allow GC to deallocate
}
// set up transport
if h.Transport == nil {
t := &HTTPTransport{
KeepAlive: &KeepAlive{
ProbeInterval: caddy.Duration(30 * time.Second),
IdleConnTimeout: caddy.Duration(2 * time.Minute),
MaxIdleConnsPerHost: 32,
},
DialTimeout: caddy.Duration(10 * time.Second),
}
err := t.Provision(ctx)
if err != nil {
return fmt.Errorf("provisioning default transport: %v", err)
}
h.Transport = t
}
// set up load balancing
if h.LoadBalancing == nil {
h.LoadBalancing = new(LoadBalancing)
}
if h.LoadBalancing.SelectionPolicy == nil {
h.LoadBalancing.SelectionPolicy = RandomSelection{}
}
if h.LoadBalancing.TryDuration > 0 && h.LoadBalancing.TryInterval == 0 {
// a non-zero try_duration with a zero try_interval
// will always spin the CPU for try_duration if the
// upstream is local or low-latency; avoid that by
// defaulting to a sane wait period between attempts
h.LoadBalancing.TryInterval = caddy.Duration(250 * time.Millisecond)
}
lbMatcherSets, err := h.LoadBalancing.RetryMatchRaw.Setup(ctx)
if err != nil {
return err
}
h.LoadBalancing.RetryMatch = lbMatcherSets
h.LoadBalancing.RetryMatchRaw = nil // allow GC to deallocate
// if active health checks are enabled, configure them and start a worker
if h.HealthChecks != nil &&
h.HealthChecks.Active != nil &&
(h.HealthChecks.Active.Path != "" || h.HealthChecks.Active.Port != 0) {
h.HealthChecks.Active.logger = h.logger.Named("health_checker.active")
timeout := time.Duration(h.HealthChecks.Active.Timeout)
if timeout == 0 {
timeout = 10 * time.Second
}
h.HealthChecks.Active.stopChan = make(chan struct{})
h.HealthChecks.Active.httpClient = &http.Client{
Timeout: timeout,
Transport: h.Transport,
}
if h.HealthChecks.Active.Interval == 0 {
h.HealthChecks.Active.Interval = caddy.Duration(30 * time.Second)
}
if h.HealthChecks.Active.ExpectBody != "" {
var err error
h.HealthChecks.Active.bodyRegexp, err = regexp.Compile(h.HealthChecks.Active.ExpectBody)
if err != nil {
return fmt.Errorf("expect_body: compiling regular expression: %v", err)
}
}
go h.activeHealthChecker()
}
// set up upstreams
for _, upstream := range h.Upstreams {
// create or get the host representation for this upstream
var host Host = new(upstreamHost)
existingHost, loaded := hosts.LoadOrStore(upstream.Dial, host)
if loaded {
host = existingHost.(Host)
}
upstream.Host = host
// give it the circuit breaker, if any
upstream.cb = h.CB
// if the passive health checker has a non-zero UnhealthyRequestCount
// but the upstream has no MaxRequests set (they are the same thing,
// but the passive health checker is a default value for for upstreams
// without MaxRequests), copy the value into this upstream, since the
// value in the upstream (MaxRequests) is what is used during
// availability checks
if h.HealthChecks != nil && h.HealthChecks.Passive != nil {
h.HealthChecks.Passive.logger = h.logger.Named("health_checker.passive")
if h.HealthChecks.Passive.UnhealthyRequestCount > 0 &&
upstream.MaxRequests == 0 {
upstream.MaxRequests = h.HealthChecks.Passive.UnhealthyRequestCount
}
}
// upstreams need independent access to the passive
// health check policy because passive health checks
// run without access to h.
if h.HealthChecks != nil {
upstream.healthCheckPolicy = h.HealthChecks.Passive
}
}
return nil
}
// Cleanup cleans up the resources made by h during provisioning.
func (h *Handler) Cleanup() error {
// stop the active health checker
if h.HealthChecks != nil &&
h.HealthChecks.Active != nil &&
h.HealthChecks.Active.stopChan != nil {
close(h.HealthChecks.Active.stopChan)
}
// TODO: Close keepalive connections on reload? https://github.com/caddyserver/caddy/pull/2507/files#diff-70219fd88fe3f36834f474ce6537ed26R762
// remove hosts from our config from the pool
for _, upstream := range h.Upstreams {
hosts.Delete(upstream.Dial)
}
return nil
}
func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
// prepare the request for proxying; this is needed only once
err := h.prepareRequest(r)
if err != nil {
return caddyhttp.Error(http.StatusInternalServerError,
fmt.Errorf("preparing request for upstream round-trip: %v", err))
}
// we will need the original headers and Host
// value if header operations are configured
reqHeader := r.Header
reqHost := r.Host
start := time.Now()
var proxyErr error
for {
// choose an available upstream
upstream := h.LoadBalancing.SelectionPolicy.Select(h.Upstreams, r)
if upstream == nil {
if proxyErr == nil {
proxyErr = fmt.Errorf("no upstreams available")
}
if !h.LoadBalancing.tryAgain(start, proxyErr, r) {
break
}
continue
}
// the dial address may vary per-request if placeholders are
// used, so perform those replacements here; the resulting
// DialInfo struct should have valid network address syntax
dialInfo, err := fillDialInfo(upstream, repl)
if err != nil {
return fmt.Errorf("making dial info: %v", err)
}
// attach to the request information about how to dial the upstream;
// this is necessary because the information cannot be sufficiently
// or satisfactorily represented in a URL
ctx := context.WithValue(r.Context(), DialInfoCtxKey, dialInfo)
r = r.WithContext(ctx)
// set placeholders with information about this upstream
repl.Set("http.handlers.reverse_proxy.upstream.address", dialInfo.String())
repl.Set("http.handlers.reverse_proxy.upstream.hostport", dialInfo.Address)
repl.Set("http.handlers.reverse_proxy.upstream.host", dialInfo.Host)
repl.Set("http.handlers.reverse_proxy.upstream.port", dialInfo.Port)
repl.Set("http.handlers.reverse_proxy.upstream.requests", strconv.Itoa(upstream.Host.NumRequests()))
repl.Set("http.handlers.reverse_proxy.upstream.max_requests", strconv.Itoa(upstream.MaxRequests))
repl.Set("http.handlers.reverse_proxy.upstream.fails", strconv.Itoa(upstream.Host.Fails()))
// mutate request headers according to this upstream;
// because we're in a retry loop, we have to copy
// headers (and the r.Host value) from the original
// so that each retry is identical to the first
if h.Headers != nil && h.Headers.Request != nil {
r.Header = make(http.Header)
copyHeader(r.Header, reqHeader)
r.Host = reqHost
h.Headers.Request.ApplyToRequest(r)
}
// proxy the request to that upstream
proxyErr = h.reverseProxy(w, r, dialInfo)
if proxyErr == nil || proxyErr == context.Canceled {
// context.Canceled happens when the downstream client
// cancels the request, which is not our failure
return nil
}
// remember this failure (if enabled)
h.countFailure(upstream)
// if we've tried long enough, break
if !h.LoadBalancing.tryAgain(start, proxyErr, r) {
break
}
}
return caddyhttp.Error(http.StatusBadGateway, proxyErr)
}
// prepareRequest modifies req so that it is ready to be proxied,
// except for directing to a specific upstream. This method mutates
// headers and other necessary properties of the request and should
// be done just once (before proxying) regardless of proxy retries.
// This assumes that no mutations of the request are performed
// by h during or after proxying.
func (h Handler) prepareRequest(req *http.Request) error {
// as a special (but very common) case, if the transport
// is HTTP, then ensure the request has the proper scheme
// because incoming requests by default are lacking it
if req.URL.Scheme == "" {
req.URL.Scheme = "http"
if ht, ok := h.Transport.(*HTTPTransport); ok && ht.TLS != nil {
req.URL.Scheme = "https"
}
}
if req.ContentLength == 0 {
req.Body = nil // Issue golang/go#16036: nil Body for http.Transport retries
}
req.Close = false
// if User-Agent is not set by client, then explicitly
// disable it so it's not set to default value by std lib
if _, ok := req.Header["User-Agent"]; !ok {
req.Header.Set("User-Agent", "")
}
reqUpType := upgradeType(req.Header)
removeConnectionHeaders(req.Header)
// Remove hop-by-hop headers to the backend. Especially
// important is "Connection" because we want a persistent
// connection, regardless of what the client sent to us.
for _, h := range hopHeaders {
hv := req.Header.Get(h)
if hv == "" {
continue
}
if h == "Te" && hv == "trailers" {
// Issue golang/go#21096: tell backend applications that
// care about trailer support that we support
// trailers. (We do, but we don't go out of
// our way to advertise that unless the
// incoming client request thought it was
// worth mentioning)
continue
}
req.Header.Del(h)
}
// After stripping all the hop-by-hop connection headers above, add back any
// necessary for protocol upgrades, such as for websockets.
if reqUpType != "" {
req.Header.Set("Connection", "Upgrade")
req.Header.Set("Upgrade", reqUpType)
}
if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
// If we aren't the first proxy retain prior
// X-Forwarded-For information as a comma+space
// separated list and fold multiple headers into one.
if prior, ok := req.Header["X-Forwarded-For"]; ok {
clientIP = strings.Join(prior, ", ") + ", " + clientIP
}
req.Header.Set("X-Forwarded-For", clientIP)
}
return nil
}
// reverseProxy performs a round-trip to the given backend and processes the response with the client.
// (This method is mostly the beginning of what was borrowed from the net/http/httputil package in the
// Go standard library which was used as the foundation.)
func (h *Handler) reverseProxy(rw http.ResponseWriter, req *http.Request, di DialInfo) error {
di.Upstream.Host.CountRequest(1)
defer di.Upstream.Host.CountRequest(-1)
// point the request to this upstream
h.directRequest(req, di)
// do the round-trip
start := time.Now()
res, err := h.Transport.RoundTrip(req)
latency := time.Since(start)
if err != nil {
return err
}
h.logger.Debug("upstream roundtrip",
zap.Object("request", caddyhttp.LoggableHTTPRequest{Request: req}),
zap.Object("headers", caddyhttp.LoggableHTTPHeader(res.Header)),
zap.Int("status", res.StatusCode),
)
// update circuit breaker on current conditions
if di.Upstream.cb != nil {
di.Upstream.cb.RecordMetric(res.StatusCode, latency)
}
// perform passive health checks (if enabled)
if h.HealthChecks != nil && h.HealthChecks.Passive != nil {
// strike if the status code matches one that is "bad"
for _, badStatus := range h.HealthChecks.Passive.UnhealthyStatus {
if caddyhttp.StatusCodeMatches(res.StatusCode, badStatus) {
h.countFailure(di.Upstream)
}
}
// strike if the roundtrip took too long
if h.HealthChecks.Passive.UnhealthyLatency > 0 &&
latency >= time.Duration(h.HealthChecks.Passive.UnhealthyLatency) {
h.countFailure(di.Upstream)
}
}
// Deal with 101 Switching Protocols responses: (WebSocket, h2c, etc)
if res.StatusCode == http.StatusSwitchingProtocols {
h.handleUpgradeResponse(rw, req, res)
return nil
}
removeConnectionHeaders(res.Header)
for _, h := range hopHeaders {
res.Header.Del(h)
}
copyHeader(rw.Header(), res.Header)
// The "Trailer" header isn't included in the Transport's response,
// at least for *http.Transport. Build it up from Trailer.
announcedTrailers := len(res.Trailer)
if announcedTrailers > 0 {
trailerKeys := make([]string, 0, len(res.Trailer))
for k := range res.Trailer {
trailerKeys = append(trailerKeys, k)
}
rw.Header().Add("Trailer", strings.Join(trailerKeys, ", "))
}
// apply any response header operations
if h.Headers != nil && h.Headers.Response != nil {
if h.Headers.Response.Require == nil ||
h.Headers.Response.Require.Match(res.StatusCode, rw.Header()) {
repl := req.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
h.Headers.Response.ApplyTo(rw.Header(), repl)
}
}
// TODO: there should be an option to return an error if the response
// matches some criteria; would solve https://github.com/caddyserver/caddy/issues/1447
// by allowing the backend to determine whether this server should treat
// a 400+ status code as an error -- but we might need to be careful that
// we do not affect the health status of the backend... still looking into
// that; if we need to avoid that, we should return a particular error type
// that the caller of this function checks for and only applies health
// status changes if the error is not this special type
rw.WriteHeader(res.StatusCode)
err = h.copyResponse(rw, res.Body, h.flushInterval(req, res))
if err != nil {
defer res.Body.Close()
// Since we're streaming the response, if we run into an error all we can do
// is abort the request. Issue golang/go#23643: ReverseProxy should use ErrAbortHandler
// on read error while copying body.
// TODO: Look into whether we want to panic at all in our case...
if !shouldPanicOnCopyError(req) {
// p.logf("suppressing panic for copyResponse error in test; copy error: %v", err)
return err
}
panic(http.ErrAbortHandler)
}
res.Body.Close() // close now, instead of defer, to populate res.Trailer
if len(res.Trailer) > 0 {
// Force chunking if we saw a response trailer.
// This prevents net/http from calculating the length for short
// bodies and adding a Content-Length.
if fl, ok := rw.(http.Flusher); ok {
fl.Flush()
}
}
if len(res.Trailer) == announcedTrailers {
copyHeader(rw.Header(), res.Trailer)
return nil
}
for k, vv := range res.Trailer {
k = http.TrailerPrefix + k
for _, v := range vv {
rw.Header().Add(k, v)
}
}
return nil
}
// tryAgain takes the time that the handler was initially invoked
// as well as any error currently obtained, and the request being
// tried, and returns true if another attempt should be made at
// proxying the request. If true is returned, it has already blocked
// long enough before the next retry (i.e. no more sleeping is
// needed). If false is returned, the handler should stop trying to
// proxy the request.
func (lb LoadBalancing) tryAgain(start time.Time, proxyErr error, req *http.Request) bool {
// if we've tried long enough, break
if time.Since(start) >= time.Duration(lb.TryDuration) {
return false
}
// if the error occurred while dialing (i.e. a connection
// could not even be established to the upstream), then it
// should be safe to retry, since without a connection, no
// HTTP request can be transmitted; but if the error is not
// specifically a dialer error, we need to be careful
if _, ok := proxyErr.(DialError); proxyErr != nil && !ok {
// if the error occurred after a connection was established,
// we have to assume the upstream received the request, and
// retries need to be carefully decided, because some requests
// are not idempotent
if lb.RetryMatch == nil && req.Method != "GET" {
// by default, don't retry requests if they aren't GET
return false
}
if !lb.RetryMatch.AnyMatch(req) {
return false
}
}
// otherwise, wait and try the next available host
time.Sleep(time.Duration(lb.TryInterval))
return true
}
// directRequest modifies only req.URL so that it points to the upstream
// in the given DialInfo. It must modify ONLY the request URL.
func (h Handler) directRequest(req *http.Request, di DialInfo) {
if req.URL.Host == "" {
// we need a host, so set the upstream's host address
reqHost := di.Address
// if the port equates to the scheme, strip the port because
// it's weird to make a request like http://example.com:80/.
if (req.URL.Scheme == "http" && di.Port == "80") ||
(req.URL.Scheme == "https" && di.Port == "443") {
reqHost = di.Host
}
req.URL.Host = reqHost
}
}
// shouldPanicOnCopyError reports whether the reverse proxy should
// panic with http.ErrAbortHandler. This is the right thing to do by
// default, but Go 1.10 and earlier did not, so existing unit tests
// weren't expecting panics. Only panic in our own tests, or when
// running under the HTTP server.
// TODO: I don't know if we want this at all...
func shouldPanicOnCopyError(req *http.Request) bool {
// if inOurTests {
// // Our tests know to handle this panic.
// return true
// }
if req.Context().Value(http.ServerContextKey) != nil {
// We seem to be running under an HTTP server, so
// it'll recover the panic.
return true
}
// Otherwise act like Go 1.10 and earlier to not break
// existing tests.
return false
}
func copyHeader(dst, src http.Header) {
for k, vv := range src {
for _, v := range vv {
dst.Add(k, v)
}
}
}
func cloneHeader(h http.Header) http.Header {
h2 := make(http.Header, len(h))
for k, vv := range h {
vv2 := make([]string, len(vv))
copy(vv2, vv)
h2[k] = vv2
}
return h2
}
func upgradeType(h http.Header) string {
if !httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade") {
return ""
}
return strings.ToLower(h.Get("Upgrade"))
}
func singleJoiningSlash(a, b string) string {
aslash := strings.HasSuffix(a, "/")
bslash := strings.HasPrefix(b, "/")
switch {
case aslash && bslash:
return a + b[1:]
case !aslash && !bslash:
return a + "/" + b
}
return a + b
}
// removeConnectionHeaders removes hop-by-hop headers listed in the "Connection" header of h.
// See RFC 7230, section 6.1
func removeConnectionHeaders(h http.Header) {
if c := h.Get("Connection"); c != "" {
for _, f := range strings.Split(c, ",") {
if f = strings.TrimSpace(f); f != "" {
h.Del(f)
}
}
}
}
// LoadBalancing has parameters related to load balancing.
type LoadBalancing struct {
SelectionPolicyRaw json.RawMessage `json:"selection_policy,omitempty"`
TryDuration caddy.Duration `json:"try_duration,omitempty"`
TryInterval caddy.Duration `json:"try_interval,omitempty"`
RetryMatchRaw caddyhttp.RawMatcherSets `json:"retry_match,omitempty"`
SelectionPolicy Selector `json:"-"`
RetryMatch caddyhttp.MatcherSets `json:"-"`
}
// Selector selects an available upstream from the pool.
type Selector interface {
Select(UpstreamPool, *http.Request) *Upstream
}
// Hop-by-hop headers. These are removed when sent to the backend.
// As of RFC 7230, hop-by-hop headers are required to appear in the
// Connection header field. These are the headers defined by the
// obsoleted RFC 2616 (section 13.5.1) and are used for backward
// compatibility.
var hopHeaders = []string{
"Connection",
"Proxy-Connection", // non-standard but still sent by libcurl and rejected by e.g. google
"Keep-Alive",
"Proxy-Authenticate",
"Proxy-Authorization",
"Te", // canonicalized version of "TE"
"Trailer", // not Trailers per URL above; https://www.rfc-editor.org/errata_search.php?eid=4522
"Transfer-Encoding",
"Upgrade",
}
// DialError is an error that specifically occurs
// in a call to Dial or DialContext.
type DialError struct {
error
}
// TODO: see if we can use this
// var bufPool = sync.Pool{
// New: func() interface{} {
// return new(bytes.Buffer)
// },
// }
// Interface guards
var (
_ caddy.Provisioner = (*Handler)(nil)
_ caddy.CleanerUpper = (*Handler)(nil)
_ caddyhttp.MiddlewareHandler = (*Handler)(nil)
)