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caddy/modules/caddyhttp/reverseproxy/healthchecks.go
2023-04-10 20:08:40 +00:00

413 lines
14 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"
"fmt"
"io"
"net"
"net/http"
"net/url"
"regexp"
"runtime/debug"
"strconv"
"strings"
"time"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"go.uber.org/zap"
)
// HealthChecks configures active and passive health checks.
type HealthChecks struct {
// Active health checks run in the background on a timer. To
// minimally enable active health checks, set either path or
// port (or both). Note that active health check status
// (healthy/unhealthy) is stored per-proxy-handler, not
// globally; this allows different handlers to use different
// criteria to decide what defines a healthy backend.
//
// Active health checks do not run for dynamic upstreams.
Active *ActiveHealthChecks `json:"active,omitempty"`
// Passive health checks monitor proxied requests for errors or timeouts.
// To minimally enable passive health checks, specify at least an empty
// config object with fail_duration > 0. Passive health check state is
// shared (stored globally), so a failure from one handler will be counted
// by all handlers; but the tolerances or standards for what defines
// healthy/unhealthy backends is configured per-proxy-handler.
//
// Passive health checks technically do operate on dynamic upstreams,
// but are only effective for very busy proxies where the list of
// upstreams is mostly stable. This is because the shared/global
// state of upstreams is cleaned up when the upstreams are no longer
// used. Since dynamic upstreams are allocated dynamically at each
// request (specifically, each iteration of the proxy loop per request),
// they are also cleaned up after every request. Thus, if there is a
// moment when no requests are actively referring to a particular
// upstream host, the passive health check state will be reset because
// it will be garbage-collected. It is usually better for the dynamic
// upstream module to only return healthy, available backends instead.
Passive *PassiveHealthChecks `json:"passive,omitempty"`
}
// ActiveHealthChecks holds configuration related to active
// health checks (that is, health checks which occur in a
// background goroutine independently).
type ActiveHealthChecks struct {
// DEPRECATED: Use 'uri' instead. This field will be removed. TODO: remove this field
Path string `json:"path,omitempty"`
// The URI (path and query) to use for health checks
URI string `json:"uri,omitempty"`
// The port to use (if different from the upstream's dial
// address) for health checks.
Port int `json:"port,omitempty"`
// HTTP headers to set on health check requests.
Headers http.Header `json:"headers,omitempty"`
// How frequently to perform active health checks (default 30s).
Interval caddy.Duration `json:"interval,omitempty"`
// How long to wait for a response from a backend before
// considering it unhealthy (default 5s).
Timeout caddy.Duration `json:"timeout,omitempty"`
// The maximum response body to download from the backend
// during a health check.
MaxSize int64 `json:"max_size,omitempty"`
// The HTTP status code to expect from a healthy backend.
ExpectStatus int `json:"expect_status,omitempty"`
// A regular expression against which to match the response
// body of a healthy backend.
ExpectBody string `json:"expect_body,omitempty"`
uri *url.URL
httpClient *http.Client
bodyRegexp *regexp.Regexp
logger *zap.Logger
}
// PassiveHealthChecks holds configuration related to passive
// health checks (that is, health checks which occur during
// the normal flow of request proxying).
type PassiveHealthChecks struct {
// How long to remember a failed request to a backend. A duration > 0
// enables passive health checking. Default is 0.
FailDuration caddy.Duration `json:"fail_duration,omitempty"`
// The number of failed requests within the FailDuration window to
// consider a backend as "down". Must be >= 1; default is 1. Requires
// that FailDuration be > 0.
MaxFails int `json:"max_fails,omitempty"`
// Limits the number of simultaneous requests to a backend by
// marking the backend as "down" if it has this many concurrent
// requests or more.
UnhealthyRequestCount int `json:"unhealthy_request_count,omitempty"`
// Count the request as failed if the response comes back with
// one of these status codes.
UnhealthyStatus []int `json:"unhealthy_status,omitempty"`
// Count the request as failed if the response takes at least this
// long to receive.
UnhealthyLatency caddy.Duration `json:"unhealthy_latency,omitempty"`
logger *zap.Logger
}
// CircuitBreaker is a type that can act as an early-warning
// system for the health checker when backends are getting
// overloaded. This interface is still experimental and is
// subject to change.
type CircuitBreaker interface {
OK() bool
RecordMetric(statusCode int, latency time.Duration)
}
// activeHealthChecker runs active health checks on a
// regular basis and blocks until
// h.HealthChecks.Active.stopChan is closed.
func (h *Handler) activeHealthChecker() {
defer func() {
if err := recover(); err != nil {
h.HealthChecks.Active.logger.Error("active health checker panicked",
zap.Any("error", err),
zap.ByteString("stack", debug.Stack()))
}
}()
ticker := time.NewTicker(time.Duration(h.HealthChecks.Active.Interval))
h.doActiveHealthCheckForAllHosts()
for {
select {
case <-ticker.C:
h.doActiveHealthCheckForAllHosts()
case <-h.ctx.Done():
ticker.Stop()
return
}
}
}
// doActiveHealthCheckForAllHosts immediately performs a
// health checks for all upstream hosts configured by h.
func (h *Handler) doActiveHealthCheckForAllHosts() {
for _, upstream := range h.Upstreams {
go func(upstream *Upstream) {
defer func() {
if err := recover(); err != nil {
h.HealthChecks.Active.logger.Error("active health check panicked",
zap.Any("error", err),
zap.ByteString("stack", debug.Stack()))
}
}()
networkAddr, err := caddy.NewReplacer().ReplaceOrErr(upstream.Dial, true, true)
if err != nil {
h.HealthChecks.Active.logger.Error("invalid use of placeholders in dial address for active health checks",
zap.String("address", networkAddr),
zap.Error(err),
)
return
}
addr, err := caddy.ParseNetworkAddress(networkAddr)
if err != nil {
h.HealthChecks.Active.logger.Error("bad network address",
zap.String("address", networkAddr),
zap.Error(err),
)
return
}
if hcp := uint(upstream.activeHealthCheckPort); hcp != 0 {
if addr.IsUnixNetwork() {
addr.Network = "tcp" // I guess we just assume TCP since we are using a port??
}
addr.StartPort, addr.EndPort = hcp, hcp
}
if addr.PortRangeSize() != 1 {
h.HealthChecks.Active.logger.Error("multiple addresses (upstream must map to only one address)",
zap.String("address", networkAddr),
)
return
}
hostAddr := addr.JoinHostPort(0)
dialAddr := hostAddr
if addr.IsUnixNetwork() {
// this will be used as the Host portion of a http.Request URL, and
// paths to socket files would produce an error when creating URL,
// so use a fake Host value instead; unix sockets are usually local
hostAddr = "localhost"
}
err = h.doActiveHealthCheck(DialInfo{Network: addr.Network, Address: dialAddr}, hostAddr, upstream)
if err != nil {
h.HealthChecks.Active.logger.Error("active health check failed",
zap.String("address", hostAddr),
zap.Error(err),
)
}
}(upstream)
}
}
// doActiveHealthCheck performs a health check to upstream which
// can be reached at address hostAddr. The actual address for
// the request will be built according to active health checker
// config. The health status of the host will be updated
// according to whether it passes the health check. An error is
// returned only if the health check fails to occur or if marking
// the host's health status fails.
func (h *Handler) doActiveHealthCheck(dialInfo DialInfo, hostAddr string, upstream *Upstream) error {
// create the URL for the request that acts as a health check
scheme := "http"
if ht, ok := h.Transport.(TLSTransport); ok && ht.TLSEnabled() {
// this is kind of a hacky way to know if we should use HTTPS, but whatever
scheme = "https"
}
u := &url.URL{
Scheme: scheme,
Host: hostAddr,
}
// if we have a provisioned uri, use that, otherwise use
// the deprecated Path option
if h.HealthChecks.Active.uri != nil {
u.Path = h.HealthChecks.Active.uri.Path
u.RawQuery = h.HealthChecks.Active.uri.RawQuery
} else {
u.Path = h.HealthChecks.Active.Path
}
// adjust the port, if configured to be different
if h.HealthChecks.Active.Port != 0 {
portStr := strconv.Itoa(h.HealthChecks.Active.Port)
host, _, err := net.SplitHostPort(hostAddr)
if err != nil {
host = hostAddr
}
u.Host = net.JoinHostPort(host, portStr)
}
// attach dialing information to this request, as well as context values that
// may be expected by handlers of this request
ctx := h.ctx.Context
ctx = context.WithValue(ctx, caddy.ReplacerCtxKey, caddy.NewReplacer())
ctx = context.WithValue(ctx, caddyhttp.VarsCtxKey, map[string]any{
dialInfoVarKey: dialInfo,
})
req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
if err != nil {
return fmt.Errorf("making request: %v", err)
}
ctx = context.WithValue(ctx, caddyhttp.OriginalRequestCtxKey, *req)
req = req.WithContext(ctx)
for key, hdrs := range h.HealthChecks.Active.Headers {
if strings.ToLower(key) == "host" {
req.Host = h.HealthChecks.Active.Headers.Get(key)
} else {
req.Header[key] = hdrs
}
}
markUnhealthy := func() {
// dispatch an event that the host newly became unhealthy
if upstream.setHealthy(false) {
h.events.Emit(h.ctx, "unhealthy", map[string]any{"host": hostAddr})
}
}
// do the request, being careful to tame the response body
resp, err := h.HealthChecks.Active.httpClient.Do(req)
if err != nil {
h.HealthChecks.Active.logger.Info("HTTP request failed",
zap.String("host", hostAddr),
zap.Error(err),
)
markUnhealthy()
return nil
}
var body io.Reader = resp.Body
if h.HealthChecks.Active.MaxSize > 0 {
body = io.LimitReader(body, h.HealthChecks.Active.MaxSize)
}
defer func() {
// drain any remaining body so connection could be re-used
_, _ = io.Copy(io.Discard, body)
resp.Body.Close()
}()
// if status code is outside criteria, mark down
if h.HealthChecks.Active.ExpectStatus > 0 {
if !caddyhttp.StatusCodeMatches(resp.StatusCode, h.HealthChecks.Active.ExpectStatus) {
h.HealthChecks.Active.logger.Info("unexpected status code",
zap.Int("status_code", resp.StatusCode),
zap.String("host", hostAddr),
)
markUnhealthy()
return nil
}
} else if resp.StatusCode < 200 || resp.StatusCode >= 400 {
h.HealthChecks.Active.logger.Info("status code out of tolerances",
zap.Int("status_code", resp.StatusCode),
zap.String("host", hostAddr),
)
markUnhealthy()
return nil
}
// if body does not match regex, mark down
if h.HealthChecks.Active.bodyRegexp != nil {
bodyBytes, err := io.ReadAll(body)
if err != nil {
h.HealthChecks.Active.logger.Info("failed to read response body",
zap.String("host", hostAddr),
zap.Error(err),
)
markUnhealthy()
return nil
}
if !h.HealthChecks.Active.bodyRegexp.Match(bodyBytes) {
h.HealthChecks.Active.logger.Info("response body failed expectations",
zap.String("host", hostAddr),
)
markUnhealthy()
return nil
}
}
// passed health check parameters, so mark as healthy
if upstream.setHealthy(true) {
h.HealthChecks.Active.logger.Info("host is up", zap.String("host", hostAddr))
h.events.Emit(h.ctx, "healthy", map[string]any{"host": hostAddr})
}
return nil
}
// countFailure is used with passive health checks. It
// remembers 1 failure for upstream for the configured
// duration. If passive health checks are disabled or
// failure expiry is 0, this is a no-op.
func (h *Handler) countFailure(upstream *Upstream) {
// only count failures if passive health checking is enabled
// and if failures are configured have a non-zero expiry
if h.HealthChecks == nil || h.HealthChecks.Passive == nil {
return
}
failDuration := time.Duration(h.HealthChecks.Passive.FailDuration)
if failDuration == 0 {
return
}
// count failure immediately
err := upstream.Host.countFail(1)
if err != nil {
h.HealthChecks.Passive.logger.Error("could not count failure",
zap.String("host", upstream.Dial),
zap.Error(err))
return
}
// forget it later
go func(host *Host, failDuration time.Duration) {
defer func() {
if err := recover(); err != nil {
h.HealthChecks.Passive.logger.Error("passive health check failure forgetter panicked",
zap.Any("error", err),
zap.ByteString("stack", debug.Stack()))
}
}()
timer := time.NewTimer(failDuration)
select {
case <-h.ctx.Done():
if !timer.Stop() {
<-timer.C
}
case <-timer.C:
}
err := host.countFail(-1)
if err != nil {
h.HealthChecks.Passive.logger.Error("could not forget failure",
zap.String("host", upstream.Dial),
zap.Error(err))
}
}(upstream.Host, failDuration)
}