tailscale/prober/http.go

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// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package prober
import (
"bytes"
"context"
"fmt"
"io"
"net/http"
)
const maxHTTPBody = 4 << 20 // MiB
// HTTP returns a Probe that healthchecks an HTTP URL.
//
// The ProbeFunc sends a GET request for url, expects an HTTP 200
// response, and verifies that want is present in the response
// body. If the URL is HTTPS, the probe further checks that the TLS
// certificate is good for at least the next 7 days.
func HTTP(url, wantText string) ProbeFunc {
return func(ctx context.Context) error {
return probeHTTP(ctx, url, []byte(wantText))
}
}
func probeHTTP(ctx context.Context, url string, want []byte) error {
req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
if err != nil {
return fmt.Errorf("constructing request: %w", err)
}
// Get a completely new transport each time, so we don't reuse a
// past connection.
tr := http.DefaultTransport.(*http.Transport).Clone()
defer tr.CloseIdleConnections()
c := &http.Client{
Transport: tr,
}
resp, err := c.Do(req)
if err != nil {
return fmt.Errorf("fetching %q: %w", url, err)
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
return fmt.Errorf("fetching %q: status code %d, want 200", url, resp.StatusCode)
}
bs, err := io.ReadAll(io.LimitReader(resp.Body, maxHTTPBody))
if err != nil {
return fmt.Errorf("reading body of %q: %w", url, err)
}
if !bytes.Contains(bs, want) {
return fmt.Errorf("body of %q does not contain %q", url, want)
}
return nil
}