VictoriaMetrics/lib/promscrape/client.go
Aliaksandr Valialkin 3e1d7d8489 lib/promscrape: send Accept header similar to Prometheus when scraping targets
This should fix scraping Spring Boot servers, which return incorrect response
unless `Accept: text/plain` request header is set.

See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/608
2020-07-08 19:48:22 +03:00

173 lines
6.3 KiB
Go

package promscrape
import (
"crypto/tls"
"flag"
"fmt"
"strings"
"time"
"github.com/VictoriaMetrics/fasthttp"
"github.com/VictoriaMetrics/metrics"
)
var (
maxScrapeSize = flag.Int("promscrape.maxScrapeSize", 16*1024*1024, "The maximum size of scrape response in bytes to process from Prometheus targets. "+
"Bigger responses are rejected")
disableCompression = flag.Bool("promscrape.disableCompression", false, "Whether to disable sending 'Accept-Encoding: gzip' request headers to all the scrape targets. "+
"This may reduce CPU usage on scrape targets at the cost of higher network bandwidth utilization. "+
"It is possible to set 'disable_compression: true' individually per each 'scrape_config' section in '-promscrape.config' for fine grained control")
disableKeepAlive = flag.Bool("promscrape.disableKeepAlive", false, "Whether to disable HTTP keep-alive connections when scraping all the targets. "+
"This may be useful when targets has no support for HTTP keep-alive connection. "+
"It is possible to set `disable_keepalive: true` individually per each 'scrape_config` section in '-promscrape.config' for fine grained control. "+
"Note that disabling HTTP keep-alive may increase load on both vmagent and scrape targets")
)
type client struct {
hc *fasthttp.HostClient
scrapeURL string
host string
requestURI string
authHeader string
disableCompression bool
disableKeepAlive bool
}
func newClient(sw *ScrapeWork) *client {
var u fasthttp.URI
u.Update(sw.ScrapeURL)
host := string(u.Host())
requestURI := string(u.RequestURI())
isTLS := string(u.Scheme()) == "https"
var tlsCfg *tls.Config
if isTLS {
tlsCfg = sw.AuthConfig.NewTLSConfig()
}
if !strings.Contains(host, ":") {
if !isTLS {
host += ":80"
} else {
host += ":443"
}
}
hc := &fasthttp.HostClient{
Addr: host,
Name: "vm_promscrape",
Dial: statDial,
IsTLS: isTLS,
TLSConfig: tlsCfg,
MaxIdleConnDuration: 2 * sw.ScrapeInterval,
ReadTimeout: sw.ScrapeTimeout,
WriteTimeout: 10 * time.Second,
MaxResponseBodySize: *maxScrapeSize,
MaxIdempotentRequestAttempts: 1,
}
return &client{
hc: hc,
scrapeURL: sw.ScrapeURL,
host: host,
requestURI: requestURI,
authHeader: sw.AuthConfig.Authorization,
disableCompression: sw.DisableCompression,
disableKeepAlive: sw.DisableKeepAlive,
}
}
func (c *client) ReadData(dst []byte) ([]byte, error) {
deadline := time.Now().Add(c.hc.ReadTimeout)
req := fasthttp.AcquireRequest()
req.SetRequestURI(c.requestURI)
req.SetHost(c.host)
// The following `Accept` header has been copied from Prometheus sources.
// See https://github.com/prometheus/prometheus/blob/f9d21f10ecd2a343a381044f131ea4e46381ce09/scrape/scrape.go#L532 .
// This is needed as a workaround for scraping stupid Java-based servers such as Spring Boot.
// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/608 for details.
// Do not bloat the `Accept` header with OpenMetrics shit, since it looks like dead standard now.
req.Header.Set("Accept", "text/plain;version=0.0.4;q=1,*/*;q=0.1")
if !*disableCompression || c.disableCompression {
req.Header.Set("Accept-Encoding", "gzip")
}
if *disableKeepAlive || c.disableKeepAlive {
req.SetConnectionClose()
}
if c.authHeader != "" {
req.Header.Set("Authorization", c.authHeader)
}
resp := fasthttp.AcquireResponse()
err := doRequestWithPossibleRetry(c.hc, req, resp, deadline)
statusCode := resp.StatusCode()
if err == nil && (statusCode == fasthttp.StatusMovedPermanently || statusCode == fasthttp.StatusFound) {
// Allow a single redirect.
// It is expected that the redirect is made on the same host.
// Otherwise it won't work.
if location := resp.Header.Peek("Location"); len(location) > 0 {
req.URI().UpdateBytes(location)
err = c.hc.DoDeadline(req, resp, deadline)
statusCode = resp.StatusCode()
}
}
fasthttp.ReleaseRequest(req)
if err != nil {
fasthttp.ReleaseResponse(resp)
if err == fasthttp.ErrTimeout {
scrapesTimedout.Inc()
return dst, fmt.Errorf("error when scraping %q with timeout %s: %w", c.scrapeURL, c.hc.ReadTimeout, err)
}
if err == fasthttp.ErrBodyTooLarge {
return dst, fmt.Errorf("the response from %q exceeds -promscrape.maxScrapeSize=%d; "+
"either reduce the response size for the target or increase -promscrape.maxScrapeSize", c.scrapeURL, *maxScrapeSize)
}
return dst, fmt.Errorf("error when scraping %q: %w", c.scrapeURL, err)
}
dstLen := len(dst)
if ce := resp.Header.Peek("Content-Encoding"); string(ce) == "gzip" {
var err error
dst, err = fasthttp.AppendGunzipBytes(dst, resp.Body())
if err != nil {
fasthttp.ReleaseResponse(resp)
scrapesGunzipFailed.Inc()
return dst, fmt.Errorf("cannot ungzip response from %q: %w", c.scrapeURL, err)
}
scrapesGunzipped.Inc()
} else {
dst = append(dst, resp.Body()...)
}
if statusCode != fasthttp.StatusOK {
metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_scrapes_total{status_code="%d"}`, statusCode)).Inc()
return dst, fmt.Errorf("unexpected status code returned when scraping %q: %d; expecting %d; response body: %q",
c.scrapeURL, statusCode, fasthttp.StatusOK, dst[dstLen:])
}
scrapesOK.Inc()
fasthttp.ReleaseResponse(resp)
return dst, nil
}
var (
scrapesTimedout = metrics.NewCounter(`vm_promscrape_scrapes_timed_out_total`)
scrapesOK = metrics.NewCounter(`vm_promscrape_scrapes_total{status_code="200"}`)
scrapesGunzipped = metrics.NewCounter(`vm_promscrape_scrapes_gunziped_total`)
scrapesGunzipFailed = metrics.NewCounter(`vm_promscrape_scrapes_gunzip_failed_total`)
)
func doRequestWithPossibleRetry(hc *fasthttp.HostClient, req *fasthttp.Request, resp *fasthttp.Response, deadline time.Time) error {
attempts := 0
again:
// Use DoDeadline instead of Do even if hc.ReadTimeout is already set in order to guarantee the given deadline
// across multiple retries.
err := hc.DoDeadline(req, resp, deadline)
if err == nil {
return nil
}
if err != fasthttp.ErrConnectionClosed {
return err
}
// Retry request if the server closes the keep-alive connection unless deadline exceeds.
attempts++
if attempts > 3 {
return fmt.Errorf("the server closed 3 subsequent connections: %w", err)
}
goto again
}