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Merge pull request #482 from prometheus/beorn7/http 

Use gzip from a pool and stream while encoding metrics
This commit is contained in:
Björn Rabenstein 2018-10-22 13:47:59 +02:00 committed by GitHub
parent 1cafe34db7 fb0f7fe8c2
commit 16f375c74d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 110 additions and 111 deletions
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105
prometheus/http.go
View File

@ -15,9 +15,7 @@ package prometheus
import (
"bufio"
"bytes"
"compress/gzip"
"fmt"
"io"
"net"
"net/http"
@ -41,19 +39,10 @@ const (
acceptEncodingHeader = "Accept-Encoding"
)
var bufPool sync.Pool
func getBuf() *bytes.Buffer {
buf := bufPool.Get()
if buf == nil {
return &bytes.Buffer{}
}
return buf.(*bytes.Buffer)
}
func giveBuf(buf *bytes.Buffer) {
buf.Reset()
bufPool.Put(buf)
var gzipPool = sync.Pool{
New: func() interface{} {
return gzip.NewWriter(nil)
},
}
// Handler returns an HTTP handler for the DefaultGatherer. It is
@ -71,58 +60,40 @@ func Handler() http.Handler {
// Deprecated: Use promhttp.HandlerFor(DefaultGatherer, promhttp.HandlerOpts{})
// instead. See there for further documentation.
func UninstrumentedHandler() http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
return http.HandlerFunc(func(rsp http.ResponseWriter, req *http.Request) {
mfs, err := DefaultGatherer.Gather()
if err != nil {
http.Error(w, "An error has occurred during metrics collection:\n\n"+err.Error(), http.StatusInternalServerError)
httpError(rsp, err)
return
}
contentType := expfmt.Negotiate(req.Header)
buf := getBuf()
defer giveBuf(buf)
writer, encoding := decorateWriter(req, buf)
enc := expfmt.NewEncoder(writer, contentType)
var lastErr error
header := rsp.Header()
header.Set(contentTypeHeader, string(contentType))
w := io.Writer(rsp)
if gzipAccepted(req.Header) {
header.Set(contentEncodingHeader, "gzip")
gz := gzipPool.Get().(*gzip.Writer)
defer gzipPool.Put(gz)
gz.Reset(w)
defer gz.Close()
w = gz
}
enc := expfmt.NewEncoder(w, contentType)
for _, mf := range mfs {
if err := enc.Encode(mf); err != nil {
lastErr = err
http.Error(w, "An error has occurred during metrics encoding:\n\n"+err.Error(), http.StatusInternalServerError)
httpError(rsp, err)
return
}
}
if closer, ok := writer.(io.Closer); ok {
closer.Close()
}
if lastErr != nil && buf.Len() == 0 {
http.Error(w, "No metrics encoded, last error:\n\n"+lastErr.Error(), http.StatusInternalServerError)
return
}
header := w.Header()
header.Set(contentTypeHeader, string(contentType))
header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
if encoding != "" {
header.Set(contentEncodingHeader, encoding)
}
w.Write(buf.Bytes())
})
}
// decorateWriter wraps a writer to handle gzip compression if requested. It
// returns the decorated writer and the appropriate "Content-Encoding" header
// (which is empty if no compression is enabled).
func decorateWriter(request *http.Request, writer io.Writer) (io.Writer, string) {
header := request.Header.Get(acceptEncodingHeader)
parts := strings.Split(header, ",")
for _, part := range parts {
part = strings.TrimSpace(part)
if part == "gzip" || strings.HasPrefix(part, "gzip;") {
return gzip.NewWriter(writer), "gzip"
}
}
return writer, ""
}
var instLabels = []string{"method", "code"}
type nower interface {
@ -503,3 +474,31 @@ func sanitizeCode(s int) string {
return strconv.Itoa(s)
}
}
// gzipAccepted returns whether the client will accept gzip-encoded content.
func gzipAccepted(header http.Header) bool {
a := header.Get(acceptEncodingHeader)
parts := strings.Split(a, ",")
for _, part := range parts {
part = strings.TrimSpace(part)
if part == "gzip" || strings.HasPrefix(part, "gzip;") {
return true
}
}
return false
}
// httpError removes any content-encoding header and then calls http.Error with
// the provided error and http.StatusInternalServerErrer. Error contents is
// supposed to be uncompressed plain text. However, same as with a plain
// http.Error, any header settings will be void if the header has already been
// sent. The error message will still be written to the writer, but it will
// probably be of limited use.
func httpError(rsp http.ResponseWriter, err error) {
rsp.Header().Del(contentEncodingHeader)
http.Error(
rsp,
"An error has occurred while serving metrics:\n\n"+err.Error(),
http.StatusInternalServerError,
)
}

104
prometheus/promhttp/http.go
View File

@ -32,7 +32,6 @@
package promhttp
import (
"bytes"
"compress/gzip"
"fmt"
"io"
@ -53,19 +52,10 @@ const (
acceptEncodingHeader = "Accept-Encoding"
)
var bufPool sync.Pool
func getBuf() *bytes.Buffer {
buf := bufPool.Get()
if buf == nil {
return &bytes.Buffer{}
}
return buf.(*bytes.Buffer)
}
func giveBuf(buf *bytes.Buffer) {
buf.Reset()
bufPool.Put(buf)
var gzipPool = sync.Pool{
New: func() interface{} {
return gzip.NewWriter(nil)
},
}
// Handler returns an http.Handler for the prometheus.DefaultGatherer, using
@ -100,19 +90,18 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
inFlightSem = make(chan struct{}, opts.MaxRequestsInFlight)
}
h := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
h := http.HandlerFunc(func(rsp http.ResponseWriter, req *http.Request) {
if inFlightSem != nil {
select {
case inFlightSem <- struct{}{}: // All good, carry on.
defer func() { <-inFlightSem }()
default:
http.Error(w, fmt.Sprintf(
http.Error(rsp, fmt.Sprintf(
"Limit of concurrent requests reached (%d), try again later.", opts.MaxRequestsInFlight,
), http.StatusServiceUnavailable)
return
}
}
mfs, err := reg.Gather()
if err != nil {
if opts.ErrorLog != nil {
@ -123,26 +112,40 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
panic(err)
case ContinueOnError:
if len(mfs) == 0 {
http.Error(w, "No metrics gathered, last error:\n\n"+err.Error(), http.StatusInternalServerError)
// Still report the error if no metrics have been gathered.
httpError(rsp, err)
return
}
case HTTPErrorOnError:
http.Error(w, "An error has occurred during metrics gathering:\n\n"+err.Error(), http.StatusInternalServerError)
httpError(rsp, err)
return
}
}
contentType := expfmt.Negotiate(req.Header)
buf := getBuf()
defer giveBuf(buf)
writer, encoding := decorateWriter(req, buf, opts.DisableCompression)
enc := expfmt.NewEncoder(writer, contentType)
header := rsp.Header()
header.Set(contentTypeHeader, string(contentType))
w := io.Writer(rsp)
if !opts.DisableCompression && gzipAccepted(req.Header) {
header.Set(contentEncodingHeader, "gzip")
gz := gzipPool.Get().(*gzip.Writer)
defer gzipPool.Put(gz)
gz.Reset(w)
defer gz.Close()
w = gz
}
enc := expfmt.NewEncoder(w, contentType)
var lastErr error
for _, mf := range mfs {
if err := enc.Encode(mf); err != nil {
lastErr = err
if opts.ErrorLog != nil {
opts.ErrorLog.Println("error encoding metric family:", err)
opts.ErrorLog.Println("error encoding and sending metric family:", err)
}
switch opts.ErrorHandling {
case PanicOnError:
@ -150,28 +153,15 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
case ContinueOnError:
// Handled later.
case HTTPErrorOnError:
http.Error(w, "An error has occurred during metrics encoding:\n\n"+err.Error(), http.StatusInternalServerError)
httpError(rsp, err)
return
}
}
}
if closer, ok := writer.(io.Closer); ok {
closer.Close()
if lastErr != nil {
httpError(rsp, lastErr)
}
if lastErr != nil && buf.Len() == 0 {
http.Error(w, "No metrics encoded, last error:\n\n"+lastErr.Error(), http.StatusInternalServerError)
return
}
header := w.Header()
header.Set(contentTypeHeader, string(contentType))
header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
if encoding != "" {
header.Set(contentEncodingHeader, encoding)
}
if _, err := w.Write(buf.Bytes()); err != nil && opts.ErrorLog != nil {
opts.ErrorLog.Println("error while sending encoded metrics:", err)
}
// TODO(beorn7): Consider streaming serving of metrics.
})
if opts.Timeout <= 0 {
@ -292,20 +282,30 @@ type HandlerOpts struct {
Timeout time.Duration
}
// decorateWriter wraps a writer to handle gzip compression if requested. It
// returns the decorated writer and the appropriate "Content-Encoding" header
// (which is empty if no compression is enabled).
func decorateWriter(request *http.Request, writer io.Writer, compressionDisabled bool) (io.Writer, string) {
if compressionDisabled {
return writer, ""
}
header := request.Header.Get(acceptEncodingHeader)
parts := strings.Split(header, ",")
// gzipAccepted returns whether the client will accept gzip-encoded content.
func gzipAccepted(header http.Header) bool {
a := header.Get(acceptEncodingHeader)
parts := strings.Split(a, ",")
for _, part := range parts {
part = strings.TrimSpace(part)
if part == "gzip" || strings.HasPrefix(part, "gzip;") {
return gzip.NewWriter(writer), "gzip"
return true
}
}
return writer, ""
return false
}
// httpError removes any content-encoding header and then calls http.Error with
// the provided error and http.StatusInternalServerErrer. Error contents is
// supposed to be uncompressed plain text. However, same as with a plain
// http.Error, any header settings will be void if the header has already been
// sent. The error message will still be written to the writer, but it will
// probably be of limited use.
func httpError(rsp http.ResponseWriter, err error) {
rsp.Header().Del(contentEncodingHeader)
http.Error(
rsp,
"An error has occurred while serving metrics:\n\n"+err.Error(),
http.StatusInternalServerError,
)
}

2
prometheus/promhttp/http_test.go
View File

@ -103,7 +103,7 @@ func TestHandlerErrorHandling(t *testing.T) {
})
wantMsg := `error gathering metrics: error collecting metric Desc{fqName: "invalid_metric", help: "not helpful", constLabels: {}, variableLabels: []}: collect error
`
wantErrorBody := `An error has occurred during metrics gathering:
wantErrorBody := `An error has occurred while serving metrics:
error collecting metric Desc{fqName: "invalid_metric", help: "not helpful", constLabels: {}, variableLabels: []}: collect error
`

10
prometheus/registry_test.go
View File

@ -250,7 +250,7 @@ metric: <
},
}
expectedMetricFamilyInvalidLabelValueAsText := []byte(`An error has occurred during metrics gathering:
expectedMetricFamilyInvalidLabelValueAsText := []byte(`An error has occurred while serving metrics:
collected metric "name" { label:<name:"constname" value:"\377" > label:<name:"labelname" value:"different_val" > counter:<value:42 > } has a label named "constname" whose value is not utf8: "\xff"
`)
@ -299,15 +299,15 @@ complex_bucket 1
},
},
}
bucketCollisionMsg := []byte(`An error has occurred during metrics gathering:
bucketCollisionMsg := []byte(`An error has occurred while serving metrics:
collected metric named "complex_bucket" collides with previously collected histogram named "complex"
`)
summaryCountCollisionMsg := []byte(`An error has occurred during metrics gathering:
summaryCountCollisionMsg := []byte(`An error has occurred while serving metrics:
collected metric named "complex_count" collides with previously collected summary named "complex"
`)
histogramCountCollisionMsg := []byte(`An error has occurred during metrics gathering:
histogramCountCollisionMsg := []byte(`An error has occurred while serving metrics:
collected metric named "complex_count" collides with previously collected histogram named "complex"
`)
@ -333,7 +333,7 @@ collected metric named "complex_count" collides with previously collected histog
},
},
}
duplicateLabelMsg := []byte(`An error has occurred during metrics gathering:
duplicateLabelMsg := []byte(`An error has occurred while serving metrics:
collected metric "broken_metric" { label:<name:"foo" value:"bar" > label:<name:"foo" value:"baz" > counter:<value:2.7 > } has two or more labels with the same name: foo
`)