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feat: Support zstd compression #1496

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2 changes: 2 additions & 0 deletions go.mod
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,9 @@ go 1.20
require (
github.com/beorn7/perks v1.0.1
github.com/cespare/xxhash/v2 v2.3.0
github.com/google/go-cmp v0.6.0
github.com/json-iterator/go v1.1.12
github.com/klauspost/compress v1.17.8
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Came here from the release page. Most people don't care about zstd, but now every user will have one more dependency. Would be better to wait for golang/go#62513 and avoid extra dependencies.

Why not let stdlib's http package handle compression negotiation? It's kind of out of scope of this library (from my POV at least).

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It's fair point we could outsource compression + negotiation to separate libs, but we wanted default client_golang without extra deps to handle that automatically for everyone. That's some choice which was already made before by adding gzip.

Most people don't care about zstd, but now every user will have one more dependency.

Fair point, hopefully we can remove it once zstd is in std. Luckly, this dep is trusted, proven and very minimal https://github.com/klauspost/compress/blob/master/go.mod - we could vendor that code, but we chosen to add one little dep -- we are open on feedback on how blocking this is for our users.

stdlib's http package handle compression negotiation

Is there std http flow for compression negotiation? I don't think so.

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Is there std http flow for compression negotiation? I don't think so.

Yes, it turns out it doesn't handle that (I didn't know). My point is that there are many things that can be improved and done that will improve how this library works (bigger picture). But this doesn't mean they should be part of this library. Imagine every library that provides e.g. http handlers also tried to take care of compression, compression negotiation, doing http/3, etc, etc, etc. Dependency sprawl quickly gets out of hand, things work differently, become incompatible. I think unix way is a better approach. Provide solution for one problem, limit the scope, reduce dependencies. But also make it possible for your consumers to solve those problems somehow (composition!). With other libraries or with stdlib or with custom code.

I wonder if it's possible to have zstd compression without this PR? Can I do it today with a previous version of this library? It seems it should be possible to have an http handler that wraps the handler of this library (or any other one) and implements compression. Perhaps this should be a separate generic library that anyone could use, contribute too. I found the chi middleware that does gzip compression. Sould be possible to have a zstd middleware? And then anyone who wants it can use it for all/any http handlers they have, not just for the metrics endpoint.

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we wanted default client_golang without extra deps to handle that automatically for everyone.

May I ask what is the motivation for this? How many users of this library have asked for this feature?

If something can be done (even if easily), doesn't mean it should be done. My gut feeling is that it is cheaper (cpu/ram/network resources) to pass uncompressed metrics to a scraper that is running in the same local network (99% of people do this?). If things are running on Kubernetes, the scraper is quite likely on the same host (as a DaemonSet)! So it's "free", virtually/almost no network cost. In that case compression is a pure waste of CPU time. Shall we add some code that detects this situation and optimizes the compression away? 😁 Why not, just a little dependency on the Kubernetes client? Let's make the library handle this case too! Ok, I hope you see my point.

p.s. I'm very grateful to people who contribute and maintain great libraries like this one. Please don't take this personally.

github.com/prometheus/client_model v0.6.1
github.com/prometheus/common v0.53.0
github.com/prometheus/procfs v0.15.1
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3 changes: 3 additions & 0 deletions go.sum
Original file line number Diff line number Diff line change
Expand Up @@ -12,11 +12,14 @@ github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg
github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
github.com/jpillora/backoff v1.0.0 h1:uvFg412JmmHBHw7iwprIxkPMI+sGQ4kzOWsMeHnm2EA=
github.com/jpillora/backoff v1.0.0/go.mod h1:J/6gKK9jxlEcS3zixgDgUAsiuZ7yrSoa/FX5e0EB2j4=
github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
github.com/klauspost/compress v1.17.8 h1:YcnTYrq7MikUT7k0Yb5eceMmALQPYBW/Xltxn0NAMnU=
github.com/klauspost/compress v1.17.8/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
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27 changes: 27 additions & 0 deletions internal/github.com/golang/gddo/LICENSE
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
Copyright (c) 2013 The Go Authors. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
* Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1 change: 1 addition & 0 deletions internal/github.com/golang/gddo/README.md
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
This source code is a stripped down version from the archived repository https://github.com/golang/gddo and licensed under BSD.
145 changes: 145 additions & 0 deletions internal/github.com/golang/gddo/httputil/header/header.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,145 @@
// Copyright 2013 The Go Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd.

// Package header provides functions for parsing HTTP headers.
package header

import (
"net/http"
"strings"
)

// Octet types from RFC 2616.
var octetTypes [256]octetType

type octetType byte

const (
isToken octetType = 1 << iota
isSpace
)

func init() {
// OCTET = <any 8-bit sequence of data>
// CHAR = <any US-ASCII character (octets 0 - 127)>
// CTL = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
// CR = <US-ASCII CR, carriage return (13)>
// LF = <US-ASCII LF, linefeed (10)>
// SP = <US-ASCII SP, space (32)>
// HT = <US-ASCII HT, horizontal-tab (9)>
// <"> = <US-ASCII double-quote mark (34)>
// CRLF = CR LF
// LWS = [CRLF] 1*( SP | HT )
// TEXT = <any OCTET except CTLs, but including LWS>
// separators = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | "\" | <">
// | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT
// token = 1*<any CHAR except CTLs or separators>
// qdtext = <any TEXT except <">>

for c := 0; c < 256; c++ {
var t octetType
isCtl := c <= 31 || c == 127
isChar := 0 <= c && c <= 127
isSeparator := strings.ContainsRune(" \t\"(),/:;<=>?@[]\\{}", rune(c))
if strings.ContainsRune(" \t\r\n", rune(c)) {
t |= isSpace
}
if isChar && !isCtl && !isSeparator {
t |= isToken
}
octetTypes[c] = t
}
}

// AcceptSpec describes an Accept* header.
type AcceptSpec struct {
Value string
Q float64
}

// ParseAccept parses Accept* headers.
func ParseAccept(header http.Header, key string) (specs []AcceptSpec) {
loop:
for _, s := range header[key] {
for {
var spec AcceptSpec
spec.Value, s = expectTokenSlash(s)
if spec.Value == "" {
continue loop
}
spec.Q = 1.0
s = skipSpace(s)
if strings.HasPrefix(s, ";") {
s = skipSpace(s[1:])
if !strings.HasPrefix(s, "q=") {
continue loop
}
spec.Q, s = expectQuality(s[2:])
if spec.Q < 0.0 {
continue loop
}
}
specs = append(specs, spec)
s = skipSpace(s)
if !strings.HasPrefix(s, ",") {
continue loop
}
s = skipSpace(s[1:])
}
}
return
}

func skipSpace(s string) (rest string) {
i := 0
for ; i < len(s); i++ {
if octetTypes[s[i]]&isSpace == 0 {
break
}
}
return s[i:]
}

func expectTokenSlash(s string) (token, rest string) {
i := 0
for ; i < len(s); i++ {
b := s[i]
if (octetTypes[b]&isToken == 0) && b != '/' {
break
}
}
return s[:i], s[i:]
}

func expectQuality(s string) (q float64, rest string) {
switch {
case len(s) == 0:
return -1, ""
case s[0] == '0':
q = 0
case s[0] == '1':
q = 1
default:
return -1, ""
}
s = s[1:]
if !strings.HasPrefix(s, ".") {
return q, s
}
s = s[1:]
i := 0
n := 0
d := 1
for ; i < len(s); i++ {
b := s[i]
if b < '0' || b > '9' {
break
}
n = n*10 + int(b) - '0'
d *= 10
}
return q + float64(n)/float64(d), s[i:]
}
49 changes: 49 additions & 0 deletions internal/github.com/golang/gddo/httputil/header/header_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,49 @@
// Copyright 2013 The Go Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd.

package header

import (
"net/http"
"testing"

"github.com/google/go-cmp/cmp"
)

var parseAcceptTests = []struct {
s string
expected []AcceptSpec
}{
{"text/html", []AcceptSpec{{"text/html", 1}}},
{"text/html; q=0", []AcceptSpec{{"text/html", 0}}},
{"text/html; q=0.0", []AcceptSpec{{"text/html", 0}}},
{"text/html; q=1", []AcceptSpec{{"text/html", 1}}},
{"text/html; q=1.0", []AcceptSpec{{"text/html", 1}}},
{"text/html; q=0.1", []AcceptSpec{{"text/html", 0.1}}},
{"text/html;q=0.1", []AcceptSpec{{"text/html", 0.1}}},
{"text/html, text/plain", []AcceptSpec{{"text/html", 1}, {"text/plain", 1}}},
{"text/html; q=0.1, text/plain", []AcceptSpec{{"text/html", 0.1}, {"text/plain", 1}}},
{"iso-8859-5, unicode-1-1;q=0.8,iso-8859-1", []AcceptSpec{{"iso-8859-5", 1}, {"unicode-1-1", 0.8}, {"iso-8859-1", 1}}},
{"iso-8859-1", []AcceptSpec{{"iso-8859-1", 1}}},
{"*", []AcceptSpec{{"*", 1}}},
{"da, en-gb;q=0.8, en;q=0.7", []AcceptSpec{{"da", 1}, {"en-gb", 0.8}, {"en", 0.7}}},
{"da, q, en-gb;q=0.8", []AcceptSpec{{"da", 1}, {"q", 1}, {"en-gb", 0.8}}},
{"image/png, image/*;q=0.5", []AcceptSpec{{"image/png", 1}, {"image/*", 0.5}}},

// bad cases
{"value1; q=0.1.2", []AcceptSpec{{"value1", 0.1}}},
{"da, en-gb;q=foo", []AcceptSpec{{"da", 1}}},
}

func TestParseAccept(t *testing.T) {
for _, tt := range parseAcceptTests {
header := http.Header{"Accept": {tt.s}}
actual := ParseAccept(header, "Accept")
if !cmp.Equal(actual, tt.expected) {
t.Errorf("ParseAccept(h, %q)=%v, want %v", tt.s, actual, tt.expected)
}
}
}
36 changes: 36 additions & 0 deletions internal/github.com/golang/gddo/httputil/negotiate.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
// Copyright 2013 The Go Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd.

package httputil

import (
"net/http"

"github.com/prometheus/client_golang/internal/github.com/golang/gddo/httputil/header"
)

// NegotiateContentEncoding returns the best offered content encoding for the
// request's Accept-Encoding header. If two offers match with equal weight and
// then the offer earlier in the list is preferred. If no offers are
// acceptable, then "" is returned.
func NegotiateContentEncoding(r *http.Request, offers []string) string {
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bestOffer := "identity"
bestQ := -1.0
specs := header.ParseAccept(r.Header, "Accept-Encoding")
for _, offer := range offers {
for _, spec := range specs {
if spec.Q > bestQ &&
(spec.Value == "*" || spec.Value == offer) {
bestQ = spec.Q
bestOffer = offer
}
}
}
if bestQ == 0 {
bestOffer = ""
}
return bestOffer
}
40 changes: 40 additions & 0 deletions internal/github.com/golang/gddo/httputil/negotiate_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
// Copyright 2013 The Go Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd.

package httputil

import (
"net/http"
"testing"
)

var negotiateContentEncodingTests = []struct {
s string
offers []string
expect string
}{
{"", []string{"identity", "gzip"}, "identity"},
{"*;q=0", []string{"identity", "gzip"}, ""},
{"gzip", []string{"identity", "gzip"}, "gzip"},
{"gzip,zstd", []string{"identity", "zstd"}, "zstd"},
{"zstd,gzip", []string{"gzip", "zstd"}, "gzip"},
{"gzip,zstd", []string{"gzip", "zstd"}, "gzip"},
{"gzip,zstd", []string{"zstd", "gzip"}, "zstd"},
{"gzip;q=0.1,zstd;q=0.5", []string{"gzip", "zstd"}, "zstd"},
{"gzip;q=1.0, identity; q=0.5, *;q=0", []string{"identity", "gzip"}, "gzip"},
{"gzip;q=1.0, identity; q=0.5, *;q=0", []string{"identity", "zstd"}, "identity"},
{"zstd", []string{"identity", "gzip"}, "identity"},
}

func TestNegotiateContentEncoding(t *testing.T) {
for _, tt := range negotiateContentEncodingTests {
r := &http.Request{Header: http.Header{"Accept-Encoding": {tt.s}}}
actual := NegotiateContentEncoding(r, tt.offers)
if actual != tt.expect {
t.Errorf("NegotiateContentEncoding(%q, %#v)=%q, want %q", tt.s, tt.offers, actual, tt.expect)
}
}
}
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