Replace compress/gzip with klauspost/compress (#139)

Replaces the stdlib `compress/gzip` with `klauspost/compress/gzip`. It
is slightly faster (by using less CPU) and results in the same allocs.
That is assuming default gzip compression (6).

Using an extraneous application to benchmark the change, I was able to
observe `10-11%` more throughput (measured in events per second) and
lower CPU usage.

Using the same container with 2vCPU set and GOMAXPROCS=2 (200% max):
- baseline: 39-40K eps - 186%-190% CPU Usage.
- klauspost: 43-44.5K eps - 159% CPU usage.
    - `+10-11%` throughput.
    - `-15%` CPU usage.

Microbenchmarks also point show decreased ns/op on my machine, although
it's not a perfect benchmark, since it's not entirely idle, but there's
improvements, even for benchmarks with a higher p.

```
$ benchstat main.txt klauspost.txt                                                                                                                                              <region:us-east-1>
goos: darwin
goarch: arm64
pkg: github.com/elastic/go-docappender
                                     │   main.txt    │            klauspost.txt            │
                                     │    sec/op     │    sec/op     vs base               │
Appender/NoCompression-4                394.8n ± 11%   389.4n ± 17%        ~ (p=0.084 n=6)
Appender/NoCompressionScaling-4         353.8n ± 13%   388.2n ± 11%        ~ (p=0.589 n=6)
Appender/BestSpeed-4                    654.5n ± 36%   572.4n ± 33%        ~ (p=0.065 n=6)
Appender/BestSpeedScaling-4             546.7n ± 25%   577.8n ± 30%        ~ (p=0.818 n=6)
Appender/DefaultCompression-4          1143.5n ± 18%   615.1n ± 43%  -46.21% (p=0.002 n=6)
Appender/DefaultCompressionScaling-4    997.9n ± 16%   640.7n ± 33%  -35.80% (p=0.002 n=6)
Appender/BestCompression-4              1.064µ ±  9%   1.098µ ± 15%        ~ (p=0.965 n=6)
Appender/BestCompressionScaling-4       1.056µ ±  9%   1.014µ ± 12%        ~ (p=0.368 n=6)
AppenderError-4                         996.3n ±  1%   997.3n ±  1%        ~ (p=0.937 n=6)
geomean                                 736.6n         654.0n        -11.22%
```

---------

Signed-off-by: Marc Lopez Rubio <[email protected]>

bulk_indexer.go

@@ -19,7 +19,6 @@ package docappender
 
 import (
 	"bytes"
-	"compress/gzip"
 	"context"
 	"fmt"
 	"io"
@@ -28,6 +27,7 @@ import (
 	"strings"
 	"unsafe"
 
+	"github.com/klauspost/compress/gzip"
 	"go.elastic.co/fastjson"
 
 	"github.com/elastic/go-elasticsearch/v8"

go.mod

@@ -5,6 +5,7 @@ go 1.21
 require (
 	github.com/elastic/go-elasticsearch/v8 v8.12.1
 	github.com/json-iterator/go v1.1.12
+	github.com/klauspost/compress v1.17.7
 	github.com/stretchr/testify v1.9.0
 	go.elastic.co/apm/module/apmelasticsearch/v2 v2.5.0
 	go.elastic.co/apm/module/apmzap/v2 v2.5.0

go.sum

@@ -26,6 +26,8 @@ github.com/joeshaw/multierror v0.0.0-20140124173710-69b34d4ec901 h1:rp+c0RAYOWj8
 github.com/joeshaw/multierror v0.0.0-20140124173710-69b34d4ec901/go.mod h1:Z86h9688Y0wesXCyonoVr47MasHilkuLMqGhRZ4Hpak=
 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 v1.17.7 h1:ehO88t2UGzQK66LMdE8tibEd1ErmzZjNEqWkjLAKQQg=
+github.com/klauspost/compress v1.17.7/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
 github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=