API client: make http reads more efficient (#976)
Replace `io.ReadAll` with `bytes.Buffer.ReadFrom`. Both need to resize a buffer until they have finished reading; the former increases by 1.25x each time while the latter uses 2x. Also added a benchmark to demonstrate the benefit: name old time/op new time/op delta Client/4KB-8 35.9µs ± 4% 35.3µs ± 3% ~ (p=0.310 n=5+5) Client/50KB-8 83.1µs ± 8% 69.5µs ± 1% -16.37% (p=0.008 n=5+5) Client/1000KB-8 891µs ± 6% 750µs ± 0% -15.83% (p=0.016 n=5+4) Client/2000KB-8 1.74ms ± 2% 1.35ms ± 1% -22.72% (p=0.008 n=5+5) name old alloc/op new alloc/op delta Client/4KB-8 20.2kB ± 0% 20.4kB ± 0% +1.26% (p=0.008 n=5+5) Client/50KB-8 218kB ± 0% 136kB ± 0% -37.65% (p=0.008 n=5+5) Client/1000KB-8 5.88MB ± 0% 2.11MB ± 0% -64.10% (p=0.008 n=5+5) Client/2000KB-8 11.7MB ± 0% 4.2MB ± 0% -63.93% (p=0.008 n=5+5) name old allocs/op new allocs/op delta Client/4KB-8 75.0 ± 0% 72.0 ± 0% -4.00% (p=0.008 n=5+5) Client/50KB-8 109 ± 0% 98 ± 0% -10.09% (p=0.079 n=4+5) Client/1000KB-8 617 ± 0% 593 ± 0% -3.89% (p=0.008 n=5+5) Client/2000KB-8 1.13k ± 0% 1.09k ± 0% -3.27% (p=0.008 n=5+5) Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
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@ -15,8 +15,8 @@
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package api
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import (
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"bytes"
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"context"
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"io/ioutil"
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"net"
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"net/http"
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"net/url"
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@ -111,7 +111,9 @@ func (c *httpClient) Do(ctx context.Context, req *http.Request) (*http.Response,
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var body []byte
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done := make(chan struct{})
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go func() {
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body, err = ioutil.ReadAll(resp.Body)
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var buf bytes.Buffer
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_, err = buf.ReadFrom(resp.Body)
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body = buf.Bytes()
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close(done)
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}()
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@ -14,7 +14,11 @@
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package api
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import (
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"bytes"
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"context"
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"fmt"
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"net/http"
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"net/http/httptest"
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"net/url"
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"testing"
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)
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@ -111,3 +115,50 @@ func TestClientURL(t *testing.T) {
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}
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}
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}
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// Serve any http request with a response of N KB of spaces.
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type serveSpaces struct {
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sizeKB int
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}
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func (t serveSpaces) ServeHTTP(w http.ResponseWriter, req *http.Request) {
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kb := bytes.Repeat([]byte{' '}, 1024)
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for i := 0; i < t.sizeKB; i++ {
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w.Write(kb)
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}
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}
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func BenchmarkClient(b *testing.B) {
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b.ReportAllocs()
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ctx := context.Background()
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for _, sizeKB := range []int{4, 50, 1000, 2000} {
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b.Run(fmt.Sprintf("%dKB", sizeKB), func(b *testing.B) {
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testServer := httptest.NewServer(serveSpaces{sizeKB})
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defer testServer.Close()
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client, err := NewClient(Config{
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Address: testServer.URL,
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})
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if err != nil {
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b.Fatalf("Failed to initialize client: %v", err)
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}
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url, err := url.Parse(testServer.URL + "/prometheus/api/v1/query?query=up")
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if err != nil {
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b.Fatalf("Failed to parse url: %v", err)
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}
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req := &http.Request{
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URL: url,
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}
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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_, _, err := client.Do(ctx, req)
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if err != nil {
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b.Fatalf("Query failed: %v", err)
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}
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}
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b.StopTimer()
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})
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}
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}
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