Fix parallel ingest when guacgql is in docker. (#900)

Signed-off-by: Jeff Mendoza <jlm@jlm.name>

cmd/guacone/cmd/files.go

@@ -19,6 +19,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net"
 	"net/http"
 	"os"
 	"strings"
@@ -227,7 +228,24 @@ func getIngestor(ctx context.Context) func(processor.DocumentTree) ([]assembler.
 }
 
 func getAssembler(ctx context.Context, graphqlEndpoint string) func([]assembler.IngestPredicates) error {
-	httpClient := http.Client{}
+	// Same as https://pkg.go.dev/net/http#DefaultTransport but with greater
+	// MaxIdleConnsPerHost so that we effectively re-use connections when doing
+	// parallel ingestion calls.
+	var dialer = &net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+	}
+	var customTransport http.RoundTripper = &http.Transport{
+		Proxy:                 http.ProxyFromEnvironment,
+		DialContext:           dialer.DialContext,
+		ForceAttemptHTTP2:     true,
+		MaxIdleConns:          100,
+		MaxIdleConnsPerHost:   30,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+	}
+	httpClient := http.Client{Transport: customTransport}
 	gqlclient := graphql.NewClient(graphqlEndpoint, &httpClient)
 	f := helpers.GetParallelAssembler(ctx, gqlclient)
 	return f