fix: [PIPE-29145]: Stop leaking file descriptors pointing to docker socket (#396)

* 67f5a3 Remove unused variable

* 7521f2 Stop leaking file descriptors pointing to docker socket

Author: vcalasansh

engine/docker/docker.go

@@ -55,9 +55,15 @@ const (
 	running                          = "running"
 )
 
+var (
+	globalDockerClient     *client.Client
+	globalDockerClientLock sync.Mutex
+)
+
 // Opts configures the Docker engine.
 type Opts struct {
-	HidePull bool
+	HidePull          bool
+	ReuseDockerClient bool
 }
 
 // Docker implements a Docker pipeline engine.
@@ -88,7 +94,19 @@ func New(client client.APIClient, opts Opts) *Docker {
 
 // NewEnv returns a new Engine from the environment.
 func NewEnv(opts Opts) (*Docker, error) {
-	cli, err := client.NewClientWithOpts(client.FromEnv)
+	var cli client.APIClient
+	var err error
+	if opts.ReuseDockerClient {
+		globalDockerClientLock.Lock()
+		defer globalDockerClientLock.Unlock()
+		// Try to (re)initialize if not set
+		if globalDockerClient == nil {
+			globalDockerClient, err = client.NewClientWithOpts(client.FromEnv)
+		}
+		cli = globalDockerClient
+	} else {
+		cli, err = client.NewClientWithOpts(client.FromEnv)
+	}
 	if err != nil {
 		return nil, err
 	}

pipeline/runtime/step_executor_stateless.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/harness/lite-engine/api"
 	"github.com/harness/lite-engine/engine"
+	"github.com/harness/lite-engine/engine/docker"
 	"github.com/harness/lite-engine/engine/spec"
 	"github.com/harness/lite-engine/errors"
 	"github.com/harness/lite-engine/logstream"
@@ -61,7 +62,7 @@ func (e *StepExecutorStateless) executeStep( //nolint:gocritic
 ) (*runtime.State, map[string]string,
 	map[string]string, []byte, []*api.OutputV2, *types.TelemetryData, string, error) {
 	runFunc := func(ctx context.Context, step *spec.Step, output io.Writer, isDrone bool, isHosted bool) (*runtime.State, error) {
-		return engine.RunStep(ctx, engine.Opts{}, step, output, cfg, isDrone, isHosted)
+		return engine.RunStep(ctx, engine.Opts{Opts: docker.Opts{ReuseDockerClient: true}}, step, output, cfg, isDrone, isHosted)
 	}
 	// Temporary: this should be removed once we have a better way of handling test intelligence.
 	tiConfig := getTiCfg(&r.TIConfig, &r.MtlsConfig)