[#72] Support soft memory limit setting

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

app.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"runtime/debug"
 	"sync"
 	"syscall"
 	"time"
@@ -128,6 +129,8 @@ func newApp(ctx context.Context, opt ...Option) App {
 	user.IDFromKey(&owner, a.key.PrivateKey.PublicKey)
 	a.owner = &owner
 
+	a.setRuntimeParameters()
+
 	a.initAppSettings()
 	a.initResolver()
 	a.initMetrics()
@@ -407,6 +410,8 @@ func (a *app) configReload(ctx context.Context) {
 		a.log.Warn(logs.FailedToReloadServerParameters, zap.Error(err))
 	}
 
+	a.setRuntimeParameters()
+
 	a.stopServices()
 	a.startServices()
 
@@ -596,3 +601,19 @@ func (a *app) initTracing(ctx context.Context) {
 		a.log.Info(logs.TracingConfigUpdated)
 	}
 }
+
+func (a *app) setRuntimeParameters() {
+	if len(os.Getenv("GOMEMLIMIT")) != 0 {
+		// default limit < yaml limit < app env limit < GOMEMLIMIT
+		a.log.Warn(logs.RuntimeSoftMemoryDefinedWithGOMEMLIMIT)
+		return
+	}
+
+	softMemoryLimit := fetchSoftMemoryLimit(a.cfg)
+	previous := debug.SetMemoryLimit(softMemoryLimit)
+	if softMemoryLimit != previous {
+		a.log.Info(logs.RuntimeSoftMemoryLimitUpdated,
+			zap.Int64("new_value", softMemoryLimit),
+			zap.Int64("old_value", previous))
+	}
+}