Increment numOfRequests metric if ssh connection is alive (#26)

Author: TomerShor

pkg/common/helpers.go

@@ -15,6 +15,12 @@
 
 package common
 
+import (
+	"os"
+
+	"github.com/nuclio/errors"
+)
+
 func StringInSlice(s string, slice []string) bool {
 	for _, str := range slice {
 		if str == s {
@@ -23,3 +29,17 @@ func StringInSlice(s string, slice []string) bool {
 	}
 	return false
 }
+
+// FileExists returns true if the given file exists
+func FileExists(filePath string) (bool, error) {
+	_, err := os.Stat(filePath)
+	if err == nil {
+		return true, nil
+
+	} else if errors.Is(err, os.ErrNotExist) {
+		return false, nil
+	}
+
+	// sanity: file may or may not exist
+	return false, err
+}

pkg/sidecarproxy/metricshandler/numofrequests/metricshandler.go

@@ -19,9 +19,11 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"net/url"
+	"os"
 	"strings"
 	"time"
 
+	"github.com/v3io/sidecar-proxy/pkg/common"
 	"github.com/v3io/sidecar-proxy/pkg/sidecarproxy/metricshandler"
 	"github.com/v3io/sidecar-proxy/pkg/sidecarproxy/metricshandler/abstract"
 
@@ -85,6 +87,8 @@ func (n *metricsHandler) Start() error {
 		return errors.Wrap(err, "Failed to initiate proxy")
 	}
 
+	go n.monitorSSHConnection()
+
 	// adds one data point on service initialization so metric will be initialized and queryable
 	n.incrementMetric()
 	return nil
@@ -145,3 +149,41 @@ func (n *metricsHandler) forwardRequest(res http.ResponseWriter, req *http.Reque
 	n.proxy.ServeHTTP(res, req)
 	return nil
 }
+
+// monitorSSHConnection runs in a goroutine and checks if the ssh connection is still alive, by reading a file shared
+// between the sidecar and main container.
+func (n *metricsHandler) monitorSSHConnection() {
+	filePath := metricshandler.OpenSSHConnectionFilePath
+
+	n.Logger.Info("Starting SSH connection monitor", "filePath", filePath)
+
+	// create a ticker that will check the file every 10 seconds
+	ticker := time.NewTicker(10 * time.Second)
+	for range ticker.C {
+
+		// if the file doesn't exist, do nothing
+		if exists, err := common.FileExists(filePath); !exists {
+			if err != nil {
+				n.Logger.WarnWith("Failed to check if file exists", "err", err)
+			}
+			continue
+		}
+
+		// file exists, read it
+		contentBytes, err := os.ReadFile(filePath)
+		if err != nil {
+			n.Logger.WarnWith("Failed to read file", "err", err)
+			continue
+		}
+
+		// convert content to a 'string'
+		content := strings.TrimSpace(string(contentBytes))
+
+		// if it contains "1", the connection is alive - increment the metric
+		// otherwise, do nothing
+		if content == metricshandler.SSHConnectionIsAlive {
+			n.Logger.Debug("SSH connection is alive, incrementing metric")
+			n.incrementMetric()
+		}
+	}
+}

pkg/sidecarproxy/metricshandler/types.go

@@ -26,3 +26,8 @@ const (
 	NumOfRequestsMetricName         MetricName = "num_of_requests"
 	JupyterKernelBusynessMetricName MetricName = "jupyter_kernel_busyness"
 )
+
+const (
+	OpenSSHConnectionFilePath = "/intercontainer/opensshconnection"
+	SSHConnectionIsAlive      = "1"
+)