Add WaitReady to VppAdapter

- this fixes issue with mocked adapter during AsyncConnect

Change-Id: I952025fec865422f9e83cec9383d96f79a639c90
Signed-off-by: Ondrej Fabry <ofabry@cisco.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/adapter/vppapiclient/vppapiclient_adapter.go b/adapter/vppapiclient/vppapiclient_adapter.go
index 74f0118..dfdd973 100644
--- a/adapter/vppapiclient/vppapiclient_adapter.go
+++ b/adapter/vppapiclient/vppapiclient_adapter.go
@@ -79,10 +79,21 @@ import "C"
 import (
 	"errors"
 	"fmt"
+	"os"
 	"reflect"
 	"unsafe"
 
 	"git.fd.io/govpp.git/adapter"
+	"github.com/fsnotify/fsnotify"
+)
+
+const (
+	// watchedFolder is a folder where vpp's shared memory is supposed to be created.
+	// File system events are monitored in this folder.
+	watchedFolder = "/dev/shm/"
+	// watchedFile is a name of the file in the watchedFolder. Once the file is present
+	// the vpp is ready to accept a new connection.
+	watchedFile = watchedFolder + "vpe-api"
 )
 
 // vppAPIClientAdapter is the opaque context of the adapter.
@@ -139,6 +150,44 @@ func (a *vppAPIClientAdapter) SetMsgCallback(cb func(context uint32, msgID uint1
 	a.callback = cb
 }
 
+// WaitReady returns func which blocks until shared memory
+// for sending bin api calls is present on the file system.
+func (a *vppAPIClientAdapter) WaitReady() func() error {
+	return func() error {
+		watcher, err := fsnotify.NewWatcher()
+		if err != nil {
+			return err
+		}
+		defer watcher.Close()
+
+		err = watcher.Add(watchedFolder)
+		if err != nil {
+			return err
+		}
+
+		if fileExists(watchedFile) {
+			return nil
+		}
+
+		for {
+			ev := <-watcher.Events
+			if ev.Name == watchedFile && (ev.Op&fsnotify.Create) == fsnotify.Create {
+				break
+			}
+		}
+		return nil
+	}
+}
+
+func fileExists(name string) bool {
+	if _, err := os.Stat(name); err != nil {
+		if os.IsNotExist(err) {
+			return false
+		}
+	}
+	return true
+}
+
 //export go_msg_callback
 func go_msg_callback(msgID C.uint16_t, context C.uint32_t, data unsafe.Pointer, size C.size_t) {
 	// convert unsafe.Pointer to byte slice