[FAB-10712] Add BeforeRetry callback to Channel Client

The use case for this is to maintain application level
metrics on how many retry attempts are made by the sdk

Change-Id: Ic2b6ae578a8ddf95e0ee4586130082c8812ae667
Signed-off-by: Divyank Katira <Divyank.Katira@securekey.com>

Author: d1vyank

pkg/client/channel/api.go

@@ -23,6 +23,7 @@ type requestOptions struct {
 	Targets       []fab.Peer // targets
 	TargetFilter  fab.TargetFilter
 	Retry         retry.Opts
+	BeforeRetry   retry.BeforeRetryHandler
 	Timeouts      map[fab.TimeoutType]time.Duration //timeout options for channel client operations
 	ParentContext reqContext.Context                //parent grpc context for channel client operations (query, execute, invokehandler)
 }
@@ -107,6 +108,14 @@ func WithRetry(retryOpt retry.Opts) RequestOption {
 	}
 }
 
+// WithBeforeRetry specifies a function to call before a retry attempt
+func WithBeforeRetry(beforeRetry retry.BeforeRetryHandler) RequestOption {
+	return func(ctx context.Client, o *requestOptions) error {
+		o.BeforeRetry = beforeRetry
+		return nil
+	}
+}
+
 //WithTimeout encapsulates key value pairs of timeout type, timeout duration to Options
 func WithTimeout(timeoutType fab.TimeoutType, timeout time.Duration) RequestOption {
 	return func(ctx context.Client, o *requestOptions) error {

pkg/client/channel/chclient.go

@@ -163,6 +163,10 @@ func (cc *Client) InvokeHandler(handler invoke.Handler, request Request, options
 		requestContext.RetryHandler,
 		retry.WithBeforeRetry(
 			func(err error) {
+				if requestContext.Opts.BeforeRetry != nil {
+					requestContext.Opts.BeforeRetry(err)
+				}
+
 				cc.greylist.Greylist(err)
 
 				// Reset context parameters

pkg/client/channel/chclient_test.go

@@ -433,6 +433,20 @@ func TestExecuteTxWithRetries(t *testing.T) {
 	assert.Equal(t, testResp, resp.Payload, "expected correct response")
 }
 
+func TestBeforeRetryOption(t *testing.T) {
+	testStatus := status.New(status.EndorserClientStatus, status.ConnectionFailed.ToInt32(), "test", nil)
+
+	testPeer1 := fcmocks.NewMockPeer("Peer1", "http://peer1.com")
+	testPeer1.Error = testStatus
+	chClient := setupChannelClient([]fab.Peer{testPeer1}, t)
+
+	var callbacks int
+
+	_, _ = chClient.Query(Request{ChaincodeID: "testCC", Fcn: "invoke", Args: [][]byte{[]byte("query"), []byte("b")}},
+		WithRetry(retry.DefaultChannelOpts), WithBeforeRetry(func(error) { callbacks++ }))
+	assert.Equal(t, retry.DefaultChannelOpts.Attempts, callbacks, "Expected callback on each attempt")
+}
+
 func TestMultiErrorPropogation(t *testing.T) {
 	testErr := fmt.Errorf("Test Error")
 

pkg/client/channel/invoke/api.go

@@ -23,6 +23,7 @@ type Opts struct {
 	Targets       []fab.Peer // targets
 	TargetFilter  fab.TargetFilter
 	Retry         retry.Opts
+	BeforeRetry   retry.BeforeRetryHandler
 	Timeouts      map[fab.TimeoutType]time.Duration
 	ParentContext reqContext.Context //parent grpc context
 }