clientv3: clarify retry interceptor logging

Log only when it errors + some clarification

Signed-off-by: Gyuho Lee <leegyuho@amazon.com>

clientv3/retry_interceptor.go

@@ -49,10 +49,15 @@ func (c *Client) unaryClientInterceptor(logger *zap.Logger, optFuncs ...retryOpt
 				return err
 			}
 			lastErr = invoker(ctx, method, req, reply, cc, grpcOpts...)
-			logger.Info("retry unary intercept", zap.Uint("attempt", attempt), zap.Error(lastErr))
 			if lastErr == nil {
 				return nil
 			}
+			logger.Warn(
+				"retrying unary intercept",
+				zap.String("target", cc.Target()),
+				zap.Uint("attempt", attempt),
+				zap.Error(lastErr),
+			)
 			if isContextError(lastErr) {
 				if ctx.Err() != nil {
 					// its the context deadline or cancellation.
@@ -64,7 +69,11 @@ func (c *Client) unaryClientInterceptor(logger *zap.Logger, optFuncs ...retryOpt
 			if callOpts.retryAuth && rpctypes.Error(lastErr) == rpctypes.ErrInvalidAuthToken {
 				gterr := c.getToken(ctx)
 				if gterr != nil {
-					logger.Info("retry failed to fetch new auth token", zap.Error(gterr))
+					logger.Warn(
+						"retry failed to fetch new auth token",
+						zap.String("target", cc.Target()),
+						zap.Error(gterr),
+					)
 					return lastErr // return the original error for simplicity
 				}
 				continue