is there any way to fix the interval of yaxix.
What do you mean by "the interval"? The difference between adjacent label values? That, too, is dependent on the actual values so that they appear neither too cramped nor too sparse. You could write a postprocessor that sets a different TickUnitSource for the range axis, though.
for few bars it not displaying the labels though the space is available to display the numbers.
It would seem that the library has a different idea of what "enough available space" is, so the answer in my previous post applies.
By the way, you can make things easier for anyone reading this post by using an image format that is displayed in browsers, like GIF, JPEG or PNG.