Add support for configuring bigqueue

[mangalaman93]

We should use a Config object to allow configuring BigQueue. We should allow a useful default value for each configuration as well as ensure that configurations are set correctly using possible checks around each parameter. We should allow creating bigqueue without the config object using the default values.

Here is the list of configuration parameters -

• [ ] Maximum size of Arena (check for a value at least as much as size of a OS page)
• [ ] Maximum memory used by BigQueue, allow an option for using minimum possible memory, or all available memory (check for a value of at least as much as 2 * Size of Arena)
• [ ] GC frequency (check for a positive value)

We will have to persist the configuration parameters so that we can read these parameters back across different invocation of same application.

I still think that we should keep the directory as an argument to NewBigQueue to ensure an explicit invocation of creating a queue using a path. Given that path is what defines a BigQueue, the expectation will be set properly in that if you lose the directory, you lose the queue

[mangalaman93]

Maximum size of Arena < total system memory / 4 so that we leave some memory for OS and ensure that we can keep 2 Arenas in memory for the queue.

[mangalaman93]

	Whether Persist	Update Allowed	Max Value	Min Value
Maximum Size of Arena	yes	no	Maximum Size of Arena < Total System Memory / 4	OS Page Size
Maximum Memory Used by BigQueue	No	yes	Total System Memory	2 * Arena Size
GC frequency	No	yes	-	-

[mangalaman93]

References

1. https://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis
2. https://commandcenter.blogspot.com/2014/01/self-referential-functions-and-design.html