class Memory::Leak::Monitor

We should be careful not to filter historical data, as some memory leaks may only become apparent after a long period of time. Any kind of filtering may prevent us from detecting such a leak.
A memory leak is characterised by the memory usage of the application continuing to rise over time. We can detect this by sampling memory usage and comparing it to the previous sample. If the memory usage is higher than the previous sample, we can say that the application has allocated more memory. Eventually we expect to see this stabilize, but if it continues to rise, we can say that the application has a memory leak.
Detects memory leaks by tracking process size increases.

def as_json(...)

@returns [Hash] A serializable representation of the cluster. 
def as_json(...)
	{
		process_id: @process_id,
		current_size: @current_size,
		maximum_size: @maximum_size,
		maximum_size_limit: @maximum_size_limit,
		threshold_size: @threshold_size,
		increase_count: @increase_count,
		increase_limit: @increase_limit,
	}
end

def current_size

@returns [Integer] The last sampled memory usage. 
def current_size
	@current_size ||= memory_usage
end

def current_size=(value)

Set the current memory usage, rather than sampling it. 
def current_size=(value)
	@current_size = value
end

def increase_limit_exceeded?

@returns [Boolean] True if a memory leak has been detected.

If the number of increasing heap size samples is greater than or equal to the increase_limit, a memory leak is assumed.

Indicates whether a memory leak has been detected. 
def increase_limit_exceeded?
	@increase_count >= @increase_limit
end

def initialize(process_id = Process.pid, maximum_size: nil, maximum_size_limit: nil, threshold_size: DEFAULT_THRESHOLD_SIZE, increase_limit: DEFAULT_INCREASE_LIMIT)

@parameter increase_limit [Numeric] The limit for the number of process size increases, before we assume a memory leak.
@parameter threshold_size [Numeric] The threshold for process size increases, in bytes.
@parameter maximum_size_limit [Numeric | Nil] The maximum process size allowed, in bytes, before we assume a memory leak.
@parameter maximum_size [Numeric] The initial process size, from which we willl track increases, in bytes.
@parameter process_id [Integer] The process ID to monitor.

Create a new monitor. 
def initialize(process_id = Process.pid, maximum_size: nil, maximum_size_limit: nil, threshold_size: DEFAULT_THRESHOLD_SIZE, increase_limit: DEFAULT_INCREASE_LIMIT)
	@process_id = process_id
	
	@current_size = nil
	@maximum_size = maximum_size
	@maximum_size_limit = maximum_size_limit
	
	@threshold_size = threshold_size
	@increase_count = 0
	@increase_limit = increase_limit
end

def leaking?

@returns [Boolean] True if a memory leak has been detected.

Indicates whether a memory leak has been detected. 
def leaking?
	increase_limit_exceeded? || maximum_size_limit_exceeded?
end

def maximum_size_limit_exceeded?

@returns [Boolean] True if the current memory usage has grown beyond the maximum size limit.

Indicates that the current memory usage has grown beyond the maximum size limit. 
def maximum_size_limit_exceeded?
	@maximum_size_limit && self.current_size > @maximum_size_limit
end

def memory_usage

@returns [Integer] Ask the system for the current memory usage. 
def memory_usage
	System.memory_usage(@process_id)
end

def sample!

@yields {|sample, monitor| ...} If a memory leak is detected.

Capture a memory usage sample and yield if a memory leak is detected. 
def sample!
	self.current_size = memory_usage
	
	if @maximum_observed_size
		delta = @current_size - @maximum_observed_size
		Console.debug(self, "Heap size captured.", current_size: @current_size, delta: delta, threshold_size: @threshold_size, maximum_observed_size: @maximum_observed_size)
		
		if delta > @threshold_size
			@maximum_observed_size = @current_size
			@increase_count += 1
			
			Console.debug(self, "Heap size increased.", maximum_observed_size: @maximum_observed_size, count: @count)
		end
	else
		Console.debug(self, "Initial heap size captured.", current_size: @current_size)
		@maximum_observed_size = @current_size
	end
	
	return @current_size
end

def to_json(...)

@returns [String] The JSON representation of the cluster. 
def to_json(...)
	as_json.to_json(...)
end