Функции фильтрации реализованы с помощью трехэтапных неблокирующих функций LuaInputFilter или разработаны как трехэтапные неблокирующие функции, использующие сопрограммы для приостановки и возобновления функции по мере того, как сегменты отправляются по цепочке фильтров. LuaOutputFilter Основная структура такой функции:

function filter(r)
 -- Our first yield is to signal that we are ready to receive buckets.
 -- Before this yield, we can set up our environment, check for conditions,
 -- and, if we deem it necessary, decline filtering a request alltogether:
 if something_bad then
 return -- This would skip this filter.
 end
 -- Regardless of whether we have data to prepend, a yield MUST be called here.
 -- Note that only output filters can prepend data. Input filters must use the 
 -- final stage to append data to the content.
 coroutine.yield([optional header to be prepended to the content])
 
 -- After we have yielded, buckets will be sent to us, one by one, and we can 
 -- do whatever we want with them and then pass on the result.
 -- Buckets are stored in the global variable 'bucket', so we create a loop
 -- that checks if 'bucket' is not nil:
 while bucket ~= nil do
 local output = mangle(bucket) -- Do some stuff to the content
 coroutine.yield(output) -- Return our new content to the filter chain
 end
 -- Once the buckets are gone, 'bucket' is set to nil, which will exit the 
 -- loop and land us here. Anything extra we want to append to the content
 -- can be done by doing a final yield here. Both input and output filters 
 -- can append data to the content in this phase.
 coroutine.yield([optional footer to be appended to the content])
end