org.apache.servicecomb.core.filter

Interface Filter

All Known Subinterfaces:

ConsumerFilter, InternalFilter, ProducerFilter

All Known Implementing Classes:

EmptyFilter, ParameterValidatorFilter, ProducerOperationFilter, ScheduleFilter, SimpleLoadBalanceFilter, TransportFilters

public interface Filter

 unified extension for replace old version extensions:
   1. Handler
   2. HttpClientFilter
   3. HttpServerFilter

 thread rule:
   assume a producer filter chains is: f1, f2, schedule, f3, f4

   schedule is a builtIn filter, which will dispatch invocations to operation related threadPool

   f1 and f2 are before "schedule" filter, default to run in eventLoop
   if developers customize filters and switch to other threads
   it's better to switch back to eventLoop, unless you know what you are doing

   f3 and f4 are after "schedule" filter, default thread depend on controller's method signature
     1. if controller method not return CompletableFuture
        then will run in a real threadPool
     2. if controller method return CompletableFuture
        then will still run in eventLoop
   so filters after "schedule" filter, are more complex than filters before "schedule"
   if developers need to do some BLOCK logic, MUST use different Strategy when running in different thread:
     1. threadPool: run do BLOCK logic directly
     2. eventLoop: MUST submit to a threadPool, and then switch back
        (reactive golden rule)
 

Method Summary

Modifier and Type	Method and Description
default List<InvocationType>	getInvocationTypes()
default String	getName()
default boolean	isEnabled()
default boolean	isInEventLoop()
CompletableFuture<Response>	onFilter(Invocation invocation, FilterNode nextNode)

Method Detail

isEnabled

default boolean isEnabled()

isInEventLoop

default boolean isInEventLoop()

getName

@Nonnull
default String getName()

getInvocationTypes

@Nonnull
default List<InvocationType> getInvocationTypes()

Returns:

can be used for the specific invocation type

onFilter

CompletableFuture<Response> onFilter(Invocation invocation,
                                     FilterNode nextNode)

Parameters:

invocation - invocation

nextNode - node filter node

Returns:

response future
even Response can express fail data
but Response only express success data in filter chain
all fail data can only express by exception

special for producer:
if response is failure, then after encode response, response.result will be exception.errorData, not a exception