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as_components A Linux C++ library for the development and testing of concurrent FastCGI application servers.

News and status

Version: pre-release.

Testing of as_components is underway before its initial release. This includes synchronization testing of fcgi::FcgiServerInterface.

Introduction

The as_components namespace includes the fcgi namespace. It also includes namespaces for the separately-useful components which were developed for fcgi. Brief descriptions of these namespaces and their main constituent classes follow. See header files and namespace README files for more information.

Namespace fcgi

The classes of namespace fcgi provide components for the development and testing of FastCGI application servers. See the namespace README for additional information which is not given here.

FastCGI application server development with FcgiServerInterface

The primary development component of as_components is FcgiServerInterface. It is a singleton class which, together with its related classes, provides an implementation of the FastCGI protocol for application servers. This implementation is designed to facilitate the development of multithreaded application servers.

FastCGI requests are represented as FcgiRequest instances. FcgiRequest instances are constructed by FcgiServerInterface as it accepts FastCGI data. FcgiRequest provides a high-level interface to FastCGI response actions such as writing to the FCGI_STDOUT stream and completing a request. This interface supports concurrent server development: the methods of FcgiRequest can be safely used in multiple threads on distinct request objects without explicit synchronization. This is even true when request objects in different threads share an underlying socket connection.

Another feature of fcgi is automatic management of low-level socket details. For example, connection acceptance, connection closure, and the monitoring of connections for incoming request data are performed implicitly through appropriate methods calls.

Application server testing with test::TestFcgiClientInterface

The client side of the FastCGI protocol is primarily implemented by HTTP servers. This presents a problem when performing unit tests on FastCGI application servers: without a component which implements the client side of the FastCGI protocol, tests must submit FastCGI requests and receive responses through an intermediary HTTP server. Such an intermediary complicates test development and interpretation.

TestFcgiClientInterface implements the client side of the FastCGI protocol! It facilitates the development of unit tests for FastCGI application servers by providing a high-level interface to the FastCGI request-response cycle. It also handles and exposes invalid FastCGI response records.

Namespace id_manager

The FastCGI protocol identifies a request based on the socket connection over which the request was sent and an integral request identifier. For typical requests, the request identifier is a small integer greater than zero. The value of the request identifier is chosen by the FastCGI client.

id_manager::IdManager is a class template which facilitates FastCGI request identifier selection and accounting. It provides a simple interface to identifier operations. Let I be an integral type. IdManager<I> offers:

I    GetId()
void ReleaseId(I i)
bool IsUsed(I i)
I    NumberOfUsedIds()

An IdManager instance stores identifier information efficiently by using an interval representation of its dynamic set of used identifiers. Efficient storage was deemed to be important as the primary client of IdManager is TestFcgiClientInterface. Load testing of FastCGI application servers may require keeping track of both a large number of concurrent requests for a given connection and a large number of concurrent connections.

Namespace socket_functions

Utility functions for socket I/O.

Features:

  • Automatic handling of interruptions due to signal receipt and short counts.
  • Support for gather writes.
  • The ability to write to a non-blocking socket with automatic blocking and descriptor monitoring for write readiness. This is available for both regular and gather writes.

Namespace testing

Namespace testing collects a small number of testing modules which are useful for testing several modules of as_components. testing also contains the gtest namespace. This namespace contains the testing modules of testing which depend on the Google Test testing framework.

Of note is testing::FileDescriptorLeakChecker. This class offers an interface for file descriptor accounting during testing.