jk_service.h

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     */
    int (JK_METHOD * start_response) (jk_ws_service_t *s,
                                      int status,
                                      const char *reason,
                                      const char *const *header_names,
                                      const char *const *header_values,
                                      unsigned num_of_headers);

    /*
     * Read a chunk of the request body into a buffer.  Attempt to read len
     * bytes into the buffer.  Write the number of bytes actually read into
     * actually_read.
     */
    int (JK_METHOD * read) (jk_ws_service_t *s,
                            void *buffer,
                            unsigned len, unsigned *actually_read);

    /*
     * Write a chunk of response data back to the browser.
     */
    int (JK_METHOD * write) (jk_ws_service_t *s,
                             const void *buffer, unsigned len);

    /*
     * Flush a chunk of response data back to the browser.
     */
    void (JK_METHOD * flush) (jk_ws_service_t *s);
};

/*
 * The endpoint 'class', which represents one end of a connection to the
 * servlet engine.  Basically, supports nothing other than forwarding the
 * request to the servlet engine.  Endpoints can be persistent (as with
 * ajp13/ajp14, where a single connection is reused many times), or can last for a
 * single request (as with ajp12, where a new connection is created for
 * every request).
 *
 * An endpoint for a given protocol is obtained by the web server plugin
 * from a worker object for that protocol.  See below for details.
 *
 * As with all the core jk classes, this is essentially an abstract base
 * class which is implemented/extended by classes which are specific to a
 * particular protocol.  By using an abstract base class in this manner,
 * plugins can be written for different servers (e.g. IIS, Apache) without
 * the plugins having to worry about which protocol they are talking.
 *
 * This particular OO-in-C system uses a 'endpoint_private' pointer to
 * point to the protocol-specific data/functions.  So in the subclasses, the
 * methods do most of their work by getting their hands on the
 * endpoint_private pointer and then using that to get at the functions for
 * their protocol.
 *
 * Try imagining this as a 'public abstract class', and the
 * endpoint_private pointer as a sort of extra 'this' reference.  Or
 * imagine that you are seeing the internal vtables of your favorite OO
 * language.  Whatever works for you.
 *
 * See jk_ajp13_worker.c/jk_ajp14_worker.c and jk_ajp12_worker.c for examples.
 */
struct jk_endpoint
{
    size_t rd;
    size_t wr;

    /*
     * A 'this' pointer which is used by the subclasses of this class to
     * point to data/functions which are specific to a given protocol
     * (e.g. ajp12 or ajp13 or ajp14).
     */
    void *endpoint_private;

    /*
     * Forward a request to the servlet engine.  The request is described
     * by the jk_ws_service_t object.
     * is_error is either 0 meaning recoverable or set to
     * the HTTP error code.
     */
    int (JK_METHOD * service) (jk_endpoint_t *e,
                               jk_ws_service_t *s,
                               jk_logger_t *l, int *is_error);

    /*
     * Called when this particular endpoint has finished processing a
     * request.  For some protocols (e.g. ajp12), this frees the memory
     * associated with the endpoint.  For others (e.g. ajp13/ajp14), this can
     * return the endpoint to a cache of already opened endpoints.
     *
     * Note that the first argument is *not* a 'this' pointer, but is
     * rather a pointer to a 'this' pointer.  This is necessary, because
     * we may need to free this object.
     */
    int (JK_METHOD * done) (jk_endpoint_t **p, jk_logger_t *l);
};

/*
 * The worker 'class', which represents something to which the web server
 * can delegate requests.
 *
 * This can mean communicating with a particular servlet engine instance,
 * using a particular protocol.  A single web server instance may have
 * multiple workers communicating with a single servlet engine (it could be
 * using ajp12 for some requests and ajp13/ajp14 for others).  Or, a single web
 * server instance could have multiple workers communicating with different
 * servlet engines using the same protocol (it could be load balancing
 * among many engines, using ajp13/ajp14 for all communication).
 *
 * There is also a load balancing worker (jk_lb_worker.c), which itself
 * manages a group of workers.
 *
 * Web servers are configured to forward requests to a given worker.  To
 * handle those requests, the worker's get_endpoint method is called, and
 * then the service() method of that endpoint is called.
 *
 * As with all the core jk classes, this is essentially an abstract base
 * class which is implemented/extended by classes which are specific to a
 * particular protocol (or request-handling system).  By using an abstract
 * base class in this manner, plugins can be written for different servers
 * (e.g. IIS, Apache) without the plugins having to worry about which
 * protocol they are talking.
 *
 * This particular OO-in-C system uses a 'worker_private' pointer to
 * point to the protocol-specific data/functions.  So in the subclasses, the
 * methods do most of their work by getting their hands on the
 * worker_private pointer and then using that to get at the functions for
 * their protocol.
 *
 * Try imagining this as a 'public abstract class', and the
 * worker_private pointer as a sort of extra 'this' reference.  Or
 * imagine that you are seeing the internal vtables of your favorite OO
 * language.  Whatever works for you.
 *
 * See jk_ajp14_worker.c, jk_ajp13_worker.c and jk_ajp12_worker.c for examples.
 */
struct jk_worker
{

    /*
     * Public property to enable the number of retry attempts
     * on this worker.
     */
    int retries;
    /*
     * A 'this' pointer which is used by the subclasses of this class to
     * point to data/functions which are specific to a given protocol
     * (e.g. ajp12 or ajp13 or ajp14).
     */
    void *worker_private;

    int   type;
    /*
     * For all of the below (except destroy), the first argument is
     * essentially a 'this' pointer.
     */

    /*
     * Given a worker which is in the process of being created, and a list
     * of configuration options (or 'properties'), check to see if it the
     * options are.  This will always be called before the init() method.
     * The init/validate distinction is a bit hazy to me.
     * See jk_ajp13_worker.c/jk_ajp14_worker.c and jk_worker.c->wc_create_worker()
     */
    int (JK_METHOD * validate) (jk_worker_t *w,
                                jk_map_t *props,
                                jk_worker_env_t *we, jk_logger_t *l);

    /*
     * Update worker either from jk_status or reloading from workers.properties
     */
    int (JK_METHOD * update) (jk_worker_t *w,
                              jk_map_t *props,
                              jk_worker_env_t *we, jk_logger_t *l);

    /*
     * Do whatever initialization needs to be done to start this worker up.
     * Configuration options are passed in via the props parameter.
     */
    int (JK_METHOD * init) (jk_worker_t *w,
                            jk_map_t *props,
                            jk_worker_env_t *we, jk_logger_t *l);


    /*
     * Obtain an endpoint to service a particular request.  A pointer to
     * the endpoint is stored in pend.
     */
    int (JK_METHOD * get_endpoint) (jk_worker_t *w,
                                    jk_endpoint_t **pend, jk_logger_t *l);

    /*
     * Shutdown this worker.  The first argument is not a 'this' pointer,
     * but rather a pointer to 'this', so that the object can be free'd (I
     * think -- though that doesn't seem to be happening.  Hmmm).
     */
    int (JK_METHOD * destroy) (jk_worker_t **w, jk_logger_t *l);

    /*
     * Maintain this worker.
     */
    int (JK_METHOD * maintain) (jk_worker_t *w, jk_logger_t *l);

};

/*
 * Essentially, an abstract base class (or factory class) with a single
 * method -- think of it as createWorker() or the Factory Method Design
 * Pattern.  There is a different worker_factory function for each of the
 * different types of workers.  The set of all these functions is created
 * at startup from the list in jk_worker_list.h, and then the correct one
 * is chosen in jk_worker.c->wc_create_worker().  See jk_worker.c and
 * jk_ajp13_worker.c/jk_ajp14_worker.c for examples.
 *
 * This allows new workers to be written without modifing the plugin code
 * for the various web servers (since the only link is through
 * jk_worker_list.h).
 */
typedef int (JK_METHOD * worker_factory) (jk_worker_t **w,
                                          const char *name,
                                          jk_logger_t *l);

void jk_init_ws_service(jk_ws_service_t *s);


#ifdef __cplusplus
}
#endif                          /* __cplusplus */

#endif                          /* JK_SERVICE_H */