evrpc.h

evrpc.h(3)                 Library Functions Manual                 evrpc.h(3)



NAME
       evrpc.h - This header files provides basic support for an RPC server
       and client.

SYNOPSIS
   Data Structures
       struct evrpc
       struct evrpc_req_generic
       struct evrpc_request_wrapper
       struct evrpc_status
           provides information about the completed RPC request.

   Defines
       #define EVRPC_GENERATE(rpcname, reqstruct, rplystruct)
           Generates the code for receiving and sending an RPC message.
       #define EVRPC_HEADER(rpcname, reqstruct, rplystruct)
           Creates the definitions and prototypes for an RPC.
       #define EVRPC_MAKE_REQUEST(name, pool, request, reply, cb, cbarg)
           evrpc_send_request_##name(pool, request, reply, cb, cbarg)
           launches an RPC and sends it to the server
       #define EVRPC_REGISTER(base, name, request, reply, callback, cbarg)
           register RPCs with the HTTP Server
       #define EVRPC_REGISTER_OBJECT(rpc, name, request, reply)
       #define EVRPC_REQUEST_DONE(rpc_req)
           Creates the reply to an RPC request.
       #define EVRPC_REQUEST_HTTP(rpc_req)   (rpc_req)->http_req
           Provides access to the HTTP request object underlying an RPC.
       #define EVRPC_STATUS_ERR_BADPAYLOAD   2
       #define EVRPC_STATUS_ERR_HOOKABORTED   4
       #define EVRPC_STATUS_ERR_NONE   0
       #define EVRPC_STATUS_ERR_TIMEOUT   1
       #define EVRPC_STATUS_ERR_UNSTARTED   3
       #define EVRPC_STRUCT(rpcname)   struct evrpc_req__##rpcname
           The type of a specific RPC Message.
       #define EVRPC_UNREGISTER(base, name)   evrpc_unregister_rpc(base,
           #name)
           Unregisters an already registered RPC.
       #define INPUT   EVRPC_INPUT
           Deprecated alias for EVRPC_INPUT.
       #define OUTPUT   EVRPC_OUTPUT
           Deprecated alias for EVRPC_OUTPUT.

   Enumerations
       enum EVRPC_HOOK_TYPE { EVRPC_INPUT, EVRPC_OUTPUT }
           Hooks for changing the input and output of RPCs; this can be used
           to implement compression, authentication, encryption, .

   Functions
       void * evrpc_add_hook (void *vbase, enum EVRPC_HOOK_TYPE hook_type,
           int(*cb)(struct evhttp_request *, struct evbuffer *, void *), void
           *cb_arg)
           adds a processing hook to either an rpc base or rpc pool
       void evrpc_free (struct evrpc_base *base)
           Frees the evrpc base.
       evrpc_base * evrpc_init (struct evhttp *server)
           Creates a new rpc base from which RPC requests can be received.
       int evrpc_make_request (struct evrpc_request_wrapper *)
       void evrpc_pool_add_connection (struct evrpc_pool *, struct
           evhttp_connection *)
       void evrpc_pool_free (struct evrpc_pool *pool)
           frees an rpc connection pool
       evrpc_pool * evrpc_pool_new (struct event_base *base)
           creates an rpc connection pool
       void evrpc_pool_set_timeout (struct evrpc_pool *pool, int
           timeout_in_secs)
           Sets the timeout in secs after which a request has to complete.
       int evrpc_register_rpc (struct evrpc_base *, struct evrpc *,
           void(*)(struct evrpc_req_generic *, void *), void *)
       int evrpc_remove_hook (void *vbase, enum EVRPC_HOOK_TYPE hook_type,
           void *handle)
           removes a previously added hook
       int evrpc_unregister_rpc (struct evrpc_base *base, const char *name)

Detailed Description
       This header files provides basic support for an RPC server and client.

       To support RPCs in a server, every supported RPC command needs to be
       defined and registered.

       EVRPC_HEADER(SendCommand, Request, Reply);

       SendCommand is the name of the RPC command. Request is the name of a
       structure generated by event_rpcgen.py. It contains all parameters
       relating to the SendCommand RPC. The server needs to fill in the Reply
       structure. Reply is the name of a structure generated by
       event_rpcgen.py. It contains the answer to the RPC.

       To register an RPC with an HTTP server, you need to first create an RPC
       base with:

       struct evrpc_base *base = evrpc_init(http);

       A specific RPC can then be registered with

       EVRPC_REGISTER(base, SendCommand, Request, Reply,  FunctionCB, arg);

       when the server receives an appropriately formatted RPC, the user
       callback is invokved. The callback needs to fill in the reply
       structure.

       void FunctionCB(EVRPC_STRUCT(SendCommand)* rpc, void *arg);

       To send the reply, call EVRPC_REQUEST_DONE(rpc);

       See the regression test for an example.

Define Documentation
   #define EVRPC_GENERATE(rpcname, reqstruct, rplystruct)
       Generates the code for receiving and sending an RPC message.

       EVRPC_GENERATE is used to create the code corresponding to sending and
       receiving a particular RPC message

       Parameters:
           rpcname the name of the RPC
           reqstruct the name of the RPC request structure
           replystruct the name of the RPC reply structure

       See also:
           EVRPC_HEADER()

   #define EVRPC_HEADER(rpcname, reqstruct, rplystruct)
       Value:

       EVRPC_STRUCT(rpcname) {               struct reqstruct* request;         struct rplystruct* reply;         struct evrpc* rpc;         struct evhttp_request* http_req;         void (*done)(struct evrpc_status *,             struct evrpc* rpc, void *request, void *reply);          };                                                                   int evrpc_send_request_##rpcname(struct evrpc_pool *,     struct reqstruct *, struct rplystruct *,     void (*)(struct evrpc_status *,         struct reqstruct *, struct rplystruct *, void *cbarg),      void *);
       Creates the definitions and prototypes for an RPC.

       You need to use EVRPC_HEADER to create structures and function
       prototypes needed by the server and client implementation. The
       structures have to be defined in an .rpc file and converted to source
       code via event_rpcgen.py

       Parameters:
           rpcname the name of the RPC
           reqstruct the name of the RPC request structure
           replystruct the name of the RPC reply structure

       See also:
           EVRPC_GENERATE()

   #define EVRPC_MAKE_REQUEST(name, pool, request, reply, cb, cbarg)
       evrpc_send_request_##name(pool, request, reply, cb, cbarg)
       launches an RPC and sends it to the server

       EVRPC_MAKE_REQUEST() is used by the client to send an RPC to the
       server.

       Parameters:
           name the name of the RPC
           pool the evrpc_pool that contains the connection objects over which
           the request should be sent.
           request a pointer to the RPC request structure - it contains the
           data to be sent to the server.
           reply a pointer to the RPC reply structure. It is going to be
           filled if the request was answered successfully
           cb the callback to invoke when the RPC request has been answered
           cbarg an additional argument to be passed to the client

       Returns:
           0 on success, -1 on failure

   #define EVRPC_REGISTER(base, name, request, reply, callback, cbarg)
       Value:

       do {     struct evrpc* rpc = (struct evrpc *)calloc(1, sizeof(struct evrpc));     EVRPC_REGISTER_OBJECT(rpc, name, request, reply);     evrpc_register_rpc(base, rpc,         (void (*)(struct evrpc_req_generic*, void *))callback, cbarg);    } while (0)
       register RPCs with the HTTP Server

       registers a new RPC with the HTTP server, each RPC needs to have a
       unique name under which it can be identified.

       Parameters:
           base the evrpc_base structure in which the RPC should be
           registered.
           name the name of the RPC
           request the name of the RPC request structure
           reply the name of the RPC reply structure
           callback the callback that should be invoked when the RPC is
           received. The callback has the following prototype void
           (*callback)(EVRPC_STRUCT(Message)* rpc, void *arg)
           cbarg an additional parameter that can be passed to the callback.
           The parameter can be used to carry around state.

   #define EVRPC_REGISTER_OBJECT(rpc, name, request, reply)
       Value:

       do {     (rpc)->uri = strdup(#name);     if ((rpc)->uri == NULL) {                          fprintf(stderr, 'failed to register object0);         exit(1);                                              }     (rpc)->request_new = (void *(*)(void))request##_new;     (rpc)->request_free = (void (*)(void *))request##_free;     (rpc)->request_unmarshal = (int (*)(void *, struct evbuffer *))request##_unmarshal;     (rpc)->reply_new = (void *(*)(void))reply##_new;     (rpc)->reply_free = (void (*)(void *))reply##_free;     (rpc)->reply_complete = (int (*)(void *))reply##_complete;     (rpc)->reply_marshal = (void (*)(struct evbuffer*, void *))reply##_marshal;   } while (0)

   #define EVRPC_REQUEST_DONE(rpc_req)
       Value:

       do {   struct evrpc_req_generic *_req = (struct evrpc_req_generic *)(rpc_req);   _req->done(_req); } while (0)
       Creates the reply to an RPC request.

       EVRPC_REQUEST_DONE is used to answer a request; the reply is expected
       to have been filled in. The request and reply pointers become invalid
       after this call has finished.

       Parameters:
           rpc_req the rpc request structure provided to the server callback

   #define EVRPC_REQUEST_HTTP(rpc_req)   (rpc_req)->http_req
       Provides access to the HTTP request object underlying an RPC.

       Access to the underlying http object; can be used to look at headers or
       for getting the remote ip address

       Parameters:
           rpc_req the rpc request structure provided to the server callback

       Returns:
           an struct evhttp_request object that can be inspected for HTTP
           headers or sender information.

   #define EVRPC_STRUCT(rpcname)   struct evrpc_req__##rpcname
       The type of a specific RPC Message.

       Parameters:
           rpcname the name of the RPC message

   #define EVRPC_UNREGISTER(base, name)   evrpc_unregister_rpc(base, #name)
       Unregisters an already registered RPC.

       Parameters:
           base the evrpc_base object from which to unregister an RPC
           name the name of the rpc to unregister

       Returns:
           -1 on error or 0 when successful.

       See also:
           EVRPC_REGISTER()

   #define INPUT   EVRPC_INPUT
       Deprecated alias for EVRPC_INPUT.

       Not available on windows, where it conflicts with platform headers.

   #define OUTPUT   EVRPC_OUTPUT
       Deprecated alias for EVRPC_OUTPUT.

       Not available on windows, where it conflicts with platform headers.

Enumeration Type Documentation
   enum EVRPC_HOOK_TYPE
       Hooks for changing the input and output of RPCs; this can be used to
       implement compression, authentication, encryption, .

       Enumerator:

       EVRPC_INPUT
              apply the function to an input hook

       EVRPC_OUTPUT
              apply the function to an output hook

Function Documentation
   void* evrpc_add_hook (void * vbase, enum EVRPC_HOOK_TYPE hook_type,
       int(*)(struct evhttp_request *, struct evbuffer *, void *) cb, void *
       cb_arg)
       adds a processing hook to either an rpc base or rpc pool

       If a hook returns -1, the processing is aborted.

       The add functions return handles that can be used for removing hooks.

       Parameters:
           vbase a pointer to either struct evrpc_base or struct evrpc_pool
           hook_type either INPUT or OUTPUT
           cb the callback to call when the hook is activated
           cb_arg an additional argument for the callback

       Returns:
           a handle to the hook so it can be removed later

       See also:
           evrpc_remove_hook()

   void evrpc_free (struct evrpc_base * base)
       Frees the evrpc base.

       For now, you are responsible for making sure that no rpcs are ongoing.

       Parameters:
           base the evrpc_base object to be freed

       See also:
           evrpc_init

   struct evrpc_base* evrpc_init (struct evhttp * server)
       Creates a new rpc base from which RPC requests can be received.

       Parameters:
           server a pointer to an existing HTTP server

       Returns:
           a newly allocated evrpc_base struct

       See also:
           evrpc_free()

   void evrpc_pool_free (struct evrpc_pool * pool)
       frees an rpc connection pool

       Parameters:
           pool a pointer to an evrpc_pool allocated via evrpc_pool_new()

       See also:
           evrpc_pool_new()

   struct evrpc_pool* evrpc_pool_new (struct event_base * base)
       creates an rpc connection pool

       a pool has a number of connections associated with it. rpc requests are
       always made via a pool.

       Parameters:
           base a pointer to an struct event_based object; can be left NULL in
           singled-threaded applications

       Returns:
           a newly allocated struct evrpc_pool object

       See also:
           evrpc_pool_free()

   void evrpc_pool_set_timeout (struct evrpc_pool * pool, int timeout_in_secs)
       Sets the timeout in secs after which a request has to complete.

       The RPC is completely aborted if it does not complete by then. Setting
       the timeout to 0 means that it never timeouts and can be used to
       implement callback type RPCs.

       Any connection already in the pool will be updated with the new
       timeout. Connections added to the pool after set_timeout has be called
       receive the pool timeout only if no timeout has been set for the
       connection itself.

       Parameters:
           pool a pointer to a struct evrpc_pool object
           timeout_in_secs the number of seconds after which a request should
           timeout and a failure be returned to the callback.

   int evrpc_remove_hook (void * vbase, enum EVRPC_HOOK_TYPE hook_type, void *
       handle)
       removes a previously added hook

       Parameters:
           vbase a pointer to either struct evrpc_base or struct evrpc_pool
           hook_type either INPUT or OUTPUT
           handle a handle returned by evrpc_add_hook()

       Returns:
           1 on success or 0 on failure

       See also:
           evrpc_add_hook()

Author
       Generated automatically by Doxygen for libevent from the source code.



libevent                          31 Mar 2010                       evrpc.h(3)