evrpc.h File Reference

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

Go to the source code of this file.

Data Structures

struct  evrpc
struct  evrpc_req_generic
struct  evrpc_request_wrapper
struct  evrpc_status
 provides information about the completed RPC request. More...

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.

Enumerations

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

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.
struct 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
struct 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 object\n");   \
      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()

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:
INPUT  apply the function to an input hook
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  )  [read]

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  )  [read]

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()

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