allow association of meta data with RPC requests for hook processing

svn:r622

ChangeLog

@@ -32,6 +32,7 @@ Changes in current version:
  o support string arrays in event_rpcgen
  o change evrpc hooking to allow pausing of RPCs; this will make it possible for the hook to do some meaning ful work; this is not backwards compatible.
  o allow an http request callback to take ownership of a request structure
+ o allow association of meta data with RPC requests for hook processing
 	
 Changes in 1.4.0:
  o allow \r or \n individually to separate HTTP headers instead of the standard "\r\n"; from Charles Kerr.

evrpc-internal.h

@@ -36,7 +36,9 @@ struct evrpc;
 struct evrpc_hook {
 	TAILQ_ENTRY(evrpc_hook) (next);
 
-	/* returns -1; if the rpc should be aborted, is allowed to rewrite */
+	/* returns EVRPC_TERMINATE; if the rpc should be aborted.
+	 * a hook is is allowed to rewrite the evbuffer
+	 */
 	int (*process)(void *, struct evhttp_request *,
 	    struct evbuffer *, void *);
 	void *process_arg;
@@ -98,4 +100,17 @@ struct evrpc_hook_ctx {
 	void (*cb)(void *, enum EVRPC_HOOK_RESULT);
 };
 
+struct evrpc_meta {
+	TAILQ_ENTRY(evrpc_meta) (next);
+	char *key;
+
+	void *data;
+	size_t data_size;
+};
+
+TAILQ_HEAD(evrpc_meta_list, evrpc_meta);
+
+/* frees the meta data associated with a request */
+static void evrpc_meta_data_free(struct evrpc_meta_list *meta_data);
+
 #endif /* _EVRPC_INTERNAL_H_ */

evrpc.c

@@ -365,6 +365,8 @@ evrpc_reqstate_free(struct evrpc_req_generic* rpc_state)
 	rpc = rpc_state->rpc;
 
 	/* clean up all memory */
+	if (rpc_state->meta_data != NULL)
+		evrpc_meta_data_free(rpc_state->meta_data);
 	if (rpc_state->request != NULL)
 		rpc->request_free(rpc_state->request);
 	if (rpc_state->reply != NULL)
@@ -477,6 +479,8 @@ evrpc_pool_new(struct event_base *base)
 static void
 evrpc_request_wrapper_free(struct evrpc_request_wrapper *request)
 {
+	if (request->meta_data != NULL)
+		evrpc_meta_data_free(request->meta_data);
 	event_free(request->name);
 	event_free(request);
 }
@@ -749,6 +753,41 @@ evrpc_make_request(struct evrpc_request_wrapper *ctx)
 	return (0);
 }
 
+
+struct evrpc_request_wrapper *
+evrpc_send_request_generic(
+	struct evrpc_pool *pool, void *request, void *reply,
+	const char *rpcname,
+	void (*req_marshal)(struct evbuffer*, void *),
+	void (*rpl_clear)(void *),
+	int (*rpl_unmarshal)(void *, struct evbuffer *),
+	void (*cb)(struct evrpc_status *, void *, void *, void *),
+	void *cbarg)
+{
+	struct evrpc_request_wrapper *ctx = (struct evrpc_request_wrapper *)
+	    event_malloc(sizeof(struct evrpc_request_wrapper));
+	if (ctx == NULL)
+		return (NULL);
+
+	ctx->pool = pool;
+	ctx->meta_data = NULL;
+	ctx->evcon = NULL;
+	ctx->name = event_strdup(rpcname);
+	if (ctx->name == NULL) {
+		event_free(ctx);
+		return (NULL);
+	}
+	ctx->cb = cb;
+	ctx->cb_arg = cbarg;
+	ctx->request = request;
+	ctx->reply = reply;
+	ctx->request_marshal = req_marshal;
+	ctx->reply_clear = rpl_clear;
+	ctx->reply_unmarshal = rpl_unmarshal;
+
+	return (ctx);
+}
+
 static void
 evrpc_reply_done_closure(void *, enum EVRPC_HOOK_RESULT);
 
@@ -864,3 +903,66 @@ evrpc_request_timeout(evutil_socket_t fd, short what, void *arg)
 
 	evhttp_connection_fail(evcon, EVCON_HTTP_TIMEOUT);
 }
+
+/*
+ * frees potential meta data associated with a request.
+ */
+
+static void
+evrpc_meta_data_free(struct evrpc_meta_list *meta_data)
+{
+	struct evrpc_meta *entry;
+	assert(meta_data != NULL);
+
+	while ((entry = TAILQ_FIRST(meta_data)) != NULL) {
+		TAILQ_REMOVE(meta_data, entry, next);
+		event_free(entry->key);
+		event_free(entry->data);
+		event_free(entry);
+	}
+
+	event_free(meta_data);
+}
+
+/* adds meta data */
+void
+evrpc_hook_add_meta(void *ctx, const char *key,
+    const void *data, size_t data_size)
+{
+	struct evrpc_request_wrapper *req = ctx;
+	struct evrpc_meta *meta = NULL;
+
+	if (req->meta_data == NULL) {
+		req->meta_data = event_malloc(sizeof(struct evrpc_meta_list));
+		assert(req->meta_data != NULL);
+		TAILQ_INIT(req->meta_data);
+	}
+
+	assert((meta = event_malloc(sizeof(struct evrpc_meta))) != NULL);
+	assert((meta->key = event_strdup(key)) != NULL);
+	meta->data_size = data_size;
+	assert((meta->data = event_malloc(data_size)) != NULL);
+	memcpy(meta->data, data, data_size);
+
+	TAILQ_INSERT_TAIL(req->meta_data, meta, next);
+}
+
+int
+evrpc_hook_find_meta(void *ctx, const char *key, void **data, size_t *data_size)
+{
+	struct evrpc_request_wrapper *req = ctx;
+	struct evrpc_meta *meta = NULL;
+
+	if (req->meta_data == NULL)
+		return (-1);
+
+	TAILQ_FOREACH(meta, req->meta_data, next) {
+		if (strcmp(meta->key, key) == 0) {
+			*data = meta->data;
+			*data_size = meta->data_size;
+			return (0);
+		}
+	}
+
+	return (-1);
+}

evrpc.h

@@ -114,9 +114,16 @@ struct evrpc {
 
 struct evhttp_request;
 struct evrpc_status;
+struct evrpc_meta_list;
 
 /* We alias the RPC specific structs to this voided one */
 struct evrpc_req_generic {
+	/*
+	 * allows association of meta data via hooks - needs to be
+	 * synchronized with evrpc_request_wrapper
+	 */
+	struct evrpc_meta_list *meta_data;
+
 	/* the unmarshaled request object */
 	void *request;
 
@@ -158,6 +165,7 @@ struct evrpc_req_generic {
  */
 #define EVRPC_HEADER(rpcname, reqstruct, rplystruct) \
 EVRPC_STRUCT(rpcname) {	\
+	struct evrpc_meta_list *meta_data; \
 	struct reqstruct* request; \
 	struct rplystruct* reply; \
 	struct evrpc* rpc; \
@@ -172,6 +180,18 @@ int evrpc_send_request_##rpcname(struct evrpc_pool *, \
 	struct reqstruct *, struct rplystruct *, void *cbarg),	\
     void *);
 
+struct evrpc_pool;
+
+/** use EVRPC_GENERATE instead */
+struct evrpc_request_wrapper *evrpc_send_request_generic(
+	struct evrpc_pool *pool, void *request, void *reply,
+	const char *rpcname,
+	void (*req_marshal)(struct evbuffer*, void *),
+	void (*rpl_clear)(void *),
+	int (*rpl_unmarshal)(void *, struct evbuffer *),
+	void (*cb)(struct evrpc_status *, void *, void *, void *),
+	void *cbarg);
+
 /** Generates the code for receiving and sending an RPC message
  *
  * EVRPC_GENERATE is used to create the code corresponding to sending
@@ -190,25 +210,15 @@ int evrpc_send_request_##rpcname(struct evrpc_pool *pool, \
     void *cbarg) { \
 	struct evrpc_status status;				    \
 	struct evrpc_request_wrapper *ctx;			    \
-	ctx = (struct evrpc_request_wrapper *) \
+	ctx = evrpc_send_request_generic(pool, request, reply,	    \
-	    malloc(sizeof(struct evrpc_request_wrapper));	    \
+	    #rpcname,						    \
+	    (void (*)(struct evbuffer *, void *))reqstruct##_marshal, \
+	    (void (*)(void *))rplystruct##_clear, \
+	    (int (*)(void *, struct evbuffer *))rplystruct##_unmarshal, \
+	    (void (*)(struct evrpc_status *, void *, void *, void *))cb, \
+	    cbarg);							\
 	if (ctx == NULL)					    \
 		goto error;					    \
-	ctx->pool = pool;					    \
-	ctx->evcon = NULL;					    \
-	ctx->name = strdup(#rpcname);				    \
-	if (ctx->name == NULL) {				    \
-		free(ctx);					    \
-		goto error;					    \
-	}							    \
-	ctx->cb = (void (*)(struct evrpc_status *, \
-		void *, void *, void *))cb;			    \
-	ctx->cb_arg = cbarg;					    \
-	ctx->request = (void *)request;				    \
-	ctx->reply = (void *)reply;				    \
-	ctx->request_marshal = (void (*)(struct evbuffer *, void *))reqstruct##_marshal; \
-	ctx->reply_clear = (void (*)(void *))rplystruct##_clear;    \
-	ctx->reply_unmarshal = (int (*)(void *, struct evbuffer *))rplystruct##_unmarshal; \
 	return (evrpc_make_request(ctx));			    \
 error:								    \
 	memset(&status, 0, sizeof(status));			    \
@@ -325,7 +335,6 @@ int evrpc_unregister_rpc(struct evrpc_base *base, const char *name);
  * Client-side RPC support
  */
 
-struct evrpc_pool;
 struct evhttp_connection;
 
 /** 
@@ -344,6 +353,12 @@ struct evrpc_status {
 };
 
 struct evrpc_request_wrapper {
+	/*
+	 * allows association of meta data via hooks - needs to be
+	 * synchronized with evrpc_req_generic.
+	 */
+	struct evrpc_meta_list *meta_data;
+
 	TAILQ_ENTRY(evrpc_request_wrapper) next;
 
         /* pool on which this rpc request is being made */
@@ -500,6 +515,33 @@ int evrpc_remove_hook(void *vbase,
 int
 evrpc_resume_request(void *vbase, void *ctx, enum EVRPC_HOOK_RESULT res);
 
+/** adds meta data to request
+ *
+ * evrpc_hook_add_meta() allows hooks to add meta data to a request. for
+ * a client requet, the meta data can be inserted by an outgoing request hook
+ * and retrieved by the incoming request hook.
+ *
+ * @param ctx the context provided to the hook call
+ * @param key a NUL-terminated c-string
+ * @param data the data to be associated with the key
+ * @param data_size the size of the data
+ */
+void evrpc_hook_add_meta(void *ctx, const char *key,
+    const void *data, size_t data_size);
+
+/** retrieves meta data previously associated
+ *
+ * evrpc_hook_find_meta() can be used to retrieve meta data associated to a
+ * request by a previous hook.
+ * @param ctx the context provided to the hook call
+ * @param key a NUL-terminated c-string
+ * @param data pointer to a data pointer that will contain the retrieved data
+ * @param data_size pointer tothe size of the data
+ * @return 0 on success or -1 on failure
+ */
+int evrpc_hook_find_meta(void *ctx, const char *key,
+    void **data, size_t *data_size);
+
 #ifdef __cplusplus
 }
 #endif

test/regress_rpc.c

@@ -417,7 +417,17 @@ rpc_hook_add_header(void *ctx, struct evhttp_request *req,
 		evhttp_add_header(req->input_headers, "X-Hook", hook_type);
 	else 
 		evhttp_add_header(req->output_headers, "X-Hook", hook_type);
-	return (0);
+
+	return (EVRPC_CONTINUE);
+}
+
+static int
+rpc_hook_add_meta(void *ctx, struct evhttp_request *req,
+    struct evbuffer *evbuf, void *arg)
+{
+	evrpc_hook_add_meta(ctx, "meta", "test", 5);
+
+	return (EVRPC_CONTINUE);
 }
 
 static int
@@ -425,12 +435,20 @@ rpc_hook_remove_header(void *ctx, struct evhttp_request *req,
     struct evbuffer *evbuf, void *arg)
 {
 	const char *header = evhttp_find_header(req->input_headers, "X-Hook");
+	void *data = NULL;
+	size_t data_len = 0;
+
 	assert(header != NULL);
 	assert(strcmp(header, arg) == 0);
+
 	evhttp_remove_header(req->input_headers, "X-Hook");
 	evhttp_add_header(req->input_headers, "X-Pool-Hook", "ran");
 
-	return (0);
+	assert(evrpc_hook_find_meta(ctx, "meta", &data, &data_len) == 0);
+	assert(data != NULL);
+	assert(data_len == 5);
+
+	return (EVRPC_CONTINUE);
 }
 
 static void
@@ -457,6 +475,7 @@ rpc_basic_client(void)
 
 	pool = rpc_pool_with_connection(port);
 
+	assert(evrpc_add_hook(pool, OUTPUT, rpc_hook_add_meta, NULL));
 	assert(evrpc_add_hook(pool, INPUT, rpc_hook_remove_header, (void*)"output"));
 
 	/* set up the basic message */