evrpc.c

/*
 * Copyright (c) 2000-2004 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#endif

#include <sys/types.h>
#ifndef WIN32
#include <sys/socket.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#include <sys/queue.h>
#include <stdio.h>
#include <stdlib.h>
#ifndef WIN32
#include <unistd.h>
#endif
#ifndef HAVE_TAILQFOREACH
#include <event-internal.h>
#endif

#include <errno.h>
#include <signal.h>
#include <string.h>
#include <assert.h>

#include "event.h"
#include "evrpc.h"
#include "evrpc-internal.h"
#include "evhttp.h"
#include "evutil.h"
#include "log.h"

struct evrpc_base *
evrpc_init(struct evhttp *http_server)
{
        struct evrpc_base* base = calloc(1, sizeof(struct evrpc_base));
        if (base == NULL)
                return (NULL);

        /* we rely on the tagging sub system */
        evtag_init();

        TAILQ_INIT(&base->registered_rpcs);
        TAILQ_INIT(&base->input_hooks);
        TAILQ_INIT(&base->output_hooks);
        base->http_server = http_server;

        return (base);
}

void
evrpc_free(struct evrpc_base *base)
{
        struct evrpc *rpc;
        struct evrpc_hook *hook;

        while ((rpc = TAILQ_FIRST(&base->registered_rpcs)) != NULL) {
                assert(evrpc_unregister_rpc(base, rpc->uri));
        }
        while ((hook = TAILQ_FIRST(&base->input_hooks)) != NULL) {
                assert(evrpc_remove_hook(base, EVRPC_INPUT, hook));
        }
        while ((hook = TAILQ_FIRST(&base->output_hooks)) != NULL) {
                assert(evrpc_remove_hook(base, EVRPC_OUTPUT, hook));
        }
        free(base);
}

void *
evrpc_add_hook(void *vbase,
    enum EVRPC_HOOK_TYPE hook_type,
    int (*cb)(struct evhttp_request *, struct evbuffer *, void *),
    void *cb_arg)
{
        struct _evrpc_hooks *base = vbase;
        struct evrpc_hook_list *head = NULL;
        struct evrpc_hook *hook = NULL;
        switch (hook_type) {
        case EVRPC_INPUT:
                head = &base->in_hooks;
                break;
        case EVRPC_OUTPUT:
                head = &base->out_hooks;
                break;
        default:
                assert(hook_type == EVRPC_INPUT || hook_type == EVRPC_OUTPUT);
        }

        hook = calloc(1, sizeof(struct evrpc_hook));
        assert(hook != NULL);
        
        hook->process = cb;
        hook->process_arg = cb_arg;
        TAILQ_INSERT_TAIL(head, hook, next);

        return (hook);
}

static int
evrpc_remove_hook_internal(struct evrpc_hook_list *head, void *handle)
{
        struct evrpc_hook *hook = NULL;
        TAILQ_FOREACH(hook, head, next) {
                if (hook == handle) {
                        TAILQ_REMOVE(head, hook, next);
                        free(hook);
                        return (1);
                }
        }

        return (0);
}

/*
 * remove the hook specified by the handle
 */

int
evrpc_remove_hook(void *vbase, enum EVRPC_HOOK_TYPE hook_type, void *handle)
{
        struct _evrpc_hooks *base = vbase;
        struct evrpc_hook_list *head = NULL;
        switch (hook_type) {
        case EVRPC_INPUT:
                head = &base->in_hooks;
                break;
        case EVRPC_OUTPUT:
                head = &base->out_hooks;
                break;
        default:
                assert(hook_type == EVRPC_INPUT || hook_type == EVRPC_OUTPUT);
        }

        return (evrpc_remove_hook_internal(head, handle));
}

static int
evrpc_process_hooks(struct evrpc_hook_list *head,
    struct evhttp_request *req, struct evbuffer *evbuf)
{
        struct evrpc_hook *hook;
        TAILQ_FOREACH(hook, head, next) {
                if (hook->process(req, evbuf, hook->process_arg) == -1)
                        return (-1);
        }

        return (0);
}

static void evrpc_pool_schedule(struct evrpc_pool *pool);
static void evrpc_request_cb(struct evhttp_request *, void *);
void evrpc_request_done(struct evrpc_req_generic*);

/*
 * Registers a new RPC with the HTTP server.   The evrpc object is expected
 * to have been filled in via the EVRPC_REGISTER_OBJECT macro which in turn
 * calls this function.
 */

static char *
evrpc_construct_uri(const char *uri)
{
        char *constructed_uri;
        int constructed_uri_len;

        constructed_uri_len = strlen(EVRPC_URI_PREFIX) + strlen(uri) + 1;
        if ((constructed_uri = malloc(constructed_uri_len)) == NULL)
                event_err(1, "%s: failed to register rpc at %s",
                    __func__, uri);
        memcpy(constructed_uri, EVRPC_URI_PREFIX, strlen(EVRPC_URI_PREFIX));
        memcpy(constructed_uri + strlen(EVRPC_URI_PREFIX), uri, strlen(uri));
        constructed_uri[constructed_uri_len - 1] = '\0';

        return (constructed_uri);
}

int
evrpc_register_rpc(struct evrpc_base *base, struct evrpc *rpc,
    void (*cb)(struct evrpc_req_generic *, void *), void *cb_arg)
{
        char *constructed_uri = evrpc_construct_uri(rpc->uri);

        rpc->base = base;
        rpc->cb = cb;
        rpc->cb_arg = cb_arg;

        TAILQ_INSERT_TAIL(&base->registered_rpcs, rpc, next);

        evhttp_set_cb(base->http_server,
            constructed_uri,
            evrpc_request_cb,
            rpc);
        
        free(constructed_uri);

        return (0);
}

int
evrpc_unregister_rpc(struct evrpc_base *base, const char *name)
{
        char *registered_uri = NULL;
        struct evrpc *rpc;

        /* find the right rpc; linear search might be slow */
        TAILQ_FOREACH(rpc, &base->registered_rpcs, next) {
                if (strcmp(rpc->uri, name) == 0)
                        break;
        }
        if (rpc == NULL) {
                /* We did not find an RPC with this name */
                return (-1);
        }
        TAILQ_REMOVE(&base->registered_rpcs, rpc, next);
        
        free((char *)rpc->uri);
        free(rpc);

        registered_uri = evrpc_construct_uri(name);

        /* remove the http server callback */
        assert(evhttp_del_cb(base->http_server, registered_uri) == 0);

        free(registered_uri);
        return (0);
}

static void
evrpc_request_cb(struct evhttp_request *req, void *arg)
{
        struct evrpc *rpc = arg;
        struct evrpc_req_generic *rpc_state = NULL;

        /* let's verify the outside parameters */
        if (req->type != EVHTTP_REQ_POST ||
            EVBUFFER_LENGTH(req->input_buffer) <= 0)
                goto error;

        /*
         * we might want to allow hooks to suspend the processing,
         * but at the moment, we assume that they just act as simple
         * filters.
         */
        if (evrpc_process_hooks(&rpc->base->input_hooks,
                req, req->input_buffer) == -1)
                goto error;

        rpc_state = calloc(1, sizeof(struct evrpc_req_generic));
        if (rpc_state == NULL)
                goto error;

        /* let's check that we can parse the request */
        rpc_state->request = rpc->request_new();
        if (rpc_state->request == NULL)
                goto error;

        rpc_state->rpc = rpc;

        if (rpc->request_unmarshal(
                    rpc_state->request, req->input_buffer) == -1) {
                /* we failed to parse the request; that's a bummer */
                goto error;
        }

        /* at this point, we have a well formed request, prepare the reply */

        rpc_state->reply = rpc->reply_new();
        if (rpc_state->reply == NULL)
                goto error;

        rpc_state->http_req = req;
        rpc_state->done = evrpc_request_done;

        /* give the rpc to the user; they can deal with it */
        rpc->cb(rpc_state, rpc->cb_arg);

        return;

error:
        evrpc_reqstate_free(rpc_state);
        evhttp_send_error(req, HTTP_SERVUNAVAIL, "Service Error");
        return;
}

void
evrpc_reqstate_free(struct evrpc_req_generic* rpc_state)
{
        /* clean up all memory */
        if (rpc_state != NULL) {
                struct evrpc *rpc = rpc_state->rpc;

                if (rpc_state->request != NULL)
                        rpc->request_free(rpc_state->request);
                if (rpc_state->reply != NULL)
                        rpc->reply_free(rpc_state->reply);
                free(rpc_state);
        }
}

void
evrpc_request_done(struct evrpc_req_generic* rpc_state)
{
        struct evhttp_request *req = rpc_state->http_req;
        struct evrpc *rpc = rpc_state->rpc;
        struct evbuffer* data = NULL;

        if (rpc->reply_complete(rpc_state->reply) == -1) {
                /* the reply was not completely filled in.  error out */
                goto error;
        }

        if ((data = evbuffer_new()) == NULL) {
                /* out of memory */
                goto error;
        }

        /* serialize the reply */
        rpc->reply_marshal(data, rpc_state->reply);

        /* do hook based tweaks to the request */
        if (evrpc_process_hooks(&rpc->base->output_hooks,
                req, data) == -1)
                goto error;

        /* on success, we are going to transmit marshaled binary data */
        if (evhttp_find_header(req->output_headers, "Content-Type") == NULL) {
                evhttp_add_header(req->output_headers,
                    "Content-Type", "application/octet-stream");
        }

        evhttp_send_reply(req, HTTP_OK, "OK", data);

        evbuffer_free(data);

        evrpc_reqstate_free(rpc_state);

        return;

error:
        if (data != NULL)
                evbuffer_free(data);
        evrpc_reqstate_free(rpc_state);
        evhttp_send_error(req, HTTP_SERVUNAVAIL, "Service Error");
        return;
}

/* Client implementation of RPC site */

static int evrpc_schedule_request(struct evhttp_connection *connection,
    struct evrpc_request_wrapper *ctx);

struct evrpc_pool *
evrpc_pool_new(struct event_base *base)
{
        struct evrpc_pool *pool = calloc(1, sizeof(struct evrpc_pool));
        if (pool == NULL)
                return (NULL);

        TAILQ_INIT(&pool->connections);
        TAILQ_INIT(&pool->requests);

        TAILQ_INIT(&pool->input_hooks);
        TAILQ_INIT(&pool->output_hooks);

        pool->base = base;
        pool->timeout = -1;

        return (pool);
}

static void
evrpc_request_wrapper_free(struct evrpc_request_wrapper *request)
{
        free(request->name);
        free(request);
}

void
evrpc_pool_free(struct evrpc_pool *pool)
{
        struct evhttp_connection *connection;
        struct evrpc_request_wrapper *request;
        struct evrpc_hook *hook;

        while ((request = TAILQ_FIRST(&pool->requests)) != NULL) {
                TAILQ_REMOVE(&pool->requests, request, next);
                /* if this gets more complicated we need our own function */
                evrpc_request_wrapper_free(request);
        }

        while ((connection = TAILQ_FIRST(&pool->connections)) != NULL) {
                TAILQ_REMOVE(&pool->connections, connection, next);
                evhttp_connection_free(connection);
        }

        while ((hook = TAILQ_FIRST(&pool->input_hooks)) != NULL) {
                assert(evrpc_remove_hook(pool, EVRPC_INPUT, hook));
        }

        while ((hook = TAILQ_FIRST(&pool->output_hooks)) != NULL) {
                assert(evrpc_remove_hook(pool, EVRPC_OUTPUT, hook));
        }

        free(pool);
}

/*
 * Add a connection to the RPC pool.   A request scheduled on the pool
 * may use any available connection.
 */

void
evrpc_pool_add_connection(struct evrpc_pool *pool,
    struct evhttp_connection *connection) {
        assert(connection->http_server == NULL);
        TAILQ_INSERT_TAIL(&pool->connections, connection, next);

        /*
         * associate an event base with this connection
         */
        if (pool->base != NULL)
                evhttp_connection_set_base(connection, pool->base);

        /* 
         * unless a timeout was specifically set for a connection,
         * the connection inherits the timeout from the pool.
         */
        if (connection->timeout == -1)
                connection->timeout = pool->timeout;

        /* 
         * if we have any requests pending, schedule them with the new
         * connections.
         */

        if (TAILQ_FIRST(&pool->requests) != NULL) {
                struct evrpc_request_wrapper *request = 
                    TAILQ_FIRST(&pool->requests);
                TAILQ_REMOVE(&pool->requests, request, next);
                evrpc_schedule_request(connection, request);
        }
}

void
evrpc_pool_set_timeout(struct evrpc_pool *pool, int timeout_in_secs)
{
        struct evhttp_connection *evcon;
        TAILQ_FOREACH(evcon, &pool->connections, next) {
                evcon->timeout = timeout_in_secs;
        }
        pool->timeout = timeout_in_secs;
}


static void evrpc_reply_done(struct evhttp_request *, void *);
static void evrpc_request_timeout(int, short, void *);

/*
 * Finds a connection object associated with the pool that is currently
 * idle and can be used to make a request.
 */
static struct evhttp_connection *
evrpc_pool_find_connection(struct evrpc_pool *pool)
{
        struct evhttp_connection *connection;
        TAILQ_FOREACH(connection, &pool->connections, next) {
                if (TAILQ_FIRST(&connection->requests) == NULL)
                        return (connection);
        }

        return (NULL);
}

/*
 * We assume that the ctx is no longer queued on the pool.
 */
static int
evrpc_schedule_request(struct evhttp_connection *connection,
    struct evrpc_request_wrapper *ctx)
{
        struct evhttp_request *req = NULL;
        struct evrpc_pool *pool = ctx->pool;
        struct evrpc_status status;
        char *uri = NULL;
        int res = 0;

        if ((req = evhttp_request_new(evrpc_reply_done, ctx)) == NULL)
                goto error;

        /* serialize the request data into the output buffer */
        ctx->request_marshal(req->output_buffer, ctx->request);

        uri = evrpc_construct_uri(ctx->name);
        if (uri == NULL)
                goto error;

        /* we need to know the connection that we might have to abort */
        ctx->evcon = connection;

        /* apply hooks to the outgoing request */
        if (evrpc_process_hooks(&pool->output_hooks,
                req, req->output_buffer) == -1)
                goto error;

        if (pool->timeout > 0) {
                /* 
                 * a timeout after which the whole rpc is going to be aborted.
                 */
                struct timeval tv;
                evutil_timerclear(&tv);
                tv.tv_sec = pool->timeout;
                evtimer_add(&ctx->ev_timeout, &tv);
        }

        /* start the request over the connection */
        res = evhttp_make_request(connection, req, EVHTTP_REQ_POST, uri);
        free(uri);

        if (res == -1)
                goto error;

        return (0);

error:
        memset(&status, 0, sizeof(status));
        status.error = EVRPC_STATUS_ERR_UNSTARTED;
        (*ctx->cb)(&status, ctx->request, ctx->reply, ctx->cb_arg);
        evrpc_request_wrapper_free(ctx);
        return (-1);
}

int
evrpc_make_request(struct evrpc_request_wrapper *ctx)
{
        struct evrpc_pool *pool = ctx->pool;

        /* initialize the event structure for this rpc */
        evtimer_set(&ctx->ev_timeout, evrpc_request_timeout, ctx);
        if (pool->base != NULL)
                event_base_set(pool->base, &ctx->ev_timeout);

        /* we better have some available connections on the pool */
        assert(TAILQ_FIRST(&pool->connections) != NULL);

        /* 
         * if no connection is available, we queue the request on the pool,
         * the next time a connection is empty, the rpc will be send on that.
         */
        TAILQ_INSERT_TAIL(&pool->requests, ctx, next);

        evrpc_pool_schedule(pool);

        return (0);
}

static void
evrpc_reply_done(struct evhttp_request *req, void *arg)
{
        struct evrpc_request_wrapper *ctx = arg;
        struct evrpc_pool *pool = ctx->pool;
        struct evrpc_status status;
        int res = -1;
        
        /* cancel any timeout we might have scheduled */
        event_del(&ctx->ev_timeout);

        memset(&status, 0, sizeof(status));
        status.http_req = req;

        /* we need to get the reply now */
        if (req != NULL) {
                /* apply hooks to the incoming request */
                if (evrpc_process_hooks(&pool->input_hooks,
                        req, req->input_buffer) == -1) {
                        status.error = EVRPC_STATUS_ERR_HOOKABORTED;
                        res = -1;
                } else {
                        res = ctx->reply_unmarshal(ctx->reply,
                            req->input_buffer);
                        if (res == -1) {
                                status.error = EVRPC_STATUS_ERR_BADPAYLOAD;
                        }
                }
        } else {
                status.error = EVRPC_STATUS_ERR_TIMEOUT;
        }

        if (res == -1) {
                /* clear everything that we might have written previously */
                ctx->reply_clear(ctx->reply);
        }

        (*ctx->cb)(&status, ctx->request, ctx->reply, ctx->cb_arg);
        
        evrpc_request_wrapper_free(ctx);

        /* the http layer owns the request structure */

        /* see if we can schedule another request */
        evrpc_pool_schedule(pool);
}

static void
evrpc_pool_schedule(struct evrpc_pool *pool)
{
        struct evrpc_request_wrapper *ctx = TAILQ_FIRST(&pool->requests);
        struct evhttp_connection *evcon;

        /* if no requests are pending, we have no work */
        if (ctx == NULL)
                return;

        if ((evcon = evrpc_pool_find_connection(pool)) != NULL) {
                TAILQ_REMOVE(&pool->requests, ctx, next);
                evrpc_schedule_request(evcon, ctx);
        }
}

static void
evrpc_request_timeout(int fd, short what, void *arg)
{
        struct evrpc_request_wrapper *ctx = arg;
        struct evhttp_connection *evcon = ctx->evcon;
        assert(evcon != NULL);

        evhttp_connection_fail(evcon, EVCON_HTTP_TIMEOUT);
}