/* ========================================================================= *
 *                                                                           *
 *                 The Apache Software License,  Version 1.1                 *
 *                                                                           *
 *          Copyright (c) 1999-2001 The Apache Software Foundation.          *
 *                           All rights reserved.                            *
 *                                                                           *
 * ========================================================================= *
 *                                                                           *
 * Redistribution and use in source and binary forms,  with or without modi- *
 * fication, are permitted provided that the following conditions are met:   *
 *                                                                           *
 * 1. Redistributions of source code  must retain the above copyright notice *
 *    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 end-user documentation  included with the redistribution,  if any, *
 *    must include the following acknowlegement:                             *
 *                                                                           *
 *       "This product includes  software developed  by the Apache  Software *
 *        Foundation <http://www.apache.org/>."                              *
 *                                                                           *
 *    Alternately, this acknowlegement may appear in the software itself, if *
 *    and wherever such third-party acknowlegements normally appear.         *
 *                                                                           *
 * 4. The names  "The  Jakarta  Project",  "Jk",  and  "Apache  Software     *
 *    Foundation"  must not be used  to endorse or promote  products derived *
 *    from this  software without  prior  written  permission.  For  written *
 *    permission, please contact <apache@apache.org>.                        *
 *                                                                           *
 * 5. Products derived from this software may not be called "Apache" nor may *
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 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES *
 * INCLUDING, BUT NOT LIMITED TO,  THE IMPLIED WARRANTIES OF MERCHANTABILITY *
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 * THE APACHE  SOFTWARE  FOUNDATION OR  ITS CONTRIBUTORS  BE LIABLE  FOR ANY *
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 * DAMAGES (INCLUDING,  BUT NOT LIMITED TO,  PROCUREMENT OF SUBSTITUTE GOODS *
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 * ANY  WAY  OUT OF  THE  USE OF  THIS  SOFTWARE,  EVEN  IF  ADVISED  OF THE *
 * POSSIBILITY OF SUCH DAMAGE.                                               *
 *                                                                           *
 * ========================================================================= *
 *                                                                           *
 * This software  consists of voluntary  contributions made  by many indivi- *
 * duals on behalf of the  Apache Software Foundation.  For more information *
 * on the Apache Software Foundation, please see <http://www.apache.org/>.   *
 *                                                                           *
 * ========================================================================= */

/***************************************************************************
 * Description: Load balancer worker, knows how to load balance among      *
 *              several workers.                                           *
 * Author:      Gal Shachor <shachor@il.ibm.com>                           *
 * Based on:                                                               *
 * Version:     $Revision: 1.13 $                                           *
 ***************************************************************************/

#include "jk_pool.h"
#include "jk_service.h"
#include "jk_util.h"
#include "jk_worker.h"
#include "jk_lb_worker.h"

/*
 * The load balancing code in this 
 */


/* 
 * Time to wait before retry...
 */
#define WAIT_BEFORE_RECOVER (60*1) 
#define ADDITINAL_WAIT_LOAD (20)

struct worker_record {
    char    *name;
    double  lb_factor;
    double  lb_value;
    int     is_local_worker;
    int     in_error_state;
    int     in_recovering;
    time_t  error_time;
    jk_worker_t *w;
};
typedef struct worker_record worker_record_t;

struct lb_worker {
    worker_record_t *lb_workers;
    unsigned num_of_workers;

    jk_pool_t p;
    jk_pool_atom_t buf[TINY_POOL_SIZE];

    char *name; 
    jk_worker_t worker;
    int  in_local_worker_mode;
    int  local_worker_only;
    int  sticky_session;
};
typedef struct lb_worker lb_worker_t;

struct lb_endpoint {    
    jk_endpoint_t *e;
    lb_worker_t *worker;
    
    jk_endpoint_t endpoint;
};
typedef struct lb_endpoint lb_endpoint_t;


/* ========================================================================= */
/* Retrieve the parameter with the given name                                */
static char *get_path_param(jk_ws_service_t *s,
                            const char *name)
{
    char *id_start = NULL;
    for(id_start = strstr(s->req_uri, name) ; 
        id_start ; 
        id_start = strstr(id_start + 1, name)) {
        if('=' == id_start[strlen(name)]) {
            /*
             * Session path-cookie was found, get it's value
             */
            id_start += (1 + strlen(name));
            if(strlen(id_start)) {
                char *id_end;
                id_start = jk_pool_strdup(s->pool, id_start);
                /* 
                 * The query string is not part of req_uri, however
                 * to be on the safe side lets remove the trailing query 
                 * string if appended...
                 */
                if(id_end = strchr(id_start, '?')) { 
                    *id_end = '\0';
                }
                return id_start;
            }
        }
    }
  
    return NULL;
}

/* ========================================================================= */
/* Retrieve the cookie with the given name                                   */
static char *get_cookie(jk_ws_service_t *s,
                        const char *name)
{
    unsigned i;

    for(i = 0 ; i < s->num_headers ; i++) {
        if(0 == strcasecmp(s->headers_names[i], "cookie")) {

            char *id_start;
            for(id_start = strstr(s->headers_values[i], name) ; 
                id_start ; 
                id_start = strstr(id_start + 1, name)) {
                if('=' == id_start[strlen(name)]) {
                    /*
                     * Session cookie was found, get it's value
                     */
                    id_start += (1 + strlen(name));
                    if(strlen(id_start)) {
                        char *id_end;
                        id_start = jk_pool_strdup(s->pool, id_start);
                        if(id_end = strchr(id_start, ';')) {
                            *id_end = '\0';
                        }
                        return id_start;
                    }
                }
            }
        }
    }

    return NULL;
}


/* ========================================================================= */
/* Retrieve session id from the cookie or the parameter                      */
/* (parameter first)                                                         */
static char *get_sessionid(jk_ws_service_t *s)
{
    char *val;
    val = get_path_param(s, JK_PATH_SESSION_IDENTIFIER);
    if(!val) {
        val = get_cookie(s, JK_SESSION_IDENTIFIER);
    }
    return val;
}

static char *get_session_route(jk_ws_service_t *s)
{
    char *sessionid = get_sessionid(s);
    char *ch;

    if(!sessionid) {
        return NULL;
    }

    /*
     * Balance parameter is appended to the end
     */  
    ch = strrchr(sessionid, '.');
    if(!ch) {
        return 0;
    }
    ch++;
    if(*ch == '\0') {
        return NULL;
    }
    return ch;
}

static void close_workers(lb_worker_t *p, 
                          int num_of_workers,
                          jk_logger_t *l)
{
    int i = 0;
    for(i = 0 ; i < num_of_workers ; i++) {
        p->lb_workers[i].w->destroy(&(p->lb_workers[i].w),
                                    l);
    }
}

static double get_max_lb(lb_worker_t *p) 
{
    unsigned i;
    double rc = 0.0;    

    for(i = 0 ; i < p->num_of_workers ; i++) {
        if(!p->lb_workers[i].in_error_state) {
            if(p->lb_workers[i].lb_value > rc) {
                rc = p->lb_workers[i].lb_value;
            }
        }            
    }

    return rc;

}

static worker_record_t *get_most_suitable_worker(lb_worker_t *p, 
                                                 jk_ws_service_t *s, int attempt)
{
    worker_record_t *rc = NULL;
    double lb_min = 0.0;    
    unsigned i;
    char *session_route = NULL;

    if (p->sticky_session) {
        session_route = get_session_route(s);
    }

    if(session_route) {
        for(i = 0 ; i < p->num_of_workers ; i++) {
            if(0 == strcmp(session_route, p->lb_workers[i].name)) {
                /* First attempt will allways be to the
                   correct host. If this is indeed down and no
                   hope of recovery, we'll go to fail-over
                */
                if(attempt>0 && p->lb_workers[i].in_error_state) {
                   break;
                } else {
                    return &(p->lb_workers[i]);
                }
            }
        }
    }

    for(i = 0 ; i < p->num_of_workers ; i++) {
        if (!p->in_local_worker_mode || p->lb_workers[i].is_local_worker || !p->local_worker_only) {
            if(p->lb_workers[i].in_error_state) {
                if(!p->lb_workers[i].in_recovering) {
                    time_t now = time(0);
                    if((now - p->lb_workers[i].error_time) > WAIT_BEFORE_RECOVER) {
                        p->lb_workers[i].in_recovering  = JK_TRUE;
                        p->lb_workers[i].error_time     = now;
                        rc = &(p->lb_workers[i]);
    
                        break;
                    }
                }
            } else {
                if(p->lb_workers[i].lb_value < lb_min || !rc) {
                    lb_min = p->lb_workers[i].lb_value;
                    rc = &(p->lb_workers[i]);
                    if (rc->is_local_worker) break;
                }
            }
        }
    }

    if(rc && !rc->is_local_worker) {
        rc->lb_value += rc->lb_factor;                
    }

    return rc;
}
    
static int JK_METHOD service(jk_endpoint_t *e, 
                             jk_ws_service_t *s,
                             jk_logger_t *l,
                             int *is_recoverable_error)
{
    jk_log(l, JK_LOG_DEBUG, 
           "Into jk_endpoint_t::service\n");

    if(e && e->endpoint_private && s && is_recoverable_error) {
        lb_endpoint_t *p = e->endpoint_private;
        jk_endpoint_t *end = NULL;
        int attempt=0;

        /* you can not recover on another load balancer */
        *is_recoverable_error = JK_FALSE;

        
        while(1) {
            worker_record_t *rec = get_most_suitable_worker(p->worker, s, attempt++);
            int rc;

            if(rec) {
                int is_recoverable = JK_FALSE;
                
                s->jvm_route = jk_pool_strdup(s->pool,  rec->name);

                rc = rec->w->get_endpoint(rec->w, &end, l);
                if(rc && end) {
                    int src = end->service(end, s, l, &is_recoverable);
                    end->done(&end, l);
                    if(src ) {                        
                        if(rec->in_recovering && rec->lb_value != 0) {
                            rec->lb_value = get_max_lb(p->worker) + ADDITINAL_WAIT_LOAD;
                        }
                        rec->in_error_state = JK_FALSE;
                        rec->in_recovering  = JK_FALSE;
                        rec->error_time     = 0;                        
                        return JK_TRUE;
                    } 
                }

                /*
                 * Service failed !!!
                 *
                 * Time for fault tolerance (if possible)...
                 */

                rec->in_error_state = JK_TRUE;
                rec->in_recovering  = JK_FALSE;
                rec->error_time     = time(0);

                if(!is_recoverable) {
                    /*
                     * Error is not recoverable - break with an error.
                     */
                    jk_log(l, JK_LOG_ERROR, 
                           "lb: unrecoverable error, request failed. Tomcat failed in the middle of request, we can't recover to another instance.\n");
                    break;
                }

                /* 
                 * Error is recoverable by submitting the request to
                 * another worker... Lets try to do that.
                 */
                 jk_log(l, JK_LOG_DEBUG, 
                        "In jk_endpoint_t::service, recoverable error... will try to recover on other host\n");
            } else {
                /* NULL record, no more workers left ... */
                 jk_log(l, JK_LOG_ERROR, 
                        "lb: All tomcat instances failed, no more workers left.\n");
                 return JK_FALSE;
                break;
            }
        }
    }

    jk_log(l, JK_LOG_ERROR, 
           "In jk_endpoint_t::service: NULL Parameters\n");

    return JK_FALSE;
}

static int JK_METHOD done(jk_endpoint_t **e,
                          jk_logger_t *l)
{
    jk_log(l, JK_LOG_DEBUG, 
           "Into jk_endpoint_t::done\n");

    if(e && *e && (*e)->endpoint_private) {
        lb_endpoint_t *p = (*e)->endpoint_private;

        if(p->e) {
            p->e->done(&p->e, l);
        }

        free(p);
        *e = NULL;
        return JK_TRUE;
    }

    jk_log(l, JK_LOG_ERROR, 
           "In jk_endpoint_t::done: NULL Parameters\n");

    return JK_FALSE;
}

static int JK_METHOD validate(jk_worker_t *pThis,
                              jk_map_t *props,                            
                              jk_worker_env_t *we,
                              jk_logger_t *l)
{
    jk_log(l, JK_LOG_DEBUG, 
           "Into jk_worker_t::validate\n");

    if(pThis && pThis->worker_private) {        
        lb_worker_t *p = pThis->worker_private;
        char **worker_names;
        unsigned num_of_workers;
        p->in_local_worker_mode = JK_FALSE;
        p->local_worker_only = jk_get_local_worker_only_flag(props, p->name);
        p->sticky_session = jk_get_is_sticky_session(props, p->name);
        
        if(jk_get_lb_worker_list(props,
                                 p->name,
                                 &worker_names, 
                                 &num_of_workers) && num_of_workers) {
            unsigned i = 0;
            unsigned j = 0;

            p->lb_workers = jk_pool_alloc(&p->p, 
                                          num_of_workers * sizeof(worker_record_t));

            if(!p->lb_workers) {
                return JK_FALSE;
            }

            for(i = 0 ; i < num_of_workers ; i++) {
                p->lb_workers[i].name = jk_pool_strdup(&p->p, worker_names[i]);
                p->lb_workers[i].lb_factor = jk_get_lb_factor(props, 
                                                               worker_names[i]);
                if(p->lb_workers[i].lb_factor < 0) {
                    p->lb_workers[i].lb_factor = -1 * p->lb_workers[i].lb_factor;
                }
                if (0 < p->lb_workers[i].lb_factor) {
                    p->lb_workers[i].lb_factor = 1/p->lb_workers[i].lb_factor;
                }

                p->lb_workers[i].is_local_worker = jk_get_is_local_worker(props, worker_names[i]);
                if (p->lb_workers[i].is_local_worker) p->in_local_worker_mode = JK_TRUE;
                /* 
                 * Allow using lb in fault-tolerant mode.
                 * A value of 0 means the worker will be used for all requests without
                 * sessions
                 */
                p->lb_workers[i].lb_value = p->lb_workers[i].lb_factor;
                p->lb_workers[i].in_error_state = JK_FALSE;
                p->lb_workers[i].in_recovering  = JK_FALSE;
                if(!wc_create_worker(p->lb_workers[i].name, 
                                     props, 
                                     &(p->lb_workers[i].w), 
                                     we,
                                     l) || !p->lb_workers[i].w) {
                    break;
                } else if (p->lb_workers[i].is_local_worker) {
                    /*
                     * If lb_value is 0 than move it at the beginning of the list
                     */
                    if (i != j) {
                        worker_record_t tmp_worker;
                        tmp_worker = p->lb_workers[j];
                        p->lb_workers[j] = p->lb_workers[i];
                        p->lb_workers[i] = tmp_worker;
                    }
                    j++;
                }
            }
            
            if (!p->in_local_worker_mode) {
                p->local_worker_only = JK_FALSE;
            }
            
            if(i != num_of_workers) {
                close_workers(p, i, l);
                jk_log(l, JK_LOG_DEBUG, 
                       "In jk_worker_t::validate: Failed to create worker %s\n",
                       p->lb_workers[i].name);

            } else {
                for (i = 0; i < num_of_workers; i++) {
                    jk_log(l, JK_LOG_DEBUG,
                        "Balanced worker %i has name %s\n",
                        i, p->lb_workers[i].name);
                }
                jk_log(l, JK_LOG_DEBUG,
                        "in_local_worker_mode: %s\n",
                        (p->in_local_worker_mode ? "true" : "false"));
                jk_log(l, JK_LOG_DEBUG,
                        "local_worker_only: %s\n",
                        (p->local_worker_only ? "true" : "false"));
                p->num_of_workers = num_of_workers;
                return JK_TRUE;
            }
        }        
    }

    jk_log(l, JK_LOG_ERROR, 
           "In jk_worker_t::validate: NULL Parameters\n");

    return JK_FALSE;
}

static int JK_METHOD init(jk_worker_t *pThis,
                          jk_map_t *props, 
                          jk_worker_env_t *we,
                          jk_logger_t *log)
{
    /* Nothing to do for now */
    return JK_TRUE;
}

static int JK_METHOD get_endpoint(jk_worker_t *pThis,
                                  jk_endpoint_t **pend,
                                  jk_logger_t *l)
{
    jk_log(l, JK_LOG_DEBUG, 
           "Into jk_worker_t::get_endpoint\n");

    if(pThis && pThis->worker_private && pend) {        
        lb_endpoint_t *p = (lb_endpoint_t *)malloc(sizeof(lb_endpoint_t));
        if(p) {
            p->e = NULL;
            p->worker = pThis->worker_private;
            p->endpoint.endpoint_private = p;
            p->endpoint.service = service;
            p->endpoint.done = done;
            *pend = &p->endpoint;

            return JK_TRUE;
        }
        jk_log(l, JK_LOG_ERROR, 
               "In jk_worker_t::get_endpoint, malloc failed\n");
    } else {
        jk_log(l, JK_LOG_ERROR, 
               "In jk_worker_t::get_endpoint, NULL parameters\n");
    }

    return JK_FALSE;
}

static int JK_METHOD destroy(jk_worker_t **pThis,
                             jk_logger_t *l)
{
    jk_log(l, JK_LOG_DEBUG, 
           "Into jk_worker_t::destroy\n");

    if(pThis && *pThis && (*pThis)->worker_private) {
        lb_worker_t *private_data = (*pThis)->worker_private;

        close_workers(private_data, 
                      private_data->num_of_workers,
                      l);

        jk_close_pool(&private_data->p);
        free(private_data);

        return JK_TRUE;
    }

    jk_log(l, JK_LOG_ERROR, 
           "In jk_worker_t::destroy, NULL parameters\n");
    return JK_FALSE;
}

int JK_METHOD lb_worker_factory(jk_worker_t **w,
                                const char *name,
                                jk_logger_t *l)
{
    jk_log(l, JK_LOG_DEBUG, 
           "Into lb_worker_factory\n");

    if(NULL != name && NULL != w) {
        lb_worker_t *private_data = 
            (lb_worker_t *)malloc(sizeof(lb_worker_t));

        if(private_data) {

            jk_open_pool(&private_data->p, 
                         private_data->buf, 
                         sizeof(jk_pool_atom_t) * TINY_POOL_SIZE);

            private_data->name = jk_pool_strdup(&private_data->p, name);          

            if(private_data->name) {
                private_data->lb_workers = NULL;
                private_data->num_of_workers = 0;
                private_data->worker.worker_private = private_data;
                private_data->worker.validate       = validate;
                private_data->worker.init           = init;
                private_data->worker.get_endpoint   = get_endpoint;
                private_data->worker.destroy        = destroy;

                *w = &private_data->worker;
                return JK_TRUE;
            }

            jk_close_pool(&private_data->p);
            free(private_data);
        }
        jk_log(l, JK_LOG_ERROR, 
               "In lb_worker_factory, malloc failed\n");
    } else {
        jk_log(l, JK_LOG_ERROR, 
               "In lb_worker_factory, NULL parameters\n");
    }

    return JK_FALSE;
}