jk_lb_worker.c

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/* ========================================================================= *
 *                                                                           *
 *                 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/>."                              *
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 *    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 <[e-mail]>.                        *
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 * 5. Products derived from this software may not be called "Apache" nor may *
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 * 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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 * POSSIBILITY OF SUCH DAMAGE.                                               *
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 * ========================================================================= *
 *                                                                           *
 * 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 <[e-mail]>                           *
 * Based on:                                                               *
 * Version:     $Revision: 1.12 $                                           *
 ***************************************************************************/

#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)
{