mod_proxy_balancer.c

apache服务器源代码（版本号：2.2.2）

            worker = (proxy_worker *)balancer->workers->elts;
            for (n = 0; n < balancer->workers->nelts; n++) {

                ap_rvputs(r, "<tr>\n<td><a href=\"", r->uri, "?b=",
                          balancer->name + sizeof("balancer://") - 1, "&w=",
                          ap_escape_uri(r->pool, worker->name),
                          "\">", NULL);
                ap_rvputs(r, worker->name, "</a></td>", NULL);
                ap_rvputs(r, "<td>", worker->s->route, NULL);
                ap_rvputs(r, "</td><td>", worker->s->redirect, NULL);
                ap_rprintf(r, "</td><td>%d</td><td>", worker->s->lbfactor);
                if (worker->s->status & PROXY_WORKER_DISABLED)
                    ap_rputs("Dis", r);
                else if (worker->s->status & PROXY_WORKER_IN_ERROR)
                    ap_rputs("Err", r);
                else if (worker->s->status & PROXY_WORKER_INITIALIZED)
                    ap_rputs("Ok", r);
                else
                    ap_rputs("-", r);
                ap_rputs("</td></tr>\n", r);

                ++worker;
            }
            ap_rputs("</table>\n", r);
            ++balancer;
        }
        ap_rputs("<hr />\n", r);
        if (wsel && bsel) {
            ap_rputs("<h3>Edit worker settings for ", r);
            ap_rvputs(r, wsel->name, "</h3>\n", NULL);
            ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
            ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
            ap_rputs("<table><tr><td>Load factor:</td><td><input name=\"lf\" type=text ", r);
            ap_rprintf(r, "value=\"%d\"></td><tr>\n", wsel->s->lbfactor);
            ap_rputs("<tr><td>Route:</td><td><input name=\"wr\" type=text ", r);
            ap_rvputs(r, "value=\"", wsel->route, NULL);
            ap_rputs("\"></td><tr>\n", r);
            ap_rputs("<tr><td>Route Redirect:</td><td><input name=\"rr\" type=text ", r);
            ap_rvputs(r, "value=\"", wsel->redirect, NULL);
            ap_rputs("\"></td><tr>\n", r);
            ap_rputs("<tr><td>Status:</td><td>Disabled: <input name=\"dw\" value=\"Disable\" type=radio", r);
            if (wsel->s->status & PROXY_WORKER_DISABLED)
                ap_rputs(" checked", r);
            ap_rputs("> | Enabled: <input name=\"dw\" value=\"Enable\" type=radio", r);
            if (!(wsel->s->status & PROXY_WORKER_DISABLED))
                ap_rputs(" checked", r);
            ap_rputs("></td><tr>\n", r);
            ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
            ap_rvputs(r, "</table>\n<input type=hidden name=\"w\" ",  NULL);
            ap_rvputs(r, "value=\"", ap_escape_uri(r->pool, wsel->name), "\">\n", NULL);
            ap_rvputs(r, "<input type=hidden name=\"b\" ", NULL);
            ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
                      "\">\n</form>\n", NULL);
            ap_rputs("<hr />\n", r);
        }
        else if (bsel) {
            ap_rputs("<h3>Edit balancer settings for ", r);
            ap_rvputs(r, bsel->name, "</h3>\n", NULL);
            ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
            ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
            ap_rputs("<table><tr><td>StickySession Identifier:</td><td><input name=\"ss\" type=text ", r);
            if (bsel->sticky)
                ap_rvputs(r, "value=\"", bsel->sticky, "\"", NULL);
            ap_rputs("></td><tr>\n<tr><td>Timeout:</td><td><input name=\"tm\" type=text ", r);
            ap_rprintf(r, "value=\"%" APR_TIME_T_FMT "\"></td></tr>\n",
                       apr_time_sec(bsel->timeout));
            ap_rputs("<tr><td>Failover Attempts:</td><td><input name=\"fa\" type=text ", r);
            ap_rprintf(r, "value=\"%d\"></td></tr>\n",
                       bsel->max_attempts);
            ap_rputs("<tr><td>LB Method:</td><td><select name=\"lm\">", r);
            {
                apr_array_header_t *methods;
                ap_list_provider_names_t *method;
                int i;
                methods = ap_list_provider_names(r->pool, PROXY_LBMETHOD, "0");
                method = (ap_list_provider_names_t *)methods->elts;
                for (i = 0; i < methods->nelts; i++) {
                    ap_rprintf(r, "<option value=\"%s\" %s>%s</option>", method->provider_name,
                       (!strcasecmp(bsel->lbmethod->name, method->provider_name)) ? "selected" : "",
                       method->provider_name);
                    method++;
                }
            }
            ap_rputs("</select></td></tr>\n", r);
            ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
            ap_rvputs(r, "</table>\n<input type=hidden name=\"b\" ", NULL);
            ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
                      "\">\n</form>\n", NULL);
            ap_rputs("<hr />\n", r);
        }
        ap_rputs(ap_psignature("",r), r);
        ap_rputs("</body></html>\n", r);
    }
    return OK;
}

static void child_init(apr_pool_t *p, server_rec *s)
{
    while (s) {
        void *sconf = s->module_config;
        proxy_server_conf *conf;
        proxy_balancer *balancer;
        int i;
        conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);

        /* Initialize shared scoreboard data */
        balancer = (proxy_balancer *)conf->balancers->elts;
        for (i = 0; i < conf->balancers->nelts; i++) {
            init_balancer_members(conf, s, balancer);
            balancer++;
        }
        s = s->next;
    }

}

/*
 * The idea behind the find_best_byrequests scheduler is the following:
 *
 * lbfactor is "how much we expect this worker to work", or "the worker's
 * normalized work quota".
 *
 * lbstatus is "how urgent this worker has to work to fulfill its quota
 * of work".
 *
 * We distribute each worker's work quota to the worker, and then look
 * which of them needs to work most urgently (biggest lbstatus).  This
 * worker is then selected for work, and its lbstatus reduced by the
 * total work quota we distributed to all workers.  Thus the sum of all
 * lbstatus does not change.(*)
 *
 * If some workers are disabled, the others will
 * still be scheduled correctly.
 *
 * If a balancer is configured as follows:
 *
 * worker     a    b    c    d
 * lbfactor  25   25   25   25
 *
 * And b gets disabled, the following schedule is produced:
 *
 *    a c d a c d a c d ...
 *
 * Note that the above lbfactor setting is the *exact* same as:
 *
 * worker     a    b    c    d
 * lbfactor   1    1    1    1
 *
 * Asymmetric configurations work as one would expect. For
 * example:
 *
 * worker     a    b    c    d
 * lbfactor   1    1    1    2
 *
 * would have a, b and c all handling about the same
 * amount of load with d handling twice what a or b
 * or c handles individually. So we could see:
 *
 *   b a d c d a c d b d ...
 *
 */

static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
                                request_rec *r)
{
    int i;
    int total_factor = 0;
    proxy_worker *worker = (proxy_worker *)balancer->workers->elts;
    proxy_worker *mycandidate = NULL;


    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "proxy: Entering byrequests for BALANCER (%s)",
                 balancer->name);

    /* First try to see if we have available candidate */
    for (i = 0; i < balancer->workers->nelts; i++) {
        /* If the worker is in error state run
         * retry on that worker. It will be marked as
         * operational if the retry timeout is elapsed.
         * The worker might still be unusable, but we try
         * anyway.
         */
        if (!PROXY_WORKER_IS_USABLE(worker))
            ap_proxy_retry_worker("BALANCER", worker, r->server);
        /* Take into calculation only the workers that are
         * not in error state or not disabled.
         */
        if (PROXY_WORKER_IS_USABLE(worker)) {
            worker->s->lbstatus += worker->s->lbfactor;
            total_factor += worker->s->lbfactor;
            if (!mycandidate || worker->s->lbstatus > mycandidate->s->lbstatus)
                mycandidate = worker;
        }
        worker++;
    }

    if (mycandidate) {
        mycandidate->s->lbstatus -= total_factor;
        mycandidate->s->elected++;
    }

    return mycandidate;
}

/*
 * The idea behind the find_best_bytraffic scheduler is the following:
 *
 * We know the amount of traffic (bytes in and out) handled by each
 * worker. We normalize that traffic by each workers' weight. So assuming
 * a setup as below:
 *
 * worker     a    b    c
 * lbfactor   1    1    3
 *
 * the scheduler will allow worker c to handle 3 times the
 * traffic of a and b. If each request/response results in the
 * same amount of traffic, then c would be accessed 3 times as
 * often as a or b. If, for example, a handled a request that
 * resulted in a large i/o bytecount, then b and c would be
 * chosen more often, to even things out.
 */
static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
                                         request_rec *r)
{
    int i;
    apr_off_t mytraffic = 0;
    apr_off_t curmin = 0;
    proxy_worker *worker = (proxy_worker *)balancer->workers->elts;
    proxy_worker *mycandidate = NULL;

    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "proxy: Entering bytraffic for BALANCER (%s)",
                 balancer->name);

    /* First try to see if we have available candidate */
    for (i = 0; i < balancer->workers->nelts; i++) {
        /* If the worker is in error state run
         * retry on that worker. It will be marked as
         * operational if the retry timeout is elapsed.
         * The worker might still be unusable, but we try
         * anyway.
         */
        if (!PROXY_WORKER_IS_USABLE(worker))
            ap_proxy_retry_worker("BALANCER", worker, r->server);
        /* Take into calculation only the workers that are
         * not in error state or not disabled.
         */
        if (PROXY_WORKER_IS_USABLE(worker)) {
            mytraffic = (worker->s->transferred/worker->s->lbfactor) +
                        (worker->s->read/worker->s->lbfactor);
            if (!mycandidate || mytraffic < curmin) {
                mycandidate = worker;
                curmin = mytraffic;
            }
        }
        worker++;
    }

    if (mycandidate) {
        mycandidate->s->elected++;
    }

    return mycandidate;
}

/*
 * How to add additional lbmethods:
 *   1. Create func which determines "best" candidate worker
 *      (eg: find_best_bytraffic, above)
 *   2. Register it as a provider.
 */
static const proxy_balancer_method byrequests =
{
    "byrequests",
    &find_best_byrequests,
    NULL
};

static const proxy_balancer_method bytraffic =
{
    "bytraffic",
    &find_best_bytraffic,
    NULL
};

static void ap_proxy_balancer_register_hook(apr_pool_t *p)
{
    /* Only the mpm_winnt has child init hook handler.
     * make sure that we are called after the mpm
     * initializes and after the mod_proxy
     */
    static const char *const aszPred[] = { "mpm_winnt.c", "mod_proxy.c", NULL};
     /* manager handler */
    ap_hook_handler(balancer_handler, NULL, NULL, APR_HOOK_FIRST);
    ap_hook_child_init(child_init, aszPred, NULL, APR_HOOK_MIDDLE);
    proxy_hook_pre_request(proxy_balancer_pre_request, NULL, NULL, APR_HOOK_FIRST);
    proxy_hook_post_request(proxy_balancer_post_request, NULL, NULL, APR_HOOK_FIRST);
    proxy_hook_canon_handler(proxy_balancer_canon, NULL, NULL, APR_HOOK_FIRST);
    ap_register_provider(p, PROXY_LBMETHOD, "bytraffic", "0", &bytraffic);
    ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
}

module AP_MODULE_DECLARE_DATA proxy_balancer_module = {
    STANDARD20_MODULE_STUFF,
    NULL,       /* create per-directory config structure */
    NULL,       /* merge per-directory config structures */
    NULL,       /* create per-server config structure */
    NULL,       /* merge per-server config structures */
    NULL,       /* command apr_table_t */
    ap_proxy_balancer_register_hook /* register hooks */
};