extensions/rt_load_balance/rt_load_balance.c

/*********************************************************************************************************
* Software License Agreement (BSD License)                                                               *
* Author: Thomas Klausner <tk@giga.or.at>                                                                *
*                                                                                                        *
* Copyright (c) 2013, 2014 Thomas Klausner                                                               *
* All rights reserved.                                                                                   *
*                                                                                                        *
* Written under contract by nfotex IT GmbH, http://nfotex.com/                                           *
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* Redistribution and use of this software in source and binary forms, with or without modification, are  *
* permitted provided that the following conditions are met:                                              *
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* * Redistributions of source code must retain the above                                                 *
*   copyright notice, this list of conditions and the                                                    *
*   following disclaimer.                                                                                *
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* * Redistributions in binary form must reproduce the above                                              *
*   copyright notice, this list of conditions and the                                                    *
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#include <freeDiameter/extension.h>

/*
 * Load balancing extension. Send request to least-loaded node.
 */

/* The callback for load balancing the requests across the peers */
static int rt_load_balancing(void * cbdata, struct msg ** pmsg, struct fd_list * candidates)
{
	struct fd_list *lic;
	struct msg * msg = *pmsg;
	
	TRACE_ENTRY("%p %p %p", cbdata, msg, candidates);
	
	CHECK_PARAMS(msg && candidates);
	
	/* Check if it is worth processing the message */
	if (FD_IS_LIST_EMPTY(candidates))
		return 0;

	/* load balancing */
	for (lic = candidates->next; lic != candidates; lic = lic->next) {
		struct rtd_candidate * cand = (struct rtd_candidate *) lic;
		struct peer_hdr *peer;
		long to_receive, to_send, load;
		int score;
		CHECK_FCT(fd_peer_getbyid(cand->diamid, cand->diamidlen, 0, &peer));
		CHECK_FCT(fd_peer_get_load_pending(peer, &to_receive, &to_send));
                load = to_receive + to_send;
		/* other routing mechanisms need to add to the
		 * appropriate entries so their base value is high
		 * enough that they are considered */

		/* logarithmic scaling */
                int load_log = 0;
                while (load > 0) {
                    load_log++;
                    load /= 2;
                }
		score = cand->score;
		cand->score -= load_log;
		TRACE_DEBUG(FULL, "evaluated peer `%.*s', score was %d, now %d", (int)cand->diamidlen, cand->diamid, score, cand->score);
	}

	return 0;
}

/* handler */
static struct fd_rt_out_hdl * rt_load_balancing_hdl = NULL;

/* entry point */
static int rt_load_balance_entry(char * conffile)
{
	/* Register the callback */
	CHECK_FCT(fd_rt_out_register(rt_load_balancing, NULL, 10, &rt_load_balancing_hdl));

	TRACE_DEBUG(INFO, "Extension 'Load Balancing' initialized");
	return 0;
}

/* Unload */
void fd_ext_fini(void)
{
	/* Unregister the callbacks */
	CHECK_FCT_DO(fd_rt_out_unregister(rt_load_balancing_hdl, NULL), /* continue */);
	return ;
}

EXTENSION_ENTRY("rt_load_balance", rt_load_balance_entry);