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haproxy/include/common/hash.h

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MEDIUM: backend: Enhance hash-type directive with an algorithm options Summary: In testing at tumblr, we found that using djb2 hashing instead of the default sdbm hashing resulted is better workload distribution to our backends. This commit implements a change, that allows the user to specify the hash function they want to use. It does not limit itself to consistent hashing scenarios. The supported hash functions are sdbm (default), and djb2. For a discussion of the feature and analysis, see mailing list thread "Consistent hashing alternative to sdbm" : http://marc.info/?l=haproxy&m=138213693909219 Note: This change does NOT make changes to new features, for instance, applying an avalance hashing always being performed before applying consistent hashing.
2013-10-30 03:30:51 +00:00
/*
* include/common/hash.h
* Macros for different hashing function.
*
* Copyright (C) 2000-2011 Willy Tarreau - w@1wt.eu
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, version 2.1
* exclusively.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _COMMON_HASH_H_
#define _COMMON_HASH_H_
BUG/MEDIUM: backend: Update hash to use unsigned int throughout When we were generating a hash, it was done using an unsigned long. When the hash was used to select a backend, it was sent as an unsigned int. This made it difficult to predict which backend would be selected. This patch updates get_hash, and the hash methods to use an unsigned int, to remain consistent throughout the codebase. This fix should be backported to 1.5 and probably in part to 1.4.
2014-07-08 15:51:03 +00:00
unsigned int hash_djb2(const char *key, int len);
unsigned int hash_wt6(const char *key, int len);
unsigned int hash_sdbm(const char *key, int len);
MINOR: hash: add new function hash_crc32 This function will be used to perform CRC32 computations. This one wa loosely inspired from crc32b found here, and focuses on size and speed at the same time : http://www.hackersdelight.org/hdcodetxt/crc.c.txt Much faster table-based versions exist but are pointless for our usage here, this hash already sustains gigabit speed which is far faster than what we'd ever need. Better preserve the CPU's cache instead.
2015-01-20 18:17:09 +00:00
unsigned int hash_crc32(const char *key, int len);
MEDIUM: backend: Enhance hash-type directive with an algorithm options Summary: In testing at tumblr, we found that using djb2 hashing instead of the default sdbm hashing resulted is better workload distribution to our backends. This commit implements a change, that allows the user to specify the hash function they want to use. It does not limit itself to consistent hashing scenarios. The supported hash functions are sdbm (default), and djb2. For a discussion of the feature and analysis, see mailing list thread "Consistent hashing alternative to sdbm" : http://marc.info/?l=haproxy&m=138213693909219 Note: This change does NOT make changes to new features, for instance, applying an avalance hashing always being performed before applying consistent hashing.
2013-10-30 03:30:51 +00:00
#endif /* _COMMON_HASH_H_ */