HaProxy的负载均衡策略roundrobin ?Each server is used in turns, according to their weights. ? ? ? ?
HaProxy的负载均衡策略
roundrobin ?Each server is used in turns, according to their weights.
? ? ? ? ? ? ? ? ?This is the smoothest and fairest algorithm when the server's
? ? ? ? ? ? ? ? ?processing time remains equally distributed. This algorithm
? ? ? ? ? ? ? ? ?is dynamic, which means that server weights may be adjusted
? ? ? ? ? ? ? ? ?on the fly for slow starts for instance. It is limited by
? ? ? ? ? ? ? ? ?design to 4128 active servers per backend. Note that in some
? ? ? ? ? ? ? ? ?large farms, when a server becomes up after having been down
? ? ? ? ? ? ? ? ?for a very short time, it may sometimes take a few hundreds
? ? ? ? ? ? ? ? ?requests for it to be re-integrated into the farm and start
? ? ? ? ? ? ? ? ?receiving traffic. This is normal, though very rare. It is
? ? ? ? ? ? ? ? ?indicated here in case you would have the chance to observe
? ? ? ? ? ? ? ? ?it, so that you don't worry.
? ? ? ? ? ? ? ? ?roundrobin:每个server根据权重依次被轮询，
这个算法是动态的，意味着
? ? ? ? ? ? ? ? ?server的权重可以实时地被调整。对于每个haproxy的backend servers的数目
? ? ? ? ? ? ? ? ?而言被限制在4128个活跃数目之内。
? ? ?static-rr ? Each server is used in turns, according to their weights.
? ? ? ? ? ? ? ? ?This algorithm is as similar to roundrobin except that it is
? ? ? ? ? ? ? ? ?static, which means that changing a server's weight on the
? ? ? ? ? ? ? ? ?fly will have no effect. On the other hand, it has no design
? ? ? ? ? ? ? ? ?limitation on the number of servers, and when a server goes
? ? ? ? ? ? ? ? ?up, it is always immediately reintroduced into the farm, once
? ? ? ? ? ? ? ? ?the full map is recomputed. It also uses slightly less CPU to
? ? ? ? ? ? ? ? ?run (around -1%).
? ? ? ? ? ? ? ? ?静态roundrobin(static-rr):跟roundrobin类似，唯一的区别是不可以动态实时
? ? ? ? ? ? ? ? ?server权重和backend 的server数目没有上限。
? ? ?leastconn ? The server with the lowest number of connections receives the
? ? ? ? ? ? ? ? ?connection. Round-robin is performed within groups of servers
? ? ? ? ? ? ? ? ?of the same load to ensure that all servers will be used. Use
? ? ? ? ? ? ? ? ?of this algorithm is recommended where very long sessions are
? ? ? ? ? ? ? ? ?expected, such as LDAP, SQL, TSE, etc... but is not very well
? ? ? ? ? ? ? ? ?suited for protocols using short sessions such as HTTP. This
? ? ? ? ? ? ? ? ?algorithm is dynamic, which means that server weights may be
? ? ? ? ? ? ? ? ?adjusted on the fly for slow starts for instance.
? ? ? ? ? ? ? ? ?最小连接数目负载均衡策略（leastconn）：round-robin适合于各个server负载相同的情况。
? ? ? ? ? ? ? ? ?最小连接数目算法适合于长时间会话，如LDAP，SQL，TSE，但是并不适合于HTTP短连接的协议。
? ? ?source ? ? ?The source IP address is hashed and divided by the total
? ? ? ? ? ? ? ? ?weight of the running servers to designate which server will
? ? ? ? ? ? ? ? ?receive the request. This ensures that the same client IP
? ? ? ? ? ? ? ? ?address will always reach the same server as long as no
? ? ? ? ? ? ? ? ?server goes down or up. If the hash result changes due to the
? ? ? ? ? ? ? ? ?number of running servers changing, many clients will be
? ? ? ? ? ? ? ? ?directed to a different server. This algorithm is generally
? ? ? ? ? ? ? ? ?used in TCP mode where no cookie may be inserted. It may also
? ? ? ? ? ? ? ? ?be used on the Internet to provide a best-effort stickiness
? ? ? ? ? ? ? ? ?to clients which refuse session cookies. This algorithm is
? ? ? ? ? ? ? ? ?static by default, which means that changing a server's
? ? ? ? ? ? ? ? ?weight on the fly will have no effect, but this can be
? ? ? ? ? ? ? ? ?changed using "hash-type".
? ? ? ? ? ? ? ? ?源IP hash散列调度：将源ip地址进行hash，再根据hasn求模或者一致性hash定位到
? ? ? ? ? ? ? ? ?hash表中的server上。相同的ip地址的请求被分发到同一个server上。但当server的数量变化时，
? ? ? ? ? ? ? ? ?来自于同一client的请求可能会被分发到不同的server上。这个算法通常用在没有cookie的tcp模式下。
? ? ?uri ? ? ? ? The left part of the URI (before the question mark) is hashed
? ? ? ? ? ? ? ? ?and divided by the total weight of the running servers. The
? ? ? ? ? ? ? ? ?result designates which server will receive the request. This
? ? ? ? ? ? ? ? ?ensures that a same URI will always be directed to the same
? ? ? ? ? ? ? ? ?server as long as no server goes up or down. This is used
? ? ? ? ? ? ? ? ?with proxy caches and anti-virus proxies in order to maximize
? ? ? ? ? ? ? ? ?the cache hit rate. Note that this algorithm may only be used
? ? ? ? ? ? ? ? ?in an HTTP backend. This algorithm is static by default,
? ? ? ? ? ? ? ? ?which means that changing a server's weight on the fly will
? ? ? ? ? ? ? ? ?have no effect, but this can be changed using "hash-type".
? ? ? ? ? ? ? ? ?This algorithm support two optional parameters "len" and
? ? ? ? ? ? ? ? ?"depth", both followed by a positive integer number. These
? ? ? ? ? ? ? ? ?options may be helpful when it is needed to balance servers
? ? ? ? ? ? ? ? ?based on the beginning of the URI only. The "len" parameter
? ? ? ? ? ? ? ? ?indicates that the algorithm should only consider that many
? ? ? ? ? ? ? ? ?characters at the beginning of the URI to compute the hash.
? ? ? ? ? ? ? ? ?Note that having "len" set to 1 rarely makes sense since most
? ? ? ? ? ? ? ? ?URIs start with a leading "/".
? ? ? ? ? ? ? ? ?The "depth" parameter indicates the maximum directory depth
? ? ? ? ? ? ? ? ?to be used to compute the hash. One level is counted for each
? ? ? ? ? ? ? ? ?slash in the request. If both parameters are specified, the
? ? ? ? ? ? ? ? ?evaluation stops when either is reached.
? ? ?url_param ? The URL parameter specified in argument will be looked up in
? ? ? ? ? ? ? ? ?the query string of each HTTP GET request.
? ? ? ? ? ? ? ? ?If the modifier "check_post" is used, then an HTTP POST
? ? ? ? ? ? ? ? ?request entity will be searched for the parameter argument,
? ? ? ? ? ? ? ? ?when it is not found in a query string after a question mark
? ? ? ? ? ? ? ? ?('?') in the URL. Optionally, specify a number of octets to
? ? ? ? ? ? ? ? ?wait for before attempting to search the message body. If the
? ? ? ? ? ? ? ? ?entity can not be searched, then round robin is used for each
? ? ? ? ? ? ? ? ?request. For instance, if your clients always send the LB
? ? ? ? ? ? ? ? ?parameter in the first 128 bytes, then specify that. The
? ? ? ? ? ? ? ? ?default is 48. The entity data will not be scanned until the
? ? ? ? ? ? ? ? ?required number of octets have arrived at the gateway, this
? ? ? ? ? ? ? ? ?is the minimum of: (default/max_wait, Content-Length or first
? ? ? ? ? ? ? ? ?chunk length). If Content-Length is missing or zero, it does
? ? ? ? ? ? ? ? ?not need to wait for more data than the client promised to
? ? ? ? ? ? ? ? ?send. When Content-Length is present and larger than
? ? ? ? ? ? ? ? ?<max_wait>, then waiting is limited to <max_wait> and it is
? ? ? ? ? ? ? ? ?assumed that this will be enough data to search for the
? ? ? ? ? ? ? ? ?presence of the parameter. In the unlikely event that
? ? ? ? ? ? ? ? ?Transfer-Encoding: chunked is used, only the first chunk is
? ? ? ? ? ? ? ? ?scanned. Parameter values separated by a chunk boundary, may
? ? ? ? ? ? ? ? ?be randomly balanced if at all.
? ? ? ? ? ? ? ? ?If the parameter is found followed by an equal sign ('=') and
? ? ? ? ? ? ? ? ?a value, then the value is hashed and divided by the total
? ? ? ? ? ? ? ? ?weight of the running servers. The result designates which
? ? ? ? ? ? ? ? ?server will receive the request.
? ? ? ? ? ? ? ? ?This is used to track user identifiers in requests and ensure
? ? ? ? ? ? ? ? ?that a same user ID will always be sent to the same server as
? ? ? ? ? ? ? ? ?long as no server goes up or down. If no value is found or if
? ? ? ? ? ? ? ? ?the parameter is not found, then a round robin algorithm is
? ? ? ? ? ? ? ? ?applied. Note that this algorithm may only be used in an HTTP
? ? ? ? ? ? ? ? ?backend. This algorithm is static by default, which means
? ? ? ? ? ? ? ? ?that changing a server's weight on the fly will have no
? ? ? ? ? ? ? ? ?effect, but this can be changed using "hash-type".
? ? ?hdr(name) ? The HTTP header <name> will be looked up in each HTTP request.
? ? ? ? ? ? ? ? ?Just as with the equivalent ACL 'hdr()' function, the header
? ? ? ? ? ? ? ? ?name in parenthesis is not case sensitive. If the header is
? ? ? ? ? ? ? ? ?absent or if it does not contain any value, the roundrobin
? ? ? ? ? ? ? ? ?algorithm is applied instead.
? ? ? ? ? ? ? ? ?An optional 'use_domain_only' parameter is available, for
? ? ? ? ? ? ? ? ?reducing the hash algorithm to the main domain part with some
? ? ? ? ? ? ? ? ?specific headers such as 'Host'. For instance, in the Host
? ? ? ? ? ? ? ? ?value "haproxy.1wt.eu", only "1wt" will be considered.
? ? ? ? ? ? ? ? ?This algorithm is static by default, which means that
? ? ? ? ? ? ? ? ?changing a server's weight on the fly will have no effect,
? ? ? ? ? ? ? ? ?but this can be changed using "hash-type".
? ? ?rdp-cookie
? ? ?rdp-cookie(name)
? ? ? ? ? ? ? ? ?The RDP cookie <name> (or "mstshash" if omitted) will be
? ? ? ? ? ? ? ? ?looked up and hashed for each incoming TCP request. Just as
? ? ? ? ? ? ? ? ?with the equivalent ACL 'req_rdp_cookie()' function, the name
? ? ? ? ? ? ? ? ?is not case-sensitive. This mechanism is useful as a degraded
? ? ? ? ? ? ? ? ?persistence mode, as it makes it possible to always send the
? ? ? ? ? ? ? ? ?same user (or the same session ID) to the same server. If the
? ? ? ? ? ? ? ? ?cookie is not found, the normal roundrobin algorithm is
? ? ? ? ? ? ? ? ?used instead.
? ? ? ? ? ? ? ? ?Note that for this to work, the frontend must ensure that an
? ? ? ? ? ? ? ? ?RDP cookie is already present in the request buffer. For this
? ? ? ? ? ? ? ? ?you must use 'tcp-request content accept' rule combined with
? ? ? ? ? ? ? ? ?a 'req_rdp_cookie_cnt' ACL.
? ? ? ? ? ? ? ? ?This algorithm is static by default, which means that
? ? ? ? ? ? ? ? ?changing a server's weight on the fly will have no effect,
? ? ? ? ? ? ? ? ?but this can be changed us
