负载均衡lvs

简介

ipvsadm 是 Linux 内核中的 IP 虚拟服务器（IPVS）管理工具。IPVS是 Linux 内核提供的一种负载均衡解决方案，它允许将入站的网络流量分发到多个后端服务器，以实现负载均衡和高可用性。IPVS通过在内核中维护一个虚拟服务器表，根据特定的负载均衡调度算法将请求转发到后端服务器。

实践

启动几台nginx 作为后台服务器

docker run -d  nginx

集群服务管理

查看

[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn

新增

[root@192-124-95-67 ~]# ipvsadm -A -t 192.124.95.67:80 -s rr
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr

修改

[root@192-124-95-67 ~]# ipvsadm -E -t 192.124.95.67:80 -s wlc
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 wlc

删除

[root@192-124-95-67 ~]# ipvsadm -D -t 192.124.95.67:8080
No such service
[root@192-124-95-67 ~]# ipvsadm -D -t 192.124.95.67:80
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn

删除整个集群

[root@192-124-95-67 ~]# ipvsadm -A -t 192.124.95.67:801 -s rr
[root@192-124-95-67 ~]#
[root@192-124-95-67 ~]# ipvsadm -A -t 192.124.95.67:80 -s rr
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr
TCP  192.124.95.67:801 rr
[root@192-124-95-67 ~]# ipvsadm -C
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn

真实服务器管理

新增

[root@192-124-95-67 ~]# ipvsadm -A -t 192.124.95.67:80 -s rr
[root@192-124-95-67 ~]# ipvsadm -a -t 192.124.95.67:80 -r 172.17.0.2:80 -m
[root@192-124-95-67 ~]# ipvsadm -a -t 192.124.95.67:80 -r 172.17.0.3:80 -m
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr-> 172.17.0.2:80                Masq    1      0          0-> 172.17.0.3:80                Masq    1      0          0

修改

[root@192-124-95-67 ~]# ipvsadm -e -t 192.124.95.67:80 -r 172.17.0.3:80 -m -w 2
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr-> 172.17.0.2:80                Masq    1      0          0-> 172.17.0.3:80                Masq    2      0          0

删除

[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr-> 172.17.0.2:80                Masq    1      0          0-> 172.17.0.3:80                Masq    2      0          0-> 172.17.0.3:81                Masq    1      0          0
[root@192-124-95-67 ~]# ipvsadm -d -t 192.124.95.67:80 -r 172.17.0.3:81
[root@192-124-95-67 ~]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr-> 172.17.0.2:80                Masq    1      0          0-> 172.17.0.3:80                Masq    2      0          0

规则表的备份与还原

[root@192-124-95-67 home]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr-> 172.17.0.2:80                Masq    1      0          0-> 172.17.0.3:80                Masq    1      0          0
TCP  192.124.95.67:801 rr
[root@192-124-95-67 home]# ipvsadm -S > ipvs.bak
[root@192-124-95-67 home]# ipvsadm -C
[root@192-124-95-67 home]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
[root@192-124-95-67 home]# ipvsadm -R < ipvs.bak
[root@192-124-95-67 home]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags-> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.124.95.67:80 rr-> 172.17.0.2:80                Masq    1      0          0-> 172.17.0.3:80                Masq    1      0          0
TCP  192.124.95.67:801 rr

[root@192-124-95-67 home]# cat ipvs.bak
-A -t 192-124-95-67:http -s rr
-a -t 192-124-95-67:http -r 172.17.0.2:http -m -w 1
-a -t 192-124-95-67:http -r 172.17.0.3:http -m -w 1
-A -t 192-124-95-67:device -s rr

帮助手册

Synopsis

ipvsadm -A|E -t|u|f service-address [-s scheduler]

[-p [timeout]] [-O] [-M netmask]
ipvsadm -D -t|u|f service-address
ipvsadm -C
ipvsadm -R
ipvsadm -S [-n]
ipvsadm -a|e -t|u|f service-address -r server-address
[-g|i|m] [-w weight] [-x upper] [-y lower]
ipvsadm -d -t|u|f service-address -r server-address
ipvsadm -L|l [options]
ipvsadm -Z [-t|u|f service-address]
ipvsadm --set tcp tcpfin udp
ipvsadm --start-daemon state [–mcast-interface interface]
[–syncid syncid]
ipvsadm --stop-daemon state
ipvsadm -h
Description
Ipvsadm(8) is used to set up, maintain or inspect the virtual server table in the Linux kernel. The Linux Virtual Server can be used to build scalable network services based on a cluster of two or more nodes. The active node of the cluster redirects service requests to a collection of server hosts that will actually perform the services. Supported features include two protocols (TCP and UDP), three packet-forwarding methods (NAT, tunneling, and direct routing), and eight load balancing algorithms (round robin, weighted round robin, least-connection, weighted least-connection, locality-based least-connection, locality-based least-connection with replication, destination-hashing, and source-hashing).

The command has two basic formats for execution:

ipvsadm COMMAND [protocol] service-address
[scheduling-method] [persistence options]
ipvsadm command [protocol] service-address
server-address [packet-forwarding-method] [weight options]
The first format manipulates a virtual service and the algorithm for assigning service requests to real servers. Optionally, a persistent timeout and network mask for the granularity of a persistent service may be specified. The second format manipulates a real server that is associated with an existing virtual service. When specifying a real server, the packet-forwarding method and the weight of the real server, relative to other real servers for the virtual service, may be specified, otherwise defaults will be used.
COMMANDS

ipvsadm(8) recognises the commands described below. Upper-case commands maintain virtual services. Lower-case commands maintain real servers that are associated with a virtual service.
-A, --add-service
Add a virtual service. A service address is uniquely defined by a triplet: IP address, port number, and protocol. Alternatively, a virtual service may be defined by a firewall-mark.
-E, --edit-service
Edit a virtual service.
-D, --delete-service
Delete a virtual service, along with any associated real servers.
-C, --clear
Clear the virtual server table.
-R, --restore
Restore Linux Virtual Server rules from stdin. Each line read from stdin will be treated as the command line options to a separate invocation of ipvsadm. Lines read from stdin can optionally begin with “ipvsadm”. This option is useful to avoid executing a large number or ipvsadm commands when constructing an extensive routing table.
-S, --save
Dump the Linux Virtual Server rules to stdout in a format that can be read by -R|–restore.
-a, --add-server
Add a real server to a virtual service.
-e, --edit-server
Edit a real server in a virtual service.
-d, --delete-server
Remove a real server from a virtual service.
-L, -l, --list
List the virtual server table if no argument is specified. If a service-address is selected, list this service only. If the -c option is selected, then display the connection table. The exact output is affected by the other arguments given.
-Z, --zero
Zero the packet, byte and rate counters in a service or all services.
–set tcp tcpfin udp
Change the timeout values used for IPVS connections. This command always takes 3 parameters, representing the timeout values (in seconds) for TCP sessions, TCP sessions after receiving a FIN packet, and UDP packets, respectively. A timeout value 0 means that the current timeout value of the corresponding entry is preserved.
–start-daemon state
Start the connection synchronization daemon. The state is to indicate that the daemon is started as master or backup. The connection synchronization daemon is implemented inside the Linux kernel. The master daemon running at the primary load balancer multicasts changes of connections periodically, and the backup daemon running at the backup load balancers receives multicast message and creates corresponding connections. Then, in case the primary load balancer fails, a backup load balancer will takeover, and it has state of almost all connections, so that almost all established connections can continue to access the service.
The sync daemon currently only supports IPv4 connections.
–stop-daemon
Stop the connection synchronization daemon.
-h, --help
Display a description of the command syntax.
PARAMETERS

The commands above accept or require zero or more of the following parameters.
-t, --tcp-service service-address
Use TCP service. The service-address is of the form host[:port]. Host may be one of a plain IP address or a hostname. Port may be either a plain port number or the service name of port. The Port may be omitted, in which case zero will be used. A Port of zero is only valid if the service is persistent as the -p|–persistent option, in which case it is a wild-card port, that is connections will be accepted to any port.
-u, --udp-service service-address
Use UDP service. See the -t|–tcp-service for the description of the service-address.
-f, --fwmark-service integer
Use a firewall-mark, an integer value greater than zero, to denote a virtual service instead of an address, port and protocol (UDP or TCP). The marking of packets with a firewall-mark is configured using the -m|–mark option to iptables(8). It can be used to build a virtual service assoicated with the same real servers, covering multiple IP address, port and protocol tripplets. If IPv6 addresses are used, the -6 option must be used.
Using firewall-mark virtual services provides a convenient method of grouping together different IP addresses, ports and protocols into a single virtual service. This is useful for both simplifying configuration if a large number of virtual services are required and grouping persistence across what would otherwise be multiple virtual services.

-s, --scheduler scheduling-method
scheduling-method Algorithm for allocating TCP connections and UDP datagrams to real servers. Scheduling algorithms are implemented as kernel modules. Ten are shipped with the Linux Virtual Server:
rr - Robin Robin: distributes jobs equally amongst the available real servers.

wrr - Weighted Round Robin: assigns jobs to real servers proportionally to there real servers’ weight. Servers with higher weights receive new jobs first and get more jobs than servers with lower weights. Servers with equal weights get an equal distribution of new jobs.

lc - Least-Connection: assigns more jobs to real servers with fewer active jobs.

wlc - Weighted Least-Connection: assigns more jobs to servers with fewer jobs and relative to the real servers’ weight (Ci/Wi). This is the default.

lblc - Locality-Based Least-Connection: assigns jobs destined for the same IP address to the same server if the server is not overloaded and available; otherwise assign jobs to servers with fewer jobs, and keep it for future assignment.

lblcr - Locality-Based Least-Connection with Replication: assigns jobs destined for the same IP address to the least-connection node in the server set for the IP address. If all the node in the server set are over loaded, it picks up a node with fewer jobs in the cluster and adds it in the sever set for the target. If the server set has not been modified for the specified time, the most loaded node is removed from the server set, in order to avoid high degree of replication.

dh - Destination Hashing: assigns jobs to servers through looking up a statically assigned hash table by their destination IP addresses.

sh - Source Hashing: assigns jobs to servers through looking up a statically assigned hash table by their source IP addresses.

sed - Shortest Expected Delay: assigns an incoming job to the server with the shortest expected delay. The expected delay that the job will experience is (Ci + 1) / Ui if sent to the ith server, in which Ci is the number of jobs on the the ith server and Ui is the fixed service rate (weight) of the ith server.

nq - Never Queue: assigns an incoming job to an idle server if there is, instead of waiting for a fast one; if all the servers are busy, it adopts the Shortest Expected Delay policy to assign the job.

-p, --persistent [timeout]
Specify that a virtual service is persistent. If this option is specified, multiple requests from a client are redirected to the same real server selected for the first request. Optionally, the timeout of persistent sessions may be specified given in seconds, otherwise the default of 300 seconds will be used. This option may be used in conjunction with protocols such as SSL or FTP where it is important that clients consistently connect with the same real server.
Note: If a virtual service is to handle FTP connections then persistence must be set for the virtual service if Direct Routing or Tunnelling is used as the forwarding mechanism. If Masquerading is used in conjunction with an FTP service than persistence is not necessary, but the ip_vs_ftp kernel module must be used. This module may be manually inserted into the kernel using insmod(8).

-M, --netmask netmask
Specify the granularity with which clients are grouped for persistent virtual services. The source address of the request is masked with this netmask to direct all clients from a network to the same real server. The default is 255.255.255.255, that is, the persistence granularity is per client host. Less specific netmasks may be used to resolve problems with non-persistent cache clusters on the client side. IPv6 netmasks should be specified as a prefix length between 1 and 128. The default prefix length is 128.
-r, --real-server server-address
Real server that an associated request for service may be assigned to. The server-address is the host address of a real server, and may plus port. Host can be either a plain IP address or a hostname. Port can be either a plain port number or the service name of port. In the case of the masquerading method, the host address is usually an RFC 1918 private IP address, and the port can be different from that of the associated service. With the tunneling and direct routing methods, port must be equal to that of the service address. For normal services, the port specified in the service address will be used if port is not specified. For fwmark services, port may be omitted, in which case the destination port on the real server will be the destination port of the request sent to the virtual service.
[packet-forwarding-method]
-g, --gatewaying Use gatewaying (direct routing). This is the default.
-i, --ipip Use ipip encapsulation (tunneling).

-m, --masquerading Use masquerading (network access translation, or NAT).

Note: Regardless of the packet-forwarding mechanism specified, real servers for addresses for which there are interfaces on the local node will be use the local forwarding method, then packets for the servers will be passed to upper layer on the local node. This cannot be specified by ipvsadm, rather it set by the kernel as real servers are added or modified.

-w, --weight weight
Weight is an integer specifying the capacity of a server relative to the others in the pool. The valid values of weight are 0 through to 65535. The default is 1. Quiescent servers are specified with a weight of zero. A quiescent server will receive no new jobs but still serve the existing jobs, for all scheduling algorithms distributed with the Linux Virtual Server. Setting a quiescent server may be useful if the server is overloaded or needs to be taken out of service for maintenance.
-x, --u-threshold uthreshold
uthreshold is an integer specifying the upper connection threshold of a server. The valid values of uthreshold are 0 through to 65535. The default is 0, which means the upper connection threshold is not set. If uthreshold is set with other values, no new connections will be sent to the server when the number of its connections exceeds its upper connection threshold.
-y, --l-threshold lthreshold
lthreshold is an integer specifying the lower connection threshold of a server. The valid values of lthreshold are 0 through to 65535. The default is 0, which means the lower connection threshold is not set. If lthreshold is set with other values, the server will receive new connections when the number of its connections drops below its lower connection threshold. If lthreshold is not set but uthreshold is set, the server will receive new connections when the number of its connections drops below three forth of its upper connection threshold.
–mcast-interface interface
Specify the multicast interface that the sync master daemon sends outgoing multicasts through, or the sync backup daemon listens to for multicasts.
–syncid syncid
Specify the syncid that the sync master daemon fills in the SyncID header while sending multicast messages, or the sync backup daemon uses to filter out multicast messages not matched with the SyncID value. The valid values of syncid are 0 through to 255. The default is 0, which means no filtering at all.
-c, --connection
Connection output. The list command with this option will list current IPVS connections.
–timeout
Timeout output. The list command with this option will display the timeout values (in seconds) for TCP sessions, TCP sessions after receiving a FIN packet, and UDP packets.
–daemon
Daemon information output. The list command with this option will display the daemon status and its multicast interface.
–stats
Output of statistics information. The list command with this option will display the statistics information of services and their servers.
–rate
Output of rate information. The list command with this option will display the rate information (such as connections/second, bytes/second and packets/second) of services and their servers.

–thresholds
Output of thresholds information. The list command with this option will display the upper/lower connection threshold information of each server in service listing.
–persistent-conn
Output of persistent connection information. The list command with this option will display the persistent connection counter information of each server in service listing. The persistent connection is used to forward the actual connections from the same client/network to the same server.
–sort
Sort the list of virtual services and real servers. The virtual service entries are sorted in ascending order by <protocol, address, port>. The real server entries are sorted in ascending order by <address, port>. (default)

–nosort
Do not sort the list of virtual services and real servers.
-O, --ops
Specify that a virtual service uses one-packet scheduling. This option can be used only for UDP services. If this option is specified, all connections are created only to schedule one packet. Option is useful to schedule UDP packets from same client port to different real servers.
-n, --numeric
Numeric output. IP addresses and port numbers will be printed in numeric format rather than as as host names and services respectively, which is the default.
–exact
Expand numbers. Display the exact value of the packet and byte counters, instead of only the rounded number in K’s (multiples of 1000) M’s (multiples of 1000K) or G’s (multiples of 1000M). This option is only relevant for the -L command.
-6
Use with -f to signify fwmark rule uses IPv6 addresses.

参考文档

http://124.220.104.235/web/chatgpt
http://www.linuxvirtualserver.org/Documents.html
https://linux.die.net/man/8/ipvsadm?__cf_chl_rt_tk=RzdazyyWRreeHdlH9SxBQsYksmP74r7Bkr7woz3Gcak-1700633510-0-gaNycGzNDaU