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https://github.com/google/seesaw

Seesaw v2 is a Linux Virtual Server (LVS) based load balancing platform.
https://github.com/google/seesaw

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Seesaw v2 is a Linux Virtual Server (LVS) based load balancing platform.

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# Seesaw v2



[![GoDoc](https://godoc.org/github.com/google/seesaw?status.svg)](https://godoc.org/github.com/google/seesaw)



Note: This is not an official Google product.



## About



Seesaw v2 is a Linux Virtual Server (LVS) based load balancing platform.



It is capable of providing basic load balancing for servers that are on the

same network, through to advanced load balancing functionality such as anycast,

Direct Server Return (DSR), support for multiple VLANs and centralised

configuration.



Above all, it is designed to be reliable and easy to maintain.



## Requirements



A Seesaw v2 load balancing cluster requires two Seesaw nodes - these can be

physical machines or virtual instances. Each node must have two network

interfaces - one for the host itself and the other for the cluster VIP. All

four interfaces should be connected to the same layer 2 network.



## Building



Seesaw v2 is developed in Go and depends on several Go packages:



- [golang.org/x/crypto/ssh](http://godoc.org/golang.org/x/crypto/ssh)

- [github.com/dlintw/goconf](http://godoc.org/github.com/dlintw/goconf)

- [github.com/golang/glog](http://godoc.org/github.com/golang/glog)

- [github.com/golang/protobuf/proto](http://godoc.org/github.com/golang/protobuf/proto)

- [github.com/miekg/dns](http://godoc.org/github.com/miekg/dns)



Additionally, there is a compile and runtime dependency on

[libnl](https://www.infradead.org/~tgr/libnl/)



On a Debian/Ubuntu style system, you should be able to prepare for building

by running:



    apt-get install golang

    apt-get install libnl-3-dev libnl-genl-3-dev



If your distro has a go version before 1.18, you may need to fetch a newer

release from https://golang.org/dl/.



If you are running before go version 1.11 or you want to set `GO111MODULE=off`,

after setting `GOPATH` to an appropriate location (for example `~/go`):



    go get -u golang.org/x/crypto/ssh

    go get -u github.com/dlintw/goconf

    go get -u github.com/golang/glog

    go get -u github.com/miekg/dns

    go get -u github.com/kylelemons/godebug/pretty

    go get -u github.com/golang/protobuf/proto



Ensure that `${GOPATH}/bin` is in your `${PATH}` and in the seesaw directory:



    make test

    make install



If you wish to regenerate the protobuf code, the protobuf compiler is needed:



    apt-get install protobuf-compiler



The protobuf code can then be regenerated with:



    make proto



## Installing



After `make install` has run successfully, there should be a number of

binaries in `${GOPATH}/bin` with a `seesaw_` prefix. Install these to the

appropriate locations:



    SEESAW_BIN="/usr/local/seesaw"

    SEESAW_ETC="/etc/seesaw"

    SEESAW_LOG="/var/log/seesaw"



    INIT=`ps -p 1 -o comm=`



    install -d "${SEESAW_BIN}" "${SEESAW_ETC}" "${SEESAW_LOG}"



    install "${GOPATH}/bin/seesaw_cli" /usr/bin/seesaw



    for component in {ecu,engine,ha,healthcheck,ncc,watchdog}; do

      install "${GOPATH}/bin/seesaw_${component}" "${SEESAW_BIN}"

    done



    if [ $INIT = "init" ]; then

      install "etc/init/seesaw_watchdog.conf" "/etc/init"

    elif [ $INIT = "systemd" ]; then

      install "etc/systemd/system/seesaw_watchdog.service" "/etc/systemd/system"

      systemctl --system daemon-reload

    fi

    install "etc/seesaw/watchdog.cfg" "${SEESAW_ETC}"



    # Enable CAP_NET_RAW for seesaw binaries that require raw sockets.

    /sbin/setcap cap_net_raw+ep "${SEESAW_BIN}/seesaw_ha"

    /sbin/setcap cap_net_raw+ep "${SEESAW_BIN}/seesaw_healthcheck"



The `setcap` binary can be found in the libcap2-bin package on Debian/Ubuntu.



## Configuring



Each node needs a `/etc/seesaw/seesaw.cfg` configuration file, which provides

information about the node and who its peer is. Additionally, each load

balancing cluster needs a cluster configuration, which is in the form of a

text-based protobuf - this is stored in `/etc/seesaw/cluster.pb`.



An example seesaw.cfg file can be found in

[etc/seesaw/seesaw.cfg.example](etc/seesaw/seesaw.cfg.example) - a minimal

seesaw.cfg provides the following:



- `anycast_enabled` - True if anycast should be enabled for this cluster.

- `name` - The short name of this cluster.

- `node_ipv4` - The IPv4 address of this Seesaw node.

- `peer_ipv4` - The IPv4 address of our peer Seesaw node.

- `vip_ipv4` - The IPv4 address for this cluster VIP.



The VIP floats between the Seesaw nodes and is only active on the current

master. This address needs to be allocated within the same netblock as both

the node IP address and peer IP address.



An example cluster.pb file can be found in

[etc/seesaw/cluster.pb.example](etc/seesaw/cluster.pb.example) - a minimal

`cluster.pb` contains a `seesaw_vip` entry and two `node` entries. For each

service that you want to load balance, a separate `vserver` entry is

needed, with one or more `vserver_entry` sections (one per port/proto pair),

one or more `backends` and one or more `healthchecks`. Further information

is available in the protobuf definition - see

[pb/config/config.proto](pb/config/config.proto).



On an upstart based system, running `restart seesaw_watchdog` will start (or

restart) the watchdog process, which will in turn start the other components.



### Anycast



Seesaw v2 provides full support for anycast VIPs - that is, it will advertise

an anycast VIP when it becomes available and will withdraw the anycast VIP if

it becomes unavailable. For this to work the Quagga BGP daemon needs to be

installed and configured, with the BGP peers accepting host-specific routes

that are advertised from the Seesaw nodes within the anycast range (currently

hardcoded as `192.168.255.0/24`).



## Command Line



Once initial configuration has been performed and the Seesaw components are

running, the state of the Seesaw can be viewed and controlled via the Seesaw

command line interface. Running `seesaw` (assuming `/usr/bin` is in your path)

will give you an interactive prompt - type `?` for a list of top level

commands. A quick summary:



- `config reload` - reload the cluster.pb from the current config source.

- `failover` - failover between the Seesaw nodes.

- `show vservers` - list all vservers configured on this cluster.

- `show vserver ` - show the current state for the named vserver.



## Troubleshooting



A Seesaw should have five components that are running under the watchdog - the

process table should show processes for:



- `seesaw_ecu`

- `seesaw_engine`

- `seesaw_ha`

- `seesaw_healthcheck`

- `seesaw_ncc`

- `seesaw_watchdog`



All Seesaw v2 components have their own logs, in addition to the logging

provided by the watchdog. If any of the processes are not running, check the

corresponding logs in `/var/log/seesaw` (e.g. `seesaw_engine.{log,INFO}`).