Cluster Ingress Gateway, GoBetween L4 Load Balancer

This feature is not enabled by default.

Role

Services with ip addresses allocated on cluster backend networks are exposable either through portmapping or through an ingress gateway.

The GoBetween ingress gateway is a L4 load-balancer configured by a OpenSVC-specific daemon to expose services through a public ip address.

Several ingress gateways can be running on the same cluster, and services can choose which gateway they want to be exposed through.

Implementation

  • A failover service. The active instance runs a GoBetween load balancer process and a janitoring daemon.
  • The GoBetween daemon is run as a docker container with an inital configuration enabling the Rest API.
  • The janitoring daemon, also run as a docker container, listens to cluster events on the opensvc daemon unix socket (bind-mounted in the container) and configures the load balancer servers through the GoBetween Rest API.
  • The janitoring daemon docker instance runs "privileged" to have r/w access to the opensvc daemon unix socket.
  • The janitoring daemon depends on the Cluster DNS, as the servers backends are deduced from SRV records.

Docker images

  • yyyar/gobetween
  • opensvc/igw_gobetween

Configure

Deploy the GoBetween service

Create the service using the following command. Change the --env options as appropriate:

$ svcmgr create -s ogwl4 \
        --config http://www.opensvc.com/init/static/templates/ogwl4.conf \
        --provision \
        --env public_interface=br-prd \
        --env public_ipaddr=192.168.100.32 \
        --env public_netmask=24

Unfreeze the service:

$ svcmgr unfreeze -s ogwl4

Expose services

The expose ip resources keyword must be set for the cluster DNS to serve the necessary SRV records.

Service exposition through this ingress gateway is controlled through env section keywords. Most keywords are optional.

General

  • igw_gobtw_bind:

    required to configure lb servers.
    <exposed_port>-<addr>:<port> [<exposed_port>-<addr>:<port> ...]
    addr default=0.0.0.0, port default=*
    * = allocated automatically from a predefined range (1024-65535)
    
  • igw_gobtw_target_lb:

    [<hostname> ...]
    optional (default : None)
    If set to a list of ingress gateway hostnames, only those gateways handle the binded servers.
    If not set, all gateways handle the binded servers.
    
  • igw_gobtw_balance:

    the policy used by gobetween to select a backend slot to handle a new connection.
    'weight' is the default balance policy.
    you can also configure to :
            iphash : target backend will be calculated using hash function of client ip address mod backends count.
            leastconn : GoBetween will select backends with least connections to it.
            roundrobin : each new connection will be proxies to next backend in the backends pool successively.
            leastbandwidth : backends with least sum of rx/tx per second traffic will be selected for next request.
    
  • igw_gobtw_protocol:

    default protocol for gobetween is tcp.
    
  • igw_gobtw_max_connections:

    default : 0
    
  • igw_gobtw_client_idle_timeout:

    default : 0
    
  • igw_gobtw_backend_idle_timeout:

    default : 0
    
  • igw_gobtw_sni:

    optional (default : None)
    
  • igw_gobtw_proxy_protocol:

    optional (default : None)
    
  • igw_gobtw_tls:

    required if protocol == "tls" (default : None)
    
  • igw_gobtw_backends_tls:

    optional : backends tls options (if present -- connect to backends through tls) (default : None)
    
  • igw_gobtw_udp:

    optional and only if protocol == "udp"  (default : None)
    
  • igw_gobtw_access:

    optional (default : None)
    

Discovery

The janitor forces GoBetween services backend discovery driver to SRV. The OpenSVC cluster DNS maintains the SRV recordsets up-to-date.

  • igw_gobtw_discovery_kind:

    default : SRV (this discovery method uses DNS lookup to build backends list)
    
  • igw_gobtw_discovery_srv_dns_protocol:

    default : tcp
    
  • igw_gobtw_discovery_srv_lookup_server:

    ip default=<from get_node_config> & port default=53
    use the keyword 'dns_port' in the env section to change the default port.
    
  • igw_gobtw_discovery_srv_lookup_pattern:

    auto configured by default
    
  • igw_gobtw_discovery_failpolicy:

    optional : keeplast or setempty - what to do with backends if discovery fails
    default : keeplast
    
  • igw_gobtw_discovery_interval:

    backends cache invalidation interval; 0 means never.
    default : 0
    
  • igw_gobtw_discovery_timeout:

    optional : max time to wait for discover until falling to failpolicy
    default : 0
    

Healthchecks

Healthchecks are used for determine service status of backend nodes pool If there are no healthcheck server section defined - backend nodes marked as "ok" can be deleted from backend according to discovery rules and intervals

  • igw_gobtw_healthcheck_kind:

    ping : check connection to backend nodes by initiate new connection from GoBetween side to each backend node from discovery list.
    
  • igw_gobtw_healthcheck_interval:

    default : 2s
    
  • igw_gobtw_healthcheck_timeout:

    max time for script to execute until mark as failed (this value should be lower than interval)
    default for ping : 500ms
    
  • igw_gobtw_healthcheck_fails:

    optional
    default : 1
    
  • igw_gobtw_healthcheck_passes:

    optional
    default : 1
    

Verify

Create a load-balanced service

Test with this simple scaler service:

$ svcmgr create -s svcweb \
        --config http://www.opensvc.com/init/static/templates/svcweb.conf \
        --provision

$ svcmgr -s svcweb unfreeze

$ svcmgr scale -s svcweb --to 4

Verify the SRV record

This service exposes 80/tcp to DNS through the following directive

$ svcmgr -s svcweb print config
...
[ip#1]
expose = 80/tcp

$ dig _http._tcp.svcweb.default.svc.cluster7 SRV @192.168.100.29 -p 5300

Adapt the DNS ip address for your context.

Verify the load-balanced server

This service is exposed through the ogwl4 load-balancer port 1024:

$ svcmgr -s svcweb print config
...
[env]
igw_gobtw_bind = 80/tcp-0.0.0.0:1024 443/tcp

$ wget -O- http://192.168.100.32:1024/

Verify the logs

$ docker logs ogwl4.container.0
$ docker logs ogwl4.container.1

Verify GoBetween configuration

$ python -c "import requests; print requests.get(\"http://192.168.100.32:8888/servers\").json()"

Adapt the GoBetween ip address and port for your context.