arcts/keepalived

A small Alpine based Docker container that provides a method of IP high availability via keepalived (VRRP failover), and optional Kubernetes API Server monitoring. If allowed to auto configure (default behaviour) it will automatically generate a unicast based failover configuration with a minimal amount of user supplied information.

For specific information on Keepalived, please see the man page on keepalived.conf or the Keepalived User Guide.

Index

• Prerequisites
• Configuration
  • Execution Control
  • Autoconfiguration Options
  • Kubernetes Options
• Suggested Kubernetes Settings
• Example keepalived Configs
• Example Run Commands

Prerequisites

Before attempting to deploy the keepalived container, the host must allow non local binding of ipv4 addresses. To do this, configure the sysctl tunable net.ipv4.ip_nonlocal_bind=1.

In addition to enabling the nonlocal binds, the container must be run with both host networking (--net=host) and security setting CAP_NET_ADMIN (--cap-add NET_ADMIN) capability. These allow the container to manage the host's networking configuration, and this is essential to the function of keepalived.

Configuration

Execution Control

• KEEPALIVED_AUTOCONF - Enables or disables the auto-configuration of keepalived.

• KEEPALIVED_CONF - The path to the keepalived configuration file.

• KEEPALIVED_CMD - The command called to execute keepalived.

• KEEPALIVED_DEBUG - Enables or disables debug level logging for keepalived (adds -D to KEEPALIVED_CMD.

Autoconfiguration Options

• KEEPALIVED_ADVERT_INT - The VRRP advertisement interval (in seconds).

• KEEPALIVED_AUTH_PASS - A shared password used to authenticate each node in a VRRP group (Note: If password is longer than 8 characters, only the first 8 characters are used).

• KEEPALIVED_INTERFACE - The host interface that keepalived will monitor and use for VRRP traffic.

• KEEPALIVED_PRIORITY - Election value, the server configured with the highest priority will become the Master.

• KEEPALIVED_STATE - Defines the server role as Master or Backup. (Options: MASTER or BACKUP).

• KEEPALIVED_TRACK_INTERFACE_### - An interface that's state should be monitored (e.g. eth0). More than one can be supplied as long as the variable name ends in a number from 0-999.

• KEEPALIVED_UNICAST_SRC_IP - The IP on the host that the keepalived daemon should bind to. Note: If not specified, it will be the first IP bound to the interface specified in KEEPALIVED_INTERFACE.

• KEEPALIVED_UNICAST_PEER_### - An IP of a peer participating in the VRRP group. More tha one can be supplied as long as the variable name ends in a number from 0-999.

• KEEPALIVED_VIRTUAL_IPADDRESS_### - An instance of an address that will be monitored and failed over from one host to another. These should be a quoted string in the form of: <IPADDRESS>/<MASK> brd <BROADCAST_IP> dev <DEVICE> scope <SCOPE> label <LABEL> At a minimum the ip address, mask and device should be specified e.g. KEEPALIVED_VIRTUAL_IPADDRESS_1="10.10.0.2/24 dev eth0". More than one can be supplied as long as the variable name ends in a number from 0-999. Note: Keepalived has a hard limit of 20 addresses that can be monitored. More can be failed over with the monitored addresses via KEEPALIVED_VIRTUAL_IPADDRESS_EXCLUDED_###.

• KEEPALIVED_VIRTUAL_IPADDRESS_EXCLUDED_### - An instance of an address that will be failed over with the monitored addresses supplied via KEEPALIVED_VIRTUAL_IPADDRESS_###. These should be a quoted string in the form of: <IPADDRESS>/<MASK> brd <BROADCAST_IP> dev <DEVICE> scope <SCOPE> label <LABEL> At a minimum the ip address, mask and device should be specified e.g. KEEPALIVED_VIRTUAL_IPADDRESS_EXCLUDED_1="172.16.1.20/24 dev eth1". More than one can be supplied as long as the variable name ends in a number from 0-999.

• KEEPALIVED_VIRTUAL_ROUTER_ID - A unique number from 0 to 255 that should identify the VRRP group. Master and Backup should have the same value. Multiple instances of keepalived can be run on the same host, but each pair MUST have a unique virtual router id.

• KEEPALIVED_KUBE_APISERVER_CHECK - If enabled it configures a simple check script for the Kubernetes API-Server. For more information on this feature, please see the Kubernetes Options section.

Kubernetes Options

• KUBE_APISERVER_ADDRESS - The Virtual IP being used for the Kube API Server. If none is supplied, it is assumed to be the lowest numbered entry in the KEEPALIVED_VIRTUAL_IPADDRESS_### variables.

• KUBE_APISERVER_PORT - The port to use in conjunction with the KUBE_APISERVER_ADDRESS.

• KUBE_APISERVER_CHK_INTERVAL - The interval in seconds between calling the script.

• KUBE_APISERVER_CHK_FALL - The number of consecutive non-zero script exits before setting the state to FAULT.

• KUBE_APISERVER_CHK_RISE - The number of consecutive zero script exits before exiting the FAULT state.

• KUBE_APISERVER_CHK_WEIGHT - The weight to apply to the priority when the service enters the FAULT state.

Suggested Kubernetes Settings

Assuming there are three nodes running the kube-apiserver, you cannot rely on setting just theKEEPALIVED_STATE parameter to manage failover across the nodes.

To manage kube-apiserver failover, enable the healthcheck option with KEEPALIVED_KUBE_APISERVER_CHECK, and set the KEEPALIVED_PRIORITY manually for the three instances.

With the default weight of -50, if node-01 has an issue, it's priority will drop to 150 and allow node-02 to take over, the same is repeated if node-02 has a failure dropping it's weight to 140 and node-03 takes over.

Recovery occurs in the same order with the system with the highest priority being promoted to master.

Example Keepalived Configs

Example Autogenerated Keepalived Master Config

vrrp_instance MAIN {
  state MASTER
  interface eth0
  virtual_router_id 2
  priority 200
  advert_int 1
  unicast_src_ip 10.10.0.21
  unicast_peer {
    10.10.0.22
  }
  authentication {
    auth_type PASS
    auth_pass pwd1
  }
  virtual_ipaddress {
    10.10.0.2/24 dev eth0
  }
  virtual_ipaddress_excluded {
    172.16.1.20/24 dev eth1
  }
  track_interface {
    eth0
    eth1
  }
}

Example Autogenerated Keepalived Backup Config

vrrp_instance MAIN {
  state BACKUP
  interface eth0
  virtual_router_id 2
  priority 100
  advert_int 1
  unicast_src_ip 10.10.0.22
  unicast_peer {
    10.10.0.21
  }
  authentication {
    auth_type PASS
    auth_pass pwd1
  }
  virtual_ipaddress {
    10.10.0.2/24 dev eth0
  }
  virtual_ipaddress_excluded {
    172.16.1.20/24 dev eth1
  }
  track_interface {
    eth0
    eth1
  }
}

Example Run Commands

Example Master Run Command

docker run -d --net=host --cap-add NET_ADMIN \
-e KEEPALIVED_AUTOCONF=true                  \
-e KEEPALIVED_STATE=MASTER                   \
-e KEEPALIVED_INTERFACE=eth0                 \
-e KEEPALIVED_VIRTUAL_ROUTER_ID=2            \
-e KEEPALIVED_UNICAST_SRC_IP=10.10.0.21      \
-e KEEPALIVED_UNICAST_PEER_0=10.10.0.22      \
-e KEEPALIVED_TRACK_INTERFACE_1=eth0         \
-e KEEPALVED_TRACK_INTERFACE_2=eth1          \
-e KEEPALIVED_VIRTUAL_IPADDRESS_1="10.10.0.3/24 dev eth0" \
-e KEEPALIVED_VIRTUAL_IPADDRESS_EXCLUDED_1="172.16.1.20/24 dev eth1" \
arcts/keepalived

Example Backup Run Command

docker run -d --net=host --cap-add NET_ADMIN \
-e KEEPALIVED_AUTOCONF=true                  \
-e KEEPALIVED_STATE=BACKUP                   \
-e KEEPALIVED_INTERFACE=eth0                 \
-e KEEPALIVED_VIRTUAL_ROUTER_ID=2            \
-e KEEPALIVED_UNICAST_SRC_IP=10.10.0.22      \
-e KEEPALIVED_UNICAST_PEER_0=10.10.0.21      \
-e KEEPALIVED_TRACK_INTERFACE_1=eth0         \
-e KEEPALVED_TRACK_INTERFACE_2=eth1          \
-e KEEPALIVED_VIRTUAL_IPADDRESS_1="10.10.0.3/24 dev eth0" \
-e KEEPALIVED_VIRTUAL_IPADDRESS_EXCLUDED_1="172.16.1.20/24 dev eth1" \
arcts/keepalived