Key-Value Store

Cilium uses an external key-value store to exchange information across multiple Cilium instances:

Layout

All data is stored under a common key prefix:

Cluster Nodes

Every agent will register itself as a node in the kvstore and make the following information available to other agents:

• Name
• IP addresses of the node
• Health checking IP addresses
• Allocation range of endpoints on the node

All node keys are attached to a lease owned by the agent of the respective node.

Services

All Kubernetes services are mirrored into the kvstore by the Cilium operator. This is required to implement multi cluster service discovery.

Identities

Any time a new endpoint is started on a Cilium node, it will determine whether the labels for the endpoint are unique and allocate an identity for that set of labels. These identities are only meaningful within the local cluster.

Endpoints

All endpoint IPs and corresponding identities are mirrored to the kvstore by the agent on the node where the endpoint is launched, to allow peer nodes to configure egress policies to endpoints backed by these IPs.

CiliumNetworkPolicyNodeStatus

If handover to Kubernetes is enabled, then each cilium-agent will propagate the state of whether it has realized a given CNP to the key-value store instead of directly writing to kube-apiserver. cilium-operator will listen for updates to this prefix from the key-value store, and will be the sole updater of statuses for CNPs in the cluster.

Heartbeat

The heartbeat key is periodically updated by the operator to contain the current time and date. It is used by agents to validate that kvstore updates can be received.

Leases

With a few exceptions, all keys in the key-value store are owned by a particular agent running on a node. All such keys have a lease attached. The lease is renewed automatically. When the lease expires, the key is removed from the key-value store. This guarantees that keys are removed from the key-value store in the event that an agent dies on a particular and never reappears.

The lease lifetime is set to 15 minutes. The exact expiration behavior is dependent on the kvstore implementation but the expiration typically occurs after double the lease lifetime.

In addition to regular entry leases, all locks in the key-value store are owned by a particular agent running on the node with a separate “lock lease” attached. The lock lease has a default lifetime of 25 seconds.

Debugging

The contents stored in the kvstore can be queued and manipulate using the cilium kvstore command. For additional details, see the command reference.

Example:

$ cilium kvstore get --recursive cilium/state/nodes/
cilium/state/nodes/v1/default/runtime1 => {"Name":"runtime1","IPAddresses":[{"AddressType":"InternalIP","IP":"10.0.2.15"}],"IPv4AllocCIDR":{"IP":"10.11.0.0","Mask":"//8AAA=="},"IPv6AllocCIDR":{"IP":"f00d::a0f:0:0:0","Mask":"//////////////////8AAA=="},"IPv4HealthIP":"","IPv6HealthIP":""}