Using Node Leases

The Sysdig agent uses Kubernetes Lease to control how and when connections are made to the Kubernetes API Server. This mechanism prevents overloading the Kubernetes API server with connection requests during agent bootup.

Kubernetes node leases are automatically created for agent version 12.0.0 and above. On versions prior to 12.0.0, you must configure node leases as given in the KB article.

Prerequisites

  • Sysdig Agent v11.3.0 or above

  • Kubernetes v1.14 or above

Types of Leases

The agent creates the following leases:

Cold Start

During boot up, the Sysdig agent connects to the Kubernetes API server to retrieve Kubernetes metadata and build a cache. The cold-start leases control the number of agents that build up this cache at any given time. An agent will grab a lease, build its cache, and then release the lease so that another agent can build its cache. This mechanism prevents agents from creating a “boot storm” which can overwhelm the API server in large clusters.

Delegation

In Kubernetes environments, two agents are marked as delegated in each cluster. The delegated agents are the designated agents to request more data from the API server and produce KubeState metrics. The delegation leases will not be released until the agent is terminated.

View Leases

To view the leases, run the following:

$ kubectl get leases -n sysdig-agent

You will see an output similar to the following:

NAME           HOLDER             AGE
cold-start-0                      20m
cold-start-1                      20m
cold-start-2                      21m
cold-start-3   ip-10-20-51-167    21m
cold-start-4                      21m
cold-start-5                      21m
cold-start-6                      20m
cold-start-7                      21m
cold-start-8                      20m
cold-start-9   ip-10-20-51-166   21m
delegation-0   ip-10-20-52-53    21m
delegation-1   ip-10-20-51-98    21m

Troubleshoot Leases

Verify Configuration

When lease-based delegation is working as expected, the agent logs show one of the following:

  • Getting pods only for node <node>

  • Getting pods for all nodes.

  • Both (occasionally on the delegated nodes)

Run the following to confirm that it is working:

$ kubectl logs sysdig-agent-9l2gf -n sysdig-agent | grep -i "getting pods"

The configuration is working as expected if the output on a pod is similar to the following:

2021-05-05 02:48:32.877, 15732.15765, Information, cointerface[15738]: Only getting pods for node ip-10-20-51-166.ec2.internal

Unable to Create Leases

The latest Sysdig ClusterRole is required for the agent to create leases. If you do not have the latest ClusterRole or if you have not configured the ClusterRole correctly, the logs show the following error:

Error, lease_pool_manager[2989554]: Cannot access leases objects: leases.coordination.k8s.io is forbidden: User "system:serviceaccount:sysdig-agent:sysdig-agent" cannot list resource "leases" in API group "coordination.k8s.io" in the namespace "sysdig-agent"

Contact Sysdig Support for help.

Optional Agent Configuration

Several configuration options exist for leases. It is recommended to not change the default settings unless prompted by Sysdig Customer Support.

Configuration

Default

Description

k8s_coldstart:
  enabled: <true/false>

true above agent versions 12.0.0

When true, the agent will attempt to create cold-start leases to control the number of agents which are allowed to build their cache at one time.

k8s_coldstart:
  max_parallel_cold_starts: <int>

10

The number of cold-start leases to be created. This is the number of agents that can connect to the API Server simultaneously during agent initialization.

k8s_coldstart:
  namespace: <string>

sysdig-agent

The namespace to be created. This shouldn’t be needed in agent version 12.0.0 because the DownwardAPI in the ClusterRole will provide the appropriate namespace.

k8s_coldstart:
  enforce_leader_election: <true/false>

false

When true, the agent will not fall back to the previous method if it cannot create leases.This can be useful if the previous method caused API Server problems.

k8s_delegation_election: <true/false>

true above agent versions 12.0.0

When true, the agent will create delegation leases to control which set of agents generate global cluster metrics.



Last modified September 15, 2021