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Kubernetes-Mesos Scheduler
Kubernetes on Mesos does not use the upstream scheduler binary, but replaces it with its own Mesos framework scheduler. The following gives an overview of the differences.
Labels and Mesos Agent Attributes
The scheduler of Kubernetes-Mesos takes labels into account: it matches specified labels in pod specs with defined labels of nodes.
In addition to user defined labels, attributes of Mesos agents are converted into node labels by the scheduler, following the pattern
k8s.mesosphere.io/attribute-<name>: value
As an example, a Mesos agent attribute of generation:2015 will result in the node label
k8s.mesosphere.io/attribute-generation: 2015
and can be used to schedule pods onto nodes which are of generation 2015.
Note: Node labels prefixed by k8s.mesosphere.io are managed by
Kubernetes-Mesos and should not be modified manually by the user or admin. For
example, the Kubernetes-Mesos executor manages k8s.mesosphere.io/attribute
labels and will auto-detect and update modified attributes when the mesos-slave
is restarted.
Tuning
The scheduler configuration can be fine-tuned using an ini-style configuration file.
The filename is passed via --scheduler-config to the km scheduler command.
Be warned though that some them are pretty low-level and one has to know the inner workings of k8sm to find sensible values. Moreover, these settings may change or even disappear from version to version without further notice.
The following settings are the default:
[scheduler]
; duration an offer is viable, prior to being expired
offer-ttl = 5s
; duration an expired offer lingers in history
offer-linger-ttl = 2m
; duration between offer listener notifications
listener-delay = 1s
; size of the pod updates channel
updates-backlog = 2048
; interval we update the frameworkId stored in etcd
framework-id-refresh-interval = 30s
; wait this amount of time after initial registration before attempting
; implicit reconciliation
initial-implicit-reconciliation-delay = 15s
; interval in between internal task status checks/updates
explicit-reconciliation-max-backoff = 2m
; waiting period after attempting to cancel an ongoing reconciliation
explicit-reconciliation-abort-timeout = 30s
initial-pod-backoff = 1s
max-pod-backoff = 60s
http-handler-timeout = 10s
http-bind-interval = 5s
Low-Level Scheduler Architecture
