Starting with descheduler release v0.10.0 container images are available in the official k8s container registry.
| Descheduler Version | Container Image | Architectures |
|---|---|---|
| v0.25.0 | k8s.gcr.io/descheduler/descheduler:v0.25.0 | AMD64 ARM64 ARMv7 |
| v0.24.1 | k8s.gcr.io/descheduler/descheduler:v0.24.1 | AMD64 ARM64 ARMv7 |
| v0.24.0 | k8s.gcr.io/descheduler/descheduler:v0.24.0 | AMD64 ARM64 ARMv7 |
| v0.23.1 | k8s.gcr.io/descheduler/descheduler:v0.23.1 | AMD64 ARM64 ARMv7 |
| v0.22.0 | k8s.gcr.io/descheduler/descheduler:v0.22.0 | AMD64 ARM64 ARMv7 |
| v0.21.0 | k8s.gcr.io/descheduler/descheduler:v0.21.0 | AMD64 ARM64 ARMv7 |
| v0.20.0 | k8s.gcr.io/descheduler/descheduler:v0.20.0 | AMD64 ARM64 |
| v0.19.0 | k8s.gcr.io/descheduler/descheduler:v0.19.0 | AMD64 |
| v0.18.0 | k8s.gcr.io/descheduler/descheduler:v0.18.0 | AMD64 |
| v0.10.0 | k8s.gcr.io/descheduler/descheduler:v0.10.0 | AMD64 |
Note that multi-arch container images cannot be pulled by kind from a registry. Therefore starting with descheduler release v0.20.0 use the below process to download the official descheduler image into a kind cluster.
kind create cluster
docker pull k8s.gcr.io/descheduler/descheduler:v0.20.0
kind load docker-image k8s.gcr.io/descheduler/descheduler:v0.20.0
The examples directory has descheduler policy configuration examples.
The descheduler has many CLI options that can be used to override its default behavior.
descheduler --help
The descheduler evicts pods which may be bound to less desired nodes
Usage:
descheduler [flags]
descheduler [command]
Available Commands:
completion generate the autocompletion script for the specified shell
help Help about any command
version Version of descheduler
Flags:
--add-dir-header If true, adds the file directory to the header of the log messages (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--alsologtostderr log to standard error as well as files (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--bind-address ip The IP address on which to listen for the --secure-port port. The associated interface(s) must be reachable by the rest of the cluster, and by CLI/web clients. If blank or an unspecified address (0.0.0.0 or ::), all interfaces will be used. (default 0.0.0.0)
--cert-dir string The directory where the TLS certs are located. If --tls-cert-file and --tls-private-key-file are provided, this flag will be ignored. (default "apiserver.local.config/certificates")
--descheduling-interval duration Time interval between two consecutive descheduler executions. Setting this value instructs the descheduler to run in a continuous loop at the interval specified.
--disable-metrics Disables metrics. The metrics are by default served through https://localhost:10258/metrics. Secure address, resp. port can be changed through --bind-address, resp. --secure-port flags.
--dry-run execute descheduler in dry run mode.
-h, --help help for descheduler
--http2-max-streams-per-connection int The limit that the server gives to clients for the maximum number of streams in an HTTP/2 connection. Zero means to use golang's default.
--kubeconfig string File with kube configuration.
--leader-elect Start a leader election client and gain leadership before executing the main loop. Enable this when running replicated components for high availability.
--leader-elect-lease-duration duration The duration that non-leader candidates will wait after observing a leadership renewal until attempting to acquire leadership of a led but unrenewed leader slot. This is effectively the maximum duration that a leader can be stopped before it is replaced by another candidate. This is only applicable if leader election is enabled. (default 15s)
--leader-elect-renew-deadline duration The interval between attempts by the acting master to renew a leadership slot before it stops leading. This must be less than or equal to the lease duration. This is only applicable if leader election is enabled. (default 10s)
--leader-elect-resource-lock string The type of resource object that is used for locking during leader election. Supported options are 'endpoints', 'configmaps', 'leases', 'endpointsleases' and 'configmapsleases'. (default "leases")
--leader-elect-resource-name string The name of resource object that is used for locking during leader election. (default "descheduler")
--leader-elect-resource-namespace string The namespace of resource object that is used for locking during leader election. (default "kube-system")
--leader-elect-retry-period duration The duration the clients should wait between attempting acquisition and renewal of a leadership. This is only applicable if leader election is enabled. (default 2s)
--log-backtrace-at traceLocation when logging hits line file:N, emit a stack trace (default :0) (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--log_dir string If non-empty, write log files in this directory (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--log_file string If non-empty, use this log file (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--log_file_max_size uint Defines the maximum size a log file can grow to. Unit is megabytes. If the value is 0, the maximum file size is unlimited. (default 1800) (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--log-flush-frequency duration Maximum number of seconds between log flushes (default 5s)
--logging-format string Sets the log format. Permitted formats: "text", "json". Non-default formats don't honor these flags: --add-dir-header, --alsologtostderr, --log-backtrace-at, --log_dir, --log_file, --log_file_max_size, --logtostderr, --skip-headers, --skip-log-headers, --stderrthreshold, --log-flush-frequency.\nNon-default choices are currently alpha and subject to change without warning. (default "text")
--logtostderr log to standard error instead of files (default true) (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--one-output If true, only write logs to their native severity level (vs also writing to each lower severity level) (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--permit-address-sharing If true, SO_REUSEADDR will be used when binding the port. This allows binding to wildcard IPs like 0.0.0.0 and specific IPs in parallel, and it avoids waiting for the kernel to release sockets in TIME_WAIT state. [default=false]
--permit-port-sharing If true, SO_REUSEPORT will be used when binding the port, which allows more than one instance to bind on the same address and port. [default=false]
--policy-config-file string File with descheduler policy configuration.
--secure-port int The port on which to serve HTTPS with authentication and authorization. If 0, don't serve HTTPS at all. (default 10258)
--skip-headers If true, avoid header prefixes in the log messages (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--skip-log-headers If true, avoid headers when opening log files (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--stderrthreshold severity logs at or above this threshold go to stderr (default 2) (DEPRECATED: will be removed in a future release, see https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components)
--tls-cert-file string File containing the default x509 Certificate for HTTPS. (CA cert, if any, concatenated after server cert). If HTTPS serving is enabled, and --tls-cert-file and --tls-private-key-file are not provided, a self-signed certificate and key are generated for the public address and saved to the directory specified by --cert-dir.
--tls-cipher-suites strings Comma-separated list of cipher suites for the server. If omitted, the default Go cipher suites will be used.
Preferred values: TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384, TLS_CHACHA20_POLY1305_SHA256, TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305, TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, TLS_RSA_WITH_AES_128_CBC_SHA, TLS_RSA_WITH_AES_128_GCM_SHA256, TLS_RSA_WITH_AES_256_CBC_SHA, TLS_RSA_WITH_AES_256_GCM_SHA384.
Insecure values: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_RC4_128_SHA, TLS_RSA_WITH_3DES_EDE_CBC_SHA, TLS_RSA_WITH_AES_128_CBC_SHA256, TLS_RSA_WITH_RC4_128_SHA.
--tls-min-version string Minimum TLS version supported. Possible values: VersionTLS10, VersionTLS11, VersionTLS12, VersionTLS13
--tls-private-key-file string File containing the default x509 private key matching --tls-cert-file.
--tls-sni-cert-key namedCertKey A pair of x509 certificate and private key file paths, optionally suffixed with a list of domain patterns which are fully qualified domain names, possibly with prefixed wildcard segments. The domain patterns also allow IP addresses, but IPs should only be used if the apiserver has visibility to the IP address requested by a client. If no domain patterns are provided, the names of the certificate are extracted. Non-wildcard matches trump over wildcard matches, explicit domain patterns trump over extracted names. For multiple key/certificate pairs, use the --tls-sni-cert-key multiple times. Examples: "example.crt,example.key" or "foo.crt,foo.key:*.foo.com,foo.com". (default [])
-v, --v Level number for the log level verbosity
--vmodule moduleSpec comma-separated list of pattern=N settings for file-filtered logging
Use "descheduler [command] --help" for more information about a command.
This section contains descriptions of real world production use cases.
When initially migrating applications from a static virtual machine infrastructure to a cloud native k8s infrastructure there can be a tendency to treat application pods like static virtual machines. One approach to help prevent developers and operators from treating pods like virtual machines is to ensure that pods only run for a fixed amount of time.
The PodLifeTime strategy can be used to ensure that old pods are evicted. It is recommended to create a
pod disruption budget for each
application to ensure application availability.
descheduler -v=3 --evict-local-storage-pods --policy-config-file=pod-life-time.yml
This policy configuration file ensures that pods created more than 7 days ago are evicted.
---
apiVersion: "descheduler/v1alpha1"
kind: "DeschedulerPolicy"
strategies:
"PodLifeTime":
enabled: true
params:
podLifeTime:
maxPodLifeTimeSeconds: 604800 # pods run for a maximum of 7 days
If your cluster has been running for a long period of time, you may find that the resource utilization is not very
balanced. The following two strategies can be used to rebalance your cluster based on cpu, memory
or number of pods.
Using LowNodeUtilization, descheduler will rebalance the cluster based on memory by evicting pods
from nodes with memory utilization over 70% to nodes with memory utilization below 20%.
apiVersion: "descheduler/v1alpha1"
kind: "DeschedulerPolicy"
strategies:
"LowNodeUtilization":
enabled: true
params:
nodeResourceUtilizationThresholds:
thresholds:
"memory": 20
targetThresholds:
"memory": 70
Using HighNodeUtilization, descheduler will rebalance the cluster based on memory by evicting pods
from nodes with memory utilization lower than 20%. This should be use NodeResourcesFit with the MostAllocated scoring strategy based on these doc.
The evicted pods will be compacted into minimal set of nodes.
apiVersion: "descheduler/v1alpha1"
kind: "DeschedulerPolicy"
strategies:
"HighNodeUtilization":
enabled: true
params:
nodeResourceUtilizationThresholds:
thresholds:
"memory": 20
Descheduler's RemovePodsViolatingNodeTaints strategy can be combined with
Node Problem Detector and
Cluster Autoscaler to automatically remove
Nodes which have problems. Node Problem Detector can detect specific Node problems and report them to the API server.
There is a feature called TaintNodeByCondition of the node controller that takes some conditions and turns them into taints. Currently, this only works for the default node conditions: PIDPressure, MemoryPressure, DiskPressure, Ready, and some cloud provider specific conditions.
The Descheduler will then deschedule workloads from those Nodes. Finally, if the descheduled Node's resource
allocation falls below the Cluster Autoscaler's scale down threshold, the Node will become a scale down candidate
and can be removed by Cluster Autoscaler. These three components form an autohealing cycle for Node problems.
NOTE
Once kubernetes/node-problem-detector#565 is available in NPD, we need to update this section.