pod-reaper: kills pods dead

A rules based pod killing container. Pod-Reaper was designed to kill pods that meet specific conditions. See the "Implemented Rules" section below for details on specific rules.

Configuring Pod Reaper

Pod-Reaper is configurable through environment variables. The pod-reaper specific environment variables are:

• NAMESPACE the kubernetes namespace where pod-reaper should look for pods
• GRACE_PERIOD duration that pods should be given to shut down before hard killing the pod
• SCHEDULE schedule for when pod-reaper should look for pods to reap
• RUN_DURATION how long pod-reaper should run before exiting
• EXCLUDE_LABEL_KEY pod metadata label (of key-value pair) that pod-reaper should exclude
• EXCLUDE_LABEL_VALUES comma-separated list of metadata label values (of key-value pair) that pod-reaper should exclude
• REQUIRE_LABEL_KEY pod metadata label (of key-value pair) that pod-reaper should require
• REQUIRE_LABEL_VALUES comma-separated list of metadata label values (of key-value pair) that pod-reaper should require

Additionally, at least one rule must be enabled, or the pod-reaper will error and exit. See the Rules section below for configuring and enabling rules.

Example environment variables:

# pod-reaper configuration
NAMESPACE=test
SCHEDULE=@every 30s
RUN_DURATION=15m
EXCLUDE_LABEL_KEY=pod-reaper
EXCLUDE_LABEL_VALUES=disabled,false

# enable at least one rule
CHAOS_CHANCE=.001

NAMESPACE

Default value: "" (which will look at ALL namespaces)

Controls which kubernetes namespace the pod-reaper is in scope for the pod-reaper. Note that the pod-reaper uses an InClusterConfig which makes use of the service account that kubernetes gives to its pods. Only pods (and namespaces) accessible to this service account will be visible to the pod-reaper.

GRACE_PERIOD

Default value: nil (indicates to the use the default specified for pods)

Controls the grace period between a soft pod termination and a hard termination. This will determine the time between when the pod's containers are send a SIGTERM signal and when they are sent a SIGKILL signal. The format follows the go-lang time.duration format (example: "1h15m30s"). A duration of 0s can be considered a hard kill of the pod.

SCHEDULE

Default value: "@every 1m"

Controls how frequently pod-reaper queries kubernetes for pods. The format follows the upstream cron library https://godoc.org/github.com/robfig/cron. For most use cases, the interval format @every 1h2m3s is sufficient. But more complex use cases can make use of the * * * * * * notation.

RUN_DURATION

Default value: "0s" (which corresponds to running indefinitely)

Controls the minimum duration that pod-reaper will run before intentionally exiting. The value of "0s" (or anything equivalent such as the empty string) will be interpreted as an indefinite run duration. The format follows the go-lang time.duration format (example: "1h15m30s"). Pod-Reaper will not wait for reap-cycles to finishing waiting and will exit immediately (with exit code 0) after the duration has elapsed.

Warnings about RUN_DURATION

• pod-rescheduling: if the reaper completes, even successfully, it may be restarted depending on the pod-spec.
• self-reaping: the pod-reaper can reap itself if configured to do so, this can cause the reaper to not run for the expected duration.

Recommendations:

One time run:

• create a pod spec and apply it to kubernetes
• make the pod spec has restartPolicy: Never
• add an exclusion label and key using EXCLUDE_LABEL_KEY and EXCLUDE_LABEL_VALUES
• make the pod spec for the reaper match an excluded label and key to prevent it from reaping itself

Sustained running:

• do not use RUN_DURATION
• manage the pod reaper via a deployment

EXCLUDE_LABEL_KEY and EXCLUDE_LABEL_VALUES

These environment variables are used to build a label selector to exclude pods from reaping. The key must be a properly formed kubernetes label key. Values are a comma-separated (without whitespace) list of kubernetes label values. Setting exactly one of the key or values environment variables will result in an error.

A pod will be excluded from the pod-reaper if the pod has a metadata label has a key corresponding to the pod-reaper's exclude label key, and that same metadata label has a value in the pod-reaper's list of excluded label values. This means that exclusion requires both the pod-reaper and pod to be configured in a compatible way.

REQUIRE_LABEL_KEY and REQUIRE_LABEL_VALUES

These environment variables build a label selector that pods must match in order to be reaped. Use them the same way as you would EXCLUDE_LABEL_KEY and EXCLUDE_LABEL_VALUES.

Logging

Pod reaper logs in JSON format using a logrus (https://github.com/sirupsen/logrus)

• rule load: customer messages for each rule are logged when the pod-reaper is starting
• reap cycle: a message is logged each time the reaper starts a cycle.
• pod reap: a message is logged (with a reason for each rule) when a pod is flag for reaping.
• exit: a message is logged when the reaper exits successfully (only is RUN_DURATION is specified)

Example Log

{"level":"info","msg":"loaded rule: chaos chance .3","time":"2017-10-18T17:09:25Z"}
{"level":"info","msg":"loaded rule: maximum run duration 2m","time":"2017-10-18T17:09:25Z"}
{"level":"info","msg":"executing reap cycle","time":"2017-10-18T17:09:55Z"}
{"level":"info","msg":"reaping pod","pod":"hello-cloud-deployment-3026746346-bj65k","reasons":["was flagged for chaos","has been running for 3m6.257891269s"],"time":"2017-10-18T17:09:55Z"}
{"level":"info","msg":"reaping pod","pod":"example-pod-deployment-125971999cgsws","reasons":["was flagged for chaos","has been running for 2m55.269615797s"],"time":"2017-10-18T17:09:55Z"}
{"level":"info","msg":"executing reap cycle","time":"2017-10-18T17:10:25Z"}
{"level":"info","msg":"reaping pod","pod":"hello-cloud-deployment-3026746346-grw12","reasons":["was flagged for chaos","has been running for 3m36.054164005s"],"time":"2017-10-18T17:10:25Z"}
{"level":"info","msg":"pod reaper is exiting","time":"2017-10-18T17:10:46Z"}

Implemented Rules

Chaos Chance

Flags a pod for reaping based on a random number generator.

Enabled and configured by setting the environment variable CHAOS_CHANCE with a floating point value. A random number generator will generate a value in range [0,1) and if the the generated value is below the configured chaos chance, the pod will be flagged for reaping.

Example:

# every 30 seconds kill 1/100 pods found (based on random chance)
SCHEDULE=@every 30s
CHAOS_CHANCE=.01

Remember that pods can be excluded from reaping if the pod has a label matching the pod-reaper's configuration. See the EXCLUDE_LABEL_KEY and EXCLUDE_LABEL_VALUES section above for more details.

Container Status

Flags a pod for reaping based on a container within a pod having a specific container status.

Enabled and configured by setting the environment variable CONTAINER_STATUSES with a coma separated list (no whitespace) of statuses. If a pod is in either a waiting or terminated state with a status in the specified list of status, the pod will be flagged for reaping.

Example:

# every 10 minutes, kill all pods with a container with a status ImagePullBackOff, ErrImagePull, or Error
SCHEDULE=@every 10m
CONTAINER_STATUSES=ImagePullBackOff,ErrImagePull,Error

Note that this will not catch statuses that are describing the entire pod like the Evicted status.

Pod Status

Flags a pod for reaping based on the pod status.

Enabled and configured by setting the environment variable POD_STATUSES with a coma separated list (no whitespace) of statuses. If the pod status in the specified list of status, the pod will be flagged for reaping.

Example:

# every 10 minutes, kill all pods with status ImagePullBackOff, ErrImagePull, or Error
SCHEDULE=@every 10m
POD_STATUSES=Evicted,Unknown

Note that pod status is different than container statuses as it checks the status of the overall pod rather than teh status of containers in the pod. The most obvious use case of this if dealing with Evicted pods.

Duration

Flags a pod for reaping based on the pods current run duration.

Enabled and configured by setting the environment variable MAX_DURATION with a valid go-lang time.duration format (example: "1h15m30s"). If a pod has been running longer than the specified duration, the pod will be flagged for reaping.

Running Pod-Reapers

Combining Rules

A pod will only be reaped if ALL rules flag the pod for reaping, but you can achieve reaping on OR logic by simply running another pod-reaper.

For example, in the same pod-reaper container:

CHAOS_CHANCE=.01
RUN_DURATION=2h

Means that 1/100 pods that also have a run duration of over 2 hours will be reaped. If you want 1/100 pods reaped regardless of duration and also want all pods with a run duration of over hours to be reaped, run two pod-reapers. one with: CHAOS_CHANCE=.01 and another with RUN_DURATION=2h.

Deployments

Multiple pod-reapers can be easily managed and configured with kubernetes deployments. It is encouraged that if you are using deployments, that you leave the RUN_DURATION environment variable unset (or "0s") to let the reaper run forever, since the deployment will reschedule it anyway. Note that the pod-reaper can and will reap itself if it is not excluded.

One Time Runs

You can run run pod-reaper as a one time, limited duration container by usable the RUN_DURATION environment variable. An example use case might be wanting to introduce a high degree of chaos into your kubernetes environment for a short duration:

# 30% chaos chance every 1 minute for 15 minutes
SCHEDULE=@every 1m
RUN_DURATION=15m
CHAOS_CHANCE=.3