node-problem-detector aims to make various node problems visible to the upstream layers in cluster management stack. It is a daemon which runs on each node, detects node problems and reports them to apiserver. node-problem-detector can either run as a DaemonSet or run standalone. Now it is running as a Kubernetes Addon enabled by default in the GCE cluster.
There are tons of node problems could possibly affect the pods running on the node such as:
- Infrastructure daemon issues: ntp service down;
- Hardware issues: Bad cpu, memory or disk, ntp service down;
- Kernel issues: Kernel deadlock, corrupted file system;
- Container runtime issues: Unresponsive runtime daemon;
Currently these problems are invisible to the upstream layers in cluster management stack, so Kubernetes will continue scheduling pods to the bad nodes.
To solve this problem, we introduced this new daemon node-problem-detector to collect node problems from various daemons and make them visible to the upstream layers. Once upstream layers have the visibility to those problems, we can discuss the remedy system.
NodeCondition to report problems to
NodeCondition: Permanent problem that makes the node unavailable for pods should be reported as
Event: Temporary problem that has limited impact on pod but is informative should be reported as
A problem daemon is a sub-daemon of node-problem-detector. It monitors a specific kind of node problems and reports them to node-problem-detector.
A problem daemon could be:
- A tiny daemon designed for dedicated usecase of Kubernetes.
- An existing node health monitoring daemon integrated with node-problem-detector.
Currently, a problem daemon is running as a goroutine in the node-problem-detector binary. In the future, we'll separate node-problem-detector and problem daemons into different containers, and compose them with pod specification.
List of supported problem daemons:
|KernelMonitor||KernelDeadlock||A system log monitor monitors kernel log and reports problem according to predefined rules.|
|AbrtAdaptor||None||Monitor ABRT log messages and report them further. ABRT (Automatic Bug Report Tool) is health monitoring daemon able to catch kernel problems as well as application crashes of various kinds occurred on the host. For more information visit the link.|
|CustomPluginMonitor||On-demand(According to users configuration)||A custom plugin monitor for node-problem-detector to invoke and check various node problems with user defined check scripts. See proposal here.|
--version: Print current version of node-problem-detector.
--address: The address to bind the node problem detector server.
--port: The port to bind the node problem detector server. Use 0 to disable.
--system-log-monitors: List of paths to system log monitor configuration files, comma separated, e.g. config/kernel-monitor.json. Node problem detector will start a separate log monitor for each configuration. You can use different log monitors to monitor different system log.
--custom-plugin-monitors: List of paths to custom plugin monitor config files, comma separated, e.g. config/custom-plugin-monitor.json. Node problem detector will start a separate custom plugin monitor for each configuration. You can use different custom plugin monitors to monitor different node problems.
--apiserver-override: A URI parameter used to customize how node-problem-detector connects the apiserver. The format is same as the
sourceflag of Heapster. For example, to run without auth, use the following config:
Refer heapster docs for a complete list of available options.
--hostname-override: A customized node name used for node-problem-detector to update conditions and emit events. node-problem-detector gets node name first from
NODE_NAMEenvironment variable and finally fall back to
git clonenode-problem-detector repo into
$GOROOT/src/k8s.iowith one of the below directions:
cd $GOPATH/src/k8s.io && git clone firstname.lastname@example.org:kubernetes/node-problem-detector.git
cd $GOROOT/src/k8s.io && git clone email@example.com:kubernetes/node-problem-detector.git
cd $GOPATH/src/k8s.io && go get k8s.io/node-problem-detector
makein the top directory. It will:
- Build the binary.
- Build the docker image. The binary and
config/are copied into the docker image.
By default node-problem-detector will be built with systemd support with
make command. This requires systemd develop files.
You should download the systemd develop files first. For Ubuntu,
libsystemd-journal-dev package should
be installed. For Debian,
libsystemd-dev package should be installed.
make push uploads the docker image to registry. By default, the image will be uploaded to
staging-k8s.gcr.io. It's easy to modify the
Makefile to push the image
to another registry.
- Edit node-problem-detector.yaml to fit your environment: Set
logvolume to your system log directory. (Used by SystemLogMonitor). For kubernetes <1.9 use node-problem-detector-old.yaml
- Create the DaemonSet with
kubectl create -f node-problem-detector.yaml
- If needed, you can use ConfigMap
to overwrite the
To run node-problem-detector standalone, you should set
teach node-problem-detector how to access apiserver with
To run node-problem-detector standalone with an insecure apiserver connection:
For more scenarios, see here
Try It Out
You can try node-problem-detector in a running cluster by injecting messages to the logs that node-problem-detector is watching. For example, Let's assume node-problem-detector is using KernelMonitor. On your workstation, run
kubectl get events -w. On the node, run
sudo sh -c "echo 'kernel: BUG: unable to handle kernel NULL pointer dereference at TESTING' >> /dev/kmsg". Then you should see the
When adding new rules or developing node-problem-detector, it is probably easier to test it on the local workstation in the standalone mode. For the API server, an easy way is to use
kubectl proxy to make a running cluster's API server available locally. You will get some errors because your local workstation is not recognized by the API server. But you should still be able to test your new rules regardless.
For example, to test KernelMonitor rules:
make(build node-problem-detector locally)
kubectl proxy --port=8080(make a running cluster's API server available locally)
- Update KernelMonitor's
logPathto your local kernel log directory. For example, on some Linux systems, it is
./bin/node-problem-detector --logtostderr --apiserver-override=http://127.0.0.1:8080?inClusterConfig=false --system-log-monitors=config/kernel-monitor.json --port=20256(or point to any API server address:port)
sudo sh -c "echo 'kernel: BUG: unable to handle kernel NULL pointer dereference at TESTING' >> /dev/kmsg"
- You can see
KernelOopsevent in the node-problem-detector log.
sudo sh -c "echo 'kernel: INFO: task docker:20744 blocked for more than 120 seconds.' >> /dev/kmsg"
- You can see
DockerHungevent and condition in the node-problem-detector log.
- You can see
DockerHungcondition at http://127.0.0.1:20256/conditions.
- You can see more rule examples under test/kernel_log_generator/problems.
- For KernelMonitor message injection, all messages should have
kernel:prefix (also note there is a space after