Merge pull request #16 from Random-Liu/add-node-problem-detector-readme

Add initial README.md for node-problem-detector.

README.md

@@ -1,2 +1,103 @@
 # node-problem-detector
-This is a place for various problem detectors running on the Kubernetes nodes.
+node-problem-detector aims to make various node problems visible to the upstream
+layers in cluster management stack. It is a [DaemonSet](http://kubernetes.io/docs/admin/daemons/)
+detecting node problems and reporting them to apiserver. Now it is running as
+a [Kubernetes Addon](https://github.com/kubernetes/kubernetes/tree/master/cluster/addons)
+enabled by default in the GCE cluster.
+
+# Background
+There are tons of node problems could possibly affect the pods running on the
+node such as:
+* Hardware issues: Bad cpu, memory or disk;
+* 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.
+
+# Problem API
+node-problem-detector uses `Event` and `NodeCondition` to report problems to
+apiserver.
+* `NodeCondition`: Permanent problem that makes the node unavailable for pods should
+be reported as `NodeCondition`.
+* `Event`: Temporary problem that has limited impact on pod but is informative
+should be reported as `Event`.
+
+# Problem Daemon
+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:
+
+| Problem Daemon |  NodeCondition  | Description |
+|----------------|:---------------:|:------------|
+| [KernelMonitor](https://github.com/kubernetes/node-problem-detector/tree/master/pkg/kernelmonitor) | KernelDeadlock | A problem daemon monitors kernel log and reports problem according to predefined rules. |
+
+# Usage
+## Build Image
+Run `make` in the top directory. It will:
+* Build the binary.
+* Build the docker image. The binary and `config/` are copied into the docker image.
+* Upload the docker image to registry. By default, the image will be uploaded to
+`gcr.io/google_containers`. It's easy to modify the `Makefile` to push the image
+to another registry
+
+## Start DaemonSet
+* Create a file node-problem-daemon.yaml with the following yaml.
+```yaml
+apiVersion: extensions/v1beta1
+kind: DaemonSet
+metadata:
+  name: node-problem-detector
+spec:
+  template:
+    spec:
+      hostNetwork: true
+      containers:
+      - name: node-problem-detector
+        image: gcr.io/google_containers/node-problem-detector:v0.1
+        imagePullPolicy: Always
+        env:
+        # Config `host` and `port` of apiserver.
+        - name: "KUBERNETES_SERVICE_HOST"
+          value: "master-node-host-name"
+        - name: "KUBERNETES_SERVICE_PORT"
+          value: "443"
+        securityContext:
+          privileged: true
+        volumeMounts:
+        - name: log
+          mountPath: /log
+          readOnly: true
+      volumes:
+      - name: log
+        # Config `log` to your system log directory
+        hostPath:
+          path: /var/log/
+```
+* Edit node-problem-detector.yaml to fit your environment: 
+  * Set environent variables `KUBERNETES_SERVICE_HOST` and `KUBERNETES_SERVICE_PORT`
+    to apiserver host ip and port.
+  * Set `log` volueme to your system log diretory. (Used by KernelMonitor)
+* Create the DaemonSet with `kubectl create -f node-problem-detector.yaml`
+* If needed, you can use [ConfigMap](http://kubernetes.io/docs/user-guide/configmap/)
+to overwrite the `config/`.
+
+# Links
+* [Design Doc](https://docs.google.com/document/d/1cs1kqLziG-Ww145yN6vvlKguPbQQ0psrSBnEqpy0pzE/edit?usp=sharing)
+* [Slides](https://docs.google.com/presentation/d/1bkJibjwWXy8YnB5fna6p-Ltiy-N5p01zUsA22wCNkXA/edit?usp=sharing)
+* [Addon Manifest](https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/node-problem-detector)

node-problem-detector.yaml

@@ -17,7 +17,7 @@ spec:
         image: gcr.io/google_containers/node-problem-detector:v0.1
         imagePullPolicy: Always
         env:
-        # Config the host ip and port of apiserver.
+        # Config `host` and `port` of apiserver.
         - name: "KUBERNETES_SERVICE_HOST"
           value: "e2e-test-lantaol-master"
         - name: "KUBERNETES_SERVICE_PORT"
@@ -33,6 +33,7 @@ spec:
           readOnly: true
       volumes:
       - name: log
+        # Config `log` to your system log directory
         hostPath:
           path: /var/log/
       - name: config