add Traefik ingress controller

SUMMARY.md

@@ -29,6 +29,7 @@
   - [Job](concepts/job.md)
   - [CronJob](concepts/cronjob.md)
   - [Ingress](concepts/ingress.md)
+    - [Traefik Ingress Controller](concepts/traefik-ingress-controller.md)
   - [ConfigMap](concepts/configmap.md)
     - [ConfigMap的热更新](concepts/configmap-hot-update.md)
   - [Horizontal Pod Autoscaling](concepts/horizontal-pod-autoscaling.md)

concepts/traefik-ingress-controller.md

@@ -0,0 +1,67 @@
+# Traefik Ingress Controller
+
+我们在前面部署了 [Traefik](https://traefik.io) 作为Ingress Controller，如果集群外部直接访问Kubenretes内部服务的话，可以直接创建Ingress如下所示：
+
+```yaml
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: traefik-ingress
+  namespace: default
+spec:
+  rules:
+  - host: traefik.nginx.io
+    http:
+      paths:
+      - path: /
+        backend:
+          serviceName: my-nginx
+          servicePort: 80
+```
+
+## Traefik Ingress Controller
+
+当我们处于迁移应用到kuberentes上的阶段时，可能有部分服务实例不在kubernetes上，服务的路由使用nginx配置，这时处于nginx和ingress共存的状态。参考下面的配置：
+
+```yaml
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: td-ingress
+  namespace: default
+  annotations:
+    traefik.frontend.rule.type: PathPrefixStrip
+    kubernetes.io/ingress.class: traefik
+spec:
+  rules:
+  - host: "*.tendcloud.com"
+    http:
+      paths:
+      - path: /docGenerate
+        backend:
+          serviceName: td-sdmk-docgenerate
+          servicePort: 80
+```
+
+注意**annotation**的配置：
+
+- `traefik.frontend.rule.type: PathPrefixStrip`：表示将截掉URL中的`path`
+- `kubernetes.io/ingress.class`：表示使用的ingress类型
+
+关于Ingress annotation的更多信息请参考：[Ingress Annotations - kubernetes.io](https://github.com/kubernetes/ingress-nginx/blob/master/docs/annotations.md)。
+
+在nginx中增加配置：
+
+```ini
+upstream docGenerate {
+       server 172.20.0.119:80;
+       keepalive 200;
+    }
+```
+
+172.20.0.119是我们的边缘节点的VIP，见[边缘节点配置](../practice/edge-node-configuration.md)。
+
+## 参考
+
+- [Kubernetes Ingress Backend - traefik.io](https://docs.traefik.io/configuration/backends/kubernetes/)
+- [Kubernetes Ingress Controller - traefik.io](http://docs.traefik.io/user-guide/kubernetes/)