Add Try Fault Injection Doc

Signed-off-by: noobwei <[email protected]>

content/en/docs/userguide/service_metrics.md

@@ -4,7 +4,7 @@ linktitle: Use Grafana to visualize service metrics
 menu:
   docs:
     parent: user guide
-    weight: 9
+    weight: 19
 title: Use Grafana to visualize service metrics
 toc: true
 type: docs

content/en/docs/userguide/try_fault_injection.md

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+---
+draft: false
+linktitle: Try Fault Injection
+menu:
+  docs:
+    parent: user guide
+    weight: 10
+title: Try Fault Injection
+toc: true
+type: docs
+
+
+---
+
+### Preparation
+
+- Set up application, refer preparation [Try Waypoint | Kmesh](https://kmesh.net/en/docs/userguide/try_waypoint/#preparation)
+
+- Apply application version routing by either performing the [request routing task or by running the following commands:
+
+  ```bash
+  kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.21/samples/bookinfo/networking/virtual-service-all-v1.yaml
+
+  kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.21/samples/bookinfo/networking/virtual-service-reviews-test-v2.yaml
+  ```
+
+- With the above configuration, this is how requests flow:
+  - `productpage` → `reviews:v2` → `ratings` (only for user `jason`)
+  - `productpage` → `reviews:v1` (for everyone else)
+
+### Injecting an HTTP delay fault
+
+To test the Bookinfo application microservices for resiliency, inject a 7s delay between the `reviews:v2` and `ratings` microservices for user `jason`. This test will uncover a bug that was intentionally introduced into the Bookinfo app.
+
+Note that the `reviews:v2` service has a 10s hard-coded connection timeout for calls to the `ratings` service. Even with the 7s delay that you introduced, you still expect the end-to-end flow to continue without any errors.
+
+1. Create a fault injection rule to delay traffic coming from the test user `jason`.
+
+```bash
+kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.21/samples/bookinfo/networking/virtual-service-ratings-test-delay.yaml
+```
+
+2. Confirm the rule was created:
+
+```bash
+kubectl get virtualservice ratings -o yaml
+```
+
+Allow several seconds for the new rule to propagate to all pods.
+
+### Testing the delay configuration
+
+1. Open the Bookinfo web application in your browser.
+
+2. On the `/productpage` web page, log in as user `jason`.
+
+   You expect the Bookinfo home page to load without errors in approximately 7 seconds. However, there is a problem: the Reviews section displays an error message:
+
+   `Sorry, product reviews are currently unavailable for this book.`
+
+3. View the web page response times
+
+![Fault_Injection1](/docs/user_guide/fault_injection1.png)
+
+### Understanding what happened
+
+As expected, the 7s delay you introduced doesn’t affect the `reviews` service because the timeout between the `reviews` and `ratings` service is hard-coded at 10s. However, there is also a hard-coded timeout between the `productpage` and the `reviews` service, coded as 3s + 1 retry for 6s total. As a result, the `productpage` call to `reviews` times out prematurely and throws an error after 6s.
+
+Bugs like this can occur in typical enterprise applications where different teams develop different microservices independently. Istio’s fault injection rules help you identify such anomalies without impacting end users.
+
+### Fixing the bug
+
+You would normally fix the problem by:
+
+1. Either increasing the `productpage` to `reviews` service timeout or decreasing the `reviews` to `ratings` timeout
+2. Stopping and restarting the fixed microservice
+3. Confirming that the `/productpage` web page returns its response without any errors.
+
+However, you already have a fix running in v3 of the `reviews` service. The `reviews:v3` service reduces the `reviews` to `ratings` timeout from 10s to 2.5s so that it is compatible with (less than) the timeout of the downstream `productpage` requests.
+
+If you migrate all traffic to `reviews:v3` as described in the [traffic shifting](https://kmesh.net/en/docs/userguide/try_traffic_shifting/) task, you can then try to change the delay rule to any amount less than 2.5s, for example 2s, and confirm that the end-to-end flow continues without any errors.
+
+### Injecting an HTTP abort fault
+
+Another way to test microservice resiliency is to introduce an HTTP abort fault. In this task, you will introduce an HTTP abort to the `ratings` microservices for the test user `jason`.
+
+In this case, you expect the page to load immediately and display the `Ratings service is currently unavailable` message.
+
+1. Create a fault injection rule to send an HTTP abort for user `jason`:
+
+`kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.21/samples/bookinfo/networking/virtual-service-ratings-test-abort.yaml`
+
+
+### Testing the abort configuration
+
+1. Open the Bookinfo web application in your browser.
+
+2. On the `/productpage`, log in as user `jason`.
+
+   If the rule propagated successfully to all pods, the page loads immediately and the `Ratings service is currently unavailable` message appears.
+
+![Fault_Injection2](/docs/user_guide/fault_injection2.png)
+
+3. If you log out from user `jason` or open the Bookinfo application in an anonymous window (or in another browser), you will see that `/productpage` still calls `reviews:v1` (which does not call `ratings` at all) for everybody but `jason`. Therefore you will not see any error message.
+
+### Cleanup
+
+1. Remove the application routing rules:
+
+```bash
+kubectl delete -f https://raw.githubusercontent.com/istio/istio/release-1.21/samples/bookinfo/networking/virtual-service-all-v1.yaml
+
+```
+
+2. If you are not planning to explore any follow-on tasks, refer to the [Install Waypoint/Cleanup](https://kmesh.net/en/docs/userguide/install_waypoint/#cleanup) instructions to shutdown the application.
+