mirror of https://github.com/istio/istio.io.git
105 lines
3.7 KiB
Markdown
105 lines
3.7 KiB
Markdown
---
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title: Fault Injection
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overview: This task shows how to inject delays and test the resiliency of your application.
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order: 60
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layout: docs
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type: markdown
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---
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{% include home.html %}
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This task shows how to inject delays and test the resiliency of your application.
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## Before you begin
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* Setup Istio by following the instructions in the
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[Installation guide](./installing-istio.html).
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* Deploy the [BookInfo]({{home}}/docs/samples/bookinfo.html) sample application.
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* Initialize the application version routing by either first doing the
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[request routing](./request-routing.html) task or by running following
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commands:
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```bash
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istioctl create -f route-rule-all-v1.yaml
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istioctl create -f route-rule-reviews-test-v2.yaml
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```
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## Fault injection
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To test our BookInfo application microservices for resiliency, we will _inject a 7s delay_
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between the reviews:v2 and ratings microservices. Since the _reviews:v2_ service has a
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10s timeout for its calls to the ratings service, we expect the end-to-end flow to
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continue without any errors.
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1. Create a fault injection rule to delay traffic coming from user "jason" (our test user)
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```bash
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istioctl create -f destination-ratings-test-delay.yaml
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```
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Confirm the rule is created:
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```bash
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istioctl get route-rule ratings-test-delay
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```
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```yaml
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destination: ratings.default.svc.cluster.local
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httpFault:
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delay:
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fixedDelay: 7s
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percent: 100
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match:
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httpHeaders:
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cookie:
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regex: "^(.*?;)?(user=jason)(;.*)?$"
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precedence: 2
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route:
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- tags:
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version: v1
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```
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Allow several seconds to account for rule propagation delay to all pods.
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1. Observe application behavior
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If the application's front page was set to correctly handle delays, we expect it
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to load within approximately 7 seconds. To see the web page response times, open the
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*Developer Tools* menu in IE, Chrome or Firefox (typically, key combination _Ctrl+Shift+I_
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or _Alt+Cmd+I_) and reload the `productpage` web page.
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You will see that the webpage loads in about 6 seconds. The reviews section will show
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*Sorry, product reviews are currently unavailable for this book*.
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## Understanding what happened
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The reason that the entire reviews service has failed is because our BookInfo application
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has a bug. The timeout between the productpage and reviews service is less (3s + 1 retry = 6s total)
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than the timeout between the reviews and ratings service (10s). These kinds of bugs can occur in
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typical enterprise applications where different teams develop different microservices
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independently. Istio's fault injection rules help you identify such anomalies without
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impacting end users.
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> Notice that we are restricting the failure impact to user "jason" only. If you login
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> as any other user, you would not experience any delays.
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**Fixing the bug:** At this point we would normally fix the problem by either increasing the
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productpage timeout or decreasing the reviews to ratings service timeout,
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terminate and restart the fixed microservice, and then confirm that the `productpage`
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returns its response without any errors.
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However, we already have this fix running in v3 of the reviews service, so we can simply
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fix the problem by migrating all
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traffic to `reviews:v3` as described in the [request routing task](./request-routing.html).
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(Left as an exercise for the reader - change the delay rule to
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use a 2.8 second delay and then run it against the v3 version of reviews.)
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## What's next
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* Learn more about [fault injection]({{home}}/docs/concepts/traffic-management/fault-injection.html).
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* Limit requests to the BookInfo `ratings` service with Istio [rate limiting](./rate-limiting.html).
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