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Lab 7 - Circuit Breaking

In this lab we will configure circuit breaking using Istio. Circuit breaking allows developers to write applications that limit the impact of failures, latency spikes, and other undesirable effects of network peculiarities. This task will show how to configure circuit breaking for connections, requests, and outlier detection.

7.1 Preparing for circuit breaking

Before we can configure circuit breaking, please try to access the product page app from within Meshery to ensure all the calls are making it through without errors as we did in Lab 4 - Telemetry - Section 4.1 (see screenshot).

7.2 Configure circuit breaking

Now that we have the needed services in place, it is time to configure circuit breaking using a destination rule.

Using Meshery, navigate to the designs page under configuration and import the below design. Make sure Istio adapter is running. Patternfile:

name: CircuitBreaker
services:
  reviews:
    name: reviews
    type: DestinationRule.Istio
    version: 1.12.9
    namespace: default
    settings:
      host: productpage
      subsets:
      - labels:
          version: v1
        name: v1
      trafficPolicy:
        connectionPool:
          http:
            http1MaxPendingRequests: 1
            maxRequestsPerConnection: 1
          tcp:
            maxConnections: 1
        outlierDetection:
          baseEjectionTime: 3m
          consecutiveErrors: 1
          interval: 1s
          maxEjectionPercent: 100
        tls:
          mode: ISTIO_MUTUAL

Manual step for can be found here

This will update the existing destination rule definition for product page service to break the circuit if there are more than one connection and more than one pending request.

In a few, we should be able to verify the destination rule by using the command below:

kubectl get destinationrule productpage -o yaml

7.3 Time to trip the circuit

In the circuit-breaker settings, we specified maxRequestsPerConnection: 1 and http1MaxPendingRequests: 1. This should mean that if we exceed more than one request per connection and more than one pending request, we should see the istio-proxy sidecar open the circuit for further requests/connections.

Let us now use Meshery to make several calls to product page app by changing the number of concurrent connections to 5 from within Meshery's Performance page.

Once you have updated the fields, you now click on Run Test.

This will run the load test and show the results in a chart. (see screenshot).

You should only see a percentage of the requests succeed and the rest trapped by the configured circuit breaker.

Continue to Lab 8 - Mutual TLS & Identity Verification

Appendix

Configure circuit breaking

kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: productpage
spec:
  host: productpage
  subsets:
  - labels:
      version: v1
    name: v1
  trafficPolicy:
    tls:
      mode: ISTIO_MUTUAL
    connectionPool:
      tcp:
        maxConnections: 1
      http:
        http1MaxPendingRequests: 1
        maxRequestsPerConnection: 1
    outlierDetection:
      consecutiveErrors: 1
      interval: 1s
      baseEjectionTime: 3m
      maxEjectionPercent: 100
EOF