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Observe Service Mesh through ALS

Envoy Access Log Service (ALS) provides full logs about RPC routed, including HTTP and TCP.

Background

The solution was initialized and firstly implemented by Sheng Wu, Hongtao Gao, Lizan Zhou, and Dhi Aurrahman at 17 May. 2019, and was presented on KubeCon China 2019. Here is the recorded video.

SkyWalking is the first open source project introducing this ALS based solution to the world. This provides a new way with very low payload to service mesh, but the same observability.

Enable ALS and SkyWalking Receiver

You need the following steps to set up ALS.

Enable envoyAccessLogService in ProxyConfig and set the ALS address to where SkyWalking OAP listens. On Istio version 1.6.0+, if Istio is installed with demo profile, you can enable ALS with command:
```
istioctl manifest apply \
  --set profile=demo \
  --set meshConfig.enableEnvoyAccessLogService=true \
  --set meshConfig.defaultConfig.envoyAccessLogService.address=<skywalking-oap.skywalking.svc:11800>
```
Note: Replace <skywalking-oap.skywalking.svc:11800> with the real address where SkyWalking OAP is deployed.
Activate SkyWalking Envoy Receiver. This is activated by default.
Choose an ALS analyzer. There are two available analyzers, k8s-mesh and mx-mesh. Set the system environment variable SW_ENVOY_METRIC_ALS_HTTP_ANALYSIS such as SW_ENVOY_METRIC_ALS_HTTP_ANALYSIS=k8s-mesh or in the application.yaml to activate the analyzer. For more about the analyzers, see SkyWalking ALS Analyzers
```
envoy-metric:
  selector: ${SW_ENVOY_METRIC:default}
  default:
    acceptMetricsService: ${SW_ENVOY_METRIC_SERVICE:true}
    alsHTTPAnalysis: ${SW_ENVOY_METRIC_ALS_HTTP_ANALYSIS:""} # Setting the system env variable would override this. 
```
To use multiple analyzers as a fallback，please use , to concatenate.

Example

Here's an example to install Istio and deploy SkyWalking by Helm chart.

istioctl install \
  --set profile=demo \
  --set meshConfig.enableEnvoyAccessLogService=true \
  --set meshConfig.defaultConfig.envoyAccessLogService.address=skywalking-oap.istio-system:11800

git clone https://github.com/apache/skywalking-kubernetes.git
cd skywalking-kubernetes/chart

helm repo add elastic https://helm.elastic.co

helm dep up skywalking

helm install 8.1.0 skywalking -n istio-system \
  --set oap.env.SW_ENVOY_METRIC_ALS_HTTP_ANALYSIS=k8s-mesh \
  --set fullnameOverride=skywalking \
  --set oap.envoy.als.enabled=true

You can use kubectl -n istio-system logs -l app=skywalking | grep "K8sALSServiceMeshHTTPAnalysis" to ensure OAP ALS k8s-mesh analyzer has been activated.

SkyWalking ALS Analyzers

There are two available analyzers, k8s-mesh and mx-mesh, you can specify one or more analyzers to analyze the access logs. When multiple analyzers are specified, it acts as a fast-success mechanism: SkyWalking loops over the analyzers and use it to analyze the logs, once there is an analyzer that is able to produce a result, it stops the loop.

`k8s-mesh`

k8s-mesh uses the metadata from Kubernetes cluster, hence in this analyzer OAP needs access roles to Pod, Service, and Endpoints.

The blog illustrates the detail of how it works, and a step-by-step tutorial to apply it into the bookinfo application.

`mx-mesh`

mx-mesh uses the Envoy metadata exchange mechanism to get the service name, etc., this analyzer requires Istio to enable the metadata exchange plugin (you can enable it by --set values.telemetry.v2.enabled=true, or if you're using Istio 1.7+ and installing it with profile demo/preview, it should be enabled then).

The blog illustrates the detail of how it works, and a step-by-step tutorial to apply it into the Online Boutique system.

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