# Observe service mesh through ALS
Envoy [ALS(access log service)](https://www.envoyproxy.io/docs/envoy/latest/api-v2/service/accesslog/v2/als.proto) provides
fully logs about RPC routed, including HTTP and TCP.

If solution initialized and first implemented by [Sheng Wu](https://github.com/wu-sheng), [Hongtao Gao](https://github.com/hanahmily), [Lizan Zhou](https://github.com/lizan), 
and [Dhi Aurrahman](https://github.com/dio) at 17 May. 2019, 
and presented on [KubeCon China 2019](https://kccncosschn19eng.sched.com/event/NroB/observability-in-service-mesh-powered-by-envoy-and-apache-skywalking-sheng-wu-lizan-zhou-tetrate).
Here is the recorded [Video](https://www.youtube.com/watch?v=tERm39ju9ew).

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.

You need three steps to open ALS.
1. Open envoyAccessLogService in istio by [enabling **envoyAccessLogService** in ProxyConfig](https://istio.io/docs/reference/config/istio.mesh.v1alpha1/#ProxyConfig).

    Upper istio 1.6.0, if istio installed by demo profile, you can open ALS ues command:
    ```
    istioctl manifest apply --set profile=demo --set meshConfig.defaultConfig.envoyAccessLogService.address=skywalking-oap.skywalking.svc:11800 --set meshConfig.enableEnvoyAccessLogService=true
    ```
    Note:Skywalking oap service is at skywalking namespace, and the port of gRPC service is 11800
    
2. Open SkyWalking [envoy receiver](../backend/backend-receivers.md).
3. Active ALS k8s-mesh analysis
```yaml
envoy-metric:
  default:
    alsHTTPAnalysis: "k8s-mesh"
```
Note multiple value，please use `,` symbol split

Notice, only use this when envoy under Istio controlled, also in k8s env. The OAP requires the read right to k8s API server for all pods IPs.

You can use `kubectl logs ${You-OAP-Pod} | grep "K8sALSServiceMeshHTTPAnalysis"` to ensure OAP ALS k8s-mesh analysis has been active.