Linkerd

Istio is focused on features, even at the expense of complexity. Linkerd is focused on simplicity, even at the expense of features. -[1]

  • Implements SMI for some APIs

Install

curl -sL https://run.linkerd.io/install | sh
export PATH=$PATH:~/.linkerd2/bin/linkerd

Components

  • sidecar runs alongside the application in the same pod. It intercepts traffic. This follows the Kubernetes [[ sidecar pattern ]]. In Linkerd’s case, this is the Linkerd2-proxy. Linkerd2-proxy uses iptables rules to intercept traffic and force it through the proxy. The iptables rules are configured through Linkerd2-proxy-init which is a Kubernetes init container. Modifying iptables requires NET_ADMIN
  • control plane: contains the configuration of sidecars and lives outside of the main traffic flow
    • web UI
  • data plane: intercepts the main traffic flow in order to provide observability, security, and reliablity features.

Features

  • load balancing – Kubernetes load balances at the connection level. Linkerd balances at the request level. This jemans that once a connection between pods is established,r equests will continue to be sent over that connection until the client requests a new connection. Linkerd maintains a connection pool and distributes requests across this pool. By default, this distribution is done based on latency using an expontentially weighted moving average. Load balancing happens client (source) side rather than server(destination) side.
  • Metrics are captured by the proxy. Linkerd’s Prometheus scrapes teh endpoints of all proxies and aggregates the metrics. The metrics endpoint can also be contacted directly for debugging.
  • Linkerd has full support for HTTP/1.1, HTTP2, and gRPC. If it’s not using one of these protocols, Linkerd will only proxy the request as a raw TCP stream and collect byte level metrics.
  • mTLS – not just encryption between two pods running the Linkerd proxy, but identity as well

    Injection

  • Kubernetes linkerd.io/inject: enabled annotation on the workload or namespace.
  • Manually modify the YAML to add the proxy and related components

Review Later

  • https://www.infoq.com/presentations/Simple-Made-Easy/
  • https://medium.com/@abhinav.mahapatra10/beginners-ml-basics-exponentially-weighted-moving-average-8ce3e75768f6
  • https://kubernetes.io/blog/2018/11/07/grpc-load-balancing-on-kubernetes-without-tears/
  • https://eng.uber.com/microservice-architecture/
  • https://acmbytecast.podbean.com/e/shwetak-patel-episode-7/
  • https://acmbytecast.podbean.com/e/don-knuth-episode-2/

References:

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Linkerd
Istio is focused on features, even at the expense of complexity. Linkerd is focused on simplicity, even at the expense...
Service Mesh
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