Ivan Pedrazas ipedrazas

References from my QCon London 2016 Keynote

The Morning Paper blog

Thinking Tools

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

That's our RC:

$ cat ws-rc.yaml
apiVersion: v1
kind: ReplicationController
metadata:
  name: webserver-rc
spec:
  replicas: 5

selector:

Project Title

One Paragraph of project description goes here

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes. See deployment for notes on how to deploy the project on a live system.

Prerequisites

Single Node Kubernetes Cluster

sudo docker run -d --net=host --privileged --name=kubestack \
-v /sys:/sys:ro \
-v /:/rootfs:ro \
-v /var/run/docker.sock:/var/run/docker.sock \
-v /var/run:/var/run:rw \
-v /var/lib/kubelet/:/var/lib/kubelet:rw \
-v /var/lib/docker/:/var/lib/docker:ro \

Expects one argument the name of the production stack file for Tutum.

(see https://support.tutum.co/support/solutions/articles/5000569899-stacks )

Requires these environment variables to be set

CLOUDFLARE_DOMAIN - root domain of your app, e.g. example.com
CLOUDFLARE_KEY - your Cloudflare API key
CLOUDFLARE_EMAIL - your Cloudflare email address e.g. [email protected]
PROJECT_NAME - a short name for your project e.g. example

The point of this is to use cheap machines with small/slow storage to coordinate client requests while dedicating the machines with the big and fast storage to doing what they do best. I found that request coordination was contributing to about half the CPU usage on our Cassandra nodes, on average. Solid state storage is quite expensive, nearly doubling the cost of typical hardware. It also means that if people have control over hardware placement within the network, they can place proxy nodes closer to the client without impacting their storage footprint or fault tolerance characteristics.

This is accomplished in Cassandra by passing the -Dcassandra.join_ring=false option when the process is started. These nodes will connect to the seeds, cache the gossip data, load the schema, and begin listening for client requests. Messages like "/x.x.x.x is now UP!" will appear on the other nodes.

There are also some more practical benefits to this. Handling client requests caused us to push the NewSize of the heap up

	#!/bin/bash

	export vault=/usr/local/bin/vault
	export VAULT_TOKEN=$(cat /root/.vault-token)
	vault_cacert='-ca-cert=/path/to/your/ca.pem'
	local_vault="-address=https://$(hostname -f):8200"
	unsealed_vault="-address=https://$(getent hosts $(dig +short vault.service.consul \| tail -n 1) \| awk '{ print $2 }'):8200"
	leader_vault="-address=https://$($vault status $vault_cacert $unsealed_vault 2> /dev/null \| grep Leader \| awk '{ print $2 }' \| sed 's/^http\(\\|s\):\/\///g'):8200"
	vault_read="$vault read $vault_cacert $leader_vault"
	vault_unseal="$vault unseal $vault_cacert $local_vault"

	---
	apiVersion: v1
	kind: Pod
	metadata:
	name: server
	spec:
	containers:
	- image: resouer/sample:v2
	name: war
	lifecycle: