Haani Niyaz haani-niyaz

Go Journal

Developer Environment

Private Repo Setup

git config --global \
  url."https://${user}:${personal_access_token}@privategitlab.com".insteadOf \
  "https://privategitlab.com"

Golang — Understanding channel, buffer, blocking, deadlock and happy groutines.

I was so confused to understand behaviior of Golang channels, buffer, blocking, deadlocking and groutines.

I read Go by Example topics.

Go (Golang) Standard Library Interfaces (Selected)

This is not an exhaustive list of all interfaces in Go's standard library. I only list those I think are important. Interfaces defined in frequently used packages (like io, fmt) are included. Interfaces that have significant importance are also included.

All of the following information is based on go version go1.8.3 darwin/amd64.

Kubernetes + HAProxy sticky session affinity

Make sure you have balance source in haproxy.
Backend server section in haproxy config should have all your k8s nodes.
sessionAffinity in k8s is irrelevant.
Exposed k8s service need to have nodePort set and this annotation:

kubectl annotate service myService service.beta.kubernetes.io/external-traffic=OnlyLocal

This will cause internal k8s loadbalancer on nodeⁿ to route traffic only to pod on nodeⁿ. From Haproxy point of view it will look like nodeⁿ:nodePort === pod on nodeⁿ:port thus disabling k8s LB completly.

Kubectl output options

Let's look at some basic kubectl output options.

Our intention is to list nodes (with their AWS InstanceId) and Pods (sorted by node).

We can start with:

kubectl get no

Deep Work

Rules for Focused Success in a Distracted World

Cal Newport, 2016 [purchase it at half-price books]

Part I: The Idea

Deep Work is valuable
Deep Work is rare
Deep Work is meaningful

Processing JSON using jq

jq is useful to slice, filter, map and transform structured json data.

Installing jq

On Mac OS

brew install jq

Postgres Cheatsheet

This is a collection of the most common commands I run while administering Postgres databases. The variables shown between the open and closed tags, "<" and ">", should be replaced with a name you choose. Postgres has multiple shortcut functions, starting with a forward slash, "". Any SQL command that is not a shortcut, must end with a semicolon, ";". You can use the keyboard UP and DOWN keys to scroll the history of previous commands you've run.

Setup

installation, Ubuntu

http://www.postgresql.org/download/linux/ubuntu/ https://help.ubuntu.com/community/PostgreSQL

With Docker 1.8.0 shipped new log-driver for GELF via UDP, this means that the logs from Docker Container(s) can be shipped directly to the ELK stack for further analysis.
This tutorial will illustrate how to use the GELF log-driver with Docker engine.
Step 1: Setup ELK Stack:
- docker run -d --name es elasticsearch
- docker run -d --name logstash --link es:elasticsearch logstash -v /tmp/logstash.conf:/config-dir/logstash.conf logstash logstash -f /config-dir/logstash.conf
- Note the config for Logstash can be found at this link
- docker run --link es:elasticsearch -d kibana
Once the ELK stack is up now let's fire up our nginx container which ships its logs to ELK stack.

LOGSTASH_ADDRESS=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}' logstash)
`docker run -d --net=host --log-driver=gelf --log-opt gelf-address=u

	* Shows a message while asserting like:

	ok: [host] => {
	"msg": "disk usage 4.2B of total 20.0GB (21.0%) (should exceed limit 90.0%)"
	}

	* Note this only looks at first mount point on current node
	* Fails if disk is near-full
	* Last step pushes to a push-based monitoring service, which will alert us if it doesn't get there after some time
	* Need to setup a variable `disk_limit`, which is the max acceptable usage ratio, e.g. set it to 0.8 if you want to keep disks within 80% of max size