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First class functions in go

This is a minimum working example to explore the usage of first class functions as presented by Dave Cheney.

• https://dave.cheney.net/2016/11/13/do-not-fear-first-class-functions
• https://www.youtube.com/watch?v=5buaPyJ0XeQ

(On the same topic Rob Pike also wrote an interesting article: https://commandcenter.blogspot.co.uk/2014/01/self-referential-functions-and-design.html)

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Add SQL Operations Studio icon

This is a desktop launcher for SQL Operations Studio (https://github.com/Microsoft/sqlopsstudio).

Assuming the application is unpacket to $HOME/src/sqlops-linux-x64, then:

• create the desktop launcher with: touch ~/.local/share/applications/sqlopsstudio.desktop;
• the desktop launcher should contain:

[Desktop Entry]

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Trubleshooting Kafka

• To consume existing topics: ./bin/kafka-console-consumer.sh --bootstrap-server <IP_ADDR>:9092 --topic my-custom-topic --from-beginning
• To check a list of topics: ./bin/kafka-topics.sh --list --zookeeper <IP_ADDR>:2181

Go sample

The following code snippets make use of sarama the Go library to connect to a cluster of Apache Kafka instance.

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Moment.js durations

var moment = require('moment-timezone');

var _timeConsumingFunc = () => {
  // wait a few seconds
  for (i = 0; i < 1000000000; i++) { 
    // do nothing
 }

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Go database operations

The following go/golang snippet:

• connect to a MS-SQL database via ODBC;
• INSERTs a new record into a table;
• disconnects from the database.

package main

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How to join processes with timeout

The process.join(NUM_SECONDS) does not fit, because the normal for loop to join all the processes waits NUM_SECONDS for each process before joining it.

We want a global amount of NUM_SECONDS to be timed out on to kill (terminate) all the outstanding processes that are still alive after NUM_SECONDS elapsed (i.e. not yet been joined already).

The following code snippet has been heavily inspired by:

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Docker stuff

This playbook works on Ubuntu and should work also on debian:

---
- name: Make sure docker is installed and configured
  hosts: my_hosts_group # cf. the hosts file below for this group of hosts
  sudo: yes
  tasks:

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How to find and list all the symbolic links created for a particular file?

$ ls -li
# take note of the symlink ID
$ find / -follow -inum 5097642 2>/dev/null
# you'll have a list of symlink to that inode

Useful bash configuration

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EC2

Generate ssh key

To be used for a user in an EC2 instance:

$ ssh-keygen -b 4096 -t rsa -f ~/.ssh/$(whoami)-<suffix-for-ec2-environment>

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Postgres

Command to display active connections to a PostgresDB: SELECT * FROM pg_stat_activity;

Connection to Redshift

$ psql -h <ENDPOINT_NAME>.us-east-1.redshift.amazonaws.com -p 5439 -d <DB_NAME> -U <DB_USERNAME>