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Session Management in an Autoscaling Environment

Problem Statement

User sessions in J2EE and LAMP stacks have traditionally been handled in memory by the application server handling the user request. Because of that, load balancers have been configured to use sticky sessions. By sticky sessions we mean that once the user has visited the site, they will be assigned an app server and will return to that server for subsequent requests. The load balancers typically handle that by referencing the users session cookie.

Elastic cloud environments differ from traditional server configurations in that they have a variable number of servers based on traffic loads whereas traditional configurations had a fixed number of servers. When traffic volumes decline it is necessary to vaporize servers. In doing so, we would lose user sessions (essentially forcing a logout) unless we come up with a new strategy for session management.

A new approach

After much research, it is clear that the best

spara

# lansatutil directory
LANDSAT = ~/landsat

# scenes to target
LANDSAT_IDS = \
	LC81220442016038LGN00 \
	LC81220452016038LGN00 \
	LC81210442014281LGN00 \
	LC81210452014281LGN00

spara

#! /bin/bash

# Convert Landsat 8 GeoTIFF images into RGB pan-sharpened JPEGs.
#
# Requirements:
#              * gdal http://www.mapbox.com/tilemill/docs/guides/gdal/
#              * convert (image-magick)
#
# Reference info:
#                 http://www.mapbox.com/blog/putting-landsat-8-bands-to-work/

spara

#! /bin/bash

# Convert Landsat 8 GeoTIFF images into RGB pan-sharpened JPEGs.
#
# Requirements:
#              * gdal http://www.mapbox.com/tilemill/docs/guides/gdal/
#              * convert (image-magick)
#
# Reference info:
#                 http://www.mapbox.com/blog/putting-landsat-8-bands-to-work/

spara

#!/usr/bin/env ruby
require 'csv'
require 'json'

if ARGV.size != 2
  puts 'Usage: csv_to_json input_file.csv output_file.json'
  puts 'This script uses the first line of the csv file as the keys for the JSON properties of the objects'
  exit(1)
end

spara

d3.unconf example gist. Fork it here.

spara

d3.unconf example gist. Fork it here.

spara

#!/bin/sh

# Converts a mysqldump file into a Sqlite 3 compatible file. It also extracts the MySQL `KEY xxxxx` from the
# CREATE block and create them in separate commands _after_ all the INSERTs.

# Awk is choosen because it's fast and portable. You can use gawk, original awk or even the lightning fast mawk.
# The mysqldump file is traversed only once.

# Usage: $ ./mysql2sqlite mysqldump-opts db-name | sqlite3 database.sqlite
# Example: $ ./mysql2sqlite --no-data -u root -pMySecretPassWord myDbase | sqlite3 database.sqlite

spara

[
   {
      "category":"Administrative",
      "category_id":"10100100",
      "type":"Region",
      "subcategory":"Consolidated City"
   },
   {
      "category":"Administrative",
      "category_id":"10100101",