Multiple SSH keys for different users

First, generate two separate keypairs, one for home and one for work:

ssh-keygen -t rsa -f ~/.ssh/id_rsa.home
ssh-keygen -t rsa -f ~/.ssh/

Next, add an entry to your ~/.ssh/config file to pick the key to use based on the server you connect to:

Host home
IdentityFile ~/.ssh/id_rsa.home
User <your home acct>

Host work
IdentityFile ~/.ssh/
User <your work acct>

Caching with Spring

  1. Know your topology.
  2. How about data consistency? Avoid real replication where possible.
  3. Avoid big heaps just for caching (because big heap 32Gb+ leads to long major GCs)
  4. Small caches are a bad idea. Many evictions fewer hits, no “hot data”. This is especially critical for replicating caches.
  5. Use a distributed cache for big amounts of data.
  6. Which data shall I cache? Make sure that only suitable data gets cached. The best cache candidates are read-mostly data, which are expensive to obtain. If you urgently must cache write-intensive data make sure to use a distributed cache and not replicated or invalidating one.
  7. Which cache shall I use? Only use existing cache implementations. Never write your own cache implementation ever.
  8. How do I introduce caching? Mind the security gap.
  9. Abstract your cache provider.

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Resolving Configuration in Spring Boot

1) Command Line Arguments – prefix any property with a double dash (for example –server.port=9000)

2) Embedded JSON in SPRING_APPLICATION_JSON (for example: SPRING_APPLICATION_JSON='{“server” : {“port” : “9000”}}’)

3) StandardServletEnvironment

  • A hierarchy within itself
    1. ServletConfig init parameters
    2. ServletContext init parameters
    3. JNDI attributes
    4. System.getProperties()
    5. OS environment vars

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Intro to JavaScript

1. Avoid using global variables.

function calculateSalary() {
	var address = "123 Main Street"; // local String variable
	age = 25;			 // global Number variable
	var married = true;		 // local boolean variable
	married = "don't remember";      // now it's String variable

2. Functions can be objects. You can create a function and then create an instance of the function.

3. You can declare a function that doesn’t belong to any class (or any instance).

4. You can declare a function and assign it to a variable, and then invoke that variable.

5. Functions can have memory.

6. Java 8 introduced Lambda expressions they are similar to JS functions.

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