DEV Community: Andrew Casarsa

Edit a previous commit during an Interactive Rebase

Andrew Casarsa — Mon, 17 May 2021 17:01:22 +0000

Before starting make sure you commit and push your code (see rebase --abort and hard reset in case you mess up and just want to start over). You should also create a backup git branch backup-your-branch-name

Steps:

git fetch
git rebase --interactive HEAD~20 NOTE: on HEAD~20 this is the number of commits into the past you will look at while inside the --interactive rebase.
Locate the commit in question
All commits will have the word pick next to them in your text editor. Change the pick next to chosen commit to edit. Save and exit. (in Nano this is ctrl-x then Y then enter). NOTE: Now if you type git log you will see that you are sitting at the place in time right after you made the commit you want to change.
git commit --amend will allow you to make changes to the previous commit
Enter git log to check and make sure your target commit is at the top of the log list.
Make your changes and run git add . to add those changes.
Run git commit --amend to open the commit message in your editor, save it, and exit. This will squash your changes into the target commit. This will change the commit hash code.
Run git rebase --continue and you should get the message Successfully rebased and updated refs/heads/<your_branch_name>.
Check to make sure everything seems normal and then do git push -f to replace the remote copy of your branch with your fixed local copy.

Prerequisites:

How is fetch different from pull?

git fetch is the command that tells your local git to retrieve the latest meta-data info from the original (yet doesn't do any file transferring. It's more like just checking to see if there are any changes available)

git pull on the other hand does that AND brings (copies) those changes from the remote repository.

What is a rebase?

git rebase rewrites the commit history in order to produce a straight, linear succession of commits. Basically what it does is take the fetched commits and your commits and reorders them in the correct way (it is actually creating new commits to do that but for a basic understanding we won't get into any of that).

The reason we do a rebase is so that when you push up your code and merge it with the main or master branch you won't rewrite anything anyone else added before you.

Tried this and it got totally f'd?

First, try to do git rebase --abort this will cancel the rebase and let you start over. If this doesn't fix your issue you can do a hard reset.

A hard reset will replace your local branch with the branch that is stored remotely. !!!BE CAREFUL!!! only do this if you are 100% sure your local branch doesn't have important new info you don't have stored remotely. You can make a backup of your branch if you're concerned. git reset --hard origin/<your-branch>

Part 3: Cloud Practitioners Exam Study Session EC2

Andrew Casarsa — Fri, 04 Dec 2020 00:46:06 +0000

I've been working on the Cloud Guru AWS Cloud Practitioners course which I started through 7-day free trial here. My Exam is scheduled for Dec. 17th! Feel free to wish me luck :) You can check out my other study guides here.

This is a long one so buckle up! EC2 is an important part of the exam so I'm outlining all the major points.

Simply put, Elastic Compute Cloud (EC2) is a virtual server(s) in the cloud. It reduces the time required to obtain and boot new server instances to minutes, allowing you to quickly scale capacity, both up and down, as your computing requirements change.

A Little History

EC2 and public cloud providers, in general, revolutionized tech because prior to EC2 it could take months to get distributions up and running. These all had to be done manually with physical servers and many labor hours setting them to the correct specifications.

Then Amazon EC2 came along and you could log into the console and get a virtual machine spun up in minutes if not seconds. This also allows businesses to expand or decrease their server needs at the click of a button, instead of being locked into 3-5 year contracts to rent physical servers.

Official Definition

Electric Compute Cloud (EC2) is a web service that provides secure, resizable compute capacity in the cloud. It is designed to make web-scale cloud computing easier for developers.

For the Exam

For the exam you'll need to know generally what EC2 is, its pricing models, and the Elastic Block Store (EBS) which is storage designed for use with EC2.

EC2 Pricing Models

On-Demand - fixed rate by the hour (or second) with no commitment
Reserved - a capacity reservation, w/ huge discount on hourly charges for an instance. Contract Terms are 1 or 3 years.
- More you pay upfront here the greater your discount is (pay all 3 years upfront and get the best discount)
- Reserved instances are the most economical option for long-term workloads with predictable usage patterns.
Spot - Bid whatever price you want for instance capacity, prices fluctuate constantly
- useful if your applications have flexible start and end times because you can save the most.
- set a bid price and when it hits that price it provisions the instance. You pay the Spot price that's in effect at the beginning of each instance-hour for your running instance
- you will never pay more than your maximum set price.
Dedicated Hosts - Physical EC2 server dedicated for your use.
- these can help reduce costs by allowing you to use your existing server-bound software licenses.

On-Demand Pricing

Offers the low cost and flexibility of Amazon EC2 w/out any up-front payment or long-term commitment

When it's useful:

apps w/ short term, spiky, or unpredictable workloads that cannot be interrupted.
apps being developed or tested on Amazon EC2 for the first time.

Reserved Pricing

Allows users to save money on total computing costs by paying more upfront

When it's useful:

apps w/ steady state or predictable usage
if app requires reserved capacity

There are different types of EC2 instances, this effects price

Reserved Pricing Types:

Standard Reserved Instances
- Up to 75% off On-Demand instances. The more you pay upfront the longer the contract and the greater the discount.
- can't change between instance family
  - e.g. can't go from high-performance memory to compute
Convertible Reserved Instances
- Up to 54% off On-Demand capability to change the attributes of the RI as long as the exchange results in the creation of RI of equal or greater value.
Scheduled Reserved Instances
- available to launch within certain time windows you reserve.
- This option allows you to match your capacity reservation to a predictable recurring schedule that only requires a fraction of a day, week, or month.
  - e.g. maybe your team only needs server access from 9-10 am so you would set it for that time

Spot Pricing

Allows users to set a maximum price they're willing to pay for an EC2 instance. Instance will terminate if Spot price exceeds that amount. Useful if your applications have flexible start and end times and it won't matter if the instance stops suddenly.

A Note about liability
If a Spot instance is terminated by Amz EC2 because it's gone over what you are willing to pay for it. You will not be charged a partial hour of usage!

However, if you terminate the instance yourself, you will be charged for any hour in which the instance ran.

When it's useful:

fault-tolerant and flexible applications
- ex: web servers, API backends, continuous integration/continuous development, and Hadoop data processing
company has heavy compute needs but flexible hours, they could run all their heavy computing in the middle of the night to save costs
users w/ urgent computing needs for large amounts of capacity
- can do a comparison between spot prices and On-Demand prices to see which is more cost-effective at the time.

Dedicated Hosts Pricing

can help reduce costs by allowing you to use your existing server-bound software licenses (not very common but for certain techs you must have them on a dedicated host as per licensing terms and conditions)

When it's useful:

regulatory requirements that may not support multi-tenant virtualization
- e.g. in government department where there's a law that says data must be on dedicated hosts.
licensing which does not support multi-tenancy or cloud deployments
- e.g. Microsoft, VMware or Oracle Licensing
can be purchased On-Demand (hourly)
can be purchased as a Reservation for up to 70% off the On-Demand price

What is AWS Elastic Block Store?

Simply, it's a virtual hard disk in the cloud that EC2 uses for storage.

EBS allows you to create storage volumes and attach them to EC2 instances. Once attached, you can create a file system on top of these volumes, run a database, or use them however you would use a block device (virtual/physical harddisk).

EBS volumes are placed in an Availability Zone, where they automatically replicate to protect you from failure of a single component.

Volume Types:

SSD

general purpose SSD (GP2) balances price and performance for a wide variety of workloads
Provisional IOPS SSD (IO1) highest-performance SSD volume for mission-critical low-latency or high-throughput workloads
- IOPS => Input Output Per Second
- e.g. If you have a really high performing DB you want IOPS instead of GP2

Magnetic

Throughput Optimized HDD (ST1) low-cost HDD volume for frequently accessed or high throughput intensive workloads
- data warehouses
Cold HDD (hard disk drive) (SC1) - lowest cost HDD vol for less frequently accessed workloads (file servers)
Magnetic - Previous Generation

Well, that wraps things up for Amazon's Elastic Compute Cloud (EC2).

Part I: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa ・ Oct 24 ・ 3 min read

#aws #cloud #awscertification

Part II: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa ・ Nov 13 ・ 4 min read

#aws #cloud #awscertification #beginners

Part II: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa — Fri, 13 Nov 2020 19:07:14 +0000

I've been working on the Cloud Guru AWS Cloud Practitioners course which I started through 7-day free trial here. At this point, I've finished all the lectures but have decided to keep a monthly membership for review and other specialty courses. I am planning to schedule my exam in a couple of weeks!

In Part I we covered an overview of high-level topics and the support plans that would be covered on the exam.

In Part II we'll focus on S3 which is one of the oldest AWS services and features heavily on the exam.

Official definition

Amazon S3 has a simple web services interface that you can use to store and retrieve any amount of data, at any time, from anywhere on the web. It gives any developer access to the same highly scalable, reliable, fast, inexpensive data storage infrastructure that Amazon uses to run its own global network of web sites. The service aims to maximize the benefits of scale and to pass those benefits on to developers.

Basics to know

Simple Definition

Amazon Simple Storage Service is storage for the Internet. It is designed to make web-scale computing easier for developers.

Overview summary

S3 is Object-based (i.e. allows you to upload flat files)
Files can be sized from 0 Bytes to 5 TB
Unlimited Storage
Files are stored in Buckets (folder in the cloud)
S3 is a universal namespace which means that bucket names must be unique globally. An S3 URL looks like this:
- https://s3-{region}.amazonaws.com/{bucket_name}
- See farther down for more details on Buckets
Not suitable to install an operating system or database on.
Successful uploads will generate an HTTP 200 status code

S3 Objects

S3 is Object-based it is a key-value store

Key (this is the name of the object -- like the filename)
Value (This is the data and is made up of a sequence of bytes)

Data Consistency Model for S3

Read after Write consistency for PUTS of new Objects
Eventual Consistency for overwrite PUTS and DELETES (can take some time to propagate)

What's this mean?

if you write a new file and read it immediately after, you will be able to view that data.
if you update AN EXISTING file or DELETE a file and read it immediately, you may get an older version, or you may not.

Features

Tiered Storage Available
Lifecycle Management
Versioning (can restore files)
Encryption
Secure your data using Access Control Lists and Bucket Policies.
- ACL is on a per-file or object basis payroll.xls
  - payroll spreadsheet - only want payroll admin to have access to that.
  - per-file level
- Bucket Policies apply across entire bucket
  - ex: deny public access
  - Bucket level security

S3 Storage Classes

General Purpose

Standard
- Low latency and high throughput performance
- High durability, availability, and performance object storage for frequently accessed data.

Unknown or changing access

Intelligent-Tiering
- machine-learning will move data into the appropriate access tier (no loss to performance or operations overhead)

Infrequent Access

Standard-IA
- accessed infrequently but rapidly when accessed
One Zone-IA
- when you want a lower-cost solution but don't need multiple availability zones

Archival

Glacier
- low-cost storage for data archiving -- retrieval minutes to hours
Glacier Deep Archive
- retrieval of 12 hours is acceptable

S3 on Outposts

Outposts storage class
- delivers object storage to on-premises AWS Outpost environments
- for workloads with local data residency requirements, and to satisfy demanding performance needs by keeping data close to on-premises applications

The exam questions will tend to focus on when a company might want one storage option over another. For a deep dive into Storage Classes check out Amazon's docs.

Buckets

Need to know Bucket info for the Exam

Bucket names are a universal namespace which means that they must be globally unique.
Buckets can be viewed globally but must be assigned an individual region.
Can replicate buckets from one region to another using Cross Region Replication (a storage backup basically)
Can change storage class and encryption on the fly
Remember that there are different storage classes (see above)
S3 Transfer Acceleration allows user to upload to local edge location then uses amazon's super-fast network to transfer to your bucket

3 Ways to Restrict Bucket Access

Bucket Policies - Applies across the whole bucket
Object Policies - Applies to individual files
IAM Policies to Users & Groups - Applies to Users & Groups (I'll cover IAM quickly below)

To restrict access to an entire bucket, you use bucket policies; and

to restrict access to an individual object, you use access control lists.

Identity Access Management (IAM)

IAM allows you to create users, groups, and roles and give different levels of access to them. Use this to restrict access to the information stored in your buckets.

IAM is Global, however, you may specify a region when dealing with IAM. When you create a user or a group, this is created globally. Roles, when applied to a service instance, take effect immediately.

IAM Roles

IAM roles are a secure way to grant permissions to entities that you trust. Examples of entities include the following:

IAM user in another account
Application code running on an EC2 instance that needs to perform actions on AWS resources
An AWS service that needs to act on resources in your account to provide its features
Users from a corporate directory who use identity federation with SAML

IAM roles issue keys that are valid for short durations, making them a more secure way to grant access.

Always use roles in place of access keys and secret access keys. They are safer and easier to manage. This may be an exam question!

That covers things for now. Next up we'll dive into Elastic Compute Cloud (EC2).

Part I: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa ・ Oct 24 ・ 3 min read

#aws #cloud #awscertification

Part I: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa — Sat, 24 Oct 2020 21:47:13 +0000

Yesterday I finally got started on studying for the AWS Practitioners Certification Exam. I'm taking advantage of the 7-day free trial that Cloud Guru offers, and so far I'm very happy with their platform and materials. It's definitely a more pleasing experience than Udemy for instance.

I've been taking some pretty detailed notes and will post a mini-guide after I finish going through this course and other supplemental information. So keep a lookout for that in a week or two!

The Practitioners level certification is the easiest level and is designed for people who have not worked with AWS before. So if you're just starting out like me, this is the exam for you.

The official content outline consists of 4 domains.

Official Content Outline

Source: AWS Certified Cloud Practitioner Exam Guide

Further Topics to Know...

The Cloud Guru course breaks down the exam into 6 major topics and 2 minor ones.

High-level concepts:

Major

Compute
Storage
Databases
AWS Cost Management
AWS Global Infrastructure

Minor

Migration & Transfer
Network & Content Delivery

Six Advantages of Cloud Computing

1. Trade capital expense for variable expense => pay only for what you use

2. Benefit from massive economies of scale => you benefit from amazon's massive scale/purchasing power

3. Stop guessing capacity => no more guessing no you infrastructure capacity needs because AWS has auto calling that scales based on metrics you can set

4. Increase speed and agility => serverless architecture - can get started quickly and at a very low cost. Cost and time to experiment and develop are cut down significantly.

5. Stop spending money running and maintaining data centers => lets someone else manage infrastructure

6. Go global in minutes => easily deploy an application in minutes with a few clicks. This lowers latency and leads to a better experience for customers at minimal cost.
Source: AWS Whitepapers

Three Types of Cloud Computing Deployment

1. Public Cloud - all parts of the application run in the cloud. Services commonly used are: AWS, Azure, GCP

This is becoming the norm for many companies - CapitalOne does this for instance

2. Hybrid - Mixture of cloud and on-premises infrastructure

If you want to keep employee info on private servers you could use this method while storing the other info on the cloud
often used to extend organizations existing infrastructure

3. Private Cloud (or on-premise) - you manage it, in your own datacenter. ex: OpenStack or VMware or HyperV

Three Types of Cloud Computing

1. Infrastructure As A Service (IAAS)

AWS - physical or virtual
Usually datacenter provider will have no access to your server
ex: EC2

2. Platform As A Service (PAAS)

someone else manages underlying hardware and operating systems and does security, patching, updates, maintenance etc.
Amazon offers this service through Lightsail
Another example would be GoDaddy.com
- All you do is upload a bunch of website code and point a domain name to it and it will show up. They manage all the rest.

3. Software As A Service (SAAS)

a completed product that is run and managed by the service provider.
GMail is a good example
- Use to send and receive email without worrying about managing feature additions or maintaining servers and the operating systems that the program runs on.

Four Support Plans

You'll be expected to know which Support Plan would be appropriate based on the needs of a company such as how fast they need customer service response time to be or whether they need a Tech Account Manager.

1. Basic - Can ask questions about account and billing | access to community forums | free

2. Developer - good for experimenting | CS response time is 12-24 business hours | $29/month

3. Business - production use of AWS | 24x7 support with 1 hour response time | $100/month

4. Enterprise - Mission-critical use of AWS and is what the fortune 500 companies use | get 15 min CS response time | 1-on-1 support from a Tech Account Manager (TAM) to help plan, develop and run AWS solutions | $15,000/month

DEV Community: Andrew Casarsa

Edit a previous commit during an Interactive Rebase

Steps:

Prerequisites:

How is fetch different from pull?

What is a rebase?

Tried this and it got totally f'd?

Part 3: Cloud Practitioners Exam Study Session EC2

A Little History

Official Definition

For the Exam

EC2 Pricing Models

On-Demand Pricing

Reserved Pricing

Spot Pricing

Dedicated Hosts Pricing

What is AWS Elastic Block Store?

Volume Types:

Part I: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa ・ Oct 24 ・ 3 min read

Part II: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa ・ Nov 13 ・ 4 min read

Part II: Notes on Studying for AWS Practitioners Exam

In Part II we'll focus on S3 which is one of the oldest AWS services and features heavily on the exam.

Official definition

Basics to know

Simple Definition

Overview summary

S3 Objects

Data Consistency Model for S3

What's this mean?

Features

S3 Storage Classes

Buckets

Need to know Bucket info for the Exam

3 Ways to Restrict Bucket Access

Identity Access Management (IAM)

IAM Roles

IAM roles are a secure way to grant permissions to entities that you trust. Examples of entities include the following:

Always use roles in place of access keys and secret access keys. They are safer and easier to manage. This may be an exam question!

Part I: Notes on Studying for AWS Practitioners Exam

Andrew Casarsa ・ Oct 24 ・ 3 min read

Part I: Notes on Studying for AWS Practitioners Exam

Official Content Outline

Further Topics to Know...

High-level concepts:

Major

Minor

Six Advantages of Cloud Computing

Three Types of Cloud Computing Deployment

Three Types of Cloud Computing

Four Support Plans

Next up is Getting Started with your AWS service with S3 (one of the most heavily tested technologies) and IAM...