Hosting Python Scripts On AWS- EC2

Author: Ishwarya Balasubramaniyan


Introduction

Downloading, extracting and uploading files to AWS S3 is achievable by python scripts. Now the question is how to achieve this without the local machine or any server machine being involved, for mounting the download of the zip folder. We introduce AWS EC2 at this point where the python script that does the action of download, extraction and upload of the file to S3 is hosted. The server instance in EC2 with necessary configuration is chosen from a lot of options provided by AWS.


Once the script is hosted in EC2 and a crontab job is scheduled for the script to be triggered everyday, the files regularly get uploaded to the configured S3 bucket from the EC2 instance and we can also clear the memory of EC2 instance by deleting the file once it is copied to the S3 bucket. This way the EC2 instance will only be the mounting point for the file extraction from the zip folder.


Step 1: Create EC2 Instance


Create an EC2 Instance in AWS. For that follow the steps: Link


Save the ssh key pair in a folder.



Step 2: Grant Access to the .pem file in the local


Run the following commands by replacing your .pem file path.


In Windows PowerShell:

PS C:\Users\ishwaryabb\Downloads\Mini Project> cd AWS

PS C:\Users\ishwaryabb\Downloads\Mini Project\AWS> $path = ".\sshkeypair.pem"

PS C:\Users\ishwaryabb\Downloads\Mini Project\AWS> icacls.exe $path /reset

PS C:\Users\ishwaryabb\Downloads\Mini Project\AWS> icacls.exe $path /GRANT:R "$($env:USERNAME):(R)"

PS C:\Users\ishwaryabb\Downloads\Mini Project\AWS> icacls.exe $path /inheritance:r


Note: Have the sshkeypair.pem file in a password protected user directory.


Step 3: Connect to EC2 Instance via CMD


Select the EC2 instance and click on the connect button.

In that copy the Example command in the SSH client.


Now open cmd prompt (or any other CLI) and navigate to the directory where the ssh key pair pem file is stored.

Paste the copied command in that directory.


Example:


ssh -i "sshkeypair.pem" ec2-user@ec2-13-233-247-25.ap-south-1.compute.amazonaws.com


Once this command is run (with proper access in case of non-root users), CLI will be connected to the EC2 Instance.


Note: Replace the sshkeypair.pem to whatever name you’ve saved your .pem file.




Step 4: Create Directory and Upload Python Script


Create the directories to organize the python script and other project related files.

Use the scp command to upload the .py script from local to the EC2 instance directory.


Example:


scp -i "C:\Users\ishwaryabb\Downloads\Mini Project\AWS\sshkeypair.pem" "C:\Users\ishwaryabb\Downloads\Mini Project\AWS\gdelt_script.py" ec2-13-233-247-25.ap-south-1.compute.amazonaws.com:/home/ec2-user/Project/script


Step 5: Install Python 3 & Download all the supporting python packages in the root directory


Run the following commands to install python 3, configure pip and install required packages.


sudo yum install python3

sudo yum install python35-pip


Example: pip install boto3


Step 6: Run the Python Script


Run the python script using python3 script_name.py command.



Step 7: Schedule a crontab


Schedule a crontab to run the python script (the instance uses UTC timezone).


Example:

sudo crontab -e – Edit your crontab file, or create one if it doesn't already exist.

36 22 * * * /usr/bin/python3 /script/gdelt_script.py

sudo crontab -l – Display your crontab file.

sudo crontab -r – Remove your crontab file.


Run this command in the EC2 instance (any directory)


Once all steps are completed and the EC2 instance is in running state, the scheduled python script will run everyday at the mentioned time. Note that crontab has to be configured every time the instance is started after stopping.



Conclusion:

Downloading, extracting and copying files to S3 is achieved in 7 steps. First an EC2 instance is created in AWS with configuration based on the maximum size of the file to be downloaded. Later the system is configured so that we can connect to the EC2 cloud instance via command line interface. Now directories are created as needed so that the python script can be hosted. Python 3 is installed and all the libraries required for the script to run are installed in the EC2 instance via the CLI. Finally the python script is scheduled using a crontab and it runs at the scheduled time.


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