Tail Cloudwatch Logs Filter

Streams logs from a specified CloudWatch log group based on a defined filter pattern.

Terminal

aws logs tail <log_group_name> --filter-pattern <pattern>

aws logs tail <log_group_name> --filter-pattern <pattern>

#!/bin/bash

# Tail Cloudwatch Logs Filter
aws logs tail {{log_group_name}} --filter-pattern {{pattern}}

import subprocess

# Tail Cloudwatch Logs Filter
# Make sure to replace <placeholders> with actual values
def run_command():
    cmd = [
        "aws",
        "logs",
        "tail",
        "<log_group_name>",
        "--filter-pattern",
        "<pattern>"
    ]
    
    try:
        print(f"Executing: {' '.join(cmd)}")
        subprocess.run(cmd, check=True)
    except subprocess.CalledProcessError as e:
        print(f"Error: {e}")
    except FileNotFoundError:
        print("Error: aws not found. Please install it first.")

if __name__ == "__main__":
    run_command()

When To Use

When needing to isolate specific log events amidst a large volume of logs.

Pro Tip

Filter patterns can significantly impact performance; ensure they are optimized to minimize false positives.

Terminal Output

Expected runtime feedback

Simulated preview

Output

START RequestId: 12345-6789-abcde 
2019-01-01T12:00:00.000Z [INFO] User logged in.
2019-01-01T12:05:00.000Z [ERROR] Failed to process request.
2019-01-01T12:10:00.000Z [INFO] User logged out.

Anatomy of Output

Understanding the result

Applying filter pattern: {{pattern}} Filter Pattern

Indicates what criteria will be used to filter logs.

... [timestamp] [filtered_log_event] Filtered Log Output

Displays only log events matching the specified filter.

Press Ctrl+C to stop the tailing! Stop Command

User should manually terminate the command to stop the stream.

Troubleshooting

Common pitfalls

InvalidFilterPatternException: The filter pattern is incorrect

Solution: Review the filter pattern syntax to ensure it conforms to AWS standards.

ResourceNotFoundException: The specified log group does not exist

Solution: Verify the log group name accuracy.

LimitExceededException: Too many concurrent filter patterns

Solution: Reduce the number of active filter commands.

Command Breakdown

What each part is doing

aws: Base Command; The executable that performs this operation. Here it runs Aws before the shell applies any redirect operators.
<log_group_name>: log group name; The value supplied for log group name.
<pattern>: pattern; The value supplied for pattern.
--filter-pattern: Command Option; Tool-specific option used by this command invocation.

How To Run

Execution path

Step 1
Run the command: aws logs tail {{log_group_name}} --filter-pattern {{pattern}}
Step 2
Verify output by checking for specific log events in the terminal.

Alternative Approaches

Comparable commands in other tools

Alternative cloud infrastructure tools for the same job.

Doctl / Get Logs For App Doctl doctl a l <app_id> Doctl / Get App Details doctl a g Cloud Init / Clean Cloud Init Logs And Artifacts cloud-init clean Nomad / Follow Alloc Logs nomad alloc logs <alloc_id>