Log groups and log streams in AWS - Step-by-Step Execution

Process Flow - Log groups and log streams

Create Log Group

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Create Log Stream inside Log Group

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Send Logs to Log Stream

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Logs Stored in Log Stream

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View Logs via Console or API

Logs are organized first by log groups, then by log streams inside those groups. Logs are sent to streams and stored there for viewing.

Execution Sample

AWS

aws logs create-log-group --log-group-name MyApp
aws logs create-log-stream --log-group-name MyApp --log-stream-name Stream1
aws logs put-log-events --log-group-name MyApp --log-stream-name Stream1 --log-events '[{"timestamp":123456789,"message":"Start"}]'

This sequence creates a log group, a log stream inside it, and sends a log message to that stream.

Process Table

Step	Action	Resource Created/Used	Result
1	Create Log Group 'MyApp'	Log Group: MyApp	Log group 'MyApp' created
2	Create Log Stream 'Stream1' in 'MyApp'	Log Stream: Stream1 in MyApp	Log stream 'Stream1' created inside 'MyApp'
3	Send log event to 'Stream1'	Log Event: timestamp=123456789, message='Start'	Log event stored in 'Stream1'
4	View logs	Log Stream: Stream1	Logs retrieved: message='Start'
5	Attempt to send log to non-existent stream	Log Stream: StreamX	Error: The specified log stream does not exist

💡 Execution stops after sending logs and viewing them; error occurs if sending logs to a non-existent stream.

Status Tracker

Resource	Initial	After Step 1	After Step 2	After Step 3	After Step 4
Log Groups	None	MyApp	MyApp	MyApp	MyApp
Log Streams in MyApp	None	None	Stream1	Stream1	Stream1
Log Events in Stream1	None	None	None	[{timestamp:123456789, message:'Start'}]	[{timestamp:123456789, message:'Start'}]

Key Moments - 2 Insights

Why do we need to create a log stream inside a log group before sending logs?

Because logs are stored inside streams, which are inside groups. Step 2 shows creating the stream; without it, step 3 fails (see step 5 error).

What happens if you try to send logs to a stream that does not exist?

An error occurs and logs are not stored, as shown in step 5 of the execution table.

Visual Quiz - 3 Questions

Look at the execution table, what resource is created at step 2?

A Log Group 'MyApp'

B Log Stream 'Stream1' inside 'MyApp'

C Log Event with message 'Start'

D Log Stream 'StreamX'

💡 Hint

Check the 'Resource Created/Used' column at step 2 in the execution table.

At which step does the log event get stored in the log stream?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Result' column for when the log event is stored.

If you skip creating the log stream, what will happen when sending logs?

A An error will occur because the stream does not exist

B Logs will be stored in the log group directly

C Logs will be stored in a default stream

D Logs will be discarded silently

💡 Hint

Refer to step 5 in the execution table showing the error when sending logs to a non-existent stream.

Concept Snapshot

Log groups organize logs by application or service.
Log streams are inside log groups and hold sequences of log events.
You must create a log group, then a log stream before sending logs.
Logs are sent to a specific stream and stored there.
Trying to send logs to a missing stream causes an error.

Full Transcript

This visual execution shows how AWS CloudWatch Logs organizes logs. First, a log group is created to group related logs. Inside this group, log streams are created to hold sequences of log events. Logs are sent to a specific log stream. The execution table traces creating a log group named 'MyApp', then a log stream 'Stream1' inside it, then sending a log event with a timestamp and message. The variable tracker shows how resources appear step by step. Key moments clarify why streams must exist before sending logs and what happens if they don't. The quiz tests understanding of resource creation and error handling. The snapshot summarizes the core concepts simply.