CloudWatch Logs in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is AWS CloudWatch Logs used for?

AWS CloudWatch Logs is used to collect, monitor, and store log files from AWS resources and applications. It helps you track system and application behavior in real time.

beginner

What is a Log Group in CloudWatch Logs?

A Log Group is a collection of log streams that share the same retention, monitoring, and access control settings. Think of it like a folder that organizes related logs.

beginner

What is a Log Stream in CloudWatch Logs?

A Log Stream is a sequence of log events from the same source, like a single server or application instance. It’s like a timeline of logs from one source.

intermediate

How does CloudWatch Logs help with troubleshooting?

CloudWatch Logs lets you search and filter logs to find errors or unusual activity quickly. You can also set alarms to get notified when specific patterns appear in logs.

beginner

What is the purpose of retention settings in CloudWatch Logs?

Retention settings control how long logs are stored before they are deleted. This helps manage storage costs and keeps only the logs you need.

What does a CloudWatch Log Group represent?

A A dashboard for monitoring metrics

B A single log event

C A collection of log streams with shared settings

D An AWS resource like an EC2 instance

A Log Group organizes multiple log streams that share retention and access settings.

Which of the following is a Log Stream?

A A timeline of logs from one source

B A group of AWS accounts

C A metric alarm

D A storage bucket

A Log Stream is a sequence of log events from a single source.

How can CloudWatch Logs notify you about specific log events?

A By setting alarms on metric filters

B By sending logs to S3

C By creating EC2 instances

D By changing IAM roles

You can create metric filters on logs and set alarms to get notifications.

What happens when log retention period expires in CloudWatch Logs?

A Logs are encrypted

B Logs are archived to Glacier

C Logs are sent to CloudTrail

D Logs are automatically deleted

Logs are deleted after the retention period to save storage.

Which AWS service is primarily used to collect and store logs?

A S3

B CloudWatch Logs

C EC2

D Lambda

CloudWatch Logs is designed to collect and store logs from AWS resources.

Explain how CloudWatch Logs organizes and stores log data.

Think about folders and files to organize logs.

Describe how you can use CloudWatch Logs to detect and respond to errors in your application.

Consider how alerts help you act quickly.

Practice

1. What is the primary purpose of a CloudWatch Logs log group?

easy

A. To act as a container for multiple log streams

B. To store individual log events directly

C. To trigger alarms based on log data

D. To archive logs permanently

Solution

1. Step 1: Understand log group role

   A log group is a container that holds multiple log streams, organizing logs by application or resource.

2. Step 2: Differentiate log streams and groups

   Log streams are individual sequences of log events within a log group, not the group itself.

3. Final Answer:

   To act as a container for multiple log streams -> Option A

4. Quick Check:

   Log group = container for streams [OK]

Hint: Log groups hold streams; streams hold logs [OK]

Common Mistakes:

• Confusing log groups with log streams
• Thinking logs are stored directly in groups
• Assuming groups trigger alarms directly

2. Which of the following is the correct AWS CLI command to create a new CloudWatch Logs log group named MyAppLogs?

easy

A. aws cloudwatch create-log-group --name MyAppLogs

B. aws logs create-log-group --log-group-name MyAppLogs

C. aws logs new-log-group --group-name MyAppLogs

D. aws logs add-log-group --name MyAppLogs

Solution

1. Step 1: Identify correct AWS CLI service and command

   The correct service is 'logs' and the command to create a log group is 'create-log-group'.

2. Step 2: Check command syntax

   The parameter for the log group name is '--log-group-name', matching aws logs create-log-group --log-group-name MyAppLogs exactly.

3. Final Answer:

   aws logs create-log-group --log-group-name MyAppLogs -> Option B

4. Quick Check:

   Correct CLI syntax = aws logs create-log-group --log-group-name MyAppLogs [OK]

Hint: Use 'aws logs create-log-group' with --log-group-name [OK]

Common Mistakes:

• Using wrong service name like 'cloudwatch' instead of 'logs'
• Incorrect command verbs like 'new-log-group'
• Wrong parameter names like '--name'

3. Given the following AWS CLI command, what will be the retention period set for the log group AppLogs?

aws logs put-retention-policy --log-group-name AppLogs --retention-in-days 14

medium

A. Logs will be kept for 7 days

B. Logs will be kept indefinitely

C. Logs will be kept for 14 days

D. Logs will be deleted immediately

Solution

1. Step 1: Understand the put-retention-policy command

   This command sets how many days logs are retained before deletion.

2. Step 2: Interpret the retention-in-days value

   The parameter '--retention-in-days 14' means logs are kept for 14 days.

3. Final Answer:

   Logs will be kept for 14 days -> Option C

4. Quick Check:

   Retention days = 14 [OK]

Hint: Retention days = value in --retention-in-days [OK]

Common Mistakes:

• Assuming default retention instead of set value
• Confusing retention period with log group creation
• Thinking logs are kept indefinitely by default

4. You run this command but get an error:

aws logs put-retention-policy --log-group-name NonExistentGroup --retention-in-days 30

What is the most likely cause?

medium

A. The log group 'NonExistentGroup' does not exist

B. Retention period 30 days is not allowed

C. You must specify a log stream name instead

D. The AWS CLI command is misspelled

Solution

1. Step 1: Check existence of log group

   The command requires the log group to exist before setting retention.

2. Step 2: Validate retention period and command syntax

   Retention of 30 days is valid and the command syntax is correct.

3. Final Answer:

   The log group 'NonExistentGroup' does not exist -> Option A

4. Quick Check:

   Retention needs existing log group [OK]

Hint: Retention policy requires existing log group [OK]

Common Mistakes:

• Assuming retention period is invalid
• Confusing log stream with log group
• Thinking command syntax is wrong

5. You want to organize logs from multiple microservices in CloudWatch Logs. Which approach best follows AWS best practices?

hard

A. Store all logs in a single log stream for simplicity

B. Create one log stream for all microservices in a single log group

C. Create one log group per instance and one log stream per microservice

D. Create one log group per microservice and multiple log streams per instance

Solution

1. Step 1: Understand log group and stream organization

   Best practice is to use log groups to separate different applications or microservices.

2. Step 2: Assign log streams per instance or source

   Within each log group, use multiple log streams to separate logs by instance or container.

3. Step 3: Evaluate options

   Create one log group per microservice and multiple log streams per instance matches best practice: one log group per microservice, multiple streams per instance.

4. Final Answer:

   Create one log group per microservice and multiple log streams per instance -> Option D

5. Quick Check:

   Group per microservice, streams per instance [OK]

Hint: Group by microservice, stream by instance [OK]

Common Mistakes:

• Mixing microservices in one log group
• Using one stream for all logs causing confusion
• Creating groups per instance instead of per service