CloudWatch metrics for DynamoDB - Step-by-Step Execution

Concept Flow - CloudWatch metrics for DynamoDB

DynamoDB Table Activity

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CloudWatch Metrics Collected

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Metrics Types: Read, Write, Throttling, Latency

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Metrics Sent to CloudWatch Dashboard

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User Views Metrics & Sets Alarms

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User Adjusts Table or Alarms Based on Metrics

DynamoDB table activity generates metrics that CloudWatch collects and displays, allowing users to monitor and react.

Execution Sample

DynamoDB

SELECT MetricName, Value, Timestamp FROM CloudWatchMetrics WHERE TableName = 'MyDynamoDBTable' ORDER BY Timestamp DESC LIMIT 5;

This query fetches the latest 5 CloudWatch metrics for a specific DynamoDB table.

Execution Table

Step	Action	MetricName	Value	Timestamp	Result
1	Fetch latest metric	ConsumedReadCapacityUnits	50	2024-06-01T12:00:00Z	Metric value retrieved
2	Fetch latest metric	ConsumedWriteCapacityUnits	30	2024-06-01T12:00:00Z	Metric value retrieved
3	Fetch latest metric	ThrottledRequests	0	2024-06-01T12:00:00Z	Metric value retrieved
4	Fetch latest metric	ReadThrottleEvents	0	2024-06-01T12:00:00Z	Metric value retrieved
5	Fetch latest metric	WriteThrottleEvents	1	2024-06-01T12:00:00Z	Metric value retrieved
6	End	-	-	-	All requested metrics fetched

💡 All requested metrics fetched for the specified DynamoDB table.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
MetricName	-	ConsumedReadCapacityUnits	ConsumedWriteCapacityUnits	ThrottledRequests	ReadThrottleEvents	WriteThrottleEvents	-
Value	-	50	30	0	0	1	-
Timestamp	-	2024-06-01T12:00:00Z	2024-06-01T12:00:00Z	2024-06-01T12:00:00Z	2024-06-01T12:00:00Z	2024-06-01T12:00:00Z	-

Key Moments - 2 Insights

Why do some metrics like 'ThrottledRequests' show zero while others have values?

Because 'ThrottledRequests' counts how many requests were denied due to limits, zero means no throttling occurred at that time (see execution_table rows 3 and 4).

Why is the timestamp the same for all metrics fetched?

Because the query fetches the latest metrics snapshot at the same time point for consistency (see execution_table timestamps in all rows).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'ConsumedWriteCapacityUnits' at step 2?

A 30

B 50

C 0

D 1

💡 Hint

Check the 'Value' column in row 2 of the execution_table.

At which step does the metric 'WriteThrottleEvents' get fetched?

A Step 3

B Step 5

C Step 1

D Step 4

💡 Hint

Look for 'WriteThrottleEvents' in the 'MetricName' column of the execution_table.

If the 'ThrottledRequests' metric value changed from 0 to 5, which part of the execution_table would change?

A Step 1 'MetricName' column

B Step 5 'Timestamp' column

C Step 3 'Value' column

D Step 2 'Result' column

💡 Hint

Focus on the 'Value' column for 'ThrottledRequests' at step 3.

Concept Snapshot

CloudWatch metrics for DynamoDB track table activity like read/write capacity and throttling.
Metrics are collected continuously and can be queried or viewed on dashboards.
Common metrics: ConsumedReadCapacityUnits, ConsumedWriteCapacityUnits, ThrottledRequests.
Use these metrics to monitor performance and set alarms for issues.
Timestamps show when metrics were recorded.
Fetching latest metrics helps understand current table health.

Full Transcript

This visual execution shows how CloudWatch collects and reports metrics for a DynamoDB table. The flow starts with DynamoDB table activity generating metrics. These metrics include read and write capacity units consumed, throttling events, and latency. CloudWatch collects these metrics and makes them available for querying or dashboard display. The example query fetches the latest five metrics for a table named 'MyDynamoDBTable'. The execution table traces each step fetching a metric, showing metric name, value, and timestamp. The variable tracker shows how metric names and values change step by step. Key moments clarify why some metrics have zero values and why timestamps are consistent. The quiz tests understanding of metric values and steps. The snapshot summarizes key points about monitoring DynamoDB with CloudWatch metrics.

Practice

1. What does the CloudWatch metric ConsumedReadCapacityUnits for a DynamoDB table represent?

easy

A. The number of read capacity units consumed by the table over a period

B. The total number of items in the table

C. The amount of storage used by the table

D. The number of write capacity units consumed by the table over a period

Solution

1. Step 1: Understand the metric name

   ConsumedReadCapacityUnits clearly indicates it measures read capacity units consumed.

2. Step 2: Relate to DynamoDB usage

   Read capacity units measure how many read operations the table performs, so this metric tracks usage over time.

3. Final Answer:

   The number of read capacity units consumed by the table over a period -> Option A

4. Quick Check:

   ConsumedReadCapacityUnits = Read usage [OK]

Hint: Look for 'Read' in metric name to identify read capacity usage [OK]

Common Mistakes:

• Confusing read capacity with write capacity
• Thinking it measures item count or storage size
• Assuming it shows total capacity, not consumed

2. Which AWS CLI command syntax correctly retrieves the ThrottledRequests metric for a DynamoDB table named Orders?

easy

A. aws cloudwatch list-metrics --metric ThrottledRequests --table Orders

B. aws cloudwatch get-metric-statistics --metric-name ThrottledRequests --namespace AWS/DynamoDB --dimensions Name=TableName,Value=Orders --start-time 2024-01-01T00:00:00Z --end-time 2024-01-01T01:00:00Z --period 60 --statistics Sum

C. aws cloudwatch describe-metrics --metric-name ThrottledRequests --table Orders

D. aws dynamodb get-metric --metric ThrottledRequests --table Orders

Solution

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

   CloudWatch metrics use aws cloudwatch get-metric-statistics to retrieve metric data.

2. Step 2: Check parameters for metric retrieval

   aws cloudwatch get-metric-statistics --metric-name ThrottledRequests --namespace AWS/DynamoDB --dimensions Name=TableName,Value=Orders --start-time 2024-01-01T00:00:00Z --end-time 2024-01-01T01:00:00Z --period 60 --statistics Sum correctly specifies metric name, namespace, dimensions (table name), time range, period, and statistics.

3. Final Answer:

   aws cloudwatch get-metric-statistics with correct parameters -> Option B

4. Quick Check:

   Use aws cloudwatch get-metric-statistics for metrics [OK]

Hint: Use 'aws cloudwatch get-metric-statistics' with proper parameters [OK]

Common Mistakes:

• Using 'aws dynamodb' instead of 'aws cloudwatch'
• Missing required parameters like dimensions or time range
• Using commands that only list or describe metrics, not retrieve data

3. Given the following AWS CLI command output snippet for ConsumedWriteCapacityUnits metric of a DynamoDB table:

{"Datapoints": [{"Timestamp": "2024-06-01T12:00:00Z", "Sum": 150}], "Label": "ConsumedWriteCapacityUnits"}

What does the value 150 represent?

medium

A. The maximum write capacity units allowed for the table

B. The average number of write capacity units available

C. The number of throttled write requests

D. The total number of write capacity units consumed during the specified period

Solution

1. Step 1: Understand the metric and statistic

   The metric is ConsumedWriteCapacityUnits and the statistic is Sum, meaning total units consumed.

2. Step 2: Interpret the value 150

   150 is the sum of write capacity units consumed during the time period ending at the timestamp.

3. Final Answer:

   The total number of write capacity units consumed during the specified period -> Option D

4. Quick Check:

   Sum of consumed write units = 150 [OK]

Hint: Sum statistic means total units consumed, not average or max [OK]

Common Mistakes:

• Confusing sum with average or max
• Thinking it shows capacity limits instead of usage
• Mixing write capacity with throttled requests

4. You wrote this AWS CLI command to get the ReadThrottleEvents metric for your DynamoDB table Users but got an error:

aws cloudwatch get-metric-statistics --metric-name ReadThrottleEvents --namespace AWS/DynamoDB --dimensions TableName=Users --start-time 2024-06-01T00:00:00Z --end-time 2024-06-01T01:00:00Z --period 60 --statistics Sum

What is the error and how do you fix it?

medium

A. The period value is too small; increase it to 300

B. The metric name is invalid; use ThrottledRequests instead

C. The dimension syntax is incorrect; use --dimensions Name=TableName,Value=Users

D. The start-time format is wrong; use MM-DD-YYYY

Solution

1. Step 1: Check dimension syntax in AWS CLI

   The correct syntax for dimensions is --dimensions Name=TableName,Value=Users, not just TableName=Users.

2. Step 2: Fix the command by correcting dimensions

   Replace --dimensions TableName=Users with --dimensions Name=TableName,Value=Users to fix the error.

3. Final Answer:

   The dimension syntax is incorrect; use --dimensions Name=TableName,Value=Users -> Option C

4. Quick Check:

   Dimensions need Name and Value keys [OK]

Hint: Dimensions require Name= and Value= pairs in AWS CLI [OK]

Common Mistakes:

• Using incorrect dimension syntax without Name= and Value=
• Confusing metric names that don't exist
• Incorrect date/time format for start-time

5. You want to monitor your DynamoDB table's performance and set an alarm if the ThrottledRequests metric exceeds 5 in any 5-minute period. Which combination of CloudWatch metric and alarm configuration is correct?

hard

A. Use metric ThrottledRequests with statistic Sum over 300 seconds period, alarm threshold > 5

B. Use metric ConsumedReadCapacityUnits with statistic Average over 60 seconds period, alarm threshold > 5

C. Use metric ThrottledRequests with statistic Maximum over 60 seconds period, alarm threshold > 5

D. Use metric ReadThrottleEvents with statistic Sum over 300 seconds period, alarm threshold > 10

Solution

1. Step 1: Identify correct metric for throttled requests

   The metric ThrottledRequests tracks throttling events, so it is the right choice.

2. Step 2: Choose appropriate statistic and period

   Sum over 300 seconds (5 minutes) aggregates total throttled requests in that period, matching the alarm condition.

3. Step 3: Set alarm threshold correctly

   Alarm triggers if sum exceeds 5, matching the requirement.

4. Final Answer:

   Use metric ThrottledRequests with statistic Sum over 300 seconds period, alarm threshold > 5 -> Option A

5. Quick Check:

   Sum over 5 minutes > 5 throttled requests triggers alarm [OK]

Hint: Sum metric over 5 minutes matches throttled requests count [OK]

Common Mistakes:

• Using wrong metric like ConsumedReadCapacityUnits
• Choosing Average or Maximum instead of Sum for count
• Setting period too short to capture throttling spikes