Metric Filters are a useful tool for managing and gaining insights from the log data generated by AWS services. Beneficial for the AWS Certified SysOps Administrator Associate exam, learning how to create and utilize metric filters increases the efficiency and effectiveness of managing AWS resources.
Understanding Metric Filters
A metric filter scans incoming logs and extracts the key values that you specify. You can create metric filters to analyze and interpret the operational state of the services or derive any particular activity based on your filters.
For example, suppose a server is generating logs for the number of requests it receives from various IP addresses. We can then use metric filters to track the number of requests from a specific address.
Before getting into the details of creating metric filters, let’s understand the structure of a metric filter pattern. It is made up of two sections – selectors and metrics.
| Selector | Metric |
| Specifies the logs that the metric filter matches | Specifies the way the metric filter extracts the data and maps it to the metric |
You need to remember, in AWS CloudWatch Logs, each log event corresponds to a JSON object. A metric filter pattern can match terms found anywhere in the log entry.
Creating a Metric Filter
Follow the steps below to create a Metric Filter:
- Open the CloudWatch console and in the navigation pane, choose
Logs. - Choose the name of the log group where you want to create a metric filter.
- Choose the
Create Metric Filterbutton near the top of the page. - In the
Filter Patternbox, enter a pattern string that will match the log events. This is to filter the logs as per our requirement. - Select
Assign metric. - Input the unique
Filter Name, and underMetrics Details, specify the details likeNamespace,Metric Name,Dimension. - After giving the required filters and metric details, Click
Next, review your metric filter configuration, and clickCreate Metric Filter.
Here is the sample code that can be put in the Filter Pattern box:
{ ($.errorCode = “ServerError”) && ($.errorMessage = “*”) }
This filter pattern scans the logs where the errorCode field is ‘ServerError’ and the errorMessage field contains any values.
Conclusion
Metric filters are crucial tools within AWS for efficient log data management. For SysOps Administrators or ones preparing for the AWS Certified SysOps Administrator Associate exam, mastering the use and creation of metric filters can be a game-changer. It helps to manage and keep track of AWS resource usage effectively. Utilized correctly, they can provide valuable insights from your log data which will assist in making fact-based decisions.
Practice Test
True or False: Metric Filters in AWS CloudWatch allow you to search and parse log data from log groups in near real-time.
- True
- False
Answer: True.
Explanation: AWS CloudWatch’s Metric Filters provide the ability to search and parse log data coming from your AWS resources which can then be visualized in dashboards, alarms or CloudWatch Events.
True or False: Metric Filters only work with JSON log formats.
- True
- False
Answer: False.
Explanation: Metric Filters can parse space-delimited and JSON log formats.
In creating Metric Filters, which of the following is the correct order of steps?
- a. Specify the filter pattern, assign a metric, name the filter
- b. Assign a metric, specify the filter pattern, name the filter
- c. Name the filter, specify the filter pattern, assign a metric
- d. Assign a metric, name the filter, specify the filter pattern
Answer: a. Specify the filter pattern, assign a metric, name the filter
Explanation: The steps to create a metric filter are: Specify the filter pattern > Assign a metric > Name the filter.
True or False: You can assign as many metrics as you want to a single filter.
- True
- False
Answer: False.
Explanation: Each metric filter is assigned with only one metric.
What is the limit of the number of metric filters you can define per log group?
- a. 100
- b. 200
- c. 500
- d. No limit
Answer: a. 100
Explanation: You can create up to 100 metric filters per log group.
True or False: Metric filters can be used to create alarms.
- True
- False
Answer: True.
Explanation: You can use metric filters to create an alarm based on a specific pattern or keyword in a log event.
True or False: A dollar sign ($) is required in the filter pattern to denote a variable.
- True
- False
Answer: True.
Explanation: A dollar sign ($) is used in the filter pattern to signify that the pattern references a variable.
True or False: You can edit a metric filter after it is created.
- True
- False
Answer: True.
Explanation: In the CloudWatch console, you have the ability to edit a metric filter after it is created.
When you create metric filters, which of the following AWS services do NOT generate supported log events?
- a. Amazon EC2
- b. AWS CloudTrail
- c. AWS Lambda
- d. Amazon S3
Answer: d. Amazon S3
Explanation: Amazon S3 does not generate supported log events for metric filters. However, you can use S3 server access logs with metric filters in CloudWatch.
True or False: You can use wildcard characters (*) in your metric filter pattern.
- True
- False
Answer: True.
Explanation: Wildcard characters can be used when creating a metric filter pattern to match multiple log events.
Metric Filters in AWS CloudWatch requires which of the following data types for the values of the metric?
- a. Integer
- b. Float
- c. String
- d. All of the above
Answer: a. Integer
Explanation: The value of the metric must be of data type integer when using Metric Filters in AWS CloudWatch.
True or false: You can assign the same metric to multiple filters.
- True
- False
Answer: True.
Explanation: The same metric can be assigned to multiple filters. Multiple filters can increment the same metric.
What service allows you to create a metric filter from AWS Management Console?
- a. Amazon EC2
- b. Cloudwatch
- c. AWS Lambda
- d. IAM
Answer: b. Cloudwatch
Explanation: You can create a metric filter directly from the AWS Cloudwatch management console.
Which among these events will a metric filter allow you to search for from your log events?
- a. Instances running low on disk space
- b. Error messages
- c. Changes to IAM user credentials
- d. All of the above
Answer: d. All of the above
Explanation: Metric Filters in Cloudwatch allow you to search, parse and visualize all these events in near real-time.
True or False: Metrics produced by metric filters are delayed and are not suitable for real-time monitoring
- True
- False
Answer: False
Explanation: Metric Filters in Cloudwatch allow you to search and visualize log data in near real-time.
Interview Questions
What is the primary purpose of creating metric filters in AWS?
The primary purpose of creating metric filters in AWS is to transform log data into actionable metrics, to monitor, troubleshoot, and automate responses to operational issues.
What AWS service provides the ability to create metric filters?
AWS CloudWatch provides the ability to create metric filters.
How can you identify specific log data to create a metric filter?
You can identify specific log data by using a filter pattern, which is a sequence of characters or a regular expression.
Can you use metric filters to set alarms?
Yes, when a metric filter is created, it can be used to set alarms, letting you react to events represented by the relevant log data.
What type of data sources can AWS metric filters scan?
AWS metric filters can scan log data from AWS S3 Buckets, CloudTrail Trails, and Log Streams in CloudWatch Log Groups.
What should be the specified value in the metric filter if you want to count the occurrences of a pattern?
If you want to count the occurrences of a pattern, the value should be set to 1 in the metric filter.
Can you create metric filters with metrics that have the same name but different namespaces?
Yes, you can create metric filters with metrics that have the same name but different namespaces.
Is it possible to edit a metric filter after it is created?
No, it is not possible to edit a metric filter after it has been created. You must first delete the existing filter and then create a new one.
What are the types of metric filter patterns supported by AWS CloudWatch?
AWS CloudWatch supports two types of metric filter patterns: a simple pattern to match terms and phrases, and a JSON pattern to match elements within a JSON-formatted log event.
Are there any charges for creating metric filters in AWS?
Yes, there are charges for creating metric filters as well as for data scanned by filters and metrics generated.
Can you track different aspects of the same event using multiple metric filters?
Yes, multiple metric filters can be used to track different aspects of the same event.
Is it possible to create a metric filter for events that do not occur?
No, it’s not possible to create a metric filter for events that do not occur. AWS CloudWatch cannot calculate the absence of events.
What is the maximum number of metric filters that can be applied to a log group?
The limit is 100 metric filters per log group.
How can metric filters help in the optimization of costs?
With metric filters, you can create CloudWatch Alarms to notify you when estimated charges exceed your predefined threshold amount, thereby optimizing costs.
In addition to CloudWatch, can other services also use data from metric filters?
Yes, services such as AWS Lambda or Amazon SNS can act on data extracted from log events by metric filters.
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