AWS CloudWatch – Certification

AWS CloudWatch

  • AWS CloudWatch monitors AWS resources and applications in real-time.
  • CloudWatch can be used to collect and track metrics, which are the variables to be measured for resources and applications.
  • CloudWatch alarms can be configured
    • to send notifications or
    • to automatically make changes to the resources based on defined rules
  • In addition to monitoring the built-in metrics that come with AWS, custom metrics can also be monitored
  • CloudWatch provides system-wide visibility into resource utilization, application performance, and operational health.
  • By default, CloudWatch stores the log data indefinitely, and the retention can be changed for each log group at any time
  • CloudWatch Alarm history is stored for only 14 days

CloudWatch Architecture

CloudWatch Architecture

  • CloudWatch collects various metrics from various resources
  • These metrics, as statistics, are available to the user through Console, CLI
  • CloudWatch allows creation of alarms with defined rules to perform actions to auto scaling or stop, start, or terminate instances
  • CloudWatch allows creation of alarms to send notifications using SNS actions on your behalf

CloudWatch Concepts

Metrics

  • Metric is the fundamental concept in CloudWatch.
  • They are uniquely defined by a name, a namespace, and one or more dimensions.
  • It represents a time-ordered set of data points published to CloudWatch.
  • Each data point has a time stamp, and (optionally) a unit of measure
  • These data points can be either custom metrics or metrics from other
    services in AWS.
  • Statistics can be retrieved about those data points as an ordered set of time-series data that occur within a specified time window.
  • When the statistics are requested, the returned data stream is identified by namespace, metric name, dimension, and (optionally) the unit.
  • Metrics exist only in the region in which they are created
  • CloudWatch stores the metric data for two weeks
  • Metrics cannot be deleted, but they automatically expire in 14 days if no new data is published to them.

Namespaces

  • CloudWatch namespaces are containers for metrics.
  • Metrics in different namespaces are isolated from each other, so that metrics from different applications are not mistakenly aggregated into the same statistics.
  • AWS namespaces all follow the convention AWS/<service>, for e.g. AWS/EC2 and AWS/ELB
  • Namespace names must be fewer than 256 characters in length.
  • There is no default namespace. Each data element put into CloudWatch must specify a namespace

Dimensions

  • A dimension is a name/value pair that uniquely identifies a metric.
  • Every metric has specific characteristics that describe it, and you can think of dimensions as categories for those characteristics.
  • Dimensions helps design a structure for the statistics plan.
  • Dimensions are part of the unique identifier for a metric, whenever a unique name pair is added to one of the metrics, a new metric is created
  • Dimensions can be used to filter result sets that CloudWatch query returns
  • A metric can be assigned up to ten dimensions to a metric.

Time Stamps

  • Each metric data point must be marked with a time stamp to identify the data point on a time series
  • Time stamp can be up to two weeks in the past and up to two hours into the future.
  • If no time stamp is provided, CloudWatch creates a time stamp based on the time the data element was received.
  • All times reflect the UTC time zone when statistics are retrieved

Units

  • Units represent the statistic’s unit of measure for e.g. count, bytes, % etc

Statistics

  • Statistics are metric data aggregations over specified periods of time
  • Aggregations are made using the namespace, metric name, dimensions, and the data point unit of measure, within the specified time period

Periods

  • Period is the length of time associated with a specific statistic.
  • Each statistic represents an aggregation of the metrics data collected for a specified period of time.
  • Although periods are expressed in seconds, the minimum granularity for a period is one minute.

Aggregation

  • CloudWatch aggregates statistics according to the period length specified in calls to GetMetricStatistics.
  • Multiple data points can be published with the same or similar time stamps. CloudWatch aggregates them by period length when the statistics about those data points are requested.
  • Aggregated statistics are only available when using detailed monitoring.
  • Instances that use basic monitoring are not included in the aggregates
  • CloudWatch does not aggregate data across regions.

Alarms

  • Alarms can automatically initiate actions on behalf of the user, based on specified parameters
  • Alarm watches a single metric over a specified time period, and performs one or more actions based on the value of the metric relative to a given threshold over a number of time periods.
  • Alarms invoke actions for sustained state changes only i.e. the state must have changed and been maintained for a specified number of periods
  • Action can be a
    • SNS notification
    • Auto Scaling policies
    • Amazon EC2 action – stop or terminate EC2 instances
  • After an alarm invokes an action due to a change in state, its subsequent behavior depends on the type of action associated with the alarm.
    • For Auto Scaling policy notifications, the alarm continues to invoke the action for every period that the alarm remains in the new state.
    • For SNS notifications, no additional actions are invoked.
  • An alarm has three possible states:
    • OK—The metric is within the defined threshold
    • ALARM—The metric is outside of the defined threshold
    • INSUFFICIENT_DATA—Alarm has just started, the metric is not available, or not enough data is available for the metric to determine the alarm state
  • Alarms exist only in the region in which they are created.
  • Alarm actions must reside in the same region as the alarm
  • Alarm history is available for the last 14 days.
  • Alarm can be tested by setting it to any state using the SetAlarmState API (mon-set-alarm-state command). This temporary state change lasts only until the next alarm comparison occurs.
  • Alarms can be disabled and enabled using the DisableAlarmActions and EnableAlarmActions APIs (mon-disable-alarm-actions and mon-enable-alarm-actions commands).

Regions

  • CloudWatch does not aggregate data across regions. Therefore, metrics are completely separate between regions.

Custom Metrics

  • CloudWatch allows publishing custom metrics with put-metric-data CLI command (or its Query API equivalent PutMetricData)
  • CloudWatch creates a new metric if put-metric-data is called with a new metric name,  else it associates the data with the specified existing metric
  • put-metric-data command can only publish one data point per call
  • CloudWatch stores data about a metric as a series of data points and each data point has an associated time stamp
  • Creating a new metric using the put-metric-data command, can take up to two minutes before statistics can be retrieved on the new metric using the get-metric-statistics command and can take up to fifteen minutes before the new metric appears in the list of metrics retrieved using the list-metrics command.
  • CloudWatch allows publishing
    • Single data point
      • Data points can be published with time stamps as granular as one-thousandth of a second, CloudWatch aggregates the data to a minimum granularity of one minute
      • CloudWatch records the average (sum of all items divided by number of items) of the values received for every 1-minute period, as well as number of samples, maximum value, and minimum value for the same time period
      • CloudWatch uses one-minute boundaries when aggregating data points
    • Aggregated set of data points called a statistics set
      • Data can also be aggregated before being published to CloudWatch
      • Aggregating data minimizes the number of calls reducing it to a single call per minute with the statistic set of data
      • Statistics include Sum, Average, Minimum, Maximum, Data Sample
  • If the application produces data that is more sporadic and have periods that have no associated data, either a the value zero (0) or no value at all can be published
  • However, it can be helpful to publish zero instead of no value
    • to monitor the health of your application for e.g. alarm can be configured to notify if no metrics published every 5 minutes
    • to track the total number of data points
    • to have statistics such as minimum and average to include data points with the value 0.

Supported Services

For Supported Services refer @ CloudWatch Supported Services

Accessing CloudWatch

  • CloudWatch can be accessed using
    • AWS CloudWatch console
    • CloudWatch CLI
    • AWS CLI
    • CloudWatch API
    • AWS SDKs

AWS Certification Exam Practice Questions

  • Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
  • AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
  • AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
  • Open to further feedback, discussion and correction.
  1. A company needs to monitor the read and write IOPs metrics for their AWS MySQL RDS instance and send real-time alerts to their operations team. Which AWS services can accomplish this? Choose 2 answers
    1. Amazon Simple Email Service (Cannot be integrated with CloudWatch directly)
    2. Amazon CloudWatch
    3. Amazon Simple Queue Service
    4. Amazon Route 53
    5. Amazon Simple Notification Service
  2. A customer needs to capture all client connection information from their load balancer every five minutes. The company wants to use this data for analyzing traffic patterns and troubleshooting their applications. Which of the following options meets the customer requirements?
    1. Enable AWS CloudTrail for the load balancer.
    2. Enable access logs on the load balancer. (Refer link)
    3. Install the Amazon CloudWatch Logs agent on the load balancer.
    4. Enable Amazon CloudWatch metrics on the load balancer
  3. A user is running a batch process on EBS backed EC2 instances. The batch process starts a few instances to process Hadoop Map reduce jobs, which can run between 50 – 600 minutes or sometimes for more time. The user wants to configure that the instance gets terminated only when the process is completed. How can the user configure this with CloudWatch?
    1. Setup the CloudWatch action to terminate the instance when the CPU utilization is less than 5%
    2. Setup the CloudWatch with Auto Scaling to terminate all the instances
    3. Setup a job which terminates all instances after 600 minutes
    4. It is not possible to terminate instances automatically
  4. A user has two EC2 instances running in two separate regions. The user is running an internal memory management tool, which captures the data and sends it to CloudWatch in US East, using a CLI with the same namespace and metric. Which of the below mentioned options is true with respect to the above statement?
    1. The setup will not work as CloudWatch cannot receive data across regions
    2. CloudWatch will receive and aggregate the data based on the namespace and metric
    3. CloudWatch will give an error since the data will conflict due to two sources
    4. CloudWatch will take the data of the server, which sends the data first
  5. A user is sending the data to CloudWatch using the CloudWatch API. The user is sending data 90 minutes in the future. What will CloudWatch do in this case?
    1. CloudWatch will accept the data
    2. It is not possible to send data of the future
    3. It is not possible to send the data manually to CloudWatch
    4. The user cannot send data for more than 60 minutes in the future
  6. A user is having data generated randomly based on a certain event. The user wants to upload that data to CloudWatch. It may happen that event may not have data generated for some period due to randomness. Which of the below mentioned options is a recommended option for this case?
    1. For the period when there is no data, the user should not send the data at all
    2. For the period when there is no data the user should send a blank value
    3. For the period when there is no data the user should send the value as 0 (Refer User Guide)
    4. The user must upload the data to CloudWatch as having no data for some period will cause an error at CloudWatch monitoring
  7. A user has a weighing plant. The user measures the weight of some goods every 5 minutes and sends data to AWS CloudWatch for monitoring and tracking. Which of the below mentioned parameters is mandatory for the user to include in the request list?
    1. Value
    2. Namespace (refer put-metric request)
    3. Metric Name
    4. Timezone
  8. A user has a refrigerator plant. The user is measuring the temperature of the plant every 15 minutes. If the user wants to send the data to CloudWatch to view the data visually, which of the below mentioned statements is true with respect to the information given above?
    1. The user needs to use AWS CLI or API to upload the data
    2. The user can use the AWS Import Export facility to import data to CloudWatch
    3. The user will upload data from the AWS console
    4. The user cannot upload data to CloudWatch since it is not an AWS service metric
  9. A user has launched an EC2 instance. The user is planning to setup the CloudWatch alarm. Which of the below mentioned actions is not supported by the CloudWatch alarm?
    1. Notify the Auto Scaling launch config to scale up
    2. Send an SMS using SNS
    3. Notify the Auto Scaling group to scale down
    4. Stop the EC2 instance
  10. A user has a refrigerator plant. The user is measuring the temperature of the plant every 15 minutes. If the user wants to send the data to CloudWatch to view the data visually, which of the below mentioned statements is true with respect to the information given above?
    1. The user needs to use AWS CLI or API to upload the data
    2. The user can use the AWS Import Export facility to import data to CloudWatch
    3. The user will upload data from the AWS console
    4. The user cannot upload data to CloudWatch since it is not an AWS service metric
  11. A user is trying to aggregate all the CloudWatch metric data of the last 1 week. Which of the below mentioned statistics is not available for the user as a part of data aggregation?
    1. Aggregate
    2. Sum
    3. Sample data
    4. Average
  12. A user has setup a CloudWatch alarm on an EC2 action when the CPU utilization is above 75%. The alarm sends a notification to SNS on the alarm state. If the user wants to simulate the alarm action how can he achieve this?
    1. Run activities on the CPU such that its utilization reaches above 75%
    2. From the AWS console change the state to ‘Alarm’
    3. The user can set the alarm state to ‘Alarm’ using CLI
    4. Run the SNS action manually
  13. A user is publishing custom metrics to CloudWatch. Which of the below mentioned statements will help the user understand the functionality better?
    1. The user can use the CloudWatch Import tool
    2. The user should be able to see the data in the console after around 15 minutes
    3. If the user is uploading the custom data, the user must supply the namespace, timezone, and metric name as part of the command
    4. The user can view as well as upload data using the console, CLI and APIs
  14. An application that you are managing has EC2 instances & Dynamo DB tables deployed to several AWS Regions. In order to monitor the performance of the application globally, you would like to see two graphs 1) Avg CPU Utilization across all EC2 instances and 2) Number of Throttled Requests for all DynamoDB tables. How can you accomplish this?
    1. Tag your resources with the application name, and select the tag name as the dimension in the CloudWatch Management console to view the respective graphs (CloudWatch metrics are regional)
    2. Use the CloudWatch CLI tools to pull the respective metrics from each regional endpoint. Aggregate the data offline & store it for graphing in CloudWatch.
    3. Add SNMP traps to each instance and DynamoDB table. Leverage a central monitoring server to capture data from each instance and table. Put the aggregate data into CloudWatch for graphing (Can’t add SNMP traps to DynamoDB as it is a managed service)
    4. Add a CloudWatch agent to each instance and attach one to each DynamoDB table. When configuring the agent set the appropriate application name & view the graphs in CloudWatch. (Can’t add agents to DynamoDB as it is a managed service)

CloudWatch Monitoring Supported AWS Services

  • CloudWatch offers either basic or detailed monitoring for supported AWS services.
  • Basic monitoring means that a service sends data points to CloudWatch every five minutes.
  • Detailed monitoring means that a service sends data points to CloudWatch every minute.
  • If the AWS service supports both basic and detailed monitoring, the basic would be enabled by default and the detailed monitoring needs to be enabled for details metrics

AWS Services with Monitoring support

  • Auto Scaling
    • By default, basic monitoring is enabled when the launch configuration is created using the AWS Management Console and detailed monitoring is enabled when the launch configuration is created using using the AWS CLI or an API
    • Auto Scaling sends data to CloudWatch every 5 minutes by default, when created from Console.
    • For an additional charge, you can enable detailed monitoring for Auto Scaling, which sends data to CloudWatch every minute.
  • Amazon CloudFront
    • Amazon CloudFront sends data to CloudWatch every minute by default.
  • Amazon CloudSearch
    • Amazon CloudSearch sends data to CloudWatch every minute by default.
  • Amazon CloudWatch Events
    • Amazon CloudWatch Events sends data to CloudWatch every minute by default.
  • Amazon CloudWatch Logs
    • Amazon CloudWatch Logs sends data to CloudWatch every minute by default.
  • Amazon DynamoDB
    • Amazon DynamoDB sends data to CloudWatch every minute for some metrics and every 5 minutes for other metrics.
  • Amazon EC2 Container Service
    • Amazon EC2 Container Service sends data to CloudWatch every minute.
  • Amazon ElastiCache
    • Amazon ElastiCache sends data to CloudWatch every minute.
  • Amazon Elastic Block Store
    • Amazon Elastic Block Store sends data to CloudWatch every 5 minutes.
    • Provisioned IOPS SSD (io1) volumes automatically send one-minute metrics to CloudWatch.
  • Amazon Elastic Compute Cloud
    • Amazon EC2 sends data to CloudWatch every 5 minutes by default. For an additional charge, you can enable detailed monitoring for Amazon EC2, which sends data to CloudWatch every minute.
  • Elastic Load Balancing
    • Elastic Load Balancing sends data to CloudWatch every minute.
  • Amazon Elastic MapReduce
    • Amazon Elastic MapReduce sends data to CloudWatch every 5 minutes.
  • Amazon Elasticsearch Service
    • Amazon Elasticsearch Service sends data to CloudWatch every minute.
  • Amazon Kinesis Streams
    • Amazon Kinesis Streams sends data to CloudWatch every minute.
  • Amazon Kinesis Firehose
    • Amazon Kinesis Firehose sends data to CloudWatch every minute.
  • AWS Lambda
    • AWS Lambda sends data to CloudWatch every minute.
  • Amazon Machine Learning
    • Amazon Machine Learning sends data to CloudWatch every 5 minutes.
  • AWS OpsWorks
    • AWS OpsWorks sends data to CloudWatch every minute.
  • Amazon Redshift
    • Amazon Redshift sends data to CloudWatch every minute.
  • Amazon Relational Database Service
    • Amazon Relational Database Service sends data to CloudWatch every minute.
  • Amazon Route 53
    • Amazon Route 53 sends data to CloudWatch every minute.
  • Amazon Simple Notification Service
    • Amazon Simple Notification Service sends data to CloudWatch every 5 minutes.
  • Amazon Simple Queue Service
    • Amazon Simple Queue Service sends data to CloudWatch every 5 minutes.
  • Amazon Simple Storage Service
    • Amazon Simple Storage Service sends data to CloudWatch once a day.
  • Amazon Simple Workflow Service
    • Amazon Simple Workflow Service sends data to CloudWatch every 5 minutes.
  • AWS Storage Gateway
    • AWS Storage Gateway sends data to CloudWatch every 5 minutes.
  • AWS WAF
    • AWS WAF sends data to CloudWatch every minute.
  • Amazon WorkSpaces
    • Amazon WorkSpaces sends data to CloudWatch every 5 minutes.

AWS Certification Exam Practice Questions

  • Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
  • AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
  • AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
  • Open to further feedback, discussion and correction.
  1. What is the minimum time Interval for the data that Amazon CloudWatch receives and aggregates?
    1. One second
    2. Five seconds
    3. One minute
    4. Three minutes
    5. Five minutes
  2. In the ‘Detailed’ monitoring data available for your Amazon EBS volumes, Provisioned IOPS volumes automatically send _____ minute metrics to Amazon CloudWatch.
    1. 3
    2. 1
    3. 5
    4. 2
  3. Using Amazon CloudWatch’s Free Tier, what is the frequency of metric updates, which you receive?
    1. 5 minutes
    2. 500 milliseconds.
    3. 30 seconds
    4. 1 minute
  4. What is the type of monitoring data (for Amazon EBS volumes) which is available automatically in 5-minute periods at no charge called?
    1. Basic
    2. Primary
    3. Detailed
    4. Local
  5. A user has created an Auto Scaling group using CLI. The user wants to enable CloudWatch detailed monitoring for that group. How can the user configure this?
    1. When the user sets an alarm on the Auto Scaling group, it automatically enables detail monitoring
    2. By default detailed monitoring is enabled for Auto Scaling
    3. Auto Scaling does not support detailed monitoring
    4. Enable detail monitoring from the AWS console
  6. A user is trying to understand the detailed CloudWatch monitoring concept. Which of the below mentioned services provides detailed monitoring with CloudWatch without charging the user extra?
    1. AWS Auto Scaling
    2. AWS Route 53
    3. AWS EMR
    4. AWS SNS
  7. A user is trying to understand the detailed CloudWatch monitoring concept. Which of the below mentioned services does not provide detailed monitoring with CloudWatch?
    1. AWS EMR
    2. AWS RDS
    3. AWS ELB
    4. AWS Route53
  8. A user has enabled detailed CloudWatch monitoring with the AWS Simple Notification Service. Which of the below mentioned statements helps the user understand detailed monitoring better?
    1. SNS will send data every minute after configuration
    2. There is no need to enable since SNS provides data every minute
    3. AWS CloudWatch does not support monitoring for SNS
    4. SNS cannot provide data every minute
  9. A user has configured an Auto Scaling group with ELB. The user has enabled detailed CloudWatch monitoring on Auto Scaling. Which of the below mentioned statements will help the user understand the functionality better?
    1. It is not possible to setup detailed monitoring for Auto Scaling
    2. In this case, Auto Scaling will send data every minute and will charge the user extra
    3. Detailed monitoring will send data every minute without additional charges
    4. Auto Scaling sends data every minute only and does not charge the user

References

AWS ELB Monitoring

Following Features can be used for Monitoring Elastic Load Balancer

Cloud Watch Metrics

  • Elastic Load Balancing publishes data points to Amazon CloudWatch about your load balancers and back-end instances
  • Elastic Load Balancing reports metrics to CloudWatch only when requests are flowing through the load balancer. If there are requests flowing through the load balancer, Elastic Load Balancing measures and sends its metrics in 60-second intervals. If there are no requests flowing through the load balancer or no data for a metric, the metric is not reported.

Following metrics are available

  • HealthyHostCount, UnHealthyHostCount
    • Number of healthy and unhealthy instances registered with the load balancer.
    • Most useful statistics are average, min, and max
  • RequestCount
    • Number of requests completed or connections made during the specified interval (1 or 5 minutes).
    • Most useful statistic is sum
  • Latency
    • Time elapsed, in seconds, after the request leaves the load balancer until the headers of the response are received.
    • Most useful statistic is average
  • SurgeQueueLength
    • Total number of requests that are pending routing.
    • Load balancer queues a request if it is unable to establish a connection with a healthy instance in order to route the request.
    • Maximum size of the queue is 1,024. Additional requests are rejected when the queue is full.
    • Most useful statistic is max, because it represents the peak of queued requests.
  • SpilloverCount
    • The total number of requests that were rejected because the surge queue is full. Should ideally be 0
    • Most useful statistic is sum.
  • HTTPCode_ELB_4XX, HTTPCode_ELB_5XX
    • Client and Server error code generated by the load balancer
    • Most useful statistic is sum.
  • HTTPCode_Backend_2XX, HTTPCode_Backend_3XX, HTTPCode_Backend_4XX, HTTPCode_Backend_5XX
    • Number of HTTP response codes generated by registered instances
    • Most useful statistic is sum.

Elastic Load Balancer access logs

  • Elastic Load Balancing provides access logs that capture detailed information about all requests sent to your load balancer.
  • Each log contains information such as the time the request was received, the client’s IP address, latencies, request paths, and server responses.
  • Elastic Load Balancing captures the logs and stores them in the Amazon S3 bucket
  • Access logging is disabled by default and can be enabled without any additional charge. You are only charged for S3 storage

CloudTrail Logs

  • AWS CloudTrail can be used to capture all calls to the Elastic Load Balancing API made by or on behalf of your AWS account and either made using Elastic Load Balancing API directly, or indirectly through the AWS Management Console or AWS CLI
  • CloudTrail stores the information as log files in an Amazon S3 bucket that you specify.
  • Logs collected by CloudTrail can be used to monitor the activity of your load balancers and determine what API call was made, what source IP address was used, who made the call, when it was made, and so on

Sample Exam Questions

  1. An admin is planning to monitor the ELB. Which of the below mentioned services does not help the admin capture the monitoring information about the ELB activity
    1. ELB Access logs
    2. ELB health check
    3. CloudWatch metrics
    4. ELB API calls with CloudTrail

 

References

Elastic Load Balance developer guide