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I gave a presentation at the AWS User Group, Singapore on 24 Oct 2013 explaining how we used EC2 Auto Scaling with CloudWatch Custom Metrics for our product.
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Auto Scaling Spot Instances with Custom CloudWatch Metrics
AWS Singapore User Group
Chris DrumgooleHead, Product Management
2
Agenda
• Quick overview of VSocial• Infrastructure Scaling Needs• Overview of EC2 Auto Scaling with AWS
– Scaling from CloudWatch
• Configuring Auto Scaling Launch Configs, Groups, and Policies
• Creating your own CloudWatch Metric• Bringing it all together
OVERVIEW
VSocial Overview
• “Social Media Enterprise Command Center”
• Core Features:– Social CRM– Social Media Community Management
• Community Managers use tool to manage FB and TW communities
• Tool helps manage conversations from multiple Social Media accounts
A glance at the infrastructure…
Public Visitors
Data Pull
Data Pull
Data Pull
Data Pull
Load Balancer
Front-End Application Server Cluster
Database Cluster
AWS SQSAWS SNS
Data Pull
Data Pull
This needs to scale!
Infrastructure Scaling Needs
• Timely Conversation Data Pulls from Social Networks
• Data Pull Processes can take longer due to:– Increased activity on channel (more tweets or FB
Messages)– Network Latency
• Slowdowns will cascade across all requests
Requirement:
Way to automatically adjust compute resources when needed based on real-time performance data,
24/7
SOLUTION
Introducing Auto Scaling (EC2)
• AWS allows two types of Auto Scaling:– Minimal Configuration and Management directly from a
CloudWatch Alarm– More advanced via SDK
• AWS Supports auto scaling On-Demand or Spot Instances, depending on needs
Spot Instances vs. On Demand Instances• Bidding System• Considerably cheaper than On Demand*
– Micro Instances:• On Demand Pricing @ $0.02/hr ~$14.40/mth• Spot Pricing @ >$0.004/hr ~$2.88/mth
– Small Instances:• On Demand Pricing @ $0.08/hr ~$57.60/mth• Spot Pricing @ >$0.01/hr ~$7.20/mth
• Spot Instances not guaranteed• Great for non-mission critical tasks
* All prices in USD for resources in the Asia Pacific Singapore Region
Spot Instances and Our Needs
• We need to be able to scale up data pull instances so we can keep up with volume (and mitigate slowdowns)
• It’s ok if the machine are taken away from us, we’ll just request more.
• Cost Savings is essential
AWS-Managed Scaling with CloudWatch
SETTING UP AUTO SCALING
Configuring Auto Scaling
Before you can finish setting up the CloudWatch Auto Scaling, you need to follow these steps:
1. Install the AWS CLI tools on your trusty Linux box2. Create an Auto Scaling Launch Config3. Create an Auto Scaling Group4. Create Scale Out (Up) and In (Down) Policies
Configuring Auto Scaling:Launch Configurations
Defines the type of Instance to create
• Create an AMI• Launch Config links to
an AMI• Define Instance Type• Define max bid price
(in USD, /hr)• Turn off Monitoring!
$as-create-launch-config \MyLaunchConfigName \--image-id ami-
123ab456 \--instance-type t1.micro
\--spot-price 0.025 \--key our_key_name \--monitoring-disabled
Configuring Auto Scaling:Scaling Groups• Create a Load
Balancer to “hold” these launch configs
• State what AZ zones you want these to be launched in
• # Instances Lower and Upper bounds
• Meta Configuration• Link to the Launch
Configuration
$as-create-auto-scaling-group \MyASGroupName \--availability-zones ap-
southeast-1a,ap-southeast-1b \--default-cooldown 120 \--load-balancers
VSocialCrons \--min-size 1 \--max-size 45 \--tag="k=Name, v=SQS-
Processor, p=true" \--launch-configuration MyLaunchConfigName
Configuring Auto Scaling:Policies• Need both Up and
Down policies• Link to the Auto
Scaling Group• Define whether it’s an
addition or subtraction for “adjustment”
$as-put-scaling-policy \MyPolicyName-add1 \--auto-scaling-group
MyASGroupName \--adjustment=1 \--type
ChangeInCapacity \--cooldown 300
$as-put-scaling-policy \MyPolicyName-del1 \--auto-scaling-group
MyASGroupName \--adjustment=-1 \--type
ChangeInCapacity \--cooldown 600
• Now you’re ready to configure your CloudWatch Alarms to utilize the auto scaling configuration!
• But wait…
CUSTOM CLOUDWATCH METRIC
We need a custom metric!
• We want to decide to scale based on something that there isn’t yet a built-in metric
• Decide Scaling at Arbitrary Levels
Creating a CloudWatch Custom Metric• Caveats:
– Custom Metrics can be stored as frequent as every 5 minutes
– After a while old data will be truncated
• Steps– Install the AWS SDK for your favorite language– Write simple script to calculate and store metric– Schedule script by cron
• Code Sections:– Set Up– Metric Data Pulls– Store New Metric
Custom Metric Code – Set Up
// Constantsdefine("CW_NAMESPACE", "Vocanic/VSocial");define("CW_MONITORING_AWS_KEY_ID", "XXXXXXXXXXXXXXXXX");define("CW_MONITORING_AWS_SECRET_ACCESS_KEY", "YYYYYYYYYYYYYYYYY"); // Includesinclude '/usr/lib/php5/amazon/sdk-1.5.17.1/sdk.class.php'; // Configure options for CloudWatch object$options = array();$options["key"] = CW_MONITORING_AWS_KEY_ID; $options["secret"] = CW_MONITORING_AWS_SECRET_ACCESS_KEY; // Set up Amazon Objects$cw = new AmazonCloudWatch($options);$cw->set_region(AmazonCloudWatch::REGION_SINGAPORE);
Custom Metric Code – Define Time Bounds // Define time bounds for pulling metric data// We're only interested in the most recent metric// These particular metrics are stored every 5 minutes)$endTime = time(); // Store current unix time in end time
variable$startTime = $endTime - 599; // Subtract 1 second less than
10 minutes $endTime = date("j F Y H:i", $endTime);$startTime = date("j F Y H:i", $startTime);
Custom Metric Code – Pull Metric Values// Get Num Deleted Metric$NumberOfMessagesDeletedMetric = $cw->get_metric_statistics(
'AWS/SQS', // CloudWatch Namespace of Metric'NumberOfMessagesDeleted', // Name of Metric$startTime, $endTime, // Timestamp bounds for pulling set
of metrics60, // Attempt to get a number every 60 seconds, but in
reality, it's every 5 min'Sum', // Statistics: Get Sum value'Count', // Unit: Get a count of the values array('Dimensions' => array(array('Name' =>'QueueName',
'Value' => 'My_SQS_Queue_Name')))// Define which SQS Queue you want this metric for);
$NumberOfMessagesDeleted = $NumberOfMessagesDeletedMetric->body-
>GetMetricStatisticsResult->Datapoints[0]->member->Sum;*Repeat for Number Sent Metric
Custom Metric Code – Store New Metric// Get Timestamp for storing in our custom metric so that timing can match up$TimeStamp = $NumberOfMessagesSentMetric->body->GetMetricStatisticsResult->Datapoints[0]->member->Timestamp; // Get Difference of Sent versus Deleted$SentVSDeleted = $NumberOfMessagesSent - $NumberOfMessagesDeleted; // Send metric to CloudWatch$response = $cw->put_metric_data(CW_NAMESPACE, array(
array('MetricName' =>
'DataPullQueueSentvsDel','Timestamp' => $TimeStamp,'Value' =>
$SentVSDeleted)));
AWS CloudWatch Custom Metric
Custom Metric in Practice
Scaling Deciding Factors
• For each scaling policy, you need to creating a specific policy from the CLI– Queue Delta >100 for 5 min, Add 1 Instance– Queue Delta >350 for 5 min, Add 2 Instances– Queue Delta >1000 for 5 min, Add 4 Instance– Queue Delta < 10 for 60 minutes, Remove 1 Instance
When Alarms are hit, Auto Scale Out policy is triggered, instances are created
Danger!Queue Delta > 1000!!
4 Instances Created
??
Thanks!
• Questions?
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