Merge pull request #4 from kvrajesh/master

Making ecs branch current

content/ecs-spot-capacity-providers/module-1/spot_inturruption_handling.md

@@ -0,0 +1,75 @@
+---
+title: "Inturruption Handling On EC2 Spot Instances"
+weight: 80
+---
+
+Amazon EC2 terminates your Spot Instance when it needs the capacity back. Amazon EC2 provides a Spot Instance interruption notice, which gives the instance a two-minute warning before it is interrupted.
+
+When Amazon EC2 is going to interrupt your Spot Instance, the interruption notification will be available in two ways
+
+1. ***Amazon EventBridge Events:*** EC2 service emits an event two minutes prior to the actual interruption. This event can be detected by Amazon CloudWatch Events.
+
+1. ***Instance-action in the MetaData service (IMDS):*** If your Spot Instance is marked to be stopped or terminated by the Spot service, the instance-action item is present in your instance metadata.
+
+look at the user data section in the Launch template configuration.
+
+```
+echo "ECS_ENABLE_SPOT_INSTANCE_DRAINING=true" >> /etc/ecs/ecs.config
+```
+
+The above configuration enables automatic draining of spot instances at the time of spot interruption notice. The ECS container agent runnining on the ECS container instances handles the interruption using the Instance Metadata service.
+
+If the application can also handle the interruption to implement any checkpointing or saving the data. The web application (app.py) we used to buld docker image in the Module-2 shows two ways to handle the spot interruption within a docker container.
+
+In the first method, it check the instance metadata service for spot interruption and display a message to web page notifying the users.
+
+Note:  The ECS tasks should not be accessing EC2 metadata. For security reasons, this should be blocked this in a Prod environment.
+
+```
+URL = "http://169.254.169.254/latest/meta-data/spot/termination-time"
+SpotInt = requests.get(URL)
+if SpotInt.status_code == 200:
+    response += "<h1>This Spot Instance Got Interruption and Termination Date is {} </h1> <hr/>".format(SpotInt.text)
+```
+
+In the second method, it listens to the **SIGTERM** signal. The ECS container agent calls StopTask API to stop all the tasks running on the Spot Instance.
+
+When StopTask is called on a task, the equivalent of docker stop is issued to the containers running in the task. This results in a **SIGTERM** value and a default 30-second timeout, after which the SIGKILL value is sent and the containers are forcibly stopped. If the container handles the **SIGTERM** value gracefully and exits within 30 seconds from receiving it, no SIGKILL value is sent.
+
+
+The application can listen to the **SIGTERM** signal and handle the interruption gracefully.
+
+```
+class Ec2SpotInterruptionHandler:
+  signals = {
+    signal.SIGINT: 'SIGINT',
+    signal.SIGTERM: 'SIGTERM'
+  }
+
+def __init__(self):
+   signal.signal(signal.SIGINT, self.exit_gracefully)
+   signal.signal(signal.SIGTERM, self.exit_gracefully)
+
+def exit_gracefully(self, signum, frame):
+   print("\nReceived {} signal".format(self.signals[signum]))
+   if self.signals[signum] == 'SIGTERM':
+     print("Looks like there is a Spot Interruption. Let's wrap up the processing to avoid forceful killing of the applucation in next 30 sec ...")
+```
+
+Spot Interruption Handling on ECS Fargate Spot
+---
+
+When tasks using Fargate Spot capacity are stopped due to a Spot interruption, a two-minute warning is sent before a task is stopped. The warning is sent as a task state change event to Amazon EventBridge
+and a SIGTERM signal to the running task. When using Fargate Spot as part of a service, the service
+scheduler will receive the interruption signal and attempt to launch additional tasks on Fargate Spot if
+capacity is available.
+
+To ensure that your containers exit gracefully before the task stops, the following can be configured:
+
+• A stopTimeout value of 120 seconds or less can be specified in the container definition that the task
+is using. Specifying a stopTimeout value gives you time between the moment the task state change event is received and the point at which the container is forcefully stopped. 
+
+• The **SIGTERM** signal must be received from within the container to perform any cleanup actions.
+
+
+***Congratulations !!!*** you have successfully completed the workshop module and learnt how to create ASG CPs and schedule ECS services across Spot and On-demand CPs. You may proceed to optional module using Fargate Spot Capacity Providers.

content/ecs-spot-capacity-providers/module-2/_index.md

@@ -10,14 +10,9 @@ Amazon EC2 terminates your Spot Instance when it needs the capacity back. Amazon
 
 When Amazon EC2 is going to interrupt your Spot Instance, the interruption notification will be available in two ways
 
-- ***Amazon EventBridge Events***
+1. ***Amazon EventBridge Events:*** EC2 service emits an event two minutes prior to the actual interruption. This event can be detected by Amazon CloudWatch Events.
 
-
-EC2 service emits an event two minutes prior to the actual interruption. This event can be detected by Amazon CloudWatch Events.
-
-- ***Instance-action in the MetaData service (IMDS)***
-
-If your Spot Instance is marked to be stopped or terminated by the Spot service, the instance-action item is present in your instance metadata.
+1. ***Instance-action in the MetaData service (IMDS):*** If your Spot Instance is marked to be stopped or terminated by the Spot service, the instance-action item is present in your instance metadata.
 
 look at the user data section in the Launch template configuration.