8.8 KiB
cloudformation-helpers
A collection of AWS Lambda funtions that fill in the gaps that existing CloudFormation resources do not cover.
AWS CloudFormation supports Custom Resources (http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources.html), which can be used to call AWS Lambda functions. CloudFormation covers much of the AWS API landscape, but does leave some gaps unsupported. AWS Lambda can contain any sort of logic, including interacting with the AWS API in ways not covered by CloudFormation. By combining the two, CloudFormation deploys should be able to approach the full resource support given by the AWS API.
Warning: most of these functions require fairly wide permissions, since they need access to resources in a general manner - much the same way CloudFormation itself has permission to do almost anything.
Usage
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Use https://s3.amazonaws.com/com.gilt.public.backoffice/cloudformation_templates/create_cloudformation_helper_functions.template to deploy a stack that creates the Lambda functions for you. Remember the stack name.
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Include the following resources in your CloudFormation template. These will create a) a nested stack that looks up the ARNs from the previous step and b) a custom resource that allows your template to read those ARNs.
"CFHelperStack": { "Type": "AWS::CloudFormation::Stack", "Properties": { "TemplateURL": "https://s3.amazonaws.com/com.gilt.public.backoffice/cloudformation_templates/lookup_stack_outputs.template" } }, "CFHelper": { "Type": "Custom::CFHelper", "Properties": { "ServiceToken": { "Fn::GetAtt" : ["CFHelperStack", "Outputs.LookupStackOutputsArn"] }, "StackName": "your-helper-stack-name-here" }, "DependsOn": [ "CFHelperStack" ] }You can either hardcode the stack name of your helper functions, or request it as a parameter.
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Use the ARNs from the previous step in a custom resource, to call those Lambda functions:
"PopulateTable": { "Type": "Custom::PopulateTable", "Properties": { "ServiceToken": { "Fn::GetAtt" : ["CFHelper", "DynamoDBPutItemsFunctionArn"] }, "TableName": "your-table-name", "Items": [ { "key": "foo1", "value": { "bar": 1.5, "baz": "qwerty" } }, { "key": "foo2", "value": false } ] }, "DependsOn": [ "CFHelper" ] }
Included functions
Create a full API in API Gateway
Pass in all of the components of the API endpoints, and the API will be created in API Gateway.
This will delete the entire API when the corresponding stack is deleted.
Parameters
name
The name of the API, seen in the list of APIs in AWS Console.
description
The description of what the API does.
endpoints
A JSON array of (see the example template below for a working example):
{
"resource": {
"sub-resource": {
"GET": {
"authorizationType": "NONE",
"integration": {
"type": "MOCK",
"contentType": "text/html"
}
}
},
"POST": {
"authorizationType": "NONE",
"integration": {
"type": "AWS",
"integrationHttpMethod": "POST",
"uri": "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/arn:aws:lambda:*:*:function:your-function-name/invocations",
"contentType": "application/json"
}
}
}
}
- The properties of the JSON document are either a) the HTTP method or b) a sub-resource.
- The resources cannot include a '/' - any resources nested in the path should also be nested in the JSON document.
- The parameters of each http method object are the same as putMethod callh ere: http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/APIGateway.html#putMethod-property - except that httpMethod, resourceId, and restApiId will be added for you.
- Each http method object can also optionally specify an "integration" property, which follows http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/APIGateway.html#putIntegration-property with the same properties automatically filled in for you.
- The "integration" property must include a "contentType" property that specifies the response Content-Type of the endpoint.
Output
baseUrl
The base url of the API endpoints. Combine this with the relative paths defined in the config to put together the full url for the API call.
restApiId
The id of the API that is created.
Reference Output Name
ApiGatewayCreateApiFunction
Example/Test Template
Insert items into DynamoDB
Pass in a list of items to be inserted into a DynamoDB table. This is useful to provide a template for the content of the table, or to populate a config table. There is no data-checking, so it is up to the client to ensure that the format of the data is correct.
Warning: it is a PUT, so it will overwrite any items that already exist for the table's primary key.
This will delete the items when the corresponding stack is deleted.
Parameters
TableName
The name of the DynamoDB table to insert into. Must exist at the time of the insert, i.e. will not create if it does not already exist.
Items
A JSON array of items to be inserted, in JSON format (not DynamoDB format).
Output
The list of TableName/Key pairs of items created.
Reference Output Name
DynamoDBPutItemsFunctionArn
Example/Test Template
Create a Kinesis stream
Mirrors the Kinesis.createStream API method. Yes, CloudFormation does support creating a Kinesis stream, but it does not allow you to specify the steam name; this helper does.
This will delete the stream when the corresponding stack is deleted.
Parameters
ShardCount
The number of shards for the stream. Required; no default.
StreamName
The name of the stream. Required.
Output
StreamName and Arn (of the stream) - matches the output of the existing CloudFormation task.
Reference Output Name
KinesisCreateStreamFunctionArn
Example/Test Template
Put S3 Objects
Mirrors the S3.putObject API method.
This will delete the objects and any added sub-objects (for "folders") when the corresponding stack is deleted.
Parameters
Bucket
The S3 bucket to put the object into
Key
The name of the object. Can include a "path" for organization in S3.
Body
The content of the object being put into S3 (a string).
Other
Please see the reference above for further parameters - these are only the most commonly-used ones.
Output
The result of the S3.PutObject API method.
Reference Output Name
S3PutObjectFunctionArn
Example/Test Template
Subscribe to SNS topics
Mirrors the SNS.Subscribe API method. To be used when the SNS topic already exists (since CloudFormation allows subscriptions to be created when creating SNS topics only).
This will delete the subscription when the corresponding stack is deleted.
Parameters
Endpoint
The endpoint that receives the SNS messages.
Protocol
The type of endpoint. Can be one of the following values: application, email, email-json, http, https, lambda, sms, sqs.
TopicArn
The SNS topic to subscribe to.
Output
The result of the SNS.Subscribe API method, i.e. SubscriptionArn
Reference Output Name
SnsSubscribeFunctionArn
Example/Test Template
Deployment (contributors)
After making changes (i.e. adding a new helper function), please do the following:
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Upload this zipped repo to the com.gilt.public.backoffice/lambda_functions bucket. To produce the .zip file:
zip -r cloudformation-helpers.zip . -x *.git* -x *cloudformation-helpers.zip*Unfortunately we can't use the Github .zip file directly, because it zips the code into a subdirectory named after the repo; AWS Lambda then can't find the .js file containing the helper functions because it is not on the top-level.
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Upload the edited create_cloudformation_helper_functions.template to com.gilt.public.backoffice/cloudformation_templates
License
Copyright 2016 Gilt Groupe, Inc.
Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0