cfn-include
is a preprocessor for CloudFormation templates which extends CloudFormation's intrinsic functions.
For example, Fn::Include
provides a convenient way to include files, which can be local, a URL or on an S3 bucket (with proper IAM authentication if necessary). It supports both JSON and YAML as input and output format. CloudFormation's tag syntax for YAML (e.g. !GetAtt
) is supported as well.
cfn-include
tries to be minimally invasive, meaning that the template will still look and feel like an ordinary CloudFormation template. This is what sets cfn-include
apart from other CloudFormation preprocessors such as CFNDSL, StackFormation and AWSBoxen. There is no need to use a scripting language or adjust to new syntax. Check them out though, they might be a better fit for you.
Functions
- cfn-include
- Installation
- Synopsis
- Fn::Include
- Fn::Map
- Fn::Flatten
- Fn::FlattenDeep
- Fn::GetEnv
- Fn::Length
- Fn::Merge
- Fn::DeepMerge
- Fn::Sequence
- Fn::Stringify
- Fn::Uniq
- Fn::Compact
- Fn::Concat
- Fn::Sort
- Fn::SortedUniq
- Fn::SortBy
- Fn::SortObject
- Fn::ObjectKeys
- Fn::ObjectValues
- Fn::Filenames
- Fn::StringSplit
- Fn::Without
- Fn::Omit
- Fn::OmitEmpty
- Fn::Eval
- Fn::IfEval
- Fn::JoinNow
- Fn::ApplyTags
- Fn::Outputs
- More Examples
- Proxy Support
- Compatibility
- Web Service
Tag-based syntax is available in YAML templates. For example,Fn::Include
becomes !Include
.
You can either install cfn-include
or use a web service to compile templates.
npm install --global cfn-include
The web service can be called with your favorite CLI tool such as curl
.
curl https://api.netcubed.de/latest/template -XPOST -d @template.json
cfn-include <path> [options]
-
path
location of template. Either path to a local file, URL or file on an S3 bucket (e.g.
s3://bucket-name/example.template
)
Options:
-
-m, --minimize
minimize JSON output [false] -
--metadata
add build metadata to output [false] -
-t, --validate
validate compiled template [false] -
-y, --yaml
output yaml instead of json [false] -
--bucket
bucket name required for templates larger than 50k -
--prefix
prefix for templates uploaded to the bucket ['cfn-include'] -
--version
print version and exit -
--context
template full path. only utilized for stdin when the template is piped to this script example:cat examples/base.template | ./bin/cli.js --context examples/base.template
-
--enable
different options / toggles: ['env','eval'] [string] [choices: 'env','eval','env.eval' etc...]-
env
pre-process env vars and inject into templates as they are processed looks for$KEY or $ {KEY} matches
-
-
-i, --inject
JSON string payload to use for template injection. (Takes precedence over process.env (if enabled) injection and will be merged on top of process.env) -
--doLog
console log out include options in recurse step.cfn-include
also accepts a template passed from stdin
cat mytemplate.yml | cfn-include
Mappings:
Region2AMI: !Include https://api.netcubed.de/latest/ami/lookup?platform=amzn2
Resources:
Instance:
Type: AWS::EC2::Instance
Properties:
ImageId: !FindInMap [Region2AMI, !Ref AWS::Region, AMI]
UserData:
Fn::Base64:
Fn::Sub: !Include { type: string, location: userdata.sh }
This is what the userdata.sh
looks like:
#!/bin/bash
/opt/aws/bin/cfn-init -s ${AWS::StackId} -r MyInstance --region ${AWS::Region}
cfn-include synopsis.json > output.template
# you can also compile remote files
cfn-include https://raw.githubusercontent.com/monken/cfn-include/master/examples/synopsis.json > output.template
The output will be something like this:
{
"AWSTemplateFormatVersion": "2010-09-09",
"Mappings": {
"Region2AMI": {
"Metadata": {
"Name": "amzn-ami-hvm-2016.09.0.20161028-x86_64-gp2",
"Owner": "amazon",
"CreationDate": "2016-10-29T00:49:47.000Z"
},
"us-east-2": {
"AMI": "ami-58277d3d"
},
// ...
} },
"Resources": {
"Instance": {
"Type": "AWS::EC2::Instance",
"Properties": {
"ImageId": {
"FindInMap": [ "Region2AMI", { "Ref": "AWS::Region" }, "AMI" ]
},
"UserData": {
"Fn::Base64": {
"Fn::Sub": {
"Fn::Join": ["", [
"#!/bin/bash\n",
"\"/opt/aws/bin/cfn-init -s ${AWS::StackId} -r MyInstance --region ${AWS::Region}\n",
""
] ] } } } } } } }
Place Fn::Include
anywhere in the template and it will be replaced by the contents it is referring to. The function accepts an object. Parameters are:
- location: The location to the file can be relative or absolute. A relative location is interpreted relative to the template. Included files can in turn include more files, i.e. recursion is supported.
- ignoreMissingVar: If set to
true
the function will not throw an error if a variable is not found (unset). Instead, the variable will be replaced by an empty string. Defaults tofalse
. - ignoreMissingFile: If set to
true
the function will not throw an error if the file is not found. Instead, the function will be replaced by an empty string. Defaults tofalse
. - type (optional): either
json
,string
orapi
. Defaults tojson
.string
will include the file literally which is useful in combination withFn::Sub
.api
will call any AWS API and return the response which can be included in the template. Choosejson
for both JSON and YAML files. Theliteral
type is deprecated and uses the infamousFn::Join
syntax. - context (optional, deprecated): If
type
isliteral
a context object with variables can be provided. The object can contain plain values or references to parameters or resources in the CloudFormation template (e.g.{ "Ref": "StackId" }
). Use Mustache like syntax in the file. This option is deprecated in favor of theFn::Sub
syntax (see examples below). - parser (optional):
- string: default is
"jmespath"
- object
{location, query, parser}
: default is"jmespath"
- array:
[location, query, parser]
: default is"lodash"
- string (split |)
location|query|parser
: default is"lodash"
- string: default is
- query (optional): If
type
isjson
,array
, orstring split |
- JMESPath query can be provided. The file to include is then queried using the value as a JMESPath expression.
- Lodash _.get query
Only applicable if type is api
:
- service: Service to call (see AWSJavaScriptSDK, case sensitive, e.g.
EC2
,CloudFormation
) - action: Action to call (case sensitive, e.g.
updateStack
,describeRegions
) - parameters (optional): Parameters passed to action (e.g.
{ StackName: "MyStack" }
) - region (optional): Either
AWS_DEFAULT_REGION
or this parameter have to be set which specifies the region where the API call is made. You can also use a plain string if you want the default behavior, which is simply including a JSON file. - isGlob (optional): Forces the usage of glob to spit out an array of includes
- inject (optional): Pass in localized env / options to be injected into a template
# all equivalent
Fn::Include:
location: ./t/includes/complex.json
query: bulb[1].c
Fn::Include:
location: ./t/includes/complex.json
query: bulb.1.c
parser: lodash
# Array parser is lodash
Fn::Include: [./t/includes/complex.json, bulb.1.c]
# Array default parser is lodash
Fn::Include:
- ./t/includes/complex.json
- bulb.1.c
# string split "|" default parser is lodash
Fn::Include: ./t/includes/complex.json|bulb.1.c
!Include https://example.com/include.json
// equivalent to
Fn::Include:
type: json
location: https://example.com/include.json
Include a file from an S3 bucket. Authentication is handled by aws-sdk
. See Setting AWS Credentials for details.
!Include s3://bucket-name/include1.json
!Include include.json
Include a file literally and make use of Fn::Sub
:
Fn::Sub:
Fn::Include:
type: string
location: https://example.com/userdata.txt
IE: loop through all regions and return the image id of a specific AMI:
Fn::Merge:
Fn::Map:
- Fn::Include:
action: describeRegions
query: "Regions[*].RegionName[]"
service: EC2
type: api
- _:
AMI:
Fn::Include:
action: describeImages
parameters:
Filters:
- Name: manifest-location
Values:
- amazon/amzn-ami-hvm-2016.03.3.x86_64-gp2
query: "Images[*].ImageId | [0]"
region: _
service: EC2
type: api
Output as JSON:
{ "ap-south-1": { "AMI": "ami-ffbdd790" },
"eu-west-1": {"AMI": "ami-f9dd458a" },
"ap-southeast-1": { "AMI": "ami-a59b49c6" },
...
}
Essentially imagine if you had several yaml or json files you wanted to include.
./src/
files/
- one.yml
- two.yml
- three.yml
- four.yml
main.yml
Before Glob you would have to do:
main.yml
Fn::Map:
- [one, two, three]
- [FILE]
- Fn::Include: ./files/${FILE}.yml
With Glob
main.yml
Fn::Include: ./files/*.yml
or (say you need to ignore something)
Fn::Include:
location: ./files/!(four).yml
isGlob: true
This feature uses the exact same logic as doEnv in that all env variables are traversed and replaced however this is with localized state for the included file.
File to inject to:
toInject.yml
- your include file
SomeResource:
Name: ${LOCALIZED_NAME}
Consume it and add some custom state
Fn::Include:
location: ./toInject.yml
inject:
LOCALIZED_NAME: CustomName
yields
SomeResource:
Name: CustomName
Fn::Map
is the equivalent of the lodash map()
function allowing for the transformation of an input array or object to an output array.
By default the string _
is used as the variable in the map function. A custom variable can be provided as a second parameter, see Fn::Flatten
for an example. If a custom variable is used, the variable will also be replaced if found in the object key, see Fn::Merge
for an example.
Fn::Map:
- [80, 443]
- CidrIp: 0.0.0.0/0
FromPort: _
ToPort: _
IpProtocol: tcp
[
{
"CidrIp": "0.0.0.0/0",
"FromPort": "80",
"ToPort": "80"
},
{
"CidrIp": "0.0.0.0/0",
"FromPort": "443",
"ToPort": "443"
}
]
Custom variables can be specified as a single value, of as a list of up to three values. If a list is specified, the second variable is used as index and the third (if present) as size.
Fn::Map:
- !Sequence [A, C]
- [NET, INDEX, N]
- Subnet${NET}:
Type: 'AWS::EC2::Subnet'
Properties:
CidrBlock: !Select [INDEX, !Cidr [MyCIDR, N, 8]]
[{
"SubnetA": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"CidrBlock": { "Fn::Select": [ 0, { "Fn::Cidr": [ "MyCIDR", 3, 8 ] } ] }
}
}
}, {
"SubnetB": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"CidrBlock": { "Fn::Select": [ 1, { "Fn::Cidr": [ "MyCIDR", 3, 8 ] } ] }
}
}
}, {
"SubnetC": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"CidrBlock": { "Fn::Select": [ 2, { "Fn::Cidr": [ "MyCIDR", 3, 8 ] } ] }
}
}
}]
This function flattens an array a single level. This is useful for flattening out nested Fn::Map
calls.
SecurityGroupIngress:
Fn::Flatten:
Fn::Map:
- [80, 443]
- $
- Fn::Map:
- [10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16]
- CidrIp: _
FromPort: $
ToPort: $
IpProtocol: tcp
Results in:
{
"SecurityGroupIngress": [
{
"CidrIp": "10.0.0.0/8",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "tcp"
},
{
"CidrIp": "172.16.0.0/12",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "tcp"
},
{
"CidrIp": "192.168.0.0/16",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "tcp"
},
{
"CidrIp": "10.0.0.0/8",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "tcp"
},
{
"CidrIp": "172.16.0.0/12",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "tcp"
},
{
"CidrIp": "192.168.0.0/16",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "tcp"
}
]
}
This function flattens an array as many levels as possible. This is useful for flattening out nested Fn::Map
calls.
SecurityGroupIngress:
Fn::FlattenDeep:
Fn::Map:
- [80, 443]
- $
- Fn::Map:
- [10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16]
- Fn::Map:
- [tcp, udp]
- PROTOCOL
- CidrIp: _
FromPort: $
ToPort: $
IpProtocol: PROTOCOL
Results in:
{
"SecurityGroupIngress": [
{
"CidrIp": "10.0.0.0/8",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "tcp"
},
{
"CidrIp": "10.0.0.0/8",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "udp"
},
{
"CidrIp": "172.16.0.0/12",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "tcp"
},
{
"CidrIp": "172.16.0.0/12",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "udp"
},
{
"CidrIp": "192.168.0.0/16",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "tcp"
},
{
"CidrIp": "192.168.0.0/16",
"FromPort": "80",
"ToPort": "80",
"IpProtocol": "udp"
},
{
"CidrIp": "10.0.0.0/8",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "tcp"
},
{
"CidrIp": "10.0.0.0/8",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "udp"
},
{
"CidrIp": "172.16.0.0/12",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "tcp"
},
{
"CidrIp": "172.16.0.0/12",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "udp"
},
{
"CidrIp": "192.168.0.0/16",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "tcp"
},
{
"CidrIp": "192.168.0.0/16",
"FromPort": "443",
"ToPort": "443",
"IpProtocol": "udp"
}
]
}
Resources:
Bucket:
Type: AWS::S3::Bucket
Properties:
BucketName: !GetEnv [BUCKET_NAME, !Ref AWS::NoValue]
The second argument is optional and provides the default value and will be used of the environmental variable is not defined. If the second argument is omitted !GetEnv BUCKET_NAME
and the environmental variable is not defined then the compilation will fail.
Fn::Length
returns the length of a list or expanded section.
Fn::Merge
will merge an array of objects into a single object. See lodash / merge for details on its behavior. This function is useful if you want to add functionality to an existing template if you want to merge objects of your template that have been created with Fn::Map
.
Fn::Merge
accepts a list of objects that will be merged together. You can use other cfn-include
functions such as Fn::Include
to pull in template from remote locations such as S3 buckets.
Fn::Merge:
- !Include s3://my-templates/my-template.json
- !Include s3://my-templates/my-other-template.json
- Parameters:
MyCustomParameter:
Type: String
Resources:
MyBucket:
Type: AWS::S3::Bucket
Fn::DeepMerge
will deeply merge an array of objects and arrays into a single object. See deepmerge for details on its behavior. This function is useful if you want to add functionality to an existing template if you want to merge objects of your template that have been created with Fn::Map
.
Fn::DeepMerge
accepts a list of objects that will be merged together. You can use other cfn-include
functions such as Fn::Include
to pull in template from remote locations such as S3 buckets.
To understand it better besides the below example refer to this test. Note that all arrays are concatenated.
Why does Fn::Merge
still exist? Answer: Backwards compatibility for expected behavior.
Fn::DeepMerge:
- !Include s3://my-templates/my-template.json
- !Include s3://my-templates/my-other-template.json
- Parameters:
MyCustomParameter:
Type: String
Resources:
MyBucket:
Type: AWS::S3::Bucket
This snippet shows how multiple subnets can be created for each AZ and then merged with the rest of the template.
Resources:
IAMUser:
Type: AWS::IAM::User
SecurityGroup:
Type: AWS::EC2::SecurityGroup
Fn::Merge:
Fn::Map:
- [A, B]
- AZ
- Subnet${AZ}:
Type: AWS::EC2::Subnet
{
"Resources": {
"SubnetA": {
"Type": "AWS::EC2::Subnet"
},
"SubnetB": {
"Type": "AWS::EC2::Subnet"
},
"SG": {
"Type": "AWS::EC2::SecurityGroup"
}
}
}
Fn::Sequence
generates a sequence of numbers of characters. You can specify the start, end and step.
!Sequence [1, 4]
# generates
[1, 2, 3 4]
!Sequence [1, 10, 2]
# generates
[1, 3, 5, 7, 9]
!Sequence [a, d]
# generates
[a, b, c, d]
Fn::Sequence
can be used in combination with Fn::Map
to generate complex objects:
Fn::Map:
- !Sequence [a, c]
- AZ
- Subnet${AZ}:
Type: AWS::EC2::Subnet
Fn::Stringify
will take the passed value and transform it to a JSON string. This is useful for parameters that require a JSON document as a string. Using this function, you can keep writing your configuration in YAML and let the function transform it into a JSON string.
Another useful application is the use of this function in a config file passed as --cli-input-json
parameter.
# stack.config.yml
StackName: MyStack
TemplateBody:
Fn::Stringify: !Include mytemplate.yml
Parameters:
- ParameterKey: Foo
ParameterValue: Bar
You can then simply run the following command to deploy a stack:
cfn-include stack.config.yml > stack.config.json
aws cloudformation create-stack --cli-input-json file://stack.config.json
This function filters only the unique elements of an array
SecurityGroupIngress:
Fn::Uniq:
Fn::Flatten:
- [1, 2]
- [3, 4]
- [1, 4, 6]
Results in:
{
"SecurityGroupIngress": [
1,
2,
3,
4,
6
]
}
This function removes falsy elements same as lodash
SecurityGroupIngress:
Fn::Compact:
- 1
- a
- ""
- false
- true
Results in:
{
"SecurityGroupIngress": [
1,
"a",
true
]
}
_.concat
Fn::Concat:
- [a, b, c]
- d
Results in:
[
"a",
"b",
"c",
"d"
]
$ ./bin/cli.js [examples/sort.yaml](examples/sort.yaml)
[
1,
20,
22,
30,
30,
33.3,
40,
5.5,
50,
50
]
$ ./bin/cli.js [examples/sortedUniq.yaml](examples/sortedUniq.yaml)
[
1,
20,
22,
30,
33.3,
40,
5.5,
50
]
$ ./bin/cli.js [examples/sortBy.yaml](examples/sortBy.yaml)
[
{
"name": "Ana",
"age": 12
},
{
"name": "Ana",
"age": 31
},
{
"name": "Bob",
"age": 17
},
{
"name": "Colby",
"age": 35
},
{
"name": "Fred",
"age": 50
},
{
"name": "Jack",
"age": 40
},
{
"name": "Ted",
"age": 20
},
{
"name": "Zed",
"age": 90
}
]
$ ./bin/cli.js examples/sortObject.yaml
{
"a": "hi",
"c": "z",
"h": 20,
"i": true,
"z": 1
}
This function uses Object.keys
FamilyNames:
Fn::ObjectKeys:
Ted: 18
Lucy: 5
Tom: 10
Results in:
FamilyNames:
- Ted
- Lucy
- Tom
This function uses Object.values
FamilyAges:
Fn::ObjectValues:
Ted: 18
Lucy: 5
Tom: 10
Results in:
FamilyAges:
- 18
- 5
- 10
Fn::Filenames:
location: "../t/fixtures"
omitExtension: true
[
"deep",
"foobar",
"subfolder",
"synopsis",
"verydeep",
"include1",
"include2"
]
Useful for injected Includes which you need to run Fn::Map
upon.
Fn::StringSplit:
string: "A,B,C"
separator: "," # defaults to this so it can be omitted
- A
- B
- C
Fn::Without:
- ["a", "b", "c", "d"]
- ["b", "c"]
- "a",
- "d"
b: b
See omitEmpty test file, file and expectations (output).
In summary falsy values are omitted from an object except false
and 0
.
Opt in to use eval
in your templates. This is disabled by default.
--enable eval
is required to turn on options.doEval in the include function.
Fn::Eval:
state: [1, 2, 3]
script: >
state.map((v) => 2 * v);
- 2
- 4
- 6
Opt in to use eval
in your templates. This is disabled by default.
--enable eval
is required to turn on options.doEval in the include function.
Fn::IfEval:
inject:
lastName: bear
# doLog: true
evalCond: ('$lastName' === 'bear')
truthy:
Name: Yogi
LastName: Bear
falsy:
Name: Fred
LastName: Flint
Name: Yogi
LastName: Bear
Fn::JoinNow:
- ""
- - "arn:aws:s3:::c1-acme-iam-cache-engine-"
- ${AWS::AccountId}
- "-us-east-1$CFT_STACK_SUFFIX"
arn:aws:s3:::c1-acme-iam-cache-engine-${AWS::AccountId}-us-east-1$CFT_STACK_SUFFIX
See ApplyTags test file.
Fields:
(T|t)ags
: sequence of {Key, Value} objects to me merged in as Tags properties of a taggable resource.
resources
: Object mapping of resources, this is usually your root CFT.Resources
block.
Name: !UpperCamelCase foo-bar # yields FooBar
This helper transformation simplifies the definition of output variables and exports.
Outputs:
Fn::Outputs:
Version: !GetEnv [VERSION, "1.0.0"]
BucketArn: ${Bucket.Arn}
BucketPolicy:
Condition: HasBucketPolicy
Value: ${BucketPolicy}
Subnets:
- ${SubnetA},${SubnetB},${Provided}
- Provided: ${SubnetC}
This will translate into:
Outputs:
Version:
Value: !Sub "1.0.0"
Export:
Name: !Sub ${AWS::StackName}:Version
BucketArn:
Value: !Sub ${Bucket.Arn}
Export:
Name: !Sub ${AWS::StackName}:BucketArn
BucketPolicy:
Value: !Sub ${BucketPolicy}
Condition: HasBucketPolicy
Export:
Name: !Sub ${AWS::StackName}:BucketPolicy
Subnets:
Value:
Fn::Sub:
- ${SubnetA},${SubnetB},${Provided}
- Provided: ${SubnetC}
Export:
Name: !Sub ${AWS::StackName}:Subnets
See /examples for templates that call an API Gateway endpoint to collect AMI IDs for all regions. There is also a good amount of tests that might be helpful.
A common pattern is to process a template, validate it against the AWS validate-template API, minimize it and upload the result to S3. You can do this with a single line of code:
cfn-include example.template -t -m | aws s3 cp - s3://bucket-name/output.template
cfn-include
honors proxy settings defined in the https_proxy
environmental variable. The module will attempt to load proxy-agent
. Make sure proxy-agent
is installed since it is not a dependency for this module.
Node.js versions 8 and up are supported both on Windows and Linux.
curl https://api.netcubed.de/latest/template?[options] -XPOST -d @<path>
-
path
the contents of
path
will bePOST
ed to the web service. Seeman curl
for details.
Options:
Options are query parameters.
validate=false
do not validate template [true]
To compile the synopsis run the following command.
curl -Ssf -XPOST https://api.netcubed.de/latest/template -d '{"Fn::Include":"https://raw.githubusercontent.com/monken/cfn-include/master/examples/synopsis.json"}' > output.template