https://github.com/paybyphone/asg53
AWS Lambda function for making Route 53 changes via ASG lifecycle hooks
https://github.com/paybyphone/asg53
aws-autoscaling aws-lambda go route53
Last synced: 6 months ago
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AWS Lambda function for making Route 53 changes via ASG lifecycle hooks
- Host: GitHub
- URL: https://github.com/paybyphone/asg53
- Owner: paybyphone
- License: other
- Created: 2016-11-13T03:27:47.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2016-11-18T01:07:46.000Z (over 9 years ago)
- Last Synced: 2024-06-20T17:35:22.213Z (about 2 years ago)
- Topics: aws-autoscaling, aws-lambda, go, route53
- Language: Go
- Size: 474 KB
- Stars: 15
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# asg53
`asg53` is a tool for [AWS Lambda][1] that allows one to process
[EC2 Auto-Scaling][2] events and make modifications in [Route 53][3]. It is
intended for use with SNS, and uses data-driven JSON representations of Route 53
change batches that can be customized with [Go templates][4], supplied as
notification metadata.
## Building
This is a Go-based Lambda function, and hence needs to be wrapped with a shim.
We use [aws-lambda-go][5], which also provides a Docker container with access
to the toolchain.
Follow the directions below to build:
```
go get github.com/paybyphone/asg53
cd $GOPATH/src/github.com/paybyphone/asg53
docker run --rm -v $GOPATH:$GOPATH -e GOPATH=$GOPATH -w `pwd` eawsy/aws-lambda-go
```
After the build is complete, upload the `handler.zip` file to Lambda.
## Usage
First you will want to read up on how to configure [Lifecycle Hooks][6] for Auto
Scaling. This is a moderately complex process that may be documented here later.
The Lambda function's role needs the following policy attached to it:
```
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "",
"Effect": "Allow",
"Action": [
"route53:ListResourceRecordSets",
"route53:ChangeResourceRecordSets"
],
"Resource": "arn:aws:route53:::hostedzone/HOSTEDZONEID"
},
{
"Sid": "",
"Effect": "Allow",
"Action": "route53:GetChange",
"Resource": "arn:aws:route53:::change/*"
},
{
"Sid": "",
"Effect": "Allow",
"Action": "ec2:DescribeInstances",
"Resource": "*"
},
{
"Sid": "",
"Effect": "Allow",
"Action": "autoscaling:CompleteLifecycleAction",
"Resource": "*"
},
{
"Sid": "",
"Effect": "Allow",
"Action": [
"logs:PutLogEvents",
"logs:DescribeLogStreams",
"logs:CreateLogStream",
"logs:CreateLogGroup"
],
"Resource": "arn:aws:logs:*:*:*"
}
]
}
```
Next, when creating your lifecycle hooks, you will want to structure your
notification metadata in the JSON format below. For example, this metadata set
could create a route 53 resource record for an instance while it's being
launched:
```
{
"HostedZoneID": "HOSTEDZONEID",
"Changes": [
{
"Action": "UPSERT",
"ResourceRecordSet": {
"Name": "{{.InstanceID}}.example.com.",
"TTL": 3600,
"Type": "A",
"ResourceRecords": [
{
"Value": "{{.InstancePublicIPAddress}}"
}
]
}
}
]
}
```
And this can be added to a termination event to delete the record.
```
{
"HostedZoneID": "HOSTEDZONEID",
"Changes": [
{
"Action": "DELETE",
"ResourceRecordSet": {
"Name": "{{.InstanceID}}.example.com.",
"TTL": 3600,
"Type": "A",
"ResourceRecords": [
{
"Value": "{{.ExistingRDataValue 0 0}}"
}
]
}
}
]
}
```
## How it Works
In the metadata you are supplying the hosted zone ID to act on, in addition to a
Route 53 change batch. The same rules apply to the latter as they would when
using the CLI, so see [there][6] for more details.
The function can operate on both `autoscaling:EC2_INSTANCE_LAUNCHING` or
`autoscaling:EC2_INSTANCE_TERMINATING` - the function does not handle one or
the other in any special way. The only caveat is that you need to be cognizant
of when you are processing termination events, as certain template fields won't
be available (see below).
## Template Reference
The data is driven by Go tempalte values (using a double-curly bracer closure -
`{{}}`) that allows you to access specific fields related to the instance.
Note that fields are interpolated on `Name` and `Value` fields only (the latter
in the `ResourceRecords` list).
Current fields are:
* `{{.InstanceID}}`, for the instance ID
* `{{.InstancePrivateIPAddress}}`, for the instance's private IP address
* `{{.InstancePublicIPAddress}}`, for the instance's public IP address
* `{{.ExistingRDataValue [set] [record]}}`, to get the existing RDATA
on a resource record set. This function operates on the existing
change set, performing a Route 53 `ListResourceRecordSets` request
looking for the record specified in the `Name` field of the change
specified by `set`, returning the `ResourceRecord` `Value` at the
index specified by `record`. It should be noted that the function is called
on the change set as it currently exists. This means that whether or not a
properly rendered `Name` field exists depends on where this function is
called - if called too early on a field that has not yet been iterated on,
the templated data will be incomplete. Lookups that result in no data
returned, an out of range value index, or a Route 53 API error will cause
an error.
### Note on terminating instances
Note that on termination events, IP address values will be rendered as
empty strings, so take care when using DELETE events that you don't
attempt to delete a non-existent, or even worse, an incorrect, record.
Use `ExistingRDataValue` to locate the existing resource record for the
value instead (as explained in the main example).
## License
```
Copyright 2016 PayByPhone Technologies, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
```
[1]: https://aws.amazon.com/lambda/
[2]: https://aws.amazon.com/autoscaling/
[3]: https://aws.amazon.com/route53/
[4]: https://golang.org/pkg/text/template/
[5]: https://github.com/eawsy/aws-lambda-go
[6]: http://docs.aws.amazon.com/autoscaling/latest/userguide/lifecycle-hooks.html
[7]: http://docs.aws.amazon.com/cli/latest/reference/route53/change-resource-record-sets.html