The plugin will automatically use the instance level security credentials (as of 0.17), but they can be provided explicitly using `cloud.aws.access_key` and `cloud.aws.secret_key`:
The `cloud.aws.region` can be set to a region and will automatically use the relevant settings for both `ec2` and `s3`. The available values are: `us-east` (`us-east-1`), `us-west` (`us-west-1`), `us-west-1`, `us-west-2``ap-southeast` (`ap-southeast-1`), `ap-northeast` (`ap-northeast-1`) `eu-west` (`eu-west-1`).
## EC2 Discovery
ec2 discovery allows to use the ec2 APIs to perform automatic discovery (similar to multicast in non hostile multicast environments). Here is a simple sample configuration:
The following are a list of settings (prefixed with `discovery.ec2`) that can further control the discovery:
*`groups`: Either a comma separated list or array based list of (security) groups. Only instances with the provided security groups will be used in the cluster discovery.
*`host_type`: The type of host type to use to communicate with other instances. Can be one of `private_ip`, `public_ip`, `private_dns`, `public_dns`. Defaults to `private_ip`.
*`availability_zones`: Either a comma separated list or array based list of availability zones. Only instances within the provided availability zones will be used in the cluster discovery.
The ec2 discovery can also filter machines to include in the cluster based on tags (and not just groups). The settings to use include the `discovery.ec2.tag.` prefix. For example, setting `discovery.ec2.tag.stage` to `dev` will only filter instances with a tag key set to `stage`, and a value of `dev`. Several tags set will require all of those tags to be set for the instance to be included.
One practical use for tag filtering is when an ec2 cluster contains many nodes that are not running elasticsearch. In this case (particularly with high `ping_timeout` values) there is a risk that a new node's discovery phase will end before it has found the cluster (which will result in it declaring itself master of a new cluster with the same name - highly undesirable). Tagging elasticsearch ec2 nodes and then filtering by that tag will resolve this issue.
### Automatic Node Attributes
Though not dependent on actually using `ec2` as discovery (but still requires the cloud aws plugin installed), the plugin can automatically add node attributes relating to ec2 (for example, availability zone, that can be used with the awareness allocation feature). In order to enable it, set `cloud.node.auto_attributes` to `true` in the settings.
## S3 Gateway
s3 based gateway allows to do long term reliable async persistency of the cluster state and indices directly to Amazon s3. Note, this is a shared gateway where the indices are periodically persisted to s3 while being served from the data location of each node.
The following are a list of settings (prefixed with `gateway.s3`) that can further control the s3 gateway:
*`chunk_size`: Big files are broken down into chunks (to overcome AWS 5g limit and use concurrent snapshotting). Default set to `100m`.
### concurrent_streams
The `gateway.s3.concurrent_streams` allow to throttle the number of streams (per node) opened against the shared gateway performing the snapshot operation. It defaults to `5`.
