Configure authentication credentials

When sending data to a secured cluster through the elasticsearch output, APM Server must either provide basic authentication credentials or present a client certificate.

To configure authentication credentials for APM Server:

Create a writer role that has the following privileges:
- Cluster: manage_index_templates and monitor
- Index: write and create_index on the APM Server indices
You can create roles from the Management / Roles UI in Kibana or through the role API. For example, the following request creates a role named apm_writer:
```
POST _security/role/apm_writer
{
  "cluster": ["manage_index_templates","monitor"],
  "indices": [
    {
      "names": [ "apm-*" ], 
      "privileges": ["write","create_index"]
    }
  ]
}
```
If you use a custom APM Server index pattern, specify that pattern instead of the default apm-* pattern.

Assign the writer role to the user that APM Server will use to connect to Elasticsearch. Make sure you also assign any roles that are required for specific features. For the list of features and required roles, see APM Server features that require authorization.
1. To authenticate as a native user, create a user for APM Server to use internally and assign it the writer role, plus any other roles that are needed.
  
  You can create users from the Management / Users UI in Kibana or through the user API. For example, following request creates a user named apm_internal that has the apm_writer and kibana_user roles:
```
POST /_security/user/apm_internal
{
  "password" : "YOUR_PASSWORD",
  "roles" : [ "apm_writer","kibana_user"],
  "full_name" : "Internal APM Server User"
}
```
2. To use PKI authentication, assign the writer role, plus any other roles that are needed, in the role_mapping.yml configuration file. Specify the user by the distinguished name that appears in its certificate:
```
apm_writer:
  - "cn=Internal APM Server User,ou=example,o=com"
kibana_user:
  - "cn=Internal APM Server User,ou=example,o=com"
```
  For more information, see Using Role Mapping Files.
In the APM Server configuration file, specify authentication credentials for the elasticsearch output:
1. To use basic authentication, configure the username and password settings. For example, the following APM Server output configuration uses the native apm_internal user to connect to Elasticsearch:
```
output.elasticsearch:
  hosts: ["localhost:9200"]
  username: "apm_internal" 
  password: "YOUR_PASSWORD" 
```
  You created this user earlier.
  
  The example shows a hard-coded password, but you should store sensitive values in the secrets keystore.
2. To use PKI authentication, configure the certificate and key settings:
```
output.elasticsearch:
  hosts: ["localhost:9200"]
  ssl.certificate: "/etc/pki/client/cert.pem" 
  ssl.key: "/etc/pki/client/cert.key"
```
  The distinguished name (DN) in the certificate must be mapped to the apm_writer and kibana_user roles in the role_mapping.yml configuration file on each node in the Elasticsearch cluster.

« APM Server features that require authorization Grant users access to APM Server indices »

	You created this user earlier.
	The example shows a hard-coded password, but you should store sensitive values in the secrets keystore.