Publish Events to NATS

MinIO AIStor supports publishing bucket notification events to a NATS service endpoint.

Prerequisites

The MinIO AIStor mc command line tool

This procedure uses the mc command line tool for certain actions. See the mc Quickstart for installation instructions.

Add a NATS endpoint to an AIStor Server

The following procedure adds a new NATS service endpoint for supporting bucket notifications in an AIStor Server.

Add the NATS endpoint to MinIO AIStor.

You can configure a new NATS service endpoint using either environment variables or by setting runtime configuration settings.
Environment Variables
MinIO AIStor supports specifying the NATS service endpoint and associated configuration settings using environment variables. The minio server process applies the specified settings on its next startup.

The minimum required variables are:
- MINIO_NOTIFY_NATS_ADDRESS
- MINIO_NOTIFY_NATS_SUBJECT
The following example code sets all environment variables related to configuring a NATS service endpoint.
```
export MINIO_NOTIFY_NATS_ENABLE_<IDENTIFIER>="on"
export MINIO_NOTIFY_NATS_ADDRESS_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_SUBJECT_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_USERNAME_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_PASSWORD_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_TOKEN_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_TLS_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_TLS_SKIP_VERIFY_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_PING_INTERVAL_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_QUEUE_DIR_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_QUEUE_LIMIT_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_CERT_AUTHORITY_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_CLIENT_CERT_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_CLIENT_KEY_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_COMMENT_<IDENTIFIER>="<string>"
export MINIO_NOTIFY_NATS_JETSTREAM_<IDENTIFIER>="<string>"
```
- Replace <IDENTIFIER> with a unique descriptive string for the NATS service endpoint. Use the same <IDENTIFIER> value for all environment variables related to the new target service endpoint. The following examples assume an identifier of primary.
  
  If the specified <IDENTIFIER> matches an existing NATS service endpoint on the AIStor Server, the new settings override any existing settings for that endpoint. Use mc admin config get notify_nats to review the currently configured NATS endpoints on the AIStor Server.
- Replace <ENDPOINT> with the hostname and port of the NATS service endpoint. For example: nats-endpoint.example.com:4222
See NATS Service for Bucket Notifications for complete documentation on each environment variable.
Configuration Settings
MinIO AIStor supports adding or updating NATS endpoints on a running minio server process using the mc admin config set command and the notify_nats configuration key. MinIO AIStor applies a new or updated configuration setting immediately, with no server restart.

The minimum required settings are:
- notify_nats address
- notify_nats subject
The following example code sets all settings related to configuring a NATS service endpoint.
```
mc admin config set ALIAS notify_nats:IDENTIFIER \
   address="HOSTNAME" \
   subject="<string>" \
   username="<string>" \
   password="<string>" \
   token="<string>" \
   nats_jetstream="<string>" \
   tls="<string>" \
   tls_skip_verify="<string>" \
   ping_interval="<string>" \
   cert_authority="<string>" \
   client_cert="<string>" \
   client_key="<string>" \
   queue_dir="<string>" \
   queue_limit="<string>" \
   comment="<string>"
```
- Replace IDENTIFIER with a unique descriptive string for the NATS service endpoint. The following examples in this procedure assume an identifier of primary.
  
  If the specified IDENTIFIER matches an existing NATS service endpoint on the AIStor Server, the new settings override any existing settings for that endpoint. Use mc admin config get notify_nats to review the currently configured NATS endpoints on the AIStor Server.
- Replace ENDPOINT with the hostname and port of the NATS service endpoint. For example: nats-endpoint.example.com:4222.
See NATS Bucket Notification Configuration Settings for complete documentation on each setting.
If you define both environment variables and configuration settings for the deployment, the settings defined by environment variables are used.
Confirm the target is registered.

MinIO AIStor applies a configuration setting change immediately.

If you configured this endpoint with environment variables, those values take precedence and mc admin config set has no effect on it. Update the environment variables on every node, then restart the deployment with the mc admin service restart command:
```
mc admin service restart ALIAS
```
Replace ALIAS with the alias of the deployment.

List the notification targets with mc event target list:
```
mc event target list ALIAS
```
The NATS target appears with an ARN similar to the following:
```
arn:minio:sqs::primary:nats
```
You must specify the ARN resource when configuring bucket notifications with the associated NATS deployment as a target.
Configure bucket notifications using the NATS endpoint as a target.

Use the mc event add command to add a new bucket notification event with the configured NATS service as a target:
```
mc event add ALIAS/BUCKET arn:minio:sqs::primary:nats \
  --event EVENTS
```
- Replace ALIAS with the alias of an AIStor Server.
- Replace BUCKET with the name of the bucket in which to configure the event.
- Replace EVENTS with a comma-separated list of events for which MinIO AIStor triggers notifications.
Use mc event ls to view all configured bucket events for a given notification target:
```
mc event ls ALIAS/BUCKET arn:minio:sqs::primary:nats
```
Validate the configured events.

Perform an action on the bucket for which you configured the new event and check the NATS service for the notification data. The action required depends on which events were specified when configuring the bucket notification.

For example, if the bucket notification configuration includes the s3:ObjectCreated:Put event, you can use the mc cp command to create a new object in the bucket and trigger a notification.
```
mc cp ~/data/new-object.txt ALIAS/BUCKET
```

Update a NATS endpoint in an AIStor Server

The following procedure updates an existing NATS service endpoint for supporting bucket notifications in an AIStor Server.

List configured NATS endpoints in the deployment.

Use the mc admin config get command to list the currently configured NATS service endpoints in the deployment:
```
mc admin config get ALIAS notify_nats
```
Replace ALIAS with the alias of the AIStor Server.

The command output resembles the following:
```
notify_nats:primary password="yoursecret" subject="" address="nats-endpoint.example.com:4222"  token="" username="yourusername" ping_interval="0" queue_limit="0" tls="off" tls_skip_verify="off" queue_dir="" streaming_enable="on" nats_jetstream="on"
notify_nats:secondary password="yoursecret" subject="" address="nats-endpoint.example.com:4222"  token="" username="yourusername" ping_interval="0" queue_limit="0" tls="off" tls_skip_verify="off" queue_dir="" streaming_enable="on" nats_jetstream="on"
```
- notify_nats is the top-level configuration key for an NATS Notification Settings.
- address specifies the NATS service endpoint for the given notify_nats key.
- The notify_nats:<IDENTIFIER> suffix describes the unique identifier for that NATS service endpoint.
Note the identifier for the NATS service endpoint you want to update for the next step.

Update the NATS endpoint.

Use the mc admin config set command to set the new configuration for the NATS service endpoint:

mc admin config set ALIAS notify_nats:IDENTIFIER \
   address="HOSTNAME" \
   subject="<string>" \
   username="<string>" \
   password="<string>" \
   token="<string>" \
   tls="<string>" \
   tls_skip_verify="<string>" \
   ping_interval="<string>" \
   nats_jetstream="<string>" \
   cert_authority="<string>" \
   client_cert="<string>" \
   client_key="<string>" \
   queue_dir="<string>" \
   queue_limit="<string>" \
   comment="<string>"

The notify_nats address and notify_nats subject configuration settings are the minimum required for a NATS service endpoint.
All other configuration settings are optional.

See NATS Notification Settings for a complete list of NATS configuration settings.

Confirm the target is registered.

MinIO AIStor applies a configuration setting change immediately.

If you configured this endpoint with environment variables, those values take precedence and mc admin config set has no effect on it. Update the environment variables on every node, then restart the deployment with the mc admin service restart command:
```
mc admin service restart ALIAS
```
Replace ALIAS with the alias of the deployment.

List the notification targets with mc event target list:
```
mc event target list ALIAS
```
The NATS target appears with an ARN similar to the following:
```
arn:minio:sqs::primary:nats
```
Validate the changes.

Perform an action on a bucket which has an event configuration using the updated NATS service endpoint and check the NATS service for the notification data. The action required depends on which events were specified when configuring the bucket notification.

For example, if the bucket notification configuration includes the s3:ObjectCreated:Put event, you can use the mc cp command to create a new object in the bucket and trigger a notification.
```
mc cp ~/data/new-object.txt ALIAS/BUCKET
```