# OPA Quickstart Guide [![Slack](https://slack.minio.io/slack?type=svg)](https://slack.minio.io)

OPA is a lightweight general-purpose policy engine that can be co-located with MinIO server, in this document we talk about how to use OPA HTTP API to authorize requests. It can be used with any type of credentials (STS based like OpenID or LDAP, regular IAM users or service accounts).

OPA is enabled through MinIO's Access Management Plugin feature.

## Get started

## Context

In Gradle we often need to serialize in-memory objects for caching, or to transmit them across process barriers, etc.
Java serialization is one way to implement this, however, despite its simplicity of implementation, it has several drawbacks:

- **Performance:**
Java's built-in serialization mechanism is often slower compared to other serialization solutions.
This is due to Java's use of reflection and the need to maintain a lot of metadata.

        DocumentBuilderFactory.newInstance().apply {
            setFeature("http://apache.org/xml/features/disallow-doctype-decl", true)
            setFeature("http://xml.org/sax/features/external-general-entities", false)
            setFeature("http://xml.org/sax/features/external-parameter-entities", false)
            setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false)

      "name": "type:critical",
      "colour": "#E84137",
      "description": "critical questions"
    },
    "question": {
      "name": "type:question",
      "colour": "#EDEDED",
      "description": "general questions"
    },
    "feature": {
      "name": "type:feature_request",
      "colour": "#43952A",
      "description": "feature request"
    },
    "invalid_question": {
      "name": "type:invalid question",

about: "Report a confirmed bug. For unconfirmed bugs please
 visit https://discuss.elastic.co/c/elasticsearch"
labels: ">bug,needs:triage"

---
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GitHub is reserved for bug reports and feature requests; it is not the place
for general questions. If you have a question or an unconfirmed bug , please
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{* ../../docs_src/websockets_/tutorial003_py310.py hl[79:81] *}

To try it out:

* Open the app with several browser tabs.
* Write messages from them.
* Then close one of the tabs.

That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:

```

 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *

 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//