# CORS (Cross-Origin Resource Sharing)

<a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS" class="external-link" target="_blank">CORS or "Cross-Origin Resource Sharing"</a> refers to the situations when a frontend running in a browser has JavaScript code that communicates with a backend, and the backend is in a different "origin" than the frontend.

## Origin

	referrerPolicy := env.Get(EnvBrowserReferrerPolicy, kvs.GetWithDefault(browserReferrerPolicy, DefaultKVS))
	switch referrerPolicy {
	case "no-referrer", "no-referrer-when-downgrade", "origin", "origin-when-cross-origin", "same-origin", "strict-origin", "strict-origin-when-cross-origin", "unsafe-url":
		cfg.ReferrerPolicy = referrerPolicy
	default:
		return cfg, fmt.Errorf("invalid value %v for %s", referrerPolicy, browserReferrerPolicy)
	}

    headers = {
        "Origin": "https://localhost.tiangolo.com",
        "Access-Control-Request-Method": "GET",
        "Access-Control-Request-Headers": "X-Example",
    }
    response = client.options("/", headers=headers)
    assert response.status_code == 200, response.text
    assert response.text == "OK"
    assert (
        response.headers["access-control-allow-origin"]
        == "https://localhost.tiangolo.com"

    public static final String SAME_ORIGIN = "same-origin";
    public static final String ORIGIN = "origin";
    public static final String STRICT_ORIGIN = "strict-origin";
    public static final String ORIGIN_WHEN_CROSS_ORIGIN = "origin-when-cross-origin";
    public static final String STRICT_ORIGIN_WHEN_CROSS_ORIGIN = "strict-origin-when-cross-origin";
    public static final String UNSAFE_URL = "unsafe-url";
  }

    public void add(final String origin, final CorsHandler handler) {
        if (logger.isDebugEnabled()) {
            logger.debug("Loaded {}", origin);
        }
        handerMap.put(origin, handler);
    }

    public CorsHandler get(final String origin) {
        final CorsHandler handler = handerMap.get(origin);
        if (handler != null) {
            return handler;
        }

    this.supportsFastOffset = supportsFastOffset;
  }

  /**
   * Returns, conceptually, "origin + distance", or equivalently, the result of calling {@link
   * #next} on {@code origin} {@code distance} times.
   */
  C offset(C origin, long distance) {
    C current = origin;
    checkNonnegative(distance, "distance");
    for (long i = 0; i < distance; i++) {
      current = next(current);

		if !versions.Contains(gvk.KubernetesGateway.Version) {
			origin := legacykube.Origin{
				Type: gvk.CustomResourceDefinition,
				FullName: resource.FullName{
					Namespace: resource.Namespace(r.Namespace),
					Name:      resource.LocalName(r.Name),
				},
				ResourceVersion: resource.Version(r.ResourceVersion),
			}
			r := &resource.Instance{
				Origin: &origin,
			}

# CORS (Cross-Origin Resource Sharing)

<a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS" class="external-link" target="_blank">Понятие CORS или "Cross-Origin Resource Sharing"</a> относится к ситуациям, при которых запущенный в браузере фронтенд содержит JavaScript-код, который взаимодействует с бэкендом, находящимся на другом "источнике" ("origin").

## Источник

```
curl http://minio1:9001/minio/health/cluster
HTTP/1.1 503 Service Unavailable
Accept-Ranges: bytes
Content-Length: 0
Server: MinIO
Vary: Origin
X-Amz-Bucket-Region: us-east-1
X-Minio-Write-Quorum: 3
X-Amz-Request-Id: 16239D6AB80EBECF
X-Xss-Protection: 1; mode=block
Date: Tue, 21 Jul 2020 00:36:14 GMT
```

### Cluster-readable probe

  V removeSuccessor(N node);

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it
   * also becomes a successor. Associates {@code value} with the edge connecting the two nodes.
   */
  void addPredecessor(N node, V value);

  /**
   * Add {@code node} as a successor to the origin node. In the case of an undirected graph, it also