Streamline S3 Repository- and Client-Settings (#37393)

* Make repository settings override static settings
* Cache clients according to settings
   * Introduce custom implementations for the AWS credentials here to be able to use them as part of a hash key

Author: original-brownbear

docs/plugins/repository-s3.asciidoc

@@ -221,6 +221,32 @@ The following settings are supported:
     currently supported by the plugin. For more information about the
     different classes, see http://docs.aws.amazon.com/AmazonS3/latest/dev/storage-class-intro.html[AWS Storage Classes Guide]
 
+NOTE: The option of defining client settings in the repository settings as documented below is considered deprecated:
+
+In addition to the above settings, you may also specify all non-secure client settings in the repository settings.
+In this case, the client settings found in the repository settings will be merged with those of the named client used by the repository.
+Conflicts between client and repository settings are resolved by the repository settings taking precedence over client settings.
+
+For example:
+
+[source,js]
+----
+PUT _snapshot/my_s3_repository
+{
+  "type": "s3",
+  "settings": {
+    "client": "my_client_name",
+    "bucket": "my_bucket_name",
+    "endpoint": "my.s3.endpoint"
+  }
+}
+----
+// CONSOLE
+// TEST[skip:we don't have s3 set up while testing this]
+
+This sets up a repository that uses all client settings from the client `my_client_named` except for the `endpoint` that is overridden
+to `my.s3.endpoint` by the repository settings.
+
 [[repository-s3-permissions]]
 ===== Recommended S3 Permissions
 

plugins/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BasicCredentials.java

@@ -0,0 +1,62 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.repositories.s3;
+
+import com.amazonaws.auth.AWSCredentials;
+
+import java.util.Objects;
+
+class S3BasicCredentials implements AWSCredentials {
+
+    private final String accessKey;
+
+    private final String secretKey;
+
+    S3BasicCredentials(String accessKey, String secretKey) {
+        this.accessKey = accessKey;
+        this.secretKey = secretKey;
+    }
+
+    @Override
+    public final String getAWSAccessKeyId() {
+        return accessKey;
+    }
+
+    @Override
+    public final String getAWSSecretKey() {
+        return secretKey;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        final S3BasicCredentials that = (S3BasicCredentials) o;
+        return accessKey.equals(that.accessKey) && secretKey.equals(that.secretKey);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(accessKey, secretKey);
+    }
+}

plugins/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BasicSessionCredentials.java

@@ -0,0 +1,57 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.repositories.s3;
+
+import com.amazonaws.auth.AWSSessionCredentials;
+
+import java.util.Objects;
+
+final class S3BasicSessionCredentials extends S3BasicCredentials implements AWSSessionCredentials {
+
+    private final String sessionToken;
+
+    S3BasicSessionCredentials(String accessKey, String secretKey, String sessionToken) {
+        super(accessKey, secretKey);
+        this.sessionToken = sessionToken;
+    }
+
+    @Override
+    public String getSessionToken() {
+        return sessionToken;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        final S3BasicSessionCredentials that = (S3BasicSessionCredentials) o;
+        return sessionToken.equals(that.sessionToken) &&
+            getAWSAccessKeyId().equals(that.getAWSAccessKeyId()) &&
+            getAWSSecretKey().equals(that.getAWSSecretKey());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(sessionToken, getAWSAccessKeyId(), getAWSSecretKey());
+    }
+}

plugins/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobStore.java

@@ -25,6 +25,7 @@
 import com.amazonaws.services.s3.model.ObjectListing;
 import com.amazonaws.services.s3.model.S3ObjectSummary;
 import com.amazonaws.services.s3.model.StorageClass;
+import org.elasticsearch.cluster.metadata.RepositoryMetaData;
 import org.elasticsearch.common.blobstore.BlobContainer;
 import org.elasticsearch.common.blobstore.BlobPath;
 import org.elasticsearch.common.blobstore.BlobStore;
@@ -39,8 +40,6 @@ class S3BlobStore implements BlobStore {
 
     private final S3Service service;
 
-    private final String clientName;
-
     private final String bucket;
 
     private final ByteSizeValue bufferSize;
@@ -51,15 +50,18 @@ class S3BlobStore implements BlobStore {
 
     private final StorageClass storageClass;
 
-    S3BlobStore(S3Service service, String clientName, String bucket, boolean serverSideEncryption,
-                ByteSizeValue bufferSize, String cannedACL, String storageClass) {
+    private final RepositoryMetaData repositoryMetaData;
+
+    S3BlobStore(S3Service service, String bucket, boolean serverSideEncryption,
+                ByteSizeValue bufferSize, String cannedACL, String storageClass,
+                RepositoryMetaData repositoryMetaData) {
         this.service = service;
-        this.clientName = clientName;
         this.bucket = bucket;
         this.serverSideEncryption = serverSideEncryption;
         this.bufferSize = bufferSize;
         this.cannedACL = initCannedACL(cannedACL);
         this.storageClass = initStorageClass(storageClass);
+        this.repositoryMetaData = repositoryMetaData;
     }
 
     @Override
@@ -68,7 +70,7 @@ public String toString() {
     }
 
     public AmazonS3Reference clientReference() {
-        return service.client(clientName);
+        return service.client(repositoryMetaData);
     }
 
     public String bucket() {