Cosmetic fixes to repository-s3

Relates AWS SDK v2 uprgade, this commit just pulls out some bits that
can go in first.

Author: DaveCTurner

modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3ClientSettings.java

@@ -121,28 +121,28 @@ final class S3ClientSettings {
     static final Setting.AffixSetting<TimeValue> READ_TIMEOUT_SETTING = Setting.affixKeySetting(
         PREFIX,
         "read_timeout",
-        key -> Setting.timeSetting(key, TimeValue.timeValueMillis(ClientConfiguration.DEFAULT_SOCKET_TIMEOUT), Property.NodeScope)
+        key -> Setting.timeSetting(key, Defaults.READ_TIMEOUT, Property.NodeScope)
     );
 
     /** The maximum number of concurrent connections to use. */
     static final Setting.AffixSetting<Integer> MAX_CONNECTIONS_SETTING = Setting.affixKeySetting(
         PREFIX,
         "max_connections",
-        key -> Setting.intSetting(key, ClientConfiguration.DEFAULT_MAX_CONNECTIONS, 1, Property.NodeScope)
+        key -> Setting.intSetting(key, Defaults.MAX_CONNECTIONS, 1, Property.NodeScope)
     );
 
     /** The number of retries to use when an s3 request fails. */
     static final Setting.AffixSetting<Integer> MAX_RETRIES_SETTING = Setting.affixKeySetting(
         PREFIX,
         "max_retries",
-        key -> Setting.intSetting(key, ClientConfiguration.DEFAULT_RETRY_POLICY.getMaxErrorRetry(), 0, Property.NodeScope)
+        key -> Setting.intSetting(key, Defaults.RETRY_COUNT, 0, Property.NodeScope)
     );
 
     /** Whether retries should be throttled (ie use backoff). */
     static final Setting.AffixSetting<Boolean> USE_THROTTLE_RETRIES_SETTING = Setting.affixKeySetting(
         PREFIX,
         "use_throttle_retries",
-        key -> Setting.boolSetting(key, ClientConfiguration.DEFAULT_THROTTLE_RETRIES, Property.NodeScope)
+        key -> Setting.boolSetting(key, Defaults.THROTTLE_RETRIES, Property.NodeScope)
     );
 
     /** Whether the s3 client should use path style access. */
@@ -335,7 +335,7 @@ S3ClientSettings refine(Settings repositorySettings) {
 
     /**
      * Load all client settings from the given settings.
-     *
+     * <p>
      * Note this will always at least return a client named "default".
      */
     static Map<String, S3ClientSettings> load(Settings settings) {
@@ -501,4 +501,11 @@ private static <T> T getRepoSettingOrDefault(Setting.AffixSetting<T> setting, Se
         }
         return defaultValue;
     }
+
+    static final class Defaults {
+        static final TimeValue READ_TIMEOUT = TimeValue.timeValueMillis(ClientConfiguration.DEFAULT_SOCKET_TIMEOUT);
+        static final int MAX_CONNECTIONS = ClientConfiguration.DEFAULT_MAX_CONNECTIONS;
+        static final int RETRY_COUNT = ClientConfiguration.DEFAULT_RETRY_POLICY.getMaxErrorRetry();
+        static final boolean THROTTLE_RETRIES = ClientConfiguration.DEFAULT_THROTTLE_RETRIES;
+    }
 }

modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3Service.java

@@ -115,8 +115,8 @@ class S3Service implements Closeable {
 
     /**
      * Refreshes the settings for the AmazonS3 clients and clears the cache of
-     * existing clients. New clients will be build using these new settings. Old
-     * clients are usable until released. On release they will be destroyed instead
+     * existing clients. New clients will be built using these new settings. Old
+     * clients are usable until released. On release, they will be destroyed instead
      * of being returned to the cache.
      */
     public synchronized void refreshAndClearCache(Map<String, S3ClientSettings> clientsSettings) {
@@ -126,7 +126,7 @@ public synchronized void refreshAndClearCache(Map<String, S3ClientSettings> clie
         this.staticClientSettings = Maps.ofEntries(clientsSettings.entrySet());
         derivedClientSettings = emptyMap();
         assert this.staticClientSettings.containsKey("default") : "always at least have 'default'";
-        // clients are built lazily by {@link client}
+        /* clients are built lazily by {@link #client} */
     }
 
     /**
@@ -341,7 +341,8 @@ public void refresh() {
      * <ul>
      * <li>Reads the location of the web identity token not from AWS_WEB_IDENTITY_TOKEN_FILE, but from a symlink
      * in the plugin directory, so we don't need to create a hardcoded read file permission for the plugin.</li>
-     * <li>Supports customization of the STS endpoint via a system property, so we can test it against a test fixture.</li>
+     * <li>Supports customization of the STS (Security Token Service) endpoint via a system property, so we can
+     * test it against a test fixture.</li>
      * <li>Supports gracefully shutting down the provider and the STS client.</li>
      * </ul>
      */
@@ -384,7 +385,7 @@ static class CustomWebIdentityTokenCredentialsProvider implements AWSCredentials
             if (roleArn == null) {
                 LOGGER.warn(
                     "Unable to use a web identity token for authentication. The AWS_WEB_IDENTITY_TOKEN_FILE environment "
-                        + "variable is set, but either AWS_ROLE_ARN is missing"
+                        + "variable is set, but AWS_ROLE_ARN is missing"
                 );
                 return;
             }