Allow to set Elasticsearch number of shards and replicas

In the current latest version of Elasticsearch, the number of shards
and replicas are set to 5 and 1 respectively if not explicitly set.

From version 7, the default number of shards will be changed to 1, and
to continue using 5 it must be explicitly set when creating the index.

Explicitly set the values when creating the index, but allow them to be
changed in the gerrit.config. Default the new configurations to 5 and 1
to be consistent with the current defaults.

Bug: Issue 9768
Change-Id: Ia6bc925757f7bf4450d4c8feb21cf838671344f8

4 files changed, 38 insertions, 6 deletions

diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 549401442c..32b1954b18 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2932,6 +2932,22 @@ The value is in the usual time-unit format like `1 m`, `5 m`.
 +
 Defaults to `30000 ms`.
 
+[[elasticsearch.numberOfShards]]elasticsearch.numberOfShards::
++
+Sets the number of shards to use per index. Refer to the
+link:https://www.elastic.co/guide/en/elasticsearch/reference/current/_basic_concepts.html#getting-started-shards-and-replicas[
+Elasticsearch documentation] for details.
++
+Defaults to 5.
+
+[[elasticsearch.numberOfReplicas]]elasticsearch.numberOfReplicas::
++
+Sets the number of replicas to use per index. Refer to the
+link:https://www.elastic.co/guide/en/elasticsearch/reference/current/_basic_concepts.html#getting-started-shards-and-replicas[
+Elasticsearch documentation] for details.
++
+Defaults to 1.
+
 ==== Elasticsearch Security
 
 When security is enabled in Elasticsearch, the username and password must be provided.
diff --git a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java
index dc8d18752d..06a30b5b60 100644
--- a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java
+++ b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java
@@ -82,6 +82,7 @@ abstract class AbstractElasticIndex<K, V> implements Index<K, V> {
     return content;
   }
 
+  private final ElasticConfiguration config;
   private final Schema<V> schema;
   private final SitePaths sitePaths;
   private final String indexNameRaw;
@@ -93,17 +94,18 @@ abstract class AbstractElasticIndex<K, V> implements Index<K, V> {
   protected final ElasticQueryBuilder queryBuilder;
 
   AbstractElasticIndex(
-      ElasticConfiguration cfg,
+      ElasticConfiguration config,
       SitePaths sitePaths,
       Schema<V> schema,
       ElasticRestClientProvider client,
       String indexName,
       String indexType) {
+    this.config = config;
     this.sitePaths = sitePaths;
     this.schema = schema;
     this.gson = new GsonBuilder().setFieldNamingPolicy(LOWER_CASE_WITH_UNDERSCORES).create();
     this.queryBuilder = new ElasticQueryBuilder();
-    this.indexName = cfg.getIndexName(indexName, schema.getVersion());
+    this.indexName = config.getIndexName(indexName, schema.getVersion());
     this.indexNameRaw = indexName;
     this.client = client;
     this.type = client.adapter().getType(indexType);
@@ -174,7 +176,7 @@ abstract class AbstractElasticIndex<K, V> implements Index<K, V> {
   protected abstract String getMappings();
 
   private String getSettings() {
-    return gson.toJson(ImmutableMap.of(SETTINGS, ElasticSetting.createSetting()));
+    return gson.toJson(ImmutableMap.of(SETTINGS, ElasticSetting.createSetting(config)));
   }
 
   protected abstract String getId(V v);
diff --git a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticConfiguration.java b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticConfiguration.java
index dce28019f7..cd7456713c 100644
--- a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticConfiguration.java
+++ b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticConfiguration.java
@@ -41,9 +41,13 @@ class ElasticConfiguration {
   static final String KEY_MAX_RETRY_TIMEOUT = "maxRetryTimeout";
   static final String KEY_PREFIX = "prefix";
   static final String KEY_SERVER = "server";
+  static final String KEY_NUMBER_OF_SHARDS = "numberOfShards";
+  static final String KEY_NUMBER_OF_REPLICAS = "numberOfReplicas";
   static final String DEFAULT_PORT = "9200";
   static final String DEFAULT_USERNAME = "elastic";
   static final int DEFAULT_MAX_RETRY_TIMEOUT_MS = 30000;
+  static final int DEFAULT_NUMBER_OF_SHARDS = 5;
+  static final int DEFAULT_NUMBER_OF_REPLICAS = 1;
   static final TimeUnit MAX_RETRY_TIMEOUT_UNIT = TimeUnit.MILLISECONDS;
 
   private final Config cfg;
@@ -52,6 +56,8 @@ class ElasticConfiguration {
   final String username;
   final String password;
   final int maxRetryTimeout;
+  final int numberOfShards;
+  final int numberOfReplicas;
   final String prefix;
 
   @Inject
@@ -72,6 +78,10 @@ class ElasticConfiguration {
                 DEFAULT_MAX_RETRY_TIMEOUT_MS,
                 MAX_RETRY_TIMEOUT_UNIT);
     this.prefix = Strings.nullToEmpty(cfg.getString(SECTION_ELASTICSEARCH, null, KEY_PREFIX));
+    this.numberOfShards =
+        cfg.getInt(SECTION_ELASTICSEARCH, null, KEY_NUMBER_OF_SHARDS, DEFAULT_NUMBER_OF_SHARDS);
+    this.numberOfReplicas =
+        cfg.getInt(SECTION_ELASTICSEARCH, null, KEY_NUMBER_OF_REPLICAS, DEFAULT_NUMBER_OF_REPLICAS);
     this.hosts = new ArrayList<>();
     for (String server : cfg.getStringList(SECTION_ELASTICSEARCH, null, KEY_SERVER)) {
       try {
diff --git a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticSetting.java b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticSetting.java
index 8dc8e8e893..98c313c78a 100644
--- a/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticSetting.java
+++ b/gerrit-elasticsearch/src/main/java/com/google/gerrit/elasticsearch/ElasticSetting.java
@@ -22,17 +22,19 @@ class ElasticSetting {
   private static final ImmutableMap<String, String> CUSTOM_CHAR_MAPPING =
       ImmutableMap.of("\\u002E", "\\u0020", "\\u005F", "\\u0020");
 
-  static SettingProperties createSetting() {
-    return new ElasticSetting.Builder().addCharFilter().addAnalyzer().build();
+  static SettingProperties createSetting(ElasticConfiguration config) {
+    return new ElasticSetting.Builder().addCharFilter().addAnalyzer().build(config);
   }
 
   static class Builder {
     private final ImmutableMap.Builder<String, FieldProperties> fields =
         new ImmutableMap.Builder<>();
 
-    SettingProperties build() {
+    SettingProperties build(ElasticConfiguration config) {
       SettingProperties properties = new SettingProperties();
       properties.analysis = fields.build();
+      properties.numberOfShards = config.numberOfShards;
+      properties.numberOfReplicas = config.numberOfReplicas;
       return properties;
     }
 
@@ -71,6 +73,8 @@ class ElasticSetting {
 
   static class SettingProperties {
     Map<String, FieldProperties> analysis;
+    Integer numberOfShards;
+    Integer numberOfReplicas;
   }
 
   static class FieldProperties {