# Elasticsearch integration **(STARTER ONLY)**

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/109 "Elasticsearch Merge Request") in GitLab [Starter](https://about.gitlab.com/pricing/) 8.4.
> - Support for [Amazon Elasticsearch](https://docs.aws.amazon.com/elasticsearch-service/latest/developerguide/es-gsg.html) was [introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/1305) in GitLab [Starter](https://about.gitlab.com/pricing/) 9.0.

This document describes how to set up Elasticsearch with GitLab. Once enabled,
you'll have the benefit of fast search response times and the advantage of two
special searches:

- [Advanced Global Search](../user/search/advanced_global_search.md)
- [Advanced Syntax Search](../user/search/advanced_search_syntax.md)

## Version Requirements

<!-- Please remember to update ee/lib/system_check/app/elasticsearch_check.rb if this changes -->

| GitLab version | Elasticsearch version |
| -------------- | --------------------- |

| GitLab Enterprise Edition 8.4 - 8.17   | Elasticsearch 2.4 with [Delete By Query Plugin](https://www.elastic.co/guide/en/elasticsearch/plugins/2.4/plugins-delete-by-query.html) installed |

| GitLab Enterprise Edition 9.0 - 11.4   | Elasticsearch 5.1 - 5.5 |

| GitLab Enterprise Edition 11.5 - 12.6  | Elasticsearch 5.6 - 6.x |
| GitLab Enterprise Edition 12.7+        | Elasticsearch 6.x - 7.x |

## Installing Elasticsearch

Elasticsearch is _not_ included in the Omnibus packages or when you install from source. You must
[install it separately](https://www.elastic.co/guide/en/elasticsearch/reference/7.x/install-elasticsearch.html "Elasticsearch 7.x installation documentation"). Be sure to select your version.

Providing detailed information on installing Elasticsearch is out of the scope
of this document.

NOTE: **Note:**
Elasticsearch should be installed on a separate server, whether you install

it yourself or use a cloud hosted offering like Elastic's [Elasticsearch Service](https://www.elastic.co/elasticsearch/service) (available on AWS, GCP, or Azure) or the
[Amazon Elasticsearch](https://docs.aws.amazon.com/elasticsearch-service/latest/developerguide/es-gsg.html) service. Running Elasticsearch on the same server as GitLab is not recommended

and will likely cause a degradation in GitLab instance performance.

NOTE: **Note:**
**For a single node Elasticsearch cluster the functional cluster health status will be yellow** (will never be green) because the primary shard is allocated but replicas can not be as there is no other node to which Elasticsearch can assign a replica.

Once the data is added to the database or repository and [Elasticsearch is

enabled in the Admin Area](#enabling-elasticsearch) the search index will be

updated automatically.

## Elasticsearch repository indexer

For indexing Git repository data, GitLab uses an [indexer written in Go](https://gitlab.com/gitlab-org/gitlab-elasticsearch-indexer).

The way you install the Go indexer depends on your version of GitLab:

- For Omnibus GitLab 11.8 and above, see [Omnibus GitLab](#omnibus-gitlab).
- For installations from source or older versions of Omnibus GitLab, install the indexer [From Source](#from-source).

### Omnibus GitLab

Since GitLab 11.8 the Go indexer is included in Omnibus GitLab.

The former Ruby-based indexer was removed in [GitLab 12.3](https://gitlab.com/gitlab-org/gitlab/-/issues/6481).

### From source

First, we need to install some dependencies, then we'll build and install
the indexer itself.

This project relies on [ICU](http://site.icu-project.org/) for text encoding,
therefore we need to ensure the development packages for your platform are
installed before running `make`.

#### Debian / Ubuntu

To install on Debian or Ubuntu, run:

```shell

sudo apt install libicu-dev
```

#### CentOS / RHEL

To install on CentOS or RHEL, run:

```shell

sudo yum install libicu-devel
```

##### Mac OSX

To install on macOS, run:

```shell

brew install icu4c
export PKG_CONFIG_PATH="/usr/local/opt/icu4c/lib/pkgconfig:$PKG_CONFIG_PATH"
```

### Building and installing

To build and install the indexer, run:

```shell

indexer_path=/home/git/gitlab-elasticsearch-indexer

# Run the installation task for gitlab-elasticsearch-indexer:
sudo -u git -H bundle exec rake gitlab:indexer:install[$indexer_path] RAILS_ENV=production
cd $indexer_path && sudo make install

```

The `gitlab-elasticsearch-indexer` will be installed to `/usr/local/bin`.

You can change the installation path with the `PREFIX` env variable.
Please remember to pass the `-E` flag to `sudo` if you do so.

Example:

```shell

PREFIX=/usr sudo -E make install
```

Once installed, enable it under your instance's Elasticsearch settings explained [below](#enabling-elasticsearch).

## System Requirements

Elasticsearch requires additional resources in excess of those documented in the

[GitLab system requirements](../install/requirements.md).

The amount of resources (memory, CPU, storage) will vary greatly, based on the amount of data being indexed into the Elasticsearch cluster. According to [Elasticsearch official guidelines](https://www.elastic.co/guide/en/elasticsearch/guide/current/hardware.html#_memory), each node should have:

- [RAM](https://www.elastic.co/guide/en/elasticsearch/guide/current/hardware.html#_disks): **8 GiB as the bare minimum**
- [CPU](https://www.elastic.co/guide/en/elasticsearch/guide/current/hardware.html#_cpus): Modern processor with multiple cores
- [Storage](https://www.elastic.co/guide/en/elasticsearch/guide/current/hardware.html#_disks): Use SSD storage. As a guide you will need enough storage for 50% of the total size of your Git repositories.

A few notes on CPU and storage:

- CPU requirements for Elasticsearch tend to be light. There are specific scenarios where this isn't true, but GitLab.com isn't using Elasticsearch in an exceptionally CPU-heavy way. More cores will be more performant than faster CPUs. Extra concurrency from multiple cores will far outweigh a slightly faster clock speed in Elasticsearch.

- Storage requirements for Elasticsearch are important, especially for indexing-heavy clusters. When possible, use SSDs, Their speed is far superior to any spinning media for Elasticsearch. In testing, nodes that use SSD storage see boosts in both query and indexing performance.

Keep in mind, these are **minimum requirements** for Elasticsearch. Heavily-utilized Elasticsearch clusters will likely require considerably more resources.

## Enabling Elasticsearch

In order to enable Elasticsearch, you need to have admin access. Navigate to
**Admin Area** (wrench icon), then **Settings > Integrations** and expand the **Elasticsearch** section.

Click **Save changes** for the changes to take effect.

The following Elasticsearch settings are available:

| Parameter                                             | Description |
| ----------------------------------------------------- | ----------- |

| `Elasticsearch indexing`                              | Enables/disables Elasticsearch indexing. You may want to enable indexing but disable search in order to give the index time to be fully completed, for example. Also, keep in mind that this option doesn't have any impact on existing data, this only enables/disables background indexer which tracks data changes. So by enabling this you will not get your existing data indexed, use special Rake task for that as explained in [Adding GitLab's data to the Elasticsearch index](#adding-gitlabs-data-to-the-elasticsearch-index). |

| `Elasticsearch pause indexing`                        | Enables/disables temporary indexing pause. This is useful for cluster migration/reindexing. All changes are still tracked, but they are not committed to the Elasticsearch index until unpaused. |

| `Search with Elasticsearch enabled`                   | Enables/disables using Elasticsearch in search. |
| `URL`                                                 | The URL to use for connecting to Elasticsearch. Use a comma-separated list to support clustering (e.g., `http://host1, https://host2:9200`). If your Elasticsearch instance is password protected, pass the `username:password` in the URL (e.g., `http://<username>:<password>@<elastic_host>:9200/`). |

| `Number of Elasticsearch shards`                      | Elasticsearch indexes are split into multiple shards for performance reasons. In general, larger indexes need to have more shards. Changes to this value do not take effect until the index is recreated. You can read more about tradeoffs in the [Elasticsearch documentation](https://www.elastic.co/guide/en/elasticsearch/reference/current/scalability.html). |

| `Number of Elasticsearch replicas`                    | Each Elasticsearch shard can have a number of replicas. These are a complete copy of the shard, and can provide increased query performance or resilience against hardware failure. Increasing this value will greatly increase total disk space required by the index. |
| `Limit namespaces and projects that can be indexed`   | Enabling this will allow you to select namespaces and projects to index. All other namespaces and projects will use database search instead. Please note that if you enable this option but do not select any namespaces or projects, none will be indexed. [Read more below](#limiting-namespaces-and-projects).

| `Using AWS hosted Elasticsearch with IAM credentials` | Sign your Elasticsearch requests using [AWS IAM authorization](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html), [AWS EC2 Instance Profile Credentials](https://docs.aws.amazon.com/codedeploy/latest/userguide/getting-started-create-iam-instance-profile.html#getting-started-create-iam-instance-profile-cli), or [AWS ECS Tasks Credentials](https://docs.aws.amazon.com/AmazonECS/latest/userguide/task-iam-roles.html). The policies must be configured to allow `es:*` actions. |

| `AWS Region`                                          | The AWS region your Elasticsearch service is located in. |
| `AWS Access Key`                                      | The AWS access key. |
| `AWS Secret Access Key`                               | The AWS secret access key. |

| `Maximum file size indexed`                           | See [the explanation in instance limits.](../administration/instance_limits.md#maximum-file-size-indexed). |

| `Maximum field length`                                | See [the explanation in instance limits.](../administration/instance_limits.md#maximum-field-length). |

| `Maximum bulk request size (MiB)` | The Maximum Bulk Request size is used by GitLab's Golang-based indexer processes and indicates how much data it ought to collect (and store in memory) in a given indexing process before submitting the payload to Elasticsearch’s Bulk API. This setting should be used with the Bulk request concurrency setting (see below) and needs to accommodate the resource constraints of both the Elasticsearch host(s) and the host(s) running GitLab's Golang-based indexer either from the `gitlab-rake` command or the Sidekiq tasks. |
| `Bulk request concurrency` | The Bulk request concurrency indicates how many of GitLab's Golang-based indexer processes (or threads) can run in parallel to collect data to subsequently submit to Elasticsearch’s Bulk API. This increases indexing performance, but fills the Elasticsearch bulk requests queue faster. This setting should be used together with the Maximum bulk request size setting (see above) and needs to accommodate the resource constraints of both the Elasticsearch host(s) and the host(s) running GitLab's Golang-based indexer either from the `gitlab-rake` command or the Sidekiq tasks. |

### Limiting namespaces and projects

If you select `Limit namespaces and projects that can be indexed`, more options will become available
![limit namespaces and projects options](img/limit_namespaces_projects_options.png)

You can select namespaces and projects to index exclusively. Please note that if the namespace is a group it will include
any sub-groups and projects belonging to those sub-groups to be indexed as well.

Elasticsearch only provides cross-group code/commit search (global) if all name-spaces are indexed. In this particular scenario where only a subset of namespaces are indexed, a global search will not provide a code or commit scope. This will be possible only in the scope of an indexed namespace. Currently there is no way to code/commit search in multiple indexed namespaces (when only a subset of namespaces has been indexed). For example if two groups are indexed, there is no way to run a single code search on both. You can only run a code search on the first group and then on the second.

You can filter the selection dropdown by writing part of the namespace or project name you're interested in.

![limit namespace filter](img/limit_namespace_filter.png)

NOTE: **Note:**

If no namespaces or projects are selected, no Elasticsearch indexing will take place.

CAUTION: **Warning:**

If you have already indexed your instance, you will have to regenerate the index in order to delete all existing data

for filtering to work correctly. To do this run the Rake tasks `gitlab:elastic:recreate_index` and

`gitlab:elastic:clear_index_status`. Afterwards, removing a namespace or a project from the list will delete the data

from the Elasticsearch index as expected.

## Disabling Elasticsearch

To disable the Elasticsearch integration:

1. Navigate to the **Admin Area** (wrench icon), then **Settings > Integrations**.
1. Expand the **Elasticsearch** section and uncheck **Elasticsearch indexing**
   and **Search with Elasticsearch enabled**.
1. Click **Save changes** for the changes to take effect.

1. (Optional) Delete the existing index:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:delete_index

   # Installations from source
   bundle exec rake gitlab:elastic:delete_index RAILS_ENV=production
   ```

## Adding GitLab's data to the Elasticsearch index

While Elasticsearch indexing is enabled, new changes in your GitLab instance will be automatically indexed as they happen.
To backfill existing data, you can use one of the methods below to index it in background jobs.

### Indexing through the administration UI

> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/15390) in [GitLab Starter](https://about.gitlab.com/pricing/) 12.3.

To index via the Admin Area:

1. [Configure your Elasticsearch host and port](#enabling-elasticsearch).

1. Create empty indexes:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:create_empty_index

   # Installations from source
   bundle exec rake gitlab:elastic:create_empty_index RAILS_ENV=production
   ```

1. [Enable **Elasticsearch indexing**](#enabling-elasticsearch).
1. Click **Index all projects** in **Admin Area > Settings > Integrations > Elasticsearch**.

1. Click **Check progress** in the confirmation message to see the status of the background jobs.

1. Personal snippets need to be indexed manually:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index_snippets

   # Installations from source
   bundle exec rake gitlab:elastic:index_snippets RAILS_ENV=production
   ```

1. After the indexing has completed, enable [**Search with Elasticsearch**](#enabling-elasticsearch).

### Indexing through Rake tasks

Indexing can be performed using Rake tasks.

#### Indexing small instances

CAUTION: **Warning:**

This will delete your existing indexes.

If the database size is less than 500 MiB, and the size of all hosted repos is less than 5 GiB:

1. [Configure your Elasticsearch host and port](#enabling-elasticsearch).

1. Index your data:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index

   # Installations from source
   bundle exec rake gitlab:elastic:index RAILS_ENV=production
   ```

1. After the indexing has completed, enable [**Search with Elasticsearch**](#enabling-elasticsearch).

#### Indexing large instances

CAUTION: **Warning:**

Performing asynchronous indexing will generate a lot of Sidekiq jobs.

Make sure to prepare for this task by having a [Scalable and Highly Available Setup](README.md)

or creating [extra Sidekiq processes](../administration/operations/extra_sidekiq_processes.md)

1. [Configure your Elasticsearch host and port](#enabling-elasticsearch).

1. Create empty indexes:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:create_empty_index

   # Installations from source
   bundle exec rake gitlab:elastic:create_empty_index RAILS_ENV=production
   ```

1. If this is a re-index of your GitLab instance, clear the index status:

   ```shell
   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:clear_index_status

   # Installations from source
   bundle exec rake gitlab:elastic:clear_index_status RAILS_ENV=production
   ```

1. [Enable **Elasticsearch indexing**](#enabling-elasticsearch).

1. Indexing large Git repositories can take a while. To speed up the process, you can [tune for indexing speed](https://www.elastic.co/guide/en/elasticsearch/reference/current/tune-for-indexing-speed.html#tune-for-indexing-speed):

   - You can temporarily disable [`refresh`](https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-refresh.html), the operation responsible for making changes to an index available to search.

   - You can set the number of replicas to 0. This setting controls the number of copies each primary shard of an index will have. Thus, having 0 replicas effectively disables the replication of shards across nodes, which should increase the indexing performance. This is an important trade-off in terms of reliability and query performance. It is important to remember to set the replicas to a considered value after the initial indexing is complete.

   In our experience, you can expect a 20% decrease in indexing time. After completing indexing in a later step, you can return `refresh` and `number_of_replicas` to their desired settings.

   NOTE: **Note:**
   This step is optional but may help significantly speed up large indexing operations.

   ```shell

   curl --request PUT localhost:9200/gitlab-production/_settings --header 'Content-Type: application/json' --data '{

       "index" : {
           "refresh_interval" : "-1",
           "number_of_replicas" : 0
       } }'
   ```

1. Index projects and their associated data:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index_projects

   # Installations from source
   bundle exec rake gitlab:elastic:index_projects RAILS_ENV=production
   ```

   This enqueues a Sidekiq job for each project that needs to be indexed.
   You can view the jobs in **Admin Area > Monitoring > Background Jobs > Queues Tab**

   and click `elastic_indexer`, or you can query indexing status using a Rake task:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index_projects_status

   # Installations from source
   bundle exec rake gitlab:elastic:index_projects_status RAILS_ENV=production

   Indexing is 65.55% complete (6555/10000 projects)
   ```

   If you want to limit the index to a range of projects you can provide the
   `ID_FROM` and `ID_TO` parameters:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index_projects ID_FROM=1001 ID_TO=2000

   # Installations from source
   bundle exec rake gitlab:elastic:index_projects ID_FROM=1001 ID_TO=2000 RAILS_ENV=production
   ```

   Where `ID_FROM` and `ID_TO` are project IDs. Both parameters are optional.
   The above example will index all projects from ID `1001` up to (and including) ID `2000`.

   TIP: **Troubleshooting:**
   Sometimes the project indexing jobs queued by `gitlab:elastic:index_projects`
   can get interrupted. This may happen for many reasons, but it's always safe
   to run the indexing task again. It will skip repositories that have
   already been indexed.

   As the indexer stores the last commit SHA of every indexed repository in the
   database, you can run the indexer with the special parameter `UPDATE_INDEX` and
   it will check every project repository again to make sure that every commit in
   a repository is indexed, which can be useful in case if your index is outdated:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index_projects UPDATE_INDEX=true ID_TO=1000

   # Installations from source
   bundle exec rake gitlab:elastic:index_projects UPDATE_INDEX=true ID_TO=1000 RAILS_ENV=production
   ```

   You can also use the `gitlab:elastic:clear_index_status` Rake task to force the
   indexer to "forget" all progress, so it will retry the indexing process from the
   start.

1. Personal snippets are not associated with a project and need to be indexed separately:

   ```shell

   # Omnibus installations
   sudo gitlab-rake gitlab:elastic:index_snippets

   # Installations from source
   bundle exec rake gitlab:elastic:index_snippets RAILS_ENV=production
   ```

1. Enable replication and refreshing again after indexing (only if you previously disabled it):

   ```shell

   curl --request PUT localhost:9200/gitlab-production/_settings --header 'Content-Type: application/json' --data '{

       "index" : {
           "number_of_replicas" : 1,
           "refresh_interval" : "1s"
       } }'
   ```

   A force merge should be called after enabling the refreshing above.

   For Elasticsearch 6.x, the index should be in read-only mode before proceeding with the force merge:

   ```shell

   curl --request PUT localhost:9200/gitlab-production/_settings --header 'Content-Type: application/json' --data '{

     "settings": {
       "index.blocks.write": true
     } }'
   ```

   Then, initiate the force merge:

   ```shell

   curl --request POST 'localhost:9200/gitlab-production/_forcemerge?max_num_segments=5'

   ```

   After this, if your index is in read-only mode, switch back to read-write:

   ```shell

   curl --request PUT localhost:9200/gitlab-production/_settings --header 'Content-Type: application/json' --data '{

     "settings": {
       "index.blocks.write": false
     } }'
   ```

1. After the indexing has completed, enable [**Search with Elasticsearch**](#enabling-elasticsearch).

### Indexing limitations

For repository and snippet files, GitLab will only index up to 1 MiB of content, in order to avoid indexing timeouts.

## Zero downtime reindexing

The idea behind this reindexing method is to leverage Elasticsearch index alias feature to atomically swap between two indices.
We will refer to each index as `primary` (online and used by GitLab for read/writes) and `secondary` (offline, for reindexing purpose).

Instead of connecting directly to the `primary` index, we'll setup an index alias such as we can change the underlying index at will.

NOTE: **Note:**
Any index attached to the production alias is deemed a `primary` and will end up being used by the GitLab Elasticsearch integration.

### Pause the indexing

Under **Admin Area > Integration > Elasticsearch**, check the **Pause Elasticsearch Indexing** setting and save.

With this, all updates that should happen on your Elasticsearch index will be buffered and caught up once unpaused.

### Setup

TIP: **Tip:**
If your index has been created with GitLab v13.0+ you can skip directly to [trigger the reindex](#trigger-the-reindex-via-the-elasticsearch-administration).

This process involves multiple shell commands and curl invocations, so a good initial setup will help down the road:

```shell
# You can find this value under Admin Area > Integration > Elasticsearch > URL
export CLUSTER_URL="http://localhost:9200"
export PRIMARY_INDEX="gitlab-production"
export SECONDARY_INDEX="gitlab-production-$(date +%s)"
```

### Reclaiming the `gitlab-production` index name

CAUTION: **Caution:**
It is highly recommended that you take a snapshot of your cluster to make sure there is a recovery path if anything goes wrong.

NOTE: **Note:**
Due to a technical limitation, there will be a slight downtime because of the fact that we need to reclaim the current `primary` index to be used as the alias.

To reclaim the `gitlab-production` index name, you need to first create a `secondary` index and then trigger the re-index from `primary`.

#### Creating a secondary index

To create a secondary index, run the following Rake task. The `SKIP_ALIAS`
environment variable will disable the automatic creation of the Elasticsearch
alias, which would conflict with the existing index under `$PRIMARY_INDEX`:

```shell
# Omnibus installation
sudo SKIP_ALIAS=1 gitlab-rake "gitlab:elastic:create_empty_index[$SECONDARY_INDEX]"

# Source installation
SKIP_ALIAS=1 bundle exec rake "gitlab:elastic:create_empty_index[$SECONDARY_INDEX]"
```

The index should be created successfully, with the latest index options and mappings.

#### Trigger the re-index from `primary`

To trigger the re-index from `primary` index:

1. Use the Elasticsearch [Reindex API](https://www.elastic.co/guide/en/elasticsearch/reference/7.6/docs-reindex.html):

    ```shell
    curl --request POST \
          --header 'Content-Type: application/json' \
          --data "{ \"source\": { \"index\": \"$PRIMARY_INDEX\" }, \"dest\": { \"index\": \"$SECONDARY_INDEX\" } }" \
          "$CLUSTER_URL/_reindex?slices=auto&wait_for_completion=false"
    ```

    There will be an output like:

    ```plaintext
    {"task":"3qw_Tr0YQLq7PF16Xek8YA:1012"}
    ```

    Note the `task` value here as it will be useful to follow the reindex progress.

1. Wait for the reindex process to complete, by checking the `completed` value.
   Using the `task` value form the previous step:

    ```shell
    export TASK_ID=3qw_Tr0YQLq7PF16Xek8YA:1012
    curl "$CLUSTER_URL/_tasks/$TASK_ID?pretty"
    ```

    The output will be like:

    ```plaintext
    {"completed":false, …}
    ```

    Once the returned value is `true`, you may continue to the next step.

1. Make sure that the secondary index has data in it. You can use the Elasticsearch
   API to look for the index size and compare our two indices:

    ```shell
    curl $CLUSTER_URL/$PRIMARY_INDEX/_count => 123123
    curl $CLUSTER_URL/$SECONDARY_INDEX/_count => 123123
    ```

    TIP: **Tip:**
    Comparing the document count is more accurate than using the index size, as improvements to the storage might cause the new index to be smaller than the original one.

1. Once you are confident your `secondary` index is valid, you can process to the creation of the alias.

    ```shell
    # Delete the original index
    curl --request DELETE $CLUSTER_URL/$PRIMARY_INDEX

    # Create the alias and add the `secondary` index to it
    curl --request POST \
          --header 'Content-Type: application/json' \
          --data "{\"actions\":[{\"add\":{\"index\":\"$SECONDARY_INDEX\",\"alias\":\"$PRIMARY_INDEX\"}}]}}" \
          $CLUSTER_URL/_aliases
    ```

    The reindexing is now completed. Your GitLab instance is now ready to use the [automated in-cluster reindexing](#trigger-the-reindex-via-the-elasticsearch-administration) feature for future reindexing.

1. Unpause the indexing

    Under **Admin Area > Integration > Elasticsearch**, uncheck the **Pause Elasticsearch Indexing** setting and save.

### Trigger the reindex via the Elasticsearch administration

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/34069) in [GitLab Starter](https://about.gitlab.com/pricing/) 13.2.
> - A scheduled index deletion and the ability to cancel it was [introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38914) in GitLab Starter 13.3.

Under **Admin Area > Integration > Elasticsearch zero-downtime reindexing**, click on **Trigger cluster reindexing**.

NOTE: **Note:**
Reindexing can be a lengthy process depending on the size of your Elasticsearch cluster.

CAUTION: **Caution:**
After the reindexing is completed, the original index will be scheduled to be deleted after 14 days. You can cancel this action by pressing the cancel button.

While the reindexing is running, you will be able to follow its progress under that same section.

## GitLab Elasticsearch Rake tasks

Rake tasks are available to:

- [Build and install](#building-and-installing) the indexer.
- Delete indexes when [disabling Elasticsearch](#disabling-elasticsearch).
- [Add GitLab data](#adding-gitlabs-data-to-the-elasticsearch-index) to an index.

The following are some available Rake tasks:

| Task                                                                                                                                                    | Description                                                                                                                                                                               |
|:--------------------------------------------------------------------------------------------------------------------------------------------------------|:------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| [`sudo gitlab-rake gitlab:elastic:index`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)                            | Enables Elasticsearch Indexing and run `gitlab:elastic:create_empty_index`, `gitlab:elastic:clear_index_status`, `gitlab:elastic:index_projects`, and `gitlab:elastic:index_snippets`.                          |

| [`sudo gitlab-rake gitlab:elastic:index_projects`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)                   | Iterates over all projects and queues Sidekiq jobs to index them in the background.                                                                                                       |
| [`sudo gitlab-rake gitlab:elastic:index_projects_status`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)            | Determines the overall status of the indexing. It is done by counting the total number of indexed projects, dividing by a count of the total number of projects, then multiplying by 100. |
| [`sudo gitlab-rake gitlab:elastic:clear_index_status`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)               | Deletes all instances of IndexStatus for all projects.                                                                                                                                    |

| [`sudo gitlab-rake gitlab:elastic:create_empty_index[<TARGET_NAME>]`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake) | Generates an empty index and assigns an alias for it on the Elasticsearch side only if it doesn't already exist.                                                                                                      |
| [`sudo gitlab-rake gitlab:elastic:delete_index[<TARGET_NAME>]`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)       | Removes the GitLab index and alias (if exists) on the Elasticsearch instance.                                                                                                                                   |
| [`sudo gitlab-rake gitlab:elastic:recreate_index[<TARGET_NAME>]`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)     | Wrapper task for `gitlab:elastic:delete_index[<TARGET_NAME>]` and `gitlab:elastic:create_empty_index[<TARGET_NAME>]`.                                                                       |

| [`sudo gitlab-rake gitlab:elastic:index_snippets`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)                   | Performs an Elasticsearch import that indexes the snippets data.                                                                                                                          |
| [`sudo gitlab-rake gitlab:elastic:projects_not_indexed`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)             | Displays which projects are not indexed.                                                                                                                                                  |

| [`sudo gitlab-rake gitlab:elastic:reindex_cluster`](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/tasks/gitlab/elastic.rake)             | Schedules a zero-downtime cluster reindexing task. This feature should be used with an index that was created after GitLab 13.0. |

NOTE: **Note:**

The `TARGET_NAME` parameter is optional and will use the default index/alias name from the current `RAILS_ENV` if not set.

### Environment variables

In addition to the Rake tasks, there are some environment variables that can be used to modify the process:

| Environment Variable | Data Type | What it does                                                                 |
| -------------------- |:---------:| ---------------------------------------------------------------------------- |
| `UPDATE_INDEX`       | Boolean   | Tells the indexer to overwrite any existing index data (true/false).         |
| `ID_TO`              | Integer   | Tells the indexer to only index projects less than or equal to the value.    |
| `ID_FROM`            | Integer   | Tells the indexer to only index projects greater than or equal to the value. |

### Indexing a specific project

Because the `ID_TO` and `ID_FROM` environment variables use the `or equal to` comparison, you can index only one project by using both these variables with the same project ID number:

```shell

root@git:~# sudo gitlab-rake gitlab:elastic:index_projects ID_TO=5 ID_FROM=5

Indexing project repositories...I, [2019-03-04T21:27:03.083410 #3384]  INFO -- : Indexing GitLab User / test (ID=33)...
I, [2019-03-04T21:27:05.215266 #3384]  INFO -- : Indexing GitLab User / test (ID=33) is done!
```

## Elasticsearch index scopes

When performing a search, the GitLab index will use the following scopes:

| Scope Name       | What it searches       |
| ---------------- | ---------------------- |
| `commits`        | Commit data            |
| `projects`       | Project data (default) |
| `blobs`          | Code                   |
| `issues`         | Issue data             |
| `merge_requests` | Merge Request data     |
| `milestones`     | Milestone data         |
| `notes`          | Note data              |
| `snippets`       | Snippet data           |
| `wiki_blobs`     | Wiki contents          |

## Tuning

### Guidance on choosing optimal cluster configuration

For basic guidance on choosing a cluster configuration you may refer to [Elastic Cloud Calculator](https://cloud.elastic.co/pricing). You can find more information below.

- Generally, you will want to use at least a 2-node cluster configuration with one replica, which will allow you to have resilience. If your storage usage is growing quickly, you may want to plan horizontal scaling (adding more nodes) beforehand.
- It's not recommended to use HDD storage with the search cluster, because it will take a hit on performance. It's better to use SSD storage (NVMe or SATA SSD drives for example).
- You can use the [GitLab Performance Tool](https://gitlab.com/gitlab-org/quality/performance) to benchmark search performance with different search cluster sizes and configurations.
- `Heap size` should be set to no more than 50% of your physical RAM. Additionally, it shouldn't be set to more than the threshold for zero-based compressed oops. The exact threshold varies, but 26 GB is safe on most systems, but can also be as large as 30 GB on some systems. See [Setting the heap size](https://www.elastic.co/guide/en/elasticsearch/reference/current/heap-size.html#heap-size) for more details.

- Number of CPUs (CPU cores) per node usually corresponds to the `Number of Elasticsearch shards` setting described below.

- A good guideline is to ensure you keep the number of shards per node below 20 per GB heap it has configured. A node with a 30GB heap should therefore have a maximum of 600 shards, but the further below this limit you can keep it the better. This will generally help the cluster stay in good health.
- Small shards result in small segments, which increases overhead. Aim to keep the average shard size between at least a few GB and a few tens of GB. Another consideration is the number of documents, you should aim for this simple formula for the number of shards: `number of expected documents / 5M +1`.
- `refresh_interval` is a per index setting. You may want to adjust that from default `1s` to a bigger value if you don't need data in realtime. This will change how soon you will see fresh results. If that's important for you, you should leave it as close as possible to the default value.
- You might want to raise [`indices.memory.index_buffer_size`](https://www.elastic.co/guide/en/elasticsearch/reference/current/indexing-buffer.html) to 30% or 40% if you have a lot of heavy indexing operations.

### Elasticsearch integration settings guidance

- The `Number of Elasticsearch shards` setting usually corresponds with the number of CPUs available in your cluster. For example, if you have a 3-node cluster with 4 cores each, this means you will benefit from having at least 3*4=12 shards in the cluster. Please note, it's only possible to change the shards number by using [Split index API](https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-split-index.html) or by reindexing to a different index with a changed number of shards.

- The `Number of Elasticsearch replicas` setting should most of the time be equal to `1` (each shard will have 1 replica). Using `0` is not recommended, because losing one node will corrupt the index.

### Deleted documents

Whenever a change or deletion is made to an indexed GitLab object (a merge request description is changed, a file is deleted from the master branch in a repository, a project is deleted, etc), a document in the index is deleted. However, since these are "soft" deletes, the overall number of "deleted documents", and therefore wasted space, increases. Elasticsearch does intelligent merging of segments in order to remove these deleted documents. However, depending on the amount and type of activity in your GitLab installation, it's possible to see as much as 50% wasted space in the index.

In general, we recommend simply letting Elasticsearch merge and reclaim space automatically, with the default settings. From [Lucene's Handling of Deleted Documents](https://www.elastic.co/blog/lucenes-handling-of-deleted-documents "Lucene's Handling of Deleted Documents"), _"Overall, besides perhaps decreasing the maximum segment size, it is best to leave Lucene's defaults as-is and not fret too much about when deletes are reclaimed."_

However, some larger installations may wish to tune the merge policy settings:

- Consider reducing the `index.merge.policy.max_merged_segment` size from the default 5 GB to maybe 2 GB or 3 GB. Merging only happens when a segment has at least 50% deletions. Smaller segment sizes will allow merging to happen more frequently.

  ```shell

  curl --request PUT localhost:9200/gitlab-production/_settings ---header 'Content-Type: application/json' --data '{

    "index" : {
      "merge.policy.max_merged_segment": "2gb"
    }
  }'
  ```

- You can also adjust `index.merge.policy.reclaim_deletes_weight`, which controls how aggressively deletions are targeted. But this can lead to costly merge decisions, so we recommend not changing this unless you understand the tradeoffs.

  ```shell

  curl --request PUT localhost:9200/gitlab-production/_settings ---header 'Content-Type: application/json' --data '{

    "index" : {
      "merge.policy.reclaim_deletes_weight": "3.0"
    }
  }'
  ```

- Do not do a [force merge](https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-forcemerge.html "Force Merge") to remove deleted documents. A warning in the [documentation](https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-forcemerge.html "Force Merge") states that this can lead to very large segments that may never get reclaimed, and can also cause significant performance or availability issues.

## Troubleshooting

### Common issues

Here are some common pitfalls and how to overcome them:

- **How can I verify my GitLab instance is using Elasticsearch?**

  The easiest method is via the rails console (`sudo gitlab-rails console`) by running the following:

  ```ruby
  u = User.find_by_username('your-username')
  s = SearchService.new(u, {:search => 'search_term'})
  pp s.search_objects.class.name
  ```

  If you see `"ActiveRecord::Relation"`, you are **not** using Elasticsearch.
  
  If you see `"Kaminari::PaginatableArray"` you are using Elasticsearch.

  NOTE: **Note:**

  The above instructions are used to verify that GitLab is using Elasticsearch only when indexing all namespaces. This is not to be used for scenarios that only index a [subset of namespaces](#limiting-namespaces-and-projects).

- **I updated GitLab and now I can't find anything**

  We continuously make updates to our indexing strategies and aim to support
  newer versions of Elasticsearch. When indexing changes are made, it may
  be necessary for you to [reindex](#adding-gitlabs-data-to-the-elasticsearch-index) after updating GitLab.

- **I indexed all the repositories but I can't find anything**

  Make sure you indexed all the database data [as stated above](#adding-gitlabs-data-to-the-elasticsearch-index).