# mongo\_replset

![](https://1982584918-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LR7OsqPORtP86IQxs6E-694727794%2Fuploads%2Fgit-blob-168d286e1c11cf6b48cd727e96b1a976c5a54572%2Fmongo_replset.png?alt=media)

The `out_mongo_replset` Output plugin writes records into [MongoDB](http://mongodb.org/), the emerging document-oriented database system.

This plugin is for users using ReplicaSet. If you are not using `ReplicaSet`, please see the [`out_mongo`](https://docs.fluentd.org/output/mongo) article instead.

This plugin has breaking changes since 0.8.0 due to mongo-ruby driver's breaking changes. If you are using a prior 0.7.x series, please be careful to upgrade 1.0.0 or later versions.

## Why Fluentd with MongoDB?

Fluentd enables your apps to insert records to MongoDB asynchronously with batch-insertion, unlike direct insertion of records from your apps. This has the following advantages:

1. less impact on application performance
2. higher MongoDB insertion throughput while maintaining JSON record structure

## Install

`out_mongo_replset` is not included in `fluent-package`, by default. Fluentd gem users will need to install the `fluent-plugin-mongo` gem using the following command:

```
$ sudo fluent-gem install fluent-plugin-mongo
```

## Example Configuration

```
# Single MongoDB
<match mongo.**>
  @type mongo_replset
  database fluentd
  collection test
  nodes localhost:27017,localhost:27018,localhost:27019

  # The name of the replica set
  replica_set myapp

  <buffer>
    # flush
    flush_interval 10s
  </buffer>
</match>
```

Please see the [Store Apache Logs into MongoDB](https://docs.fluentd.org/how-to-guides/apache-to-mongodb) article for real-world use cases.

Please see the [Configuration File](https://docs.fluentd.org/configuration/config-file) article for the basic structure and syntax of the configuration file.

For `<buffer>`, refer to [Buffer Section Configuration](https://docs.fluentd.org/configuration/buffer-section).

## Parameters

### `@type`

The value must be `mongo`.

### `nodes`

| type   | default            | version |
| ------ | ------------------ | ------- |
| string | required parameter | 1.0.0   |

The comma-separated node strings (e.g. host1:27017,host2:27017,host3:27017).

### `database`

| type   | default            | version |
| ------ | ------------------ | ------- |
| string | required parameter | 1.0.0   |

The database name.

### collection

| type   | default                                | version |
| ------ | -------------------------------------- | ------- |
| string | required parameter if not `tag_mapped` | 1.0.0   |

The collection name.

### `capped`

| type   | default  | version |
| ------ | -------- | ------- |
| string | optional | 1.0.0   |

This option enables the capped collection. This is always recommended because MongoDB is not suited to storing large amounts of historical data.

### `capped_size`

| type | default  | version |
| ---- | -------- | ------- |
| size | optional | 1.0.0   |

Sets the capped collection size.

### `user`

| type   | default  | version |
| ------ | -------- | ------- |
| string | optional | 1.0.0   |

The username to use for authentication.

### `password`

| type   | default  | version |
| ------ | -------- | ------- |
| string | optional | 1.0.0   |

The password to use for authentication.

### `tag_mapped`

| type   | default  | version |
| ------ | -------- | ------- |
| string | optional | 1.0.0   |

This option allows `out_mongo` to use Fluentd's tag to determine the destination collection.

For example, if you generate records with tags `mongo.foo`, the records will be inserted into the `foo` collection within the `fluentd` database:

```
<match mongo.*>
  @type mongo_replset
  database fluentd
  nodes localhost:27017,localhost:27018,localhost:27019

  # Set 'tag_mapped' if you want to use tag mapped mode.
  tag_mapped

  # If the tag is "mongo.foo", then the prefix "mongo." is removed.
  # The inserted collection name is "foo".
  remove_tag_prefix mongo.

  # This configuration is used if the tag is not found. The default is 'untagged'.
  collection misc
</match>
```

### `replica_set`

| type   | default            | version |
| ------ | ------------------ | ------- |
| string | required parameter | 1.0.0   |

The name of the replica set.

### `read`

| type   | default | version |
| ------ | ------- | ------- |
| string | `nil`   | 1.0.0   |

The `ReplicaSet` read preference (e.g. secondary, etc.).

### `num_retries`

| type    | default | version |
| ------- | ------- | ------- |
| integer | 60      | 1.0.0   |

The `ReplicaSet` failover threshold. The default threshold is 60. If the retry count reaches this threshold, the plugin raises an exception.

## Common Output / Buffer parameters

For common output / buffer parameters, please check the following articles:

* [Output Plugin Overview](https://docs.fluentd.org/output)
* [Buffer Section Configuration](https://docs.fluentd.org/configuration/buffer-section)

## Further Readings

* [`fluent-plugin-webhdfs mongo`](https://github.com/fluent/fluent-plugin-mongo)

If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open). [Fluentd](http://www.fluentd.org/) is an open-source project under [Cloud Native Computing Foundation (CNCF)](https://cncf.io/). All components are available under the Apache 2 License.