# Configure consistent view
<a name="emrfs-configure-consistent-view"></a>

You can configure additional settings for consistent view by providing them using configuration properties for `emrfs-site` properties. For example, you can choose a different default DynamoDB throughput by supplying the following arguments to the CLI `--emrfs` option, using the emrfs-site configuration classification (Amazon EMR release version 4.x and later only), or a bootstrap action to configure the emrfs-site.xml file on the master node:

**Example Changing default metadata read and write values at cluster launch**  

```
aws emr create-cluster --release-label emr-7.12.0 --instance-type m5.xlarge \
--emrfs Consistent=true,Args=[fs.s3.consistent.metadata.read.capacity=600,\
fs.s3.consistent.metadata.write.capacity=300] --ec2-attributes KeyName=myKey
```

Alternatively, use the following configuration file and save it locally or in Amazon S3:

```
[
    {
      "Classification": "emrfs-site",
      "Properties": {
        "fs.s3.consistent.metadata.read.capacity": "600",
        "fs.s3.consistent.metadata.write.capacity": "300"
      }
    }
 ]
```

Use the configuration you created with the following syntax:

```
aws emr create-cluster --release-label emr-7.12.0 --applications Name=Hive \
--instance-type m5.xlarge --instance-count 2 --configurations file://./myConfig.json
```

**Note**  
Linux line continuation characters (\$1) are included for readability. They can be removed or used in Linux commands. For Windows, remove them or replace with a caret (^).

The following options can be set using configurations or AWS CLI `--emrfs` arguments. For information about those arguments, see the [AWS CLI Command Reference](https://docs.aws.amazon.com/cli/latest/reference/).


**`emrfs-site.xml` Properties for consistent view**  

| Property  | Default value | Description  | 
| --- | --- | --- | 
| fs.s3.consistent | false |  When set to **true**, this property configures EMRFS to use DynamoDB to provide consistency.  | 
| fs.s3.consistent.retryPolicyType | exponential | This property identifies the policy to use when retrying for consistency issues. Options include: exponential, fixed, or none. | 
| fs.s3.consistent.retryPeriodSeconds | 1 | This property sets the length of time to wait between consistency retry attempts. | 
| fs.s3.consistent.retryCount | 10 | This property sets the maximum number of retries when inconsistency is detected. | 
| fs.s3.consistent.throwExceptionOnInconsistency | true | This property determines whether to throw or log a consistency exception. When set to true, a ConsistencyException is thrown. | 
| fs.s3.consistent.metadata.autoCreate | true | When set to true, this property enables automatic creation of metadata tables. | 
| fs.s3.consistent.metadata.etag.verification.enabled | true | With Amazon EMR 5.29.0, this property is enabled by default. When enabled, EMRFS uses S3 ETags to verify that objects being read are the latest available version. This feature is helpful for read-after-update use cases in which files on S3 are being overwritten while retaining the same name. This ETag verification capability currently does not work with S3 Select. | 
| fs.s3.consistent.metadata.tableName | EmrFSMetadata | This property specifies the name of the metadata table in DynamoDB. | 
| fs.s3.consistent.metadata.read.capacity | 500 | This property specifies the DynamoDB read capacity to provision when the metadata table is created. | 
| fs.s3.consistent.metadata.write.capacity | 100 | This property specifies the DynamoDB write capacity to provision when the metadata table is created. | 
| fs.s3.consistent.fastList | true | When set to true, this property uses multiple threads to list a directory (when necessary). Consistency must be enabled in order to use this property. | 
| fs.s3.consistent.fastList.prefetchMetadata | false | When set to true, this property enables metadata prefetching for directories containing more than 20,000 items. | 
| fs.s3.consistent.notification.CloudWatch | false | When set to true, CloudWatch metrics are enabled for FileSystem API calls that fail due to Amazon S3 eventual consistency issues. | 
| fs.s3.consistent.notification.SQS | false | When set to true, eventual consistency notifications are pushed to an Amazon SQS queue. | 
| fs.s3.consistent.notification.SQS.queueName | EMRFS-Inconsistency-<jobFlowId> | Changing this property allows you to specify your own SQS queue name for messages regarding Amazon S3 eventual consistency issues. | 
| fs.s3.consistent.notification.SQS.customMsg | none | This property allows you to specify custom information included in SQS messages regarding Amazon S3 eventual consistency issues. If a value is not specified for this property, the corresponding field in the message is empty.  | 
| fs.s3.consistent.dynamodb.endpoint | none | This property allows you to specify a custom DynamoDB endpoint for your consistent view metadata. | 
| fs.s3.useRequesterPaysHeader | false | When set to true, this property allows Amazon S3 requests to buckets with the request payer option enabled.  |