# Amazon AWS S3 This guide describes the instructions to configure [Amazon AWS S3](https://aws.amazon.com/s3/) as Alluxio's under storage system. Amazon AWS S3, or Amazon Simple Storage Service, is an object storage service offering industry-leading scalability, data availability, security, and performance. For more information about Amazon AWS S3, please read its [documentation](https://docs.aws.amazon.com/s3/index.html). ## Prerequisites Before you get started, please ensure you have the required information listed below: In preparation for using Amazon AWS S3 with Alluxio: | `` | [Create a new S3 bucket](https://docs.ceph.com/en/quincy/radosgw/s3/bucketops/) or use an existing bucket | | -------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `` | The directory you want to use in that container, either by creating a new directory or using an existing one. | | `` | Used to sign programmatic requests made to AWS. See [How to Obtain Access Key ID and Secret Access Key](https://docs.aws.amazon.com/powershell/latest/userguide/pstools-appendix-sign-up.html) | | `` | Used to sign programmatic requests made to AWS. See [How to Obtain Access Key ID and Secret Access Key](https://docs.aws.amazon.com/powershell/latest/userguide/pstools-appendix-sign-up.html) | ## Basic Setup Use the [mount table operations](https://documentation.alluxio.io/ee-da-en/da-3.5/architecture/namespace#mount-table-operations) to add a new mount point, specifying the Alluxio path to create the mount on and the S3 path as the UFS URI. Credentials and configuration options can also be specified as part of the mount command by specifying the `--option` flag as described by [configuring mount points](https://documentation.alluxio.io/ee-da-en/da-3.5/architecture/namespace#use-different-configurations-for-different-mount-points). An example command to mount `s3:///` to `/s3`: ```shell bin/alluxio mount add --path /s3/ --ufs-uri s3:/// \ --option s3.accessKeyId= --option s3.secretKey= ``` Note that if you want to mount the root of the S3 bucket, add a trailing slash after the bucket name (e.g. `s3://S3_BUCKET/`). For other methods of setting AWS credentials, see the credentials section in [Advanced Setup](#advanced-credentials-setup). ## Advanced Setup Note that configuration options can be specified as mount options or as configuration properties in `conf/alluxio-site.properties`. The following sections will describe how to set configurations as properties, but they can also be set as mount options via `--option =`. ### Configure S3 Region Configuring the S3 region when accessing S3 buckets will improve performance. Otherwise, global S3 bucket access will be enabled which introduces extra requests. S3 region can be set with the property `alluxio.underfs.s3.region`. ```properties alluxio.underfs.s3.region=us-west-1 ``` Note that if the [S3 endpoint](#specify-an-endpoint-for-non-standard-configurations) is set, this property is ignored in favor of the endpoint specific region property. ### Advanced Credentials Setup You can specify credentials in different ways, from highest to lowest priority: 1. `s3a.accessKeyId` and `s3a.secretKey` specified as mount options 2. `s3a.accessKeyId` and `s3a.secretKey` specified as Java system properties 3. `s3a.accessKeyId` and `s3a.secretKey` in `alluxio-site.properties` 4. Environment Variables `AWS_ACCESS_KEY_ID` or `AWS_ACCESS_KEY` (either is acceptable) and `AWS_SECRET_ACCESS_KEY` or `AWS_SECRET_KEY` (either is acceptable) on the Alluxio servers 5. Profile file containing credentials at `~/.aws/credentials` 6. AWS Instance profile credentials, if you are using an EC2 instance When using an AWS Instance profile as the credentials' provider: * Create an [IAM Role](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html) with access to the mounted bucket * Create an [Instance profile](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html#ec2-instance-profile) as a container for the defined IAM Role * Launch an EC2 instance using the created profile Note that the IAM role will need access to both the files in the bucket as well as the bucket itself in order to determine the bucket's owner. Automatically assigning an owner to the bucket can be avoided by setting the property `alluxio.underfs.s3.inherit.acl=false`. See [Amazon's documentation](http://docs.aws.amazon.com/java-sdk/latest/developer-guide/credentials.html#id6) for more details. ### Enabling HTTPS To enable the use of the HTTPS protocol for secure communication with S3 with an additional layer of security for data transfers, configure the following setting in conf/alluxio-site.properties: ```properties alluxio.underfs.s3.secure.http.enabled=true ``` ### Enabling Server Side Encryption You may encrypt your data stored in S3. The encryption is only valid for data at rest in S3 and will be transferred in decrypted form when read by clients. Note, enabling this will also enable HTTPS to comply with requirements for reading/writing objects. Enable this feature by configuring `conf/alluxio-site.properties`: ```properties alluxio.underfs.s3.server.side.encryption.enabled=true ``` ### DNS-Buckets By default, a request directed at the bucket named "mybucket" will be sent to the host name "mybucket.s3.amazonaws.com". You can enable DNS-Buckets to use path style data access, for example: "" by setting the following configuration: ```properties alluxio.underfs.s3.disable.dns.buckets=true ``` ### Accessing S3 through a proxy To communicate with S3 through a proxy, modify `conf/alluxio-site.properties` to include: ```properties alluxio.underfs.s3.proxy.host= alluxio.underfs.s3.proxy.port= ``` `` and `` should be replaced by the host and port of your proxy. ### Specify an endpoint for non-standard configurations If you want to access a specific endpoint such as AWS VPC endpoint or a non-Amazon service provider, modify `conf/alluxio-site.properties` to include: ```properties alluxio.underfs.s3.endpoint= alluxio.underfs.s3.endpoint.region= ``` Both the endpoint and region value need to be set. Note that when an endpoint is set, `alluxio.underfs.s3.region=` will no longer take effect. In the case of a non-Amazon service provider, set the hostname and port of the S3 service as the ``. ### Connecting to Oracle Cloud Infrastructure (OCI) object storage Both the endpoint and region value need to be updated to use non-home region. ```properties alluxio.underfs.s3.endpoint= alluxio.underfs.s3.endpoint.region= ``` All OCI object storage regions need to use `PathStyleAccess` ```properties alluxio.underfs.s3.disable.dns.buckets=true alluxio.underfs.s3.inherit.acl=false ``` ### Using v2 S3 Signatures Some S3 service providers only support v2 signatures. For these S3 providers, you can enforce using the v2 signatures by setting the `alluxio.underfs.s3.signer.algorithm` to `S3SignerType`. ### \[Experimental] S3 streaming upload S3 is an object store and because of this feature, the whole file is sent from client to worker, stored in the local disk temporary directory, and uploaded in the `close()` method by default. To enable S3 streaming upload, you need to modify `conf/alluxio-site.properties` to include: ```properties alluxio.underfs.s3.streaming.upload.enabled=true ``` The default upload process is safer but has the following issues: * Slow upload time. The file has to be sent to Alluxio worker first and then Alluxio worker is responsible for uploading the file to S3. The two processes are sequential. * The temporary directory must have the capacity to store the whole file. * Slow `close()`. The execution time of `close()` method is proportional to the file size and inversely proportional to the bandwidth. That is O(FILE\_SIZE/BANDWIDTH). The S3 streaming upload feature addresses the above issues and is based on the [S3 low-level multipart upload](https://docs.aws.amazon.com/AmazonS3/latest/dev/mpListPartsJavaAPI.html). The S3 streaming upload has the following advantages: * Shorter upload time. Alluxio worker uploads buffered data while receiving new data. The total upload time will be at least as fast as the default method. * Smaller capacity requirement. Our data is buffered and uploaded according to partitions (`alluxio.underfs.s3.streaming.upload.partition.size` which is 64MB by default). When a partition is successfully uploaded, this partition will be deleted. * Faster `close()`. We begin uploading data when data buffered reaches the partition size instead of uploading the whole file in `close()`. If a S3 streaming upload is interrupted, there may be intermediate partitions uploaded to S3 and S3 will charge for the stored data. To reduce the charges, users can modify `conf/alluxio-site.properties` to include: ```properties alluxio.underfs.cleanup.enabled=true ``` Intermediate multipart uploads in all non-readonly S3 mount points older than the clean age (configured by `alluxio.underfs.s3.intermediate.upload.clean.age`) will be cleaned when a cleanup interval (configured by `alluxio.underfs.cleanup.interval`) is reached. ### \[Experimental] S3 multipart upload The default upload method uploads one file completely from start to end in one go. We use multipart-upload method to upload one file by multiple parts, every part will be uploaded in one thread. It won't generate any temporary files while uploading. *It will consume more memory but faster than streaming upload mode*. To enable S3 multipart upload, you need to modify `conf/alluxio-site.properties` to include: ```properties alluxio.underfs.s3.multipart.upload.enabled=true ``` There are other parameters you can specify in `conf/alluxio-site.properties` to make the process faster and better. ```properties # Timeout for uploading part when using multipart upload. alluxio.underfs.object.store.multipart.upload.timeout ``` ```properties # Multipart upload partition size for S3. The default partition size is `64MB` alluxio.underfs.s3.multipart.upload.partition.size ``` ### Setting Request Retry Policy Sometimes there may be an error in accessing UFS because the server is temporarily unable to respond. You can configure a retry policy for UFS requests. Each request sent to UnderFS like getObjectData, getObjectStatus, listObjects, Alluxio will check the response. If the response is an error, and the error code suggests it may be retryable, the request will be resubmitted according to the retry policy in configuration. Alluxio will keep trying until the request is successful or reaches the maximum number of retries. The wait interval between successive retries will gradually increase from the configured base sleep time to the maximum sleep time. The following error codes are categorized as retryable: `500 HTTP_INTERNAL_ERROR`, `502 HTTP_BAD_GATEWAY`, `503 HTTP_UNAVAILABLE`, `503 Slow Down`, and `504 HTTP_GATEWAY_TIMEOUT`. **Note:** * 4xx status code usually represents client errors, such as NOT\_FOUND, PERMISSION\_DENIED, UNAUTHENTICATED, etc. Such errors should never be retried since the issue is on the client side. * 5xx status code usually represents server errors, but not all 5xx error should be retried. For example, `501 HTTP_NOT_IMPLEMENTED` should not be retried. If you want to set the retry policy for the UFS accessing request, you need to modify `conf/alluxio-site.properties` to include: ```properties # the max number of retry in one UnderFS accessing request. alluxio.underfs.business.retry.max.num=10 # the sleep time between the two retries after the initial failure alluxio.underfs.business.retry.base.sleep=30ms # the max sleep time between two retries alluxio.underfs.business.retry.max.sleep=30s ``` ### Setting Larger Timeout If the S3 connection is slow, a larger timeout is useful: ```properties alluxio.underfs.s3.socket.timeout=500sec alluxio.underfs.s3.request.timeout=5min ``` ### Tuning for High Concurrency When accessing S3 through Alluxio with a large number of clients per Alluxio server, it is important to increase the S3 connection pool size to avoid performance issues. If the connection pool size is too small, it may result in S3 request failures with errors such as `"Unable to execute HTTP request: Timeout waiting for connection from pool"` due to high competition for available connections. Increasing the pool size ensures smoother communication and optimal performance by setting: ```properties alluxio.underfs.s3.connections.max=2048 ``` ## Identity and Access Control of S3 Objects [S3 identity and access management](https://docs.aws.amazon.com/AmazonS3/latest/dev/s3-access-control.html) is very different from the traditional POSIX permission model. For instance, S3 ACL does not support groups or directory-level settings. Alluxio makes the best effort to inherit permission information including file owner, group and permission mode from S3 ACL information. ### Why is 403 Access Denied Error Returned The S3 credentials set in Alluxio configuration corresponds to an AWS user. If this user does not have the required permissions to access an S3 bucket or object, a 403 permission denied error will be returned. If you see a 403 error in Alluxio server log when accessing an S3 service, you should double-check 1. You are using the correct AWS credentials. See [credentials setup](#advanced-credentials-setup). 2. Your AWS user has permissions to access the buckets and objects mounted to Alluxio. Read more [AWS troubleshooting guidance](https://aws.amazon.com/premiumsupport/knowledge-center/s3-troubleshoot-403/) for 403 error. ### File Owner and Group Alluxio file system sets the file owner based on the AWS account configured in Alluxio to connect to S3. Since there is no group in S3 ACL, the owner is reused as the group. By default, Alluxio extracts the display name of this AWS account as the file owner. In case this display name is not available, this AWS user's [canonical user ID](https://docs.aws.amazon.com/general/latest/gr/acct-identifiers.html) will be used. This canonical user ID is typically a long string (like `79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be`), thus often inconvenient to read and use in practice. Optionally, the property `alluxio.underfs.s3.owner.id.to.username.mapping` can be used to specify a preset mapping from canonical user IDs to Alluxio usernames, in the format "id1=user1;id2=user2". For example, edit `alluxio-site.properties` to include ```properties alluxio.underfs.s3.owner.id.to.username.mapping=\ 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be=john ``` This configuration helps Alluxio recognize all objects owned by this AWS account as owned by the user `john` in Alluxio namespace. To find out the AWS S3 canonical ID of your account, check the console `https://console.aws.amazon.com/iam/home?#/security_credentials`, expand the "Account Identifiers" tab and refer to "Canonical User ID". ### Changing Permissions `chown`, `chgrp`, and `chmod` of Alluxio directories and files do **NOT** propagate to the underlying S3 buckets nor objects. ### Using AWS AssumeRole Alluxio supports authentication via the \[AWS AssumeRole API]\( .com/STS/latest/APIReference/API\_AssumeRole.html) to connect to AWS S3. When AssumeRole is enabled, the AWS access key and secret key will only be used to obtain temporary security credentials. All subsequent accesses will utilize these temporary credentials, which are generated through AssumeRole. To enable AssumeRole in Alluxio, the following properties are required on workers and coordinators: ```properties alluxio.underfs.s3.assumerole.enabled=true alluxio.underfs.s3.assumerole.rolearn=arn:aws:iam::123456:role/example-role ``` Note: Ensure the specified role exists, and the user associated with the provided access key and secret key has permission to assume the role defined by the target role ARN. In addition to the mandatory properties, you can also configure the following optional settings for greater control over session behavior and network configurations: ```properties # Specifies a name for the session. # Temporary credentials will be associated with this session. # A random string is suffixed to ensure uniqueness. alluxio.underfs.s3.assumerole.session.prefix="alluxio-assume-role" # Specifies the session duration in seconds. Typically, this is between 900 and 3600 seconds. # The session will be automatically refreshed by the AWS client, # so no manual intervention is needed to refresh the temporary credentials. alluxio.underfs.s3.assumerole.session.duration.second=900 # Enables the HTTPS protocol for AssumeRole requests. The default value is true. alluxio.underfs.s3.assumerole.https.enabled=true # Enables the HTTPS protocol for the AssumeRole proxy. The default value is false. alluxio.underfs.s3.assumerole.proxy.https.enabled=false # Specifies the proxy host for AssumeRole requests. Both proxy host and proxy port must be set # in the Alluxio configuration; otherwise, the proxy settings will default to your system's # environment configuration. alluxio.underfs.s3.assumerole.proxy.host= # Specifies the proxy port for AssumeRole requests. Both proxy host and proxy port must be set # in the Alluxio configuration; otherwise, the proxy settings will default to your system's # environment configuration. alluxio.underfs.s3.assumerole.proxy.port= ``` Note: If the proxy host and port are not set in the Alluxio configuration, the JVM/System environment variables `HTTP(S)_PROXY`, `http(s)_proxy`, `http(s).proxyHost`, and `http(s).proxyPort` will automatically be picked up by the AWS SDK. Below is a sample configuration for setting up AssumeRole in Alluxio: ```properties aws.accessKeyId=FOO aws.secretKey=BAR alluxio.underfs.s3.assumerole.enabled=true alluxio.underfs.s3.assumerole.session.duration.second=1000 alluxio.underfs.s3.assumerole.session.prefix="alluxio" alluxio.underfs.s3.assumerole.rolearn=arn:aws:iam::123456:role/example-role ``` Summary: * **Temporary Credentials**: AWS access keys are only used to request temporary credentials; all future operations rely on those credentials. * **Automatic Session Refresh**: Sessions are automatically refreshed by the AWS SDK, requiring no manual intervention. * **Customizable Configuration**: You can modify session duration, proxy settings, and session prefixes to suit your security and environment needs. By setting up these properties, Alluxio can effectively authenticate and manage access to AWS S3 using the temporary credentials obtained via AssumeRole. ## Troubleshooting ### Enabling AWS-SDK Debug Level If issues are encountered when running against your S3 backend, enable additional logging to track HTTP traffic. Modify `conf/log4j2.xml` to add the following properties: ```properties ``` See [Amazon's documentation](https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/logging-slf4j.html) for more details. ### Prevent Creating Zero-byte Files Alluxio may create zero-byte files in S3 as a performance optimization when listing the contents of the underlying storage. If a bucket is mounted with read-only access, creating zero-byte file creation via S3 PUT operation will be disallowed. To disable this optimization, set the following configuration. ```properties alluxio.underfs.object.store.breadcrumbs.enabled=false ```