Use S3 offloader with Pulsar

S3 offloader is introduced to serve S3-compatible storage, which means that the storage employs the S3 API as its "language" and applications that speak the S3 API are able to plug and play with S3-compatible storage.

This chapter guides you through every step of installing and configuring the S3 offloader and using it with Pulsar.

Installation

Prerequisite

• Pulsar: 2.9.3 or later versions

Steps

Follow the steps below to install the S3 offloader.

1. Download the Pulsar tarball.
2. Download and untar the Pulsar offloaders package, then copy the Pulsar offloaders as offloaders in the Pulsar directory. See Install tiered storage offloaders.

Configuration

note

Before offloading data from BookKeeper to S3-compatible storage, you need to configure some properties of the S3 offload driver. Besides, you can also configure the S3 offloader to run it automatically or trigger it manually.

Configure S3 offloader driver

You can configure the S3 offloader driver in the configuration file broker.conf or standalone.conf.

• Required configurations are as below.

  Required configuration	Description	Example value
  managedLedgerOffloadDriver	Offloader driver name, which is case-insensitive.	S3
  offloadersDirectory	Offloader directory	offloaders
  managedLedgerOffloadBucket	Bucket	pulsar-topic-offload
  managedLedgerOffloadServiceEndpoint	Endpoint	http://localhost:9000

• Optional configurations are as below.

  Optional	Description	Default value
  managedLedgerOffloadReadBufferSizeInBytes	Block size for each individual read when reading back data from S3-compatible storage.	1 MB
  managedLedgerOffloadMaxBlockSizeInBytes	Maximum block size sent during a multi-part upload to S3-compatible storage. It cannot be smaller than 5 MB.	64 MB
  managedLedgerMinLedgerRolloverTimeMinutes	Minimum time between ledger rollover for a topic. Note: It's not recommended to change the default value in a production environment.	10
  managedLedgerMaxEntriesPerLedger	Maximum number of entries to append to a ledger before triggering a rollover. Note: It's not recommended to change the default value in a production environment.	50000

Bucket (required)

A bucket is a basic container that holds your data. Everything you store in S3-compatible storage must be contained in a bucket. You can use a bucket to organize your data and control access to your data, but unlike directory and folder, you cannot nest a bucket.

Example

This example names the bucket pulsar-topic-offload.

managedLedgerOffloadBucket=pulsar-topic-offload

Endpoint (required)

The endpoint is the region where a bucket is located.

Example

This example sets the endpoint as localhost.

managedLedgerOffloadServiceEndpoint=http://localhost:9000

Authentication

To be able to access S3-compatible storage, you need to authenticate with S3-compatible storage.

Set the environment variables ACCESS_KEY_ID and ACCESS_KEY_SECRET in conf/pulsar_env.sh.

export ACCESS_KEY_ID=ABC123456789
export ACCESS_KEY_SECRET=ded7db27a4558e2ea8bbf0bf37ae0e8521618f366c

note

Exporting these environment variables makes them available in the environment of spawned processes.

Credentials in offload policies

Pulsar also accepts credentials from the effective offload policy for the S3 and aliyun-oss drivers. The fields are named s3ManagedLedgerOffloadCredentialId and s3ManagedLedgerOffloadCredentialSecret for both drivers. They can be supplied through namespace or topic offload policies, allowing different workloads to use different storage credentials.

For the admin CLI's set-offload-policies command, the corresponding options are --aws-id and --aws-secret, including with --driver aliyun-oss. Include the intended bucket, endpoint, and other policy settings when setting a policy; this operation does not just patch the credentials.

When either configured credential field is nonblank, both must be present. Configured credentials take precedence over environment variables; an incomplete configured pair fails rather than falling back. Without a configured pair, the driver uses ACCESS_KEY_ID and ACCESS_KEY_SECRET, falling back to the corresponding ALIYUN_OSS_ACCESS_KEY_ID and ALIYUN_OSS_ACCESS_KEY_SECRET variables when the generic values are empty. If you use the Aliyun-specific variables, avoid setting conflicting generic values in the same broker environment.

Policy credentials are stored with the offload policy. Restrict access to policy administration and inspection, and avoid putting literal credentials into shared command histories. After changing credentials, verify both new offloads and reads of previously offloaded ledgers.

Run S3 offloader automatically

Namespace policy can be configured to offload data automatically once a threshold is reached. The threshold is based on the size of data that a topic has stored in a Pulsar cluster. Once the topic reaches the threshold, an offloading operation is triggered automatically.

Threshold value	Action
> 0	It triggers the offloading operation if the topic storage reaches its threshold.
= 0	It causes a broker to offload data as soon as possible.
< 0	It disables automatic offloading operation.

Automatic offloading runs when a new segment is added to a topic log. If you set the threshold for a namespace, but few messages are being produced to the topic, the offloader does not work until the current segment is full.

You can configure the threshold size using CLI tools, such as pulsar-admin.

The offload configurations in broker.conf and standalone.conf are used for the namespaces that do not have namespace-level offload policies. Each namespace can have its offload policy. If you want to set an offload policy for a specific namespace, use the command pulsar-admin namespaces set-offload-policies options command.

Example

This example sets the S3 offloader threshold size to 10 MB using pulsar-admin.

bin/pulsar-admin namespaces set-offload-threshold --size 10M my-tenant/my-namespace

tip

For more information about the pulsar-admin namespaces set-offload-threshold options command, including flags, descriptions, and default values, see Pulsar admin docs.

Run S3 offloader manually

For individual topics, you can trigger the S3 offloader manually using one of the following methods:

• Use REST endpoint.

• Use CLI tools, such as pulsar-admin.

To trigger it via CLI tools, you need to specify the maximum amount of data (threshold) that should be retained in a Pulsar cluster for a topic. If the size of the topic data in the Pulsar cluster exceeds this threshold, segments from the topic are moved to S3-compatible storage until the threshold is no longer exceeded. Older segments are moved first.

Example

• This example triggers the S3 offloader to run manually using pulsar-admin.

  bin/pulsar-admin topics offload --size-threshold 10M my-tenant/my-namespace/topic1

  Output

  Offload triggered for persistent://my-tenant/my-namespace/topic1 for messages before 2:0:-1

  tip

  For more information about the pulsar-admin topics offload options command, including flags, descriptions, and default values, see Pulsar admin docs.

• This example checks the S3 offloader status using pulsar-admin.

  bin/pulsar-admin topics offload-status persistent://my-tenant/my-namespace/topic1

  Output

  Offload is currently running

  To wait for the S3 offloader to complete the job, add the -w flag.

  bin/pulsar-admin topics offload-status -w persistent://my-tenant/my-namespace/topic1

  Output

  Offload was a success

  If there is an error in offloading, the error is propagated to the pulsar-admin topics offload-status command.

  bin/pulsar-admin topics offload-status persistent://my-tenant/my-namespace/topic1

  Output

  Error in offload
  null
  
  Reason: Error offloading: org.apache.bookkeeper.mledger.ManagedLedgerException: java.util.concurrent.CompletionException: com.amazonaws.services.s3.model.AmazonS3Exception: Anonymous users cannot initiate multipart uploads.  Please authenticate. (Service: Amazon S3; Status Code: 403; Error Code: AccessDenied; Request ID: 798758DE3F1776DF; S3 Extended Request ID: dhBFz/lZm1oiG/oBEepeNlhrtsDlzoOhocuYMpKihQGXe6EG8puRGOkK6UwqzVrMXTWBxxHcS+g=), S3 Extended Request ID: dhBFz/lZm1oiG/oBEepeNlhrtsDlzoOhocuYMpKihQGXe6EG8puRGOkK6UwqzVrMXTWBxxHcS+g=

  tip

  For more information about the pulsar-admin topics offload-status options command, including flags, descriptions, and default values, see Pulsar admin docs.