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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 configurationDescriptionExample value
    managedLedgerOffloadDriverOffloader driver name, which is case-insensitive.S3
    offloadersDirectoryOffloader directoryoffloaders
    managedLedgerOffloadBucketBucketpulsar-topic-offload
    managedLedgerOffloadServiceEndpointEndpointhttp://localhost:9000

  • Optional configurations are as below.

    OptionalDescriptionDefault value
    managedLedgerOffloadReadBufferSizeInBytesBlock size for each individual read when reading back data from S3-compatible storage.1 MB
    managedLedgerOffloadMaxBlockSizeInBytesMaximum block size sent during a multi-part upload to S3-compatible storage. It cannot be smaller than 5 MB.64 MB
    managedLedgerMinLedgerRolloverTimeMinutesMinimum time between ledger rollover for a topic.

    Note: It's not recommended to change the default value in a production environment.    		10
    managedLedgerMaxEntriesPerLedgerMaximum 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 (optional)​

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.

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

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