Use Azure BlobStore offloader with Pulsar

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

Installation

Follow the steps below to install the Azure BlobStore offloader.

Prerequisite

• Pulsar: 2.6.2 or later versions

Step

This example uses Pulsar 2.6.2.

1. Download the Pulsar tarball using one of the following ways:

   • Download from the Apache mirror

   • Download from the Pulsar downloads page

   • Use wget:

   
   wget https://archive.apache.org/dist/pulsar/pulsar-2.6.2/apache-pulsar-2.6.2-bin.tar.gz
   

2. Download and untar the Pulsar offloaders package.

   
   wget https://downloads.apache.org/pulsar/pulsar-2.6.2/apache-pulsar-offloaders-2.6.2-bin.tar.gz
   tar xvfz apache-pulsar-offloaders-2.6.2-bin.tar.gz
   

3. Copy the Pulsar offloaders as offloaders in the Pulsar directory.

   
   mv apache-pulsar-offloaders-2.6.2/offloaders apache-pulsar-2.6.2/offloaders
   
   ls offloaders
   

   Output

   As shown from the output, Pulsar uses Apache jclouds to support AWS S3, GCS and Azure for long term storage.

   
   tiered-storage-file-system-2.6.2.nar
   tiered-storage-jcloud-2.6.2.nar
   
   note

   • If you are running Pulsar in a bare metal cluster, make sure that offloaders tarball is unzipped in every broker's Pulsar directory.
   • If you are running Pulsar in Docker or deploying Pulsar using a Docker image (such as K8s and DCOS), you can use the apachepulsar/pulsar-all image instead of the apachepulsar/pulsar image. apachepulsar/pulsar-all image has already bundled tiered storage offloaders.

Configuration

note

Before offloading data from BookKeeper to Azure BlobStore, you need to configure some properties of the Azure BlobStore offload driver.

Besides, you can also configure the Azure BlobStore offloader to run it automatically or trigger it manually.

Configure Azure BlobStore offloader driver

You can configure the Azure BlobStore 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	azureblob
  offloadersDirectory	Offloader directory	offloaders
  managedLedgerOffloadBucket	Bucket	pulsar-topic-offload

• Optional configurations are as below.

  Optional	Description	Example value
  managedLedgerOffloadReadBufferSizeInBytes	Size of block read	1 MB
  managedLedgerOffloadMaxBlockSizeInBytes	Size of block write	64 MB
  managedLedgerMinLedgerRolloverTimeMinutes	Minimum time between ledger rollover for a topic Note: it is not recommended that you set this configuration in the production environment.	2
  managedLedgerMaxEntriesPerLedger	Maximum number of entries to append to a ledger before triggering a rollover. Note: it is not recommended that you set this configuration in the production environment.	5000

Bucket (required)

A bucket is a basic container that holds your data. Everything you store in Azure BlobStore 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 as pulsar-topic-offload.

managedLedgerOffloadBucket=pulsar-topic-offload

Authentication (required)

To be able to access Azure BlobStore, you need to authenticate with Azure BlobStore.

• Set the environment variables AZURE_STORAGE_ACCOUNT and AZURE_STORAGE_ACCESS_KEY in conf/pulsar_env.sh.

  "export" is important so that the variables are made available in the environment of spawned processes.

  
  export AZURE_STORAGE_ACCOUNT=ABC123456789
  export AZURE_STORAGE_ACCESS_KEY=ded7db27a4558e2ea8bbf0bf37ae0e8521618f366c
  

Size of block read/write

You can configure the size of a request sent to or read from Azure BlobStore in the configuration file broker.conf or standalone.conf.

Configuration	Description	Default value
managedLedgerOffloadReadBufferSizeInBytes	Block size for each individual read when reading back data from Azure BlobStore store.	1 MB
managedLedgerOffloadMaxBlockSizeInBytes	Maximum size of a "part" sent during a multipart upload to Azure BlobStore store. It cannot be smaller than 5 MB.	64 MB

Configure Azure BlobStore offloader to run 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 on 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 on a namespace, but few messages are being produced to the topic, 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 own offload policy. If you want to set offload policy for each namespace, use the command pulsar-admin namespaces set-offload-policies options command.

Example

This example sets the Azure BlobStore 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 here.

Configure Azure BlobStore offloader to run manually

For individual topics, you can trigger Azure BlobStore 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 on a Pulsar cluster for a topic. If the size of the topic data on the Pulsar cluster exceeds this threshold, segments from the topic are moved to Azure BlobStore until the threshold is no longer exceeded. Older segments are moved first.

Example

• This example triggers the Azure BlobStore 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 here.

• This example checks the Azure BlobStore 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 Azure BlobStore 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:
  
  tip

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