Use filesystem offloader with Pulsar

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

Installation

Follow the steps below to install the filesystem offloader.

Prerequisite

• Pulsar: 2.4.2 or later versions

• Hadoop: 3.x.x

Step

This example uses Pulsar 2.5.1.

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

   • Download from the Apache mirror

   • Download from the Pulsar download page

   • Use wget

     wget https://archive.apache.org/dist/pulsar/pulsar-2.5.1/apache-pulsar-2.5.1-bin.tar.gz

2. Download and untar the Pulsar offloaders package.

   wget https://downloads.apache.org/pulsar/pulsar-2.5.1/apache-pulsar-offloaders-2.5.1-bin.tar.gz
   tar xvfz apache-pulsar-offloaders-2.5.1-bin.tar.gz

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.

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

   mv apache-pulsar-offloaders-2.5.1/offloaders apache-pulsar-2.5.1/offloaders
   ls offloaders

   Output

   tiered-storage-file-system-2.5.1.nartiered-storage-jcloud-2.5.1.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 filesystem, you need to configure some properties of the filesystem offloader driver.

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

Configure filesystem offloader driver

You can configure filesystem 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.	filesystem
  fileSystemURI	Connection address	hdfs://127.0.0.1:9000
  fileSystemProfilePath	Hadoop profile path	../conf/filesystem_offload_core_site.xml

• Optional configurations are as below.

  Optional configuration	Description	Example value
  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

Offloader driver (required)

Offloader driver name, which is case-insensitive.

This example sets the offloader driver name as filesystem.

managedLedgerOffloadDriver=filesystem

Connection address (required)

Connection address is the URI to access the default Hadoop distributed file system.

Example

This example sets the connection address as hdfs://127.0.0.1:9000.

fileSystemURI=hdfs://127.0.0.1:9000

Hadoop profile path (required)

The configuration file is stored in the Hadoop profile path. It contains various settings for Hadoop performance tuning.

Example

This example sets the Hadoop profile path as ../conf/filesystem_offload_core_site.xml.

fileSystemProfilePath=../conf/filesystem_offload_core_site.xml

You can set the following configurations in the filesystem_offload_core_site.xml file.

<property>    <name>fs.defaultFS</name>    <value></value></property>
<property>    <name>hadoop.tmp.dir</name>    <value>pulsar</value></property>
<property>    <name>io.file.buffer.size</name>    <value>4096</value></property>
<property>    <name>io.seqfile.compress.blocksize</name>    <value>1000000</value></property><property>
    <name>io.seqfile.compression.type</name>    <value>BLOCK</value></property>
<property>    <name>io.map.index.interval</name>    <value>128</value></property>

tip

For more information about the Hadoop HDFS, see here.

Configure filesystem 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 offload 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 offload 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.

Example

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

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, default values, and shorthands, see here.

Configure filesystem offloader to run manually

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

• Use REST endpoint.

• Use CLI tools (such as pulsar-admin).

To trigger 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 offloaded to the filesystem until the threshold is no longer exceeded. Older segments are offloaded first.

Example

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

  pulsar-admin topics offload --size-threshold 10M persistent://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, default values, and shorthands, see here.

• This example checks filesystem offloader status using pulsar-admin.

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

  Output

  Offload is currently running

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

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

  Output

  Offload was a success

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

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

  Output

  Error in offloadnull
  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, default values, and shorthands, see here.

Tutorial

For the complete and step-by-step instructions on how to use the filesystem offloader with Pulsar, see here.