Checkpoint Storage

Introduction

Checkpoint is a fault-tolerant recovery mechanism. This mechanism ensures that when the program is running, it can recover itself even if it suddenly encounters an exception.

Checkpoint Storage

Checkpoint Storage is a storage mechanism for storing checkpoint data.

SeaTunnel Engine supports the following checkpoint storage types:

• HDFS (S3,HDFS,LocalFile)
• LocalFile (native), (it's deprecated: use Hdfs(LocalFile) instead.

We used the microkernel design pattern to separate the checkpoint storage module from the engine. This allows users to implement their own checkpoint storage modules.

checkpoint-storage-api is the checkpoint storage module API, which defines the interface of the checkpoint storage module.

if you want to implement your own checkpoint storage module, you need to implement the CheckpointStorage and provide the corresponding CheckpointStorageFactory implementation.

Checkpoint Storage Configuration

The configuration of the seatunnel-server module is in the seatunnel.yaml file.

seatunnel:
    engine:
        checkpoint:
            storage:
                type: hdfs #plugin name of checkpoint storage, we support hdfs(S3, local, hdfs), localfile (native local file) is the default, but this plugin is de
              # plugin configuration
                plugin-config: 
                  namespace: #checkpoint storage parent path, the default value is /seatunnel/checkpoint
                  K1: V1 # plugin other configuration
                  K2: V2 # plugin other configuration   

S3

S3 base on hdfs-file, so you can refer hadoop docs to config s3.

Except when interacting with public S3 buckets, the S3A client needs the credentials needed to interact with buckets. The client supports multiple authentication mechanisms and can be configured as to which mechanisms to use, and their order of use. Custom implementations of com.amazonaws.auth.AWSCredentialsProvider may also be used. if you used SimpleAWSCredentialsProvider (can be obtained from the Amazon Security Token Service), these consist of an access key, a secret key. you can config like this:

``` yaml

seatunnel:
    engine:
        checkpoint:
            interval: 6000
            timeout: 7000
            max-concurrent: 5
            tolerable-failure: 2
            storage:
                type: hdfs
                max-retained: 3
                plugin-config:
                    storage-type: s3
                    s3.bucket: your-bucket
                    fs.s3a.endpoint: your-endpoint
                    fs.s3a.access-key: your-access-key
                    fs.s3a.secret-key: your-secret-key
                    fs.s3a.aws.credentials.provider: org.apache.hadoop.fs.s3a.SimpleAWSCredentialsProvider
                    

if you used InstanceProfileCredentialsProvider, this supports use of instance profile credentials if running in an EC2 VM, you could check iam-roles-for-amazon-ec2. you can config like this:

seatunnel:
  engine:
    checkpoint:
      interval: 6000
      timeout: 7000
      max-concurrent: 5
      tolerable-failure: 2
      storage:
        type: hdfs
        max-retained: 3
        plugin-config:
          storage-type: s3
          s3.bucket: your-bucket
          fs.s3a.endpoint: your-endpoint
          fs.s3a.aws.credentials.provider: org.apache.hadoop.fs.s3a.InstanceProfileCredentialsProvider

For additional reading on the Hadoop Credential Provider API see: Credential Provider API.

HDFS

if you used HDFS, you can config like this:

seatunnel:
  engine:
    checkpoint:
      storage:
        type: hdfs
        max-retained: 3
        plugin-config:
          storage-type: hdfs
            fs.defaultFS: hdfs://localhost:9000
            // if you used kerberos, you can config like this:
            kerberosPrincipal: your-kerberos-principal
            kerberosKeytab: your-kerberos-keytab  

LocalFile

seatunnel:
  engine:
    checkpoint:
      interval: 6000
      timeout: 7000
      max-concurrent: 5
      tolerable-failure: 2
      storage:
        type: hdfs
        max-retained: 3
        plugin-config:
          namespace: /tmp/seatunnel/checkpoint_snapshot    
          storage-type: hdfs

Notice

Because of original binary package lack of class file about hadoop, so, if you use hdfs as checkpoint type, you need to download following package and put it in the directory $SEATUNNEL_HOME/lib. The problem will be fixd in the next version.

https://repo1.maven.org/maven2/org/apache/seatunnel/seatunnel-hadoop3-3.1.4-uber/2.3.0/seatunnel-hadoop3-3.1.4-uber-2.3.0-optional.jar