Preconditions

In AWS Data Pipeline, a precondition is a pipeline component containing conditional statements that must be true before an activity can run. For example, a precondition can check whether source data is present before a pipeline activity attempts to copy it. AWS Data Pipeline provides several pre-packaged preconditions that accommodate common scenarios, such as whether a database table exists, whether an Amazon S3 key is present, and so on. However, preconditions are extensible and allow you to run your own custom scripts to support endless combinations.

There are two types of preconditions: system-managed preconditions and user-managed preconditions. System-managed preconditions are run by the AWS Data Pipeline web service on your behalf and do not require a computational resource. User-managed preconditions only run on the computational resource that you specify using the runsOn or workerGroup fields. The workerGroup resource is derived from the activity that uses the precondition.

System-Managed Preconditions

DynamoDBDataExists

Checks whether data exists in a specific DynamoDB table.

DynamoDBTableExists

Checks whether a DynamoDB table exists.

S3KeyExists

Checks whether an Amazon S3 key exists.

S3PrefixNotEmpty

Checks whether an Amazon S3 prefix is empty.

User-Managed Preconditions

Exists

Checks whether a data node exists.

ShellCommandPrecondition

Runs a custom Unix/Linux shell command as a precondition.