Checklist

User Stories Documented
User Stories Reviewed
Design Reviewed
APIs reviewed
Release priorities assigned
Test cases reviewed
Blog post

Introduction

Enhancements to wrangler. Ability to read connect to external sources like Database, Kafka and perform wrangler directives on them for data preparation.

Goals

Ability to dynamically load plugins from CDAP Service.

User Stories

User wants to load the database driver artifact in wranger and execute database commands to load data. Once data is loaded they want to execute wrangler directives on the loaded data.
User adds kafka artifact, immediately wants to load the kafka artifact in wrangler and read data from a kafka topic, once data is loaded, they want to execute wrangler directives on the loaded data.
User Story #3

Design

Background :

1) Currently plugins that required by programs are configured at configure time. these plugin artifacts get localized to the program containers.

2) At runtime, these plugins can be instantiated by their plugin id

3) we want to be able to dynamically instantiate plugins based on plugin type, name and version at runtime (not possible currently).

Example :

user uploads a POSTGres JDBC Driver

wants to load this POSTGres driver in wrangler,

configure connection and execute a query to select data and perform wrangler directives on the data.

Currently the wrangler service cannot load the PostGres driver, as the PostGres driver was not configured as a plugin in the service configuration. it was not localized to the container and we won't be able to instantiate it.

Cover details on assumptions made, design alternatives considered, high level design

Approach

Approach #1

Approach #2

API changes

New Programmatic APIs

New Java APIs introduced (both user facing and internal)

public interface Admin extends DatasetManager, SecureStoreManager, MessagingAdmin, ArtifactManager {

}

/**
 * Provides access to information about artifacts
 */
interface ArtifactManager {

/**
 * returns the list of artifacts available in current namespace and system namespace.
 */
List<ArtifactDetail> listArtifacts();

/**
 * Create and return class loader with the contents of artifactDetail, with the parentClassLoader as parent, 
 * if parentClassLoader is null we will use boot strap class loader as the parent.
 * @return ClassLoader
 */
ClassLoader createClassLoader(ArtifactDetail artifactDetail, @Nullable ClassLoader parentClassLoader);

...
}

Notes :

1) ArtifactId class is available in cdap-api, we might want to move ArtifactDetail or create another object in cdap-api exposing artifact details, With Admin, CDAP developers can access the ArtifactManager and get information about artifacts

2) How the user can instantiate the plugin ?

Since InstantatiorFactory is available as part of cdap-common, Once they have loaded the desired plugin class, they can use the instantiatorFactory to instantiate the plugin.

Deprecated Programmatic APIs

New REST APIs

Path

Method

Description

Response Code

Response

/v3/apps/<app-id>

GET

Returns the application spec for a given application

200 - On success

404 - When application is not available

500 - Any internal errors

Deprecated REST API

Path	Method	Description
/v3/apps/<app-id>	GET	Returns the application spec for a given application

CLI Impact or Changes

Impact #1
Impact #2
Impact #3

UI Impact or Changes

Impact #1
Impact #2
Impact #3

Security Impact

What's the impact on Authorization and how does the design take care of this aspect

Impact on Infrastructure Outages

System behavior (if applicable - document impact on downstream [ YARN, HBase etc ] component failures) and how does the design take care of these aspect

Test Scenarios

Test ID	Test Description	Expected Results

CDAP

Wrangler Enhancements