Overview 

This addition will allow users to see the history of directives made to a column of data.

Goals

User should be able to see lineage information, ie. directives, for columns

Storing lineage information should have minimal/no impact to the wrangler application

User Stories

• As a user, I should be able to see the directives applied to a column of data.

• As a user, I should be able to see the directives applied to a column of data over any period of time.

• As a user, I should be able to see how any column got to its current state as well as other columns that were impacted by it

• As a user, I should be able to add tags and properties to specific columns of data (stretch)

Design

Save directives for each column in AST format after parsing of directives along with necessary information (time, dataset/stream name/id, etc.).Use TMS input and output schemas.

prepareRun() api to send information to platform.Unmarshal

***release 4.4 onwards implementations can be found in branches feature/implement-transform-publishLineage and feature/field-level-lineage***

Unmarshall and connect into graph and store in HBase.

Access to lineage should only be available through the platform

Questions

• How to get source and sink datasets?
• How to ensure this works with multiple transform nodes, even just wrangler nodes?
• How to send and consume data from wrangler to CDAP?
• Does ParseTree have all necessary information for every directive?

Approach

Computing Lineage Approach #1:

Store directives during execution of each step

Advantages:

• Less assumptions

Disadvantages:

• Add getter to each step class + sometimes (~30%) local variable
• Slower

Computing Lineage Approach #2 (Preferred):

Compute lineage without looking at data by backtracking

Advantages:

• No instance variables added to step classes
• Faster

Disadvantages:

• Requires stricter rule on directives, ie. every rename must give old and new name. See * below for why
• More assumption based

*Backtrack starting with columns A,B,C. Previous directive is "set-columns A B C". The directive before that is "lowercase <column>" where <column> is nameOfOwner. No way of knowing what nameOfOwner refers to without looking at data.

Storage Approach #1:

Key is dataset name + column name + down/up

• Each time a pipeline is run each column will be appended with more lineage information and timestamp
• On retrieval get one key and display until time reached.

Storage Approach #2:

Key is dataset name + column name + time of execution + down/up

• Each time a pipeline is run each column will get its own addition to the HDFS table
• On retrieval get all for column that match time range and display by adding all together

API changes

New Programmatic APIs

FieldLevelLineage is a Java class that contains all the necessary information to be sent to the CDAP platform

Approach

• Each directive implements `public MutationDefinition lineage()`
• prepareRun() function in Wrangler.java creates FieldLevelLineage instance and sends it to CDAP
• CDAP receives all instances of FieldLevelLineage from all transform stages and takes 4 variables to build graph:
  • ProgramRunId
  • PipelinePhase
  • Mapping of stage name to FieldLevelLineage for all transform stages
  • Mapping of stage name to Dataset name for sources and sinks
• Graph is generated and stored in HBase in a way that is easily accessible to UI

API changes

New Programmatic APIs:

TransformStep:

TransformStep is a Java interface that represents a modification done to a dataset by a transform stage.

/**
 * <p>
 *   A TransformStep represents a modification done by a Transform.
 * </p>
 */
public interface TransformStep {

  /**
   * @return the name of this modification
   */
  String getName();

  /**
   * @return additional information about this modification
   */
  @Nullable
  String getInformation();
}

FieldLevelLineage:

FieldLevelLineage is a Java interface that contains all the necessary field-level lineage information to be sent to the CDAP platform, for transform stages.

import java.util.List;
import java.util.Map;

/**
 * <p>FieldLevelLineage is a DataType for computing lineage for each field in a dataset.
 * An instance of this type can be sent to be sent to platform through API for transform stages.</p>
 */
public interface FieldLevelLineage {

  /**
   * <p>A BranchingTransformStepNode represents a linking between a {@link TransformStep} and a field of data.
   * It contains data about how this TransformStep affected this field.</p>
   */
  interface BranchingTransformStepNode {

    /**
     * @return the index of the TransformStep in {@link #getSteps()}
     */
    int getTransformStepNumber();

    /**
     * @return true if this TransformStep does not add this field
     */
    boolean continueBackward(); // continue down

    /**
     * @return true if this TransformStep does not drop this field
     */
    boolean continueForward();  // continue up

    /**
     * This map should contain every other field that was impacted by this field in this TransformStep
     * @return A map from field name to the index of the next TransformStep using {@link #getLineage()}
     * Usage: getLineage().get(field).get(index).
     */
    Map<String, Integer> getImpactedBranches();  // getUpBranches

    /**
     * This map should contain every other field that impacted this field with this TransformStep
     * @return A map from field name to the index of the previous transformation step in {@link #getLineage()}
     * Usage: getLineage().get(field).get(index).
     */
    Map<String, Integer> getImpactingBranches();  // getDownBranches
  }

  /**
   * @return a list of all TransformSteps executed by this Transform in order.
   */
  List<TransformStep> getSteps();

  /**
   * @return a mapping of field names to a list of {@link BranchingTransformStepNode} in reverse order.
   */
  Map<String, List<BranchingTransformStepNode>> getLineage();
}

WranglerFieldLevelLineage:

Instance should be initialized per wrangler node passing in a list of final start and end columns (input and output schema) after parsing the directives.

storebuild() takes a ParseTree List<MutationDefinition> and stores all the necessary information into lineages.

Stores lineage for each column in lineage instance variable which is a map to ASTs.

/**
 * WranglerFieldLevelLineage is a data type for computing lineage for all columns in Wrangler.
 * An instance of this type to be sent to platform through prepareRun API.
 */
public final class WranglerFieldLevelLineage implements FieldLevelLineage {
  /**
   * A WranglerBranchingStepNode is a data private enum Type { ADD, DROP, MODIFY, READ, RENAME }
  class BranchingStepNode {
    boolean continueUp, continueDown;
    String directive;
    Map<String, Integer> upBranches, downBranches;
    // constructors, toString(), ...
  }
  private static final String PROGRAM = "wrangler";
  private final long startTime;
  private Set<String> startColumns;type for linking columns to directives as well as other columns.
   */
  public final class WranglerBranchingStepNode implements BranchingTransformStepNode {
    private final int stepNumber;
    private boolean continueUp;
    private boolean continueDown;
    private final Map<String, Integer> upBranches;
    private final Map<String, Integer> downBranches;

    private WranglerBranchingStepNode(int stepNumber, boolean continueUp, boolean continueDown) {
      this.stepNumber = stepNumber;
      this.continueUp = continueUp;
      this.continueDown = continueDown;
      this.upBranches = new HashMap<>();
      this.downBranches = new HashMap<>();
    }
	
	// Internal functions

    @Override
    public int getTransformStepNumber() {
      return stepNumber;
    }

    @Override
    public boolean continueBackward() {
      return continueUp;
    }

    @Override
    public boolean continueForward() {
      return continueDown;
    }

    @Override
    public Map<String, Integer> getImpactedBranches() {
      return Collections.unmodifiableMap(downBranches);
    }

    @Override
    public Map<String, Integer> getImpactingBranches() {
      return Collections.unmodifiableMap(upBranches);
    }

    @Override
    public String toString() {
      return "(StepNumber: " + stepNumber + ", Continue Backward: " + continueUp + ", " + upBranches +
          ", Continue Forward: " + continueDown + ", " + downBranches + ")";
    }
  }

  private final Set<String> currentColumns, endColumnsList<TransformStep> steps;
  private final Map<String, List<BranchingStepNode>>List<BranchingTransformStepNode>> lineage;


 public FieldLevelLineage(String[] columnNames // Internal functions

  // Shows lineage in tree format
  void prettyPrint(String column, boolean forward) {...}

  // getters@Override
  public List<TransformStep> getSteps() {
    return Collections.unmodifiableList(this.steps);
  //}
helpers
for store @Override
  public Map<String, voidList<BranchingTransformStepNode>> store(ParseTree tree) {
	/**
getLineage() {
    return Collections.unmodifiableMap(this.lineage);
  }

  @Override
* Go throughpublic treeString onetoString() directive{
at a time  return "Column Directives: " *+ Forlineage each column associated with the directive get label
 + "\n" + "Steps: " + steps;
  }

  /**
Store directive for this* columnBuilder correctlyclass intofor lineage based on label
	{@link WranglerFieldLevelLineage}.
   */
  public static class }Builder {
     // toString()
}

 Internal functions
	public Builder(List<String> startColumns, List<String> finalColumns) {...}
    public WranglerFieldLevelLineage build(List<MutationDefinition> parseTree) throws LineageGenerationException {...}
  }
}

parseTree should contain all columns affected per directive.

Labels:

• All columns should be labeled one of:  {Read, Drop, Modify, Add, Rename}
• Read: column's name or values are read. Including reading values and modifying. ie. "filter-rows-on..."
• Drop: column is dropped
• Add: column is added
• Rename: column's name is replaced with another name
• Modify: column's values altered and doesn't fit in any of the other categories, ie. "lowercase"

For Read, Drop, Modify, and Add the column and associated label should be something like -> Column: Name, Label: add.

For Rename the column and associated label should be something like  -> Column: body_5 DOB, Label: rename. // Basically some way of having both names, currently using a space. Old/new for rename. Swap example: A B, Label: rename and B A, Label: rename. The new name could be part of the information being sent.

For Read, Modify, and Add there is another option; instead of column name can return {"all columns", "all columns minus _ _ _ _ ", "all columns formatted %s_%d"}, along with label. ie. Column: "all columns minus body", Label: add. "all columns" refers to all columns present in dataset after execution of this step.

For Rename, and Drop this option is not available; must explicitly return name of all columns involved.

**Assumption (can be changed): In ParseTree all columns should be in order of impact. ie. If directive is "copy A A_copy". "A, Label: read" should be before "A_copy, Label: add".

Algorithm visual:  Example wrangler application  application                                                                                     -->      forward lineage           -->    ASTs for each column

Image Removed      Image Removed     Image Removed  

                backward lineage  

Image Added Image Added Image Added

FieldLevelLineageStorageNode (IN BRANCH feature/field-level-lineage-storage):

FieldLevelLineageStorageNode is a Java interface that represents an element being stored in HBase.

These nodes are created and connected in an AST format by FieldLevelLineageStorageGraph.

/**
 * <p>A FieldLevelLineageStorageNode represents a node of field-level lineage information.</p>
 */
public interface FieldLevelLineageStorageNode {

  /**
   * @return the ID of the pipeline
   */
  ProgramRunId getPipeline();

  /**
   * @return the name of the stage
   */
  String getStage();

  /**
   * @return the name of the field
   */
  String getField();
}

FieldLevelLineageStorageGraph (IN BRANCH feature/field-level-lineage-storage):

FieldLevelLineageStorageGraph is a Java class that transforms many instances of FieldLevelLineage into a graph of FieldLevelLineageStorageNodes for storage.

One instance of this type should be created per pipeline. Created from many instances of FieldLevelLineage, some graph representation of the pipeline, a mapping between reference names and stage names for sources/sinks, and ProgramRunId.

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.HashBasedTable;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Table;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public final class FieldLevelLineageStorageGraph {
  private final ProgramRunId pipelineId;
  private final PipelinePhase pipeline; // Or another type of graph of the pipeline
  private final Map<String, FieldLevelLineage> stages;
  private final Map<String, String> stageToDataSet;
  private final Map<FieldLevelLineageStorageNode, FieldLevelLineageStorageNode> nodeRetriever;
  private final Table<String, String, DataSetFieldNode> history; // Storage
  private final Map<FieldStepNode, TransformStep> stepInformation; // Storage
  private final ListMultimap<FieldLevelLineageStorageNode, FieldLevelLineageStorageNode> pastEdges; // Storage
  private final ListMultimap<FieldLevelLineageStorageNode, FieldLevelLineageStorageNode> futureEdges; // Storage

  public FieldLevelLineageStorageGraph(ProgramRunId PipelineId, PipelinePhase pipeline,
                                       Map<String, FieldLevelLineage> stages, Map<String, String> stageToDataSet) {
    this.pipelineId = PipelineId;
    this.pipeline = pipeline;
    this.stages = stages;
    this.stageToDataSet = stageToDataSet;
    this.nodeRetriever = new HashMap<>();
    this.history = HashBasedTable.create();
    this.stepInformation = new HashMap<>();
    this.pastEdges = ArrayListMultimap.create();
    this.futureEdges = ArrayListMultimap.create();
  }

  // helpers for make()

  private void make() {...} // makes the graph
}

Visual:

  Image Added  

Publishing Lineage Information:

Will be done through new prepareRun() function in the Transform class and new recordLineage(FieldLevelLineage f) function in StageSubmitter interface. Each transform plugin stage will have option to publish field-level lineage.

Wrangler Example:

...
@Override
public void prepareRun(StageSubmitter<TransformContext> context) throws Exception {
  if (context.getContext().getArguments().has("enable.wrangler.field.lineage")) {
    List<String> startColumns, endColumns;
    Schema inputSchema, outputSchema;
    inputSchema = context.getContext().getInputSchema();
    outputSchema = context.getContext().getOutputSchema();
    if (inputSchema == null || inputSchema.getFields() == null) {
      startColumns = new ArrayList<>(0);
    } else {
      startColumns = new ArrayList<>(inputSchema.getFields().size());
      for (Schema.Field field : inputSchema.getFields()) {
        startColumns.add(field.getName());
      }
    }
    if (outputSchema == null || outputSchema.getFields() == null) {
      endColumns = new ArrayList<>(0);
    } else {
      endColumns = new ArrayList<>(outputSchema.getFields().size());
      for (Schema.Field field : outputSchema.getFields()) {
        endColumns.add(field.getName());
      }
    }
    FieldLevelLineage f;
    store = new DefaultTransientStore();
    registry = new CompositeDirectiveRegistry(
      new SystemDirectiveRegistry(),
      new UserDirectiveRegistry(context.getContext())
    );
    RecipeParser directives = new GrammarBasedParser(new MigrateToV2(config.directives).migrate(), registry);
    ExecutorContext ctx = new WranglerPipelineContext(ExecutorContext.Environment.TRANSFORM,
                                                      context.getContext(), store);
    try {
      // Create the pipeline executor with context being set.
      pipeline = new RecipePipelineExecutor();
      pipeline.initialize(directives, ctx);
    } catch (Exception e) {
      throw new Exception(
        String.format("Stage:%s - %s", context.getContext().getStageName(), e.getMessage())
      );
    }
    try {
      f = (new WranglerFieldLevelLineage.Builder(startColumns, endColumns)).build(pipeline.lineage());
    } catch (LineageGenerationException e) {
      LOG.warn(
        String.format("Unable to generate lineage: %s", e.getMessage())
      );
      f = null;
    }
    LOG.info(
      "Field-level lineage generated"
    );
    // context.recordLineage(f);
  }
}
...

New REST APIs

/v3/namespaces/{namespace-id}/datasets/{dataset-id}/columns/{column-id}/lineage?start=<start-ts>&end=<end-ts>&maxLevels=<max-levels>

/v3/namespaces/{namespace-id}/streams/{stream-id}/columns/{column-id}/lineage?start=<start-ts>&end=<end-ts>&maxLevels=<max-levels>

CLI Impact or Changes

TBD

UI Impact or Changes

• Option 2: Add interface to metadata table when viewing dataset to see lineage of columns possibly by clicking on column:                                                          ->   When a column is clicked on will look something like:
      ->   
• Option 2: Show all columns at once directly on lineage tab from clicking on dataset, tab between field level and dataset level:
  
  
  

Security Impact 

Should be none, TBD

Future Work

Taking this work to completion is seen in branches 'feature/implement-transform-publishLineage' and 'feature/field-level-lineage'.

These branches show implementations of recordLineage as well as the graph that can be used to join many instances of FieldLevelLineage together.

Beginnings of designing data sets for storing the information in HBase is present in 'feature/field-level-lineage'.

Impact on Infrastructure Outages 

Storage in HBase. Key being dataset reference name + field name + ProgramRunId. For each pipeline a node is added to this key; Impact TBD.

Test Scenarios

Releases

Release 4.3.0

Release 4.4.0

Related Work

• Fixing TextDirectives and parsing of directives in general