refactor(spark-lineage): enhance logging and documentation (#4113)

metadata-integration/java/spark-lineage/README.md

@@ -47,6 +47,14 @@ spark = SparkSession.builder()
         .enableHiveSupport()
         .getOrCreate();
  ```
+ 
+### Enable https and authentication token
+Add below config in spark config
+
+```
+spark.datahub.rest.server                   https://<server URL>
+spark.datahub.rest.token                    <token>
+```
 
 ## What to Expect: The Metadata Model
 
@@ -100,6 +108,37 @@ Effectively, these support data sources/sinks corresponding to Hive, HDFS and JD
 - If spark execution fails, then an empty pipeline would still get created, but it may not have any tasks.
 - For HDFS sources, the folder (name) is regarded as the dataset (name) to align with typical storage of parquet/csv formats.
 
+### Debugging
+
+- Following info logs are generated
+
+On Spark context startup
+```
+YY/MM/DD HH:mm:ss INFO DatahubSparkListener: DatahubSparkListener initialised.
+YY/MM/DD HH:mm:ss INFO SparkContext: Registered listener datahub.spark.DatahubSparkListener
+```
+On application start
+```
+YY/MM/DD HH:mm:ss INFO DatahubSparkListener: Application started: SparkListenerApplicationStart(AppName,Some(local-1644489736794),1644489735772,user,None,None)
+YY/MM/DD HH:mm:ss INFO McpEmitter: REST Emitter Configuration: GMS url <rest.server>
+YY/MM/DD HH:mm:ss INFO McpEmitter: REST Emitter Configuration: Token XXXXX
+```
+On pushing data to server
+```
+YY/MM/DD HH:mm:ss INFO McpEmitter: MetadataWriteResponse(success=true, responseContent={"value":"<URN>"}, underlyingResponse=HTTP/1.1 200 OK [Date: day, DD month year HH:mm:ss GMT, Content-Type: application/json, X-RestLi-Protocol-Version: 2.0.0, Content-Length: 97, Server: Jetty(9.4.20.v20190813)] [Content-Length: 97,Chunked: false])
+```
+On application end
+```
+YY/MM/DD HH:mm:ss INFO DatahubSparkListener: Application ended : AppName AppID
+```
+
+- To enable debugging logs, add below configuration in log4j.properties file
+
+```
+log4j.logger.datahub.spark=DEBUG
+log4j.logger.datahub.client.rest=DEBUG
+```
+
 ## Known limitations
 - Only postgres supported for JDBC sources in this initial release. Support for other driver URL formats will be added in future.
 - Behavior with cached datasets is not fully specified/defined in context of lineage.

metadata-integration/java/spark-lineage/src/main/java/datahub/spark/DatahubSparkListener.java

@@ -61,6 +61,10 @@ public class DatahubSparkListener extends SparkListener {
   private final Map<String, Map<Long, SQLQueryExecStartEvent>> appSqlDetails = new ConcurrentHashMap<>();
   private final Map<String, ExecutorService> appPoolDetails = new ConcurrentHashMap<>();
   private final Map<String, McpEmitter> appEmitters = new ConcurrentHashMap<>();
+  
+  public DatahubSparkListener() {
+    log.info("DatahubSparkListener initialised.");
+  }
 
   private class SqlStartTask implements Runnable {
 
@@ -164,7 +168,7 @@ public class DatahubSparkListener extends SparkListener {
   @Override
   public void onApplicationStart(SparkListenerApplicationStart applicationStart) {
     try {
-      log.debug("App started: " + applicationStart);
+      log.info("Application started: " + applicationStart);
       LineageUtils.findSparkCtx().foreach(new AbstractFunction1<SparkContext, Void>() {
 
         @Override
@@ -202,7 +206,7 @@ public class DatahubSparkListener extends SparkListener {
 
         @Override
         public Void apply(SparkContext sc) {
-          log.debug("Application end event received for appId :" + sc.appName());
+          log.info("Application ended : {} {}", sc.appName(), sc.applicationId());
           AppStartEvent start = appDetails.remove(sc.appName());
           appPoolDetails.remove(sc.appName()).shutdown();
           appSqlDetails.remove(sc.appName());
@@ -313,7 +317,6 @@ public class DatahubSparkListener extends SparkListener {
             .map(x -> LineageUtils.getConsumer(x)).filter(Objects::nonNull).collect(Collectors.toList());
       } else {
         return Collections.emptyList();
-        //singletonList(LineageUtils.getConsumer(DATAHUB_EMITTER));
       }
 
     }

metadata-integration/java/spark-lineage/src/main/java/datahub/spark/consumer/impl/McpEmitter.java

@@ -28,6 +28,7 @@ public class McpEmitter implements LineageConsumer {
     if (emitter.isPresent()) {
       mcpws.stream().map(mcpw -> {
         try {
+          log.debug("emitting mcpw: " + mcpw);
           return emitter.get().emit(mcpw);
         } catch (IOException ioException) {
           log.error("Failed to emit metadata to DataHub", ioException);
@@ -35,7 +36,7 @@ public class McpEmitter implements LineageConsumer {
         }
       }).filter(Objects::nonNull).collect(Collectors.toList()).forEach(future -> {
         try {
-          future.get();
+          log.info(future.get().toString());
         } catch (InterruptedException | ExecutionException e) {
           // log error, but don't impact thread
           log.error("Failed to emit metadata to DataHub", e);

metadata-integration/java/spark-lineage/src/test/resources/org/apache/spark/log4j-defaults.properties

@@ -5,4 +5,5 @@ log4j.appender.console.target=System.out
 log4j.appender.console.layout=org.apache.log4j.PatternLayout
 log4j.appender.console.layout.ConversionPattern=%d{yy/MM/dd HH:mm:ss} %p %c{1}: %m%n
 
-log4j.logger.com.linkedin.datahub.lineage=DEBUG
+log4j.logger.datahub.spark=DEBUG
+log4j.logger.datahub.client.rest=DEBUG