Monitoring with Spark History Server in Apache Spark

Introduction

The Spark History Server helps you see what happened during your Spark jobs after they finish. It shows details about job progress and performance so you can understand and improve your work.

You want to check how long each part of your Spark job took after it finished.

You need to find out why a Spark job was slow or failed.

You want to keep a record of past Spark jobs to compare performance over time.

You want to share Spark job details with your team without rerunning the job.

You want a simple web interface to explore Spark job logs and stages.

Syntax

Apache Spark

spark.eventLog.enabled           true
spark.eventLog.dir               hdfs://path/to/eventlog
spark.history.fs.logDirectory   hdfs://path/to/eventlog
spark.history.ui.port           18080

Enable event logging in Spark to save job info for the History Server.

Set the directory where Spark saves event logs; the History Server reads from here.

Examples

This turns on event logging so Spark saves job info.

Apache Spark

spark.eventLog.enabled true

Save event logs locally in the /tmp/spark-events folder.

Apache Spark

spark.eventLog.dir file:/tmp/spark-events

Tell the History Server where to find the saved event logs.

Apache Spark

spark.history.fs.logDirectory file:/tmp/spark-events

Set the web port for the History Server UI to 18080.

Apache Spark

spark.history.ui.port 18080

Sample Program

This configuration enables event logging, sets the local directory for logs, and starts the Spark History Server on port 18080. You can then open your browser to see past Spark job details.

Apache Spark

# In spark-defaults.conf or spark-submit options
spark.eventLog.enabled true
spark.eventLog.dir file:/tmp/spark-events
spark.history.fs.logDirectory file:/tmp/spark-events
spark.history.ui.port 18080

# Start Spark History Server
$SPARK_HOME/sbin/start-history-server.sh

# Access the UI at http://localhost:18080

Important Notes

Make sure the event log directory is accessible by both Spark jobs and the History Server.

Event logging can add some overhead; use it mainly for debugging or monitoring.

History Server UI is read-only; it does not affect running Spark jobs.

Summary

Spark History Server shows details of completed Spark jobs through saved event logs.

Enable event logging and set the log directory for the History Server to read.

Start the History Server and open its web UI to monitor past Spark job performance.

Practice

1. What is the main purpose of the Spark History Server in monitoring Spark applications?

easy

A. To monitor real-time streaming data only

B. To view details of completed Spark jobs using saved event logs

C. To configure Spark cluster resources dynamically

D. To submit new Spark jobs to the cluster

Solution

1. Step 1: Understand Spark History Server role

   The Spark History Server reads event logs from completed jobs to provide detailed information about them.

2. Step 2: Differentiate from other Spark components

   Unlike job submission or real-time monitoring, it focuses on past job performance using saved logs.

3. Final Answer:

   To view details of completed Spark jobs using saved event logs -> Option B

4. Quick Check:

   Spark History Server = View completed job details [OK]

Hint: History Server shows past jobs, not live or submission tasks [OK]

Common Mistakes:

• Confusing History Server with job submission tools
• Thinking it monitors only live streaming jobs
• Assuming it manages cluster resources

2. Which Spark configuration property must be set to enable event logging for the History Server?

easy

A. spark.sql.shuffle.partitions

B. spark.history.fs.logDirectory

C. spark.executor.memory

D. spark.eventLog.enabled

Solution

1. Step 1: Identify event logging property

   The property spark.eventLog.enabled controls whether Spark saves event logs for completed jobs.

2. Step 2: Differentiate from other configs

   spark.history.fs.logDirectory sets log location, not enabling logging; others relate to memory or shuffle partitions.

3. Final Answer:

   spark.eventLog.enabled -> Option D

4. Quick Check:

   Enable event logging = spark.eventLog.enabled [OK]

Hint: Enable event logging with spark.eventLog.enabled true [OK]

Common Mistakes:

• Confusing log directory with enabling logging
• Choosing unrelated Spark properties
• Assuming memory or shuffle configs enable logging

3. Given the configuration:

spark.eventLog.enabled=true
spark.history.fs.logDirectory=/tmp/spark-events

What will happen after a Spark job finishes?

medium

A. Event logs will be saved to /tmp/spark-events for History Server access

B. No event logs will be saved because logging is disabled

C. Logs will be saved but History Server cannot read them

D. Spark job will fail due to invalid log directory

Solution

1. Step 1: Check event logging enabled

   Since spark.eventLog.enabled=true, Spark saves event logs after job completion.

2. Step 2: Confirm log directory setting

   The logs are saved to /tmp/spark-events, which the History Server reads to show job details.

3. Final Answer:

   Event logs will be saved to /tmp/spark-events for History Server access -> Option A

4. Quick Check:

   Logging enabled + valid directory = logs saved [OK]

Hint: True eventLog.enabled + valid directory = logs saved [OK]

Common Mistakes:

• Assuming logs are not saved if directory is custom
• Thinking logging is off despite true setting
• Believing job fails due to log directory path

4. You started the Spark History Server but see no jobs listed in the UI. Which is the most likely cause?

medium

A. The Spark History Server UI port is blocked by firewall

B. Spark jobs are still running and not completed

C. spark.eventLog.enabled is set to false or event logs are missing

D. The Spark History Server service is running on the wrong machine

Solution

1. Step 1: Check event logging status

   If spark.eventLog.enabled is false or event logs are missing, History Server has no data to show.

2. Step 2: Understand UI port and job status

   Firewall blocking UI port prevents access but not empty job list; running jobs don't appear until finished.

3. Final Answer:

   spark.eventLog.enabled is set to false or event logs are missing -> Option C

4. Quick Check:

   No jobs in UI = logging off or missing logs [OK]

Hint: No jobs shown? Check if event logging is enabled [OK]

Common Mistakes:

• Assuming firewall blocks job list display
• Expecting running jobs to appear in History Server
• Thinking server machine location affects job visibility

5. You want to monitor completed Spark jobs on a cluster. Which sequence of steps correctly sets up the Spark History Server?

hard

A. Enable event logging, set log directory, start History Server, open UI

B. Start History Server, submit jobs, enable event logging, open UI

C. Set log directory, open UI, enable event logging, start History Server

D. Submit jobs, start History Server, set log directory, enable event logging

Solution

1. Step 1: Enable event logging and set log directory

   First, enable spark.eventLog.enabled=true and set spark.history.fs.logDirectory so logs are saved properly.

2. Step 2: Start History Server and open UI

   Then start the History Server to read logs and open its web UI to monitor completed jobs.

3. Final Answer:

   Enable event logging, set log directory, start History Server, open UI -> Option A

4. Quick Check:

   Enable logging + set dir + start server + open UI = monitor jobs [OK]

Hint: Enable logging first, then start History Server and open UI [OK]

Common Mistakes:

• Starting History Server before enabling logging
• Opening UI before logs exist
• Setting log directory after starting server