WebHCat

Kevin Feasel

2017-03-08

Hadoop

Jiang Mouren has a two-parter on WebHCat.  First, how it works:

SSH shell/Oozie hive action directly interact with YARN for HIVE execution where as Program using HdInsight Jobs SDK/ADF (Azure Data Factory) uses WebHCat REST interface to submit the jobs.

WebHCat is a REST interface for remote jobs (Hive, Pig, Scoop, MapReduce) execution. WebHCat translates the job submission requests into YARN applications and reports the status based on the YARN application status. WebHCat results are coming from YARN and troubleshooting some of them needs to go to YARN.

Then, how to debug issues:

2.1.2. WebHCat times out

HDInsight Gateway times out responses which take longer than 2Minutes resulting in “502 BadGateway”. WebHCat queries YARN services for job status and if they take longer than the request might timeout.

When this happens collect the following logs for further investigation:

/var/log/webchat. Typical contents of directory will be like

  • webhcat.log is the log4j log to which server writes logs
  • webhcat-console.log is stdout of server is started.
  • webhcat-console-error.log is stderr of server process

NOTE: webhcat.log will roll-over daily hence files like webhcat.log.YYYY-MM-DD will also present. For logs to a specific time range make sure that appropriate file is selected.

Because HDInsight doesn’t support WebHDFS, WebHCat is the primary method for cluster access, so it’s good to know.

Related Posts

Replicating Data In HDFS Between Clusters

Murali Ramasami and Niru Anisetti have an article showing how to use the Hortonworks Data Lifecycle Manager to set up replication between two Hadoop clusters: Data Lifecycle Manager (DLM) delivers on the promise of location-agnostic, secure replication by encapsulating and copying data seamlessly across physical private storage and public cloud environments. This empowers businesses to […]

Read More

Installing Confluent Platform On Windows

Niels Berglund shows how to install Confluent Platform (the Confluent branded version of Apache Kafka) on a Windows machine using the Windows Subsystem for Linux: WSL is primarily aimed at developers, and it allows you to run Linux environments directly on Windows in a native format and without the overhead of a virtual machine. Let us […]

Read More

Categories

March 2017
MTWTFSS
« Feb Apr »
 12345
6789101112
13141516171819
20212223242526
2728293031