Saturday, December 12, 2020

What does "enable_table_replication" do internally in Hbase replication?

Goal:

This article explains what does the command "enable_table_replication" do internally in Hbase replication by looking into the source code.

It also explains the difference between below 2 commands which are shown on different articles.

hbase shell> enable_table_replication "t1"

vs.

hbase shell> disable 't1'
hbase shell> alter 't1', {NAME => 'column_family_name', REPLICATION_SCOPE => '1'}
hbase shell> enable 't1'

Friday, December 11, 2020

Hbase master failed to start with error "java.io.IOException: Timedout 300000ms waiting for namespace table to be assigned"

Symptom:

Hbase master failed to start with error "java.io.IOException: Timedout 300000ms waiting for namespace table to be assigned".

It could happen when starting or switching to master. 

Sample error messages are:

2000-01-01 01:01:01,999 FATAL [myhost:16000.activeMasterManager] master.HMaster: Unhandled exception. Starting shutdown.
java.io.IOException: Timedout 300000ms waiting for namespace table to be assigned
at org.apache.hadoop.hbase.master.TableNamespaceManager.start(TableNamespaceManager.java:104)
at org.apache.hadoop.hbase.master.HMaster.initNamespace(HMaster.java:1005)
at org.apache.hadoop.hbase.master.HMaster.finishActiveMasterInitialization(HMaster.java:799)
at org.apache.hadoop.hbase.master.HMaster.access$500(HMaster.java:191)
at org.apache.hadoop.hbase.master.HMaster$1.run(HMaster.java:1783)
at java.lang.Thread.run(Thread.java:745)

Or

2000-01-01 01:01:01,999 FATAL [myhost:16000.activeMasterManager] master.HMaster: Failed to become active master
java.io.IOException: Timedout 300000ms waiting for namespace table to be assigned
at org.apache.hadoop.hbase.master.TableNamespaceManager.start(TableNamespaceManager.java:104)
at org.apache.hadoop.hbase.master.HMaster.initNamespace(HMaster.java:1005)
at org.apache.hadoop.hbase.master.HMaster.finishActiveMasterInitialization(HMaster.java:799)
at org.apache.hadoop.hbase.master.HMaster.access$500(HMaster.java:191)
at org.apache.hadoop.hbase.master.HMaster$1.run(HMaster.java:1783)
at java.lang.Thread.run(Thread.java:745)

Hbase replication cheat sheet

 Goal:

This article records the common commands and issues for hbase replication.


Friday, January 31, 2020

Hands-on MKE(MapR Kubernetes Ecosystem ) 1.0 release

Goal:

【Note:MKE is no longer available so below MapR Doc links are invalid. 】

HPE Ezmeral Container Platform is where Kubernetes operators will be made available.】

MKE(MapR Kubernetes Ecosystem ) 1.0 has been released.
Basically it puts Spark and Drill into Kubernetes environment in this release.
Below is the architecture from the documentation Operators and Compute Spaces

This article shares the step-by-step commands used to install and configure a MKE 1.0 env.

Thursday, December 12, 2019

How to use nodeSelector to constrain POD csi-controller-kdf-0 to only be able to run on particular Node(s)

Goal:

This article explains how to use nodeSelector to constrain POD csi-controller-kdf-0 to only be able to run on particular Node(s).

How to create a MapR PACC using mapr-setup.sh to submit a Spark sample job

Goal:

This article shares the detailed steps on how to create a MapR Persistent Application Client Container(PACC) using mapr-setup.sh to submit a Spark sample job towards a secured MapR cluster.

Friday, December 6, 2019

Spark Streaming sample scala code for different sources

Goal:

This article shares some sample Spark Streaming scala code for different sources -- socket text, text files in MapR-FS directory, kafka broker and MapR Event Store for Apache Kafka(MapR Streams).
These are wordcount code which can be run directly from spark-shell.

Wednesday, December 4, 2019

How to mount a PersistentVolume for Static Provisioning using MapR CSI in GKE

Goal:

This article explains the detailed steps on how to mount a PersistentVolume for Static Provisioning using MapR Container Storage Interface(CSI) in Google Kubernetes Engine(GKE).

How to submit REST requests to a distributed Kafka Connect cluster

Goal:

This article shares the examples of curl commands to submit REST requests to a distributed Kafka Connect cluster.

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