Flume Troubleshooting | Flume Known Issues & Its Compatibility

1. Objective – Flume Troubleshooting

As we know, while working with Flume, there may problems occur. So, in this blog, we will learn steps to Flume Troubleshooting. Also, we will see how to handle agent failures in flume know issue. Moreover, we will learn about its compatibility factor and Flume Troubleshooting FAQ.

So, let’s start Apache Flume Troubleshooting.

Apache Flume Troubleshooting | Flume Know Issues

Apache Flume Troubleshooting | Flume Know Issues

2. Apache Flume Troubleshooting

a. Handling Agent Failures

Basically, all the flows hosted on that agent are aborted, if the Flume agent goes down. However, as soon as the agent is restarted, then the flow will resume. By using file channel or another stable channel, the flow will resume processing events where it left off. Also, we have an option to migrate the database to another hardware and set up a new Flume agent that can resume processing the events saved in the DB, if the agent can’t be restarted on the same hardware. In addition, to move the Flume agent to another host database HA futures can be leveraged.
Read about Apache Flume Architecture in detail

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3. Apache Flume Compatibility

i. HDFS

However, Flume Currently supports HDFS 0.20.2 and 0.23.

ii. AVRO

Not supportable yet. But, might possible in Future.

iii. Additional version requirements

Not supportable yet. But, might possible in Future.

iv. Tracing

Not supportable yet. But, might possible in Future.

v. More Sample Configs

Not supportable yet. But, might possible in Future.
Read about Apache Flume Sink & Apache Flume Channel

Hadoop Quiz

4. Flume Troubleshooting FAQ

a. Configuration and Settings

i. How can I tell if I have a library loaded when flume runs?
Ans.  Basically, we can run flume classpath to see the jars and the order Flume is attempting to load them in, from the command line.
ii. How can I tell if a plugin has been loaded by a flume node?
Ans. However, we can look at the node’s plugin status web page – http://<master>:35871/extension.jsp. Apart from that, we can also look at the logs.
iii. Why does the master need to have plugins installed?
Ans. In order to validate configs it is sending to nodes, the master needs to have plugins installed.
iv. How can I tell if a plugin has been loaded by a flume master?
Ans. However, we can look at the node’s plugin status web page – http://<master>:35871/masterext.jsp
Apart from that, we can also look at the logs.
Let’s read about Apache Flume Event Serializers & Apache Flume Channel Selectors

b. Operations

i. I lose my configurations when I restart the master. What’s happening?
Ans. Basically, the default path to write information is set to this value. Also, we may want to override this to a place will be persistent across reboots. like:  /var/lib/flume.
<property>
<name>flume.master.zk.logdir</name>
<value>/tmp/flume-$
Unknown macro: {user.name}
-zk</value>
<description>The base directory in which the ZBCS stores data.</description>
</property>
ii. How can I get metrics from a node?
Ans. Basically, to debug and to see progress Flume nodes report metrics which we can use. Moreover, we can look at a node’s status web page by pointing our browser to port 35862. (http://<node>:35862).
iii. How can I tell if data is arriving at the collector?
Ans. However, the source counters will increment on the node’s metric page while events arrive at a collector. For example, if we have a node called foo1 we should see the following fields have growing values when we refresh the page.
LogicalNodeManager.foo1.source.CollectorSource.number of bytes
LogicalNodeManager.foo1.source.CollectorSource.number of events.
iv. How can I tell if data is being written to HDFS?
Ans. Basically, in HDFS, Data doesn’t “arrive”  until the file is closed or certain size thresholds are met. Although, the sink counters on the collector’s metric page will be incrementing since events are written to HDFS. However,  in particular, look for fields that match the following names:
*.Collector.GunzipDecorator.UnbatchingDecorator.AckChecksumChecker.InsistentAppend.append*
*.appendSuccesses are successful writes.
Follow this link to know about data transfer from Flume to HDFS

5. Conclusion

As a result, we have seen the possible Flume Troubleshooting steps or flume known issues with Flume Compatibilities. Also, we have discussed some important FAQs, that will help if any problem occurs. Thus, we hope this really helps you. Still, if you have any query, feel free to ask in a comment section. However, we will surely get back to you regarding same.

For reference

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