Logstash Interview Questions And Answers

Logstash Interview Questions And Answers. Here Coding compiler sharing a list of 20 Logstash questions. These questions were asked in various Logstash interviews and prepared by Logstash experts. All the best for your future and happy learning.

Logstash Interview Questions

  1. What is Logstash? Explain?
  2. What is Logstash used for?
  3. What does Logstash forwarder do?
  4. What is ELK Stack (Elastic Stack)?
  5. What is the Power of Logstash?
  6. What are Logs and Metrics in Logstash?
  7. How does Logstash work with the web?
  8. Which Java version is required to install Logstash?
  9. What are the two required elements in Logstash pipeline?
  10. What is Filebeat?

Logstash Interview Questions And Answers

1) What is Logstash? Explain?

A) Logstash is an open source data collection engine with real-time pipelining capabilities. Logstash can dynamically unify data from disparate sources and normalize the data into destinations of your choice. Cleanse and democratize all your data for diverse advanced downstream analytics and visualization use cases.

2) What is Logstash used for?

A) Logstash is an open source tool for collecting, parsing, and storing logs for future use. Kibana 3 is a web interface that can be used to search and view the logs that Logstash has indexed. Both of these tools are based on Elasticsearch.

3) What does Logstash forwarder do?

A) Filebeat is based on the Logstash Forwarder source code and replaces Logstash Forwarder as the method to use for tailing log files and forwarding them to Logstash. The registry file, which stores the state of the currently read files, was changed.

4) What is ELK Stack (Elastic Stack)?

A) Elasticsearch, Logstash, and Kibana, when used together is known as an ELK stack.

5) What is the Power of Logstash?

A) The ingestion workhorse for Elasticsearch and more – Horizontally scalable data processing pipeline with strong Elasticsearch and Kibana synergy

Pluggable pipeline architecture – Mix, match, and orchestrate different inputs, filters, and outputs to play in pipeline harmony

Community-extensible and developer-friendly plugin ecosystem – Over 200 plugins available, plus the flexibility of creating and contributing your own

6) What are Logs and Metrics in Logstash?

A) Logs and Metrics – Logstash handle all types of logging data.

Easily ingest a multitude of web logs like Apache, and application logs like log4j for Java
Capture many other log formats like syslog, networking and firewall logs, and more
Enjoy complimentary secure log forwarding capabilities with Filebeat
Collect metrics from Ganglia, collectd, NetFlow, JMX, and many other infrastructure and application platforms over TCP and UDP

7) How does Logstash work with the web?

A) Transform HTTP requests into events

  • Consume from web service firehoses like Twitter for social sentiment analysis
  • Webhook support for GitHub, HipChat, JIRA, and countless other applications
  • Enables many Watcher alerting use cases
  • Create events by polling HTTP endpoints on demand
  • Universally capture health, performance, metrics, and other types of data from web application interfaces
  • Perfect for scenarios where the control of polling is preferred over receiving

8) Which Java version is required to install Logstash?

A) Logstash requires Java 8. Java 9 is not supported.

9) What are the two required elements in Logstash pipeline?

A) A Logstash pipeline has two required elements, input and output, and one optional element, filter. The input plugins consume data from a source, the filter plugins modify the data as you specify, and the output plugins write the data to a destination.

10) What is Filebeat?

A) The Filebeat client is a lightweight, resource-friendly tool that collects logs from files on the server and forwards these logs to your Logstash instance for processing.

Filebeat is designed for reliability and low latency. Filebeat has a light resource footprint on the host machine, and the Beats input plugin minimizes the resource demands on the Logstash instance.

Elasticsearch Logstash Interview Questions

11) What is grok filter plugin?

A) The grok filter plugin enables you to parse the unstructured log data into something structured and queryable.

Because the grok filter plugin looks for patterns in the incoming log data, configuring the plugin requires you to make decisions about how to identify the patterns that are of interest to your use case.

12) What is geoip plugin?

A) geoip plugin looks up IP addresses, derives geographic location information from the addresses, and adds that location information to the logs

13) How do you read data from a Twitter Feed?

A) To add a Twitter feed, you use the twitter input plugin. To configure the plugin, you need several pieces of information:

A consumer key, which uniquely identifies your Twitter app.
A consumer secret, which serves as the password for your Twitter app.
One or more keywords to search in the incoming feed. The example shows using “cloud” as a keyword, but you can use whatever you want.
An oauth token, which identifies the Twitter account using this app.
An oauth token secret, which serves as the password of the Twitter account.

14) Can you explain how Logstash Works?

A) The Logstash event processing pipeline has three stages: inputs -> filters -> outputs. Inputs generate events, filters modify them, and outputs ship them elsewhere. Inputs and outputs support codecs that enable you to encode or decode the data as it enters or exits the pipeline without having to use a separate filter.

15) What are Inputs in Logstash?

A) You use inputs to get data into Logstash.

Some of the more commonly-used inputs are: file, syslog, redis, and beats.

file: reads from a file on the filesystem, much like the UNIX command tail -0F
syslog: listens on the well-known port 514 for syslog messages and parses according to the RFC3164 format
redis: reads from a redis server, using both redis channels and redis lists. Redis is often used as a “broker” in a centralized Logstash installation, which queues Logstash events from remote Logstash “shippers”.
beats: processes events sent by Filebeat.

16) What are Filters in Logstash?

A) Filters are intermediary processing devices in the Logstash pipeline. You can combine filters with conditionals to perform an action on an event if it meets certain criteria. Some useful filters include:

grok: parse and structure arbitrary text. Grok is currently the best way in Logstash to parse unstructured log data into something structured and queryable. With 120 patterns built-in to Logstash, it’s more than likely you’ll find one that meets your needs!

mutate: perform general transformations on event fields. You can rename, remove, replace, and modify fields in your events.

drop: drop an event completely, for example, debug events.

clone: make a copy of an event, possibly adding or removing fields.

geoip: add information about geographical location of IP addresses (also displays amazing charts in Kibana!)

17) What are Outputs in Logstash?

A) Outputs are the final phase of the Logstash pipeline. An event can pass through multiple outputs, but once all output processing is complete, the event has finished its execution. Some commonly used outputs include:

elasticsearch: send event data to Elasticsearch. If you’re planning to save your data in an efficient, convenient, and easily queryable format.

file: write event data to a file on disk.

graphite: send event data to graphite, a popular open source tool for storing and graphing metrics.

statsd: send event data to statsd, a service that “listens for statistics, like counters and timers, sent over UDP and sends aggregates to one or more pluggable backend services”. If you’re already using statsd, this could be useful for you!

18) What are Codecs in Logstash?

A) Codecs are basically streamed filters that can operate as part of an input or output. Codecs enable you to easily separate the transport of your messages from the serialization process. Popular codecs include json, msgpack, and plain (text).

json: encode or decode data in the JSON format.

multiline: merge multiple-line text events such as java exception and stacktrace messages into a single event.

19) Explain the Execution Model of Logstash?

A) The Logstash event processing pipeline coordinates the execution of inputs, filters, and outputs.

Each input stage in the Logstash pipeline runs in its own thread. Inputs write events to a central queue that is either in memory (default) or on disk.

Each pipeline worker thread takes a batch of events off this queue, runs the batch of events through the configured filters, and then runs the filtered events through any outputs.

20) How many types of Logstash Configuration Files are there?

A) Logstash has two types of configuration files: pipeline configuration files, which define the Logstash processing pipeline, and settings files, which specify options that control Logstash startup and execution.

Source: Logstash Documentation


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