Logstash Interview Questions

Checkout Vskills Interview questions with answers in Logstash to prepare for your next job role. The questions are submitted by professionals to help you to prepare for the Interview.    

Q.1 What is Logstash?

Logstash is an open source data collection engine having real-time pipelining capabilities. Logstash is sued to integrate data from different sources and normalize the data into destinations as per requirement.

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Q.2 What is use of Logstash?

Logstash is an open source tool for collecting, parsing, and storing logs for future use.

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Q.3 What is the role of Logstash forwarder?

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.

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Q.4 What is ELK Stack or Elastic Stack?

ELK stack expands to Elasticsearch, Logstash, and Kibana, when used together is known as an ELK stack.

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Q.5 What do you mean by Logs and Metrics in Logstash?

Logstash handle various types of logging data like web logs of Apache, and application logs like log4j for Java. It can capture many other log formats like syslog, networking and firewall logs, and more. It also offers secure log forwarding capabilities with Filebeat. It can collect metrics from Ganglia, collectd, NetFlow, JMX, and many other infrastructure and application platforms over TCP and UDP protocol.

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Q.6 How does Logstash work with the web?

Logstash work with the web by - transforming HTTP requests into events and creating events by polling HTTP endpoints on demand

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Q.7 Which Java version is required to install Logstash?

Logstash requires Java 8.

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Q.8 Which Java version is not supported by Logstash?

Java 9 is not supported.

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Q.9 Which Logstash plugin enables you to parse the unstructured log data into something structured and queryable?

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

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Q.10 What are the required elements in Logstash pipeline?

A Logstash pipeline has two required elements which are 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.

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Q.11 What is Filebeat in Logstash?

The Filebeat client is a lightweight tool to collect logs from files on the server and forwards these logs to Logstash instance for processing.

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Q.12 What is geoip plugin in Logstash?

The geoip plugin in Logstash is used to add locational data to logs. It looks up IP addresses, derives geographic location information from the addresses, and adds that location information to the logs

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Q.13 Can you explain how Logstash Works?

The Logstash event processing pipeline has three stages: inputs then filters and lastly 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.

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Q.14 What is Logstash?

Logstash is an open-source data processing pipeline that ingests, transforms, and sends data to various outputs.

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Q.15 What in Logstash can extract unstructured event data into fields using delimiters other than the Grok plugin?

The Dissect plugin in Logstash can extract unstructured event data into fields using delimiters

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Q.16 What are the key components of Logstash?

Logstash consists of input plugins, filter plugins, output plugins, and a central processing engine.

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Q.17 What do you understand by Inputs in Logstash?

Inputs in Logstash is used to get data into Logstash. Some of the more commonly-used inputs are: file (reads from a file on the filesystem), syslog(listens for syslog messages and parses them), redis (reads from a redis server) and beats(processes events sent by Filebeat)

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Q.18 What is an input plugin in Logstash?

An input plugin in Logstash is responsible for collecting data from various sources, such as logs or databases.

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Q.19 What do you understand by Filters in Logstash?

Filters are intermediary processing devices in the Logstash pipeline. Filters can be combined with conditionals to perform an action on an event if it meets certain criteria. Some Filters in Logstash are grok (to parse and structure arbitrary text), mutate( to rename, remove, replace, and modify fields in your events.), drop(to drop an event completely), clone( to make a copy of an event, possibly adding or removing fields.), etc.

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Q.20 Give examples of Logstash input plugins.

Examples include file, stdin, beats, kafka, jdbc, and many more, each designed for specific data sources.

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Q.21 What do you understand by Outputs in Logstash?

Outputs in Logstash 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 are elasticsearch (send event data to Elasticsearch), file (write event data to a file on disk), graphite (send event data to graphite), statsd (send event data to statsd)

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Q.22 What is a filter plugin in Logstash?

A filter plugin processes and transforms data received from input plugins before sending it to outputs.

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Q.23 What is Codecs in Logstash?

Codecs in Logstash are streamed filters which 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).

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Q.24 Provide examples of Logstash filter plugins.

Examples include grok, mutate, date, json, and geoip, which perform tasks like parsing, formatting, and enriching data.

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Q.25 Explain the Execution Model of Logstash?

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.

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Q.26 What is an output plugin in Logstash?

An output plugin is responsible for sending processed data to various destinations, like Elasticsearch or a file.

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Q.27 How many types of Logstash Configuration Files are there?

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.

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Q.28 Give examples of Logstash output plugins.

Examples include elasticsearch, stdout, file, http, and kafka, each tailored for specific data destinations.

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Q.29 List the syntax for a grok pattern in Logstash

The syntax for a grok pattern is %{SYNTAX:SEMANTIC}

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Q.30 How does Logstash handle data transformation?

Logstash uses filter plugins like grok and mutate to transform data by parsing, enriching, and altering its format.

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Q.31 Comments in the configuration file of Logstash starts with

A comment in the configuration file of Logstash starts with a # character, and does not need to be at the beginning of a line.

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Q.32 What is a Logstash pipeline?

A Logstash pipeline is a series of stages where data flows from input through filter plugins to output destinations.

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Q.33 If you need to run more than one pipeline in the same process in Logstash, the configuration file is called as

Logstash provides a way to run more than one pipeline in the same process through a configuration file called pipelines.yml.

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Q.34 What is the role of a Logstash configuration file?

The configuration file defines the input, filter, and output plugins, specifying how data should be processed.

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Q.35 Where should pipelines.yml be placed in Logstash

The pipelines.yml file must be placed in the path.settings folder in Logstash

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Q.36 How does Logstash handle data ingestion from multiple sources?

Logstash can configure multiple input plugins, each collecting data from a different source or file.

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Q.37 How you keep yourself updated of new trends in Logstash?

Logstash and log management is seeing newer development every year and I update myself by attending industry seminars, conferences as available online or offline.

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Q.38 What is the Elastic Stack, and how does Logstash fit in?

The Elastic Stack (formerly ELK Stack) includes Elasticsearch, Logstash, and Kibana, with Logstash handling data processing.

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Q.39 How do you see yourself in next five year in Logstash?

I foresee a bright future as I will gain more skills and knowledge in the domain of Logstash management by adding new technologies as needed by my organization.

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Q.40 Explain Logstash's role in log aggregation.

Logstash can aggregate logs from various sources, parse them, and send the structured data to Elasticsearch for storage and analysis.

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Q.41 What are your strengths as a Logstash professional?

As a Logstash professional I am having extensive experience on the new devops technologies as well as managing the Logstash. I also have the requisite managerial skills for managing team and achieve the assigned tasks.

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Q.42 How does Logstash handle data parsing using grok?

Logstash's grok filter plugin allows you to define custom patterns to extract structured data from unstructured log messages.

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Q.43 How do you prioritize Logstash related tasks?

Logstash management involves many tasks on a day to day basis. Tasks also need to be prioritized to accomplish the organizational goals as per the specified KPIs (key performance indicators). Prioritization of tasks is done on the basis of various factors like: the tasks relevance, urgency, cost involved and resource availability.

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Q.44 What is the purpose of Logstash's mutate filter plugin?

The mutate plugin enables field manipulation, renaming, and removal, allowing you to reshape data as needed.

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Q.45 How you manage your time for Logstash management?

Logstash management involves lots of tasks which need to be completed in a specific time frame. Hence time management is of utmost importance and is applied by: using to do lists, being aware of time wasters and optimizing work environment

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Q.46 What is Logstash's role in data enrichment using geoip?

The geoip filter plugin adds geographical information to events based on IP addresses, enhancing data with location data.

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Q.47 Why do you want the Logstash job?

I want the Logstash job as I am passionate about making companies more efficient by using new technologies and take stock of present technology portfolio to maximize their utility.

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Q.48 How does Logstash support date parsing and formatting?

Logstash's date filter plugin helps parse and format timestamps in various formats to ensure uniformity and readability.

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Q.49 What is Logstash's role in handling JSON data?

Logstash can parse, manipulate, and generate JSON data using filter plugins like json and json_encode.

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Q.50 How does Logstash handle data output to Elasticsearch?

Logstash's elasticsearch output plugin allows you to send processed data to Elasticsearch for indexing and search.

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Q.51 Explain how Logstash can handle data output to files.

Logstash can write processed data to files in various formats using the file output plugin, suitable for archiving or backup.

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Q.52 What is the role of the Logstash stdout output plugin?

The stdout plugin is mainly used for testing and debugging purposes, as it outputs processed data to the console.

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Q.53 How does Logstash handle data output to messaging systems like Kafka?

Logstash's kafka output plugin facilitates sending data to Apache Kafka, a distributed streaming platform.

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Q.54 What is Logstash's role in handling HTTP requests and responses?

The http output plugin allows Logstash to send data to HTTP endpoints, making it versatile for integrating with various services.

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Q.55 How can you install Logstash on different platforms?

Logstash can be installed on Linux, Windows, and macOS by downloading and configuring the appropriate package or archive.

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Q.56 What is the purpose of Logstash's startup options and flags?

Startup options and flags enable you to customize Logstash's behavior, such as specifying a configuration file or pipeline settings.

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Q.57 How does Logstash manage plugins and extensions?

Logstash's plugin management system, "bin/logstash-plugin," allows you to install, update, and manage plugins easily.

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Q.58 What are the common Logstash log files, and where are they located?

Common log files include the main Logstash log and pipeline-specific logs, typically found in the Logstash installation directory.

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Q.59 How can you troubleshoot Logstash configuration issues?

You can use the "config.test_and_exit" option to validate your Logstash configuration without running Logstash itself.

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Q.60 What is the role of Logstash's Dead Letter Queue (DLQ)?

The DLQ is used to store events that Logstash cannot process or send to their intended destinations, helping prevent data loss.

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Q.61 How can you monitor Logstash performance and health?

Tools like Logstash monitoring APIs, third-party solutions, and Kibana can be used to monitor Logstash's performance and status.

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Q.62 What is the purpose of Logstash's persistent queues?

Persistent queues help prevent data loss during failures by storing events on disk until they can be successfully processed.

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Q.63 How can you scale Logstash for high availability and load balancing?

Logstash can be scaled horizontally by running multiple instances and using load balancers to distribute data processing tasks.

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Q.64 What is the role of Logstash's conditionals in configuration?

Conditionals allow you to apply filters or outputs based on specific criteria, enabling flexible data processing workflows.

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Q.65 Explain the role of Logstash's multiline codec and filter.

The multiline codec and filter are used to handle multi-line log entries, grouping them into a single event for processing.

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Q.66 How does Logstash handle data encryption and security?

Logstash can encrypt data in transit and supports secure communication with external systems, enhancing data security.

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Q.67 What is the role of Logstash's grok patterns in data parsing?

Grok patterns are predefined regular expressions that simplify the extraction of structured data from unstructured logs.

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Q.68 How can you use environment variables in Logstash configuration?

Environment variables can be interpolated in the Logstash configuration file to make it more dynamic and portable.

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Q.69 What is the purpose of Logstash's drop filter plugin?

The drop filter allows you to discard events that meet specific conditions, useful for filtering out unwanted data.

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Q.70 How does Logstash handle data input from relational databases using JDBC?

Logstash's JDBC input plugin connects to relational databases, fetches data, and ingests it for further processing.

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Q.71 What is the role of Logstash's fingerprint filter plugin?

The fingerprint filter generates unique identifiers (hashes) for events based on specified fields, aiding in deduplication and tracking.

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Q.72 How does Logstash handle data input from messaging systems like RabbitMQ?

Logstash's rabbitmq input plugin allows you to consume data from RabbitMQ message queues.

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Q.73 What is Logstash's role in handling data input from cloud platforms like AWS S3?

Logstash can retrieve data from cloud storage services like AWS S3 using the s3 input plugin.

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Q.74 How can you parse and ingest XML data using Logstash?

Logstash can parse and process XML data using the xml filter plugin, making it suitable for working with XML-based logs.

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Q.75 What is the Logstash JDBC streaming filter plugin used for?

The JDBC streaming filter enables real-time data streaming from relational databases to Logstash for processing and analysis.

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Q.76 How does Logstash handle data input from various syslog sources?

Logstash supports data ingestion from syslog sources like rsyslog, syslog-ng, and Windows Event Logs using the syslog input plugin.

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Q.77 What is the role of the Logstash pipeline worker and batch size settings?

Pipeline workers and batch size settings determine how Logstash processes events in parallel, impacting performance and resource usage.

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Q.78 How does Logstash manage backpressure in data processing?

Logstash uses a backpressure mechanism to manage the flow of data when outputs are slower than the rate of data ingestion.

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Q.79 Explain the use of Logstash pipelines for data segregation.

Pipelines in Logstash allow you to separate and process different types of data or data from various sources independently.

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Q.80 What is the Logstash persistent queue's default behavior during data backup?

By default, the persistent queue attempts to write data to disk and acknowledges receipt to the input plugin, ensuring data durability.

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Q.81 How can you handle JSON array data using Logstash?

Logstash can parse and flatten JSON arrays into individual events using filter plugins like split and json.

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Q.82 What is the role of Logstash's translate filter plugin?

The translate filter maps values from one field to another based on predefined dictionaries, facilitating data enrichment.

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Q.83 How does Logstash support data input from cloud services like Azure Blob Storage?

Logstash can retrieve data from Azure Blob Storage using the azure_blob_storage input plugin.

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Q.84 What is the significance of Logstash's stdout codec configuration?

The stdout codec configures the format and layout of Logstash's console output for debugging and testing purposes.

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Q.85 How can you customize Logstash's error handling and logging?

Logstash allows you to configure error handling, logging levels, and destinations in its configuration file.

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Q.86 What is the purpose of Logstash's multiline filter in processing logs?

The multiline filter is used to combine log lines into a single event when logs span multiple lines, ensuring accurate parsing.

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Q.87 How does Logstash handle data input from cloud storage services like Google Cloud Storage?

Logstash supports data ingestion from Google Cloud Storage using the google_cloud_storage input plugin.

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Q.88 What is the role of Logstash's throttle filter plugin?

The throttle filter plugin limits the rate at which events are processed, helping prevent resource exhaustion during high loads.

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Q.89 How can you use Logstash's clone filter plugin?

The clone filter plugin allows you to duplicate events within the pipeline for parallel processing or storing in different destinations.

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Q.90 What is the purpose of Logstash's kv filter plugin?

The kv filter parses key-value pairs within a string and adds them as fields to the event, simplifying data extraction.

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Q.91 How does Logstash support data input from cloud services like Google Cloud Pub/Sub?

Logstash can consume data from Google Cloud Pub/Sub using the google_pubsub input plugin.

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Q.92 What is Logstash's role in handling data input from message brokers like Apache Pulsar?

Logstash can ingest data from message brokers like Apache Pulsar using the pulsar input plugin.

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Q.93 Explain how to use conditionals in Logstash's configuration.

Conditionals allow you to apply filters or outputs selectively based on event fields, tags, or other criteria.

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Q.94 How does Logstash handle data input from cloud platforms like AWS Kinesis?

Logstash supports data ingestion from AWS Kinesis data streams using the kinesis input plugin.

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Q.95 What is the purpose of Logstash's dissect filter plugin?

The dissect filter plugin allows for structured data extraction using predefined patterns, simplifying parsing tasks.

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Q.96 How does Logstash handle data input from cloud platforms like Google Cloud Bigtable?

Logstash can fetch data from Google Cloud Bigtable using the google_bigtable input plugin.

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Q.97 What is Logstash's role in handling data input from messaging systems like IBM MQ?

Logstash can consume messages from IBM MQ message queues using the ibmmq input plugin.

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Q.98 How can you use the Logstash translate filter plugin for data enrichment?

The translate filter maps values from source fields to target fields using dictionaries, enhancing event data.

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Q.99 How does Logstash handle data input from cloud storage services like Microsoft Azure Data Lake Storage?

Logstash supports data ingestion from Azure Data Lake Storage using the azure_data_lake_storage input plugin.

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Q.100 What is the role of the Logstash metrics filter plugin?

The metrics filter plugin gathers performance metrics about Logstash and its pipelines, aiding in monitoring and troubleshooting.

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Q.101 How does Logstash handle data input from cloud services like AWS SQS (Simple Queue Service)?

Logstash can fetch data from AWS SQS using the sqs input plugin, facilitating the consumption of queue messages.

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Q.102 What is the purpose of Logstash's truncate filter plugin?

The truncate filter truncates field values to a specified length, useful for data reduction or ensuring field consistency.

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Q.103 How does Logstash handle data input from cloud platforms like Google Cloud Firestore?

Logstash supports data ingestion from Google Cloud Firestore using the google_firestore input plugin.

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Q.104 What is Logstash's role in handling data input from cloud services like AWS SNS (Simple Notification Service)?

Logstash can process notifications from AWS SNS topics using the sns input plugin.

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Q.105 How can you use the Logstash metrics filter plugin to monitor pipeline performance?

The metrics filter plugin collects statistics about events processed by each pipeline, which can be visualized for monitoring.

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Q.106 What is the purpose of Logstash's urldecode filter plugin?

The urldecode filter decodes URL-encoded strings, making them more human-readable and facilitating further processing.

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Q.107 How does Logstash handle data input from cloud platforms like Google Cloud Pub/Sub Lite?

Logstash can consume data from Google Cloud Pub/Sub Lite using the google_pubsub_lite input plugin.

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Q.108 What is Logstash's role in handling data input from cloud storage services like AWS DynamoDB?

Logstash can ingest data from AWS DynamoDB streams using the dynamodb input plugin.

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Q.109 How can you use the Logstash prune filter plugin to remove fields selectively?

The prune filter allows you to remove specified fields or fields matching certain conditions from events.

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Q.110 Explain how to configure Logstash to handle data input from the HTTP protocol.

Logstash can act as an HTTP server using the http input plugin, allowing you to receive data via HTTP requests.

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