Installation and setup in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Elasticsearch service status check

After installing Elasticsearch on a Linux system, you run the command systemctl status elasticsearch. What output indicates that Elasticsearch is running correctly?

A Failed to start elasticsearch.service: Unit elasticsearch.service not found.

B Active: inactive (dead) since Mon 2024-06-10 10:00:00 UTC; 5min ago

C Active: active (running) since Mon 2024-06-10 10:00:00 UTC; 5min ago

D Active: activating (start) since Mon 2024-06-10 10:00:00 UTC; 5min ago

💡 Hint

Look for the word 'active' and 'running' in the status output.

The status output shows 'active (running)' when Elasticsearch is successfully running as a service.

🧠 Conceptual

intermediate

Default Elasticsearch port

What is the default port number Elasticsearch listens on for HTTP requests after installation?

A 9200

B 9300

C 8080

D 5601

💡 Hint

This port is used to send REST API requests to Elasticsearch.

Elasticsearch listens on port 9200 by default for HTTP REST API calls.

🔧 Debug

advanced

Elasticsearch JVM memory setting error

You set ES_JAVA_OPTS="-Xms2g -Xmx2g" in your environment but Elasticsearch fails to start. Which option shows a likely cause?

A The system has only 1GB of RAM available, so Elasticsearch cannot allocate 2GB.

B The syntax for ES_JAVA_OPTS is incorrect; it should be <code>ES_JAVA_OPTS=-Xms2g -Xmx2g</code> without quotes.

C Elasticsearch requires at least 4GB of RAM to start, so 2GB is too low.

D The environment variable ES_JAVA_OPTS is ignored; memory must be set in elasticsearch.yml.

💡 Hint

Check if the system has enough memory to allocate the requested heap size.

If the system has less RAM than the requested JVM heap size, Elasticsearch will fail to start.

📝 Syntax

advanced

Correct syntax for Elasticsearch repository installation on Debian

Which command correctly adds the Elasticsearch GPG key and repository on a Debian-based system?

A sudo rpm --import https://artifacts.elastic.co/GPG-KEY-elasticsearch && sudo yum-config-manager --add-repo https://artifacts.elastic.co/packages/8.x/yum stable main && sudo yum update

B curl -fsSL https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add - && sudo sh -c 'echo "deb https://artifacts.elastic.co/packages/8.x/apt stable main" > /etc/apt/sources.list.d/elastic-8.x.list' && sudo apt update

C sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys https://artifacts.elastic.co/GPG-KEY-elasticsearch && sudo add-apt-repository 'deb https://artifacts.elastic.co/packages/8.x/apt stable main' && sudo apt update

D wget -qO - https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add - && sudo sh -c 'echo "deb https://artifacts.elastic.co/packages/8.x/apt stable main" > /etc/apt/sources.list.d/elastic-8.x.list' && sudo apt update

💡 Hint

Debian uses apt-key and sources.list.d for repositories.

Option D correctly downloads the GPG key, adds it, writes the repo to sources.list.d, and updates apt.

🚀 Application

expert

Elasticsearch cluster initial master nodes setting

You are setting up a new Elasticsearch cluster with 3 nodes. To avoid split-brain issues, which setting must you add to elasticsearch.yml on each node before starting the cluster?

A discovery.seed_hosts: ["node1", "node2", "node3"]

B cluster.initial_master_nodes: ["node1", "node2", "node3"]

C node.master: true

D cluster.name: my-cluster

💡 Hint

This setting tells Elasticsearch which nodes can be elected as master during the first cluster formation.

The cluster.initial_master_nodes setting is required on new clusters to specify the initial master-eligible nodes and prevent split-brain.

Practice

1. What is the first step to install Elasticsearch on your computer?

easy

A. Run the Elasticsearch service

B. Configure the Elasticsearch index

C. Access http://localhost:9200/ to test

D. Download and extract the Elasticsearch package

Solution

1. Step 1: Understand the installation process

   The first step is to get the Elasticsearch files by downloading and extracting them to your machine.

2. Step 2: Recognize the order of setup steps

   Running the service and testing come after downloading and extracting the files.

3. Final Answer:

   Download and extract the Elasticsearch package -> Option D

4. Quick Check:

   First step = Download and extract [OK]

Hint: Start by getting the files before running anything [OK]

Common Mistakes:

• Trying to run Elasticsearch before downloading
• Testing setup before starting the service
• Configuring index before installation

2. Which command correctly starts Elasticsearch on a Unix-like system after installation?

easy

A. ./bin/elasticsearch

B. start elasticsearch

C. run elasticsearch.exe

D. elasticsearch start

Solution

1. Step 1: Identify the correct executable path

   On Unix-like systems, Elasticsearch is started by running the executable in the 'bin' folder with './bin/elasticsearch'.

2. Step 2: Eliminate incorrect commands

   Commands like 'start elasticsearch' or 'elasticsearch start' are not valid shell commands for starting Elasticsearch directly.

3. Final Answer:

   ./bin/elasticsearch -> Option A

4. Quick Check:

   Unix start command = ./bin/elasticsearch [OK]

Hint: Use ./bin/elasticsearch to start on Unix systems [OK]

Common Mistakes:

• Using Windows commands on Unix
• Omitting './' before the executable
• Trying to run non-existent commands

3. After starting Elasticsearch, what is the expected output of running curl http://localhost:9200/?

medium

A. {"name":"your-node-name","cluster_name":"elasticsearch","version":{"number":"8.0.0"},"tagline":"You Know, for Search"}

B. Error: Connection refused

C. 404 Not Found

D. Elasticsearch service stopped

Solution

1. Step 1: Understand the curl command purpose

   The curl command requests the root URL of Elasticsearch, which returns JSON with node and cluster info.

2. Step 2: Recognize the expected JSON response

   The response includes keys like 'name', 'cluster_name', 'version', and 'tagline' confirming the service is running.

3. Final Answer:

   {"name":"your-node-name","cluster_name":"elasticsearch","version":{"number":"8.0.0"},"tagline":"You Know, for Search"} -> Option A

4. Quick Check:

   curl root URL returns JSON info [OK]

Hint: curl localhost:9200 returns JSON if Elasticsearch runs [OK]

Common Mistakes:

• Expecting plain text instead of JSON
• Not starting Elasticsearch before curl
• Using wrong URL or port

4. You tried to start Elasticsearch but got the error: "Address already in use". What is the most likely cause?

medium

A. You did not download the package

B. Elasticsearch is not installed

C. Another service is using port 9200

D. Your firewall is blocking Elasticsearch

Solution

1. Step 1: Interpret the error message

   "Address already in use" means the network port Elasticsearch wants to use (default 9200) is busy.

2. Step 2: Identify the cause of port conflict

   Another program or service is likely running on port 9200, preventing Elasticsearch from binding to it.

3. Final Answer:

   Another service is using port 9200 -> Option C

4. Quick Check:

   Port conflict error = Another service using port [OK]

Hint: Check if port 9200 is busy before starting Elasticsearch [OK]

Common Mistakes:

• Assuming Elasticsearch is not installed
• Ignoring port conflicts
• Blaming firewall without checking ports

5. You want to automate testing if Elasticsearch is running after setup. Which script snippet correctly checks the service by using curl and exits with code 0 if successful?

hard

A. curl http://localhost:9200/ && echo 'Running' || echo 'Stopped'

B. curl -s http://localhost:9200/ | grep -q 'You Know, for Search' && exit 0 || exit 1

C. curl -X POST http://localhost:9200/ && exit 0

D. curl http://localhost:9200/_search && exit 1

Solution

1. Step 1: Understand the test goal

   The script should silently check Elasticsearch root URL and confirm the expected tagline text.

2. Step 2: Analyze each option's behavior

   curl -s http://localhost:9200/ | grep -q 'You Know, for Search' && exit 0 || exit 1 uses curl quietly (-s), searches for the tagline, and exits 0 if found, else 1. This correctly tests service availability.

3. Final Answer:

   curl -s http://localhost:9200/ | grep -q 'You Know, for Search' && exit 0 || exit 1 -> Option B

4. Quick Check:

   Silent curl + grep tagline + exit code 0 if found [OK]

Hint: Use curl with grep for tagline, exit 0 if found [OK]

Common Mistakes:

• Using POST instead of GET for root URL
• Not checking output content
• Exiting with wrong code on success