Consul 1.15 Practice Questions 1 — 50 Questions

Question 1

Where can you define health checks in Consul? (Select THREE)

Accepted Answer

Agent configuration files. Checks can be defined in configuration files, via the HTTP API, or within a service definition.

Answer

Consul UI

Answer

Consul KV store

Question 2

Which HTTP method is used to create or update a key in the Consul KV store?

Accepted Answer

PUT. The PUT method is the standard HTTP verb used for key creation and updates in the Consul API.

Answer

GET

Answer

DELETE

Answer

POST

Question 3

When using Consul KV for distributed locking, why is it recommended to use a session?

Accepted Answer

It allows for TTL-based automatic lock release.. Sessions provide a mechanism for TTL-based auto-release, which prevents deadlocks if an application crashes while holding a lock.

Answer

It encrypts the lock data.

Answer

It allows for multiple lock holders.

Answer

It speeds up read operations.

Question 4

What is the consequence of having a service with no health checks registered?

Accepted Answer

The service status is 'passing'. If no health checks are provided, the service is assumed to be healthy by default as long as the service is registered in the catalog.

Answer

The agent will error out

Answer

The service is ignored by DNS

Answer

The service is critical

Question 5

What is the recommended approach for running health checks on a service that is part of a non-containerized, multi-process architecture?

Accepted Answer

Run one check per service definition. Defining separate health checks for each process or a single composite check that monitors the aggregate health is the standard practice.

Answer

Only check the parent process

Answer

Use only TCP checks

Answer

Use a single script check that kills the service

Question 6

An operator observes that a service is failing its HTTP health check because the application takes 15 seconds to start up, exceeding the default timeout. Which parameter should be adjusted in the service definition to prevent premature failure?

Accepted Answer

Timeout. The 'timeout' parameter defines how long the agent waits for a response; increasing it allows the service time to initialize.

Answer

InitialStatus

Answer

Interval

Answer

DeregisterCriticalServiceAfter

Question 7

When using the HTTP health check type, how can you verify that a specific header is included in the health check request?

Accepted Answer

By adding the 'header' object to the check definition. The 'header' field within the HTTP check configuration allows specifying custom HTTP headers for the check request.

Answer

By appending it to the URL string

Answer

It is not possible

Answer

By setting the environment variable

Question 8

In a Consul health check, what does the 'notes' field provide?

Accepted Answer

A human-readable description. The 'notes' field allows operators to add human-readable descriptions of what the health check monitors.

Answer

The trigger time

Answer

The expected result

Answer

The logic for the check

Question 9

Which HTTP status code range does Consul interpret as a passing state for an HTTP health check?

Accepted Answer

2xx. Consul considers any 2xx status code as a passing health check. Codes 4xx and 5xx result in a critical state.

Answer

3xx

Answer

Any code less than 500

Answer

1xx

Question 10

Which agent configuration allows you to specify the local address that the Consul agent binds to for performing health checks?

Accepted Answer

bind_addr. The 'bind_addr' configuration defines the address the agent binds to, which is used for health check traffic initiated by that agent.

Answer

advertise_addr

Answer

client_addr

Answer

check_addr

Question 11

A service has a TTL check configured with a 30-second TTL. If the application crashes and stops sending heartbeats, when will the service status change to 'critical'?

Accepted Answer

After 30 seconds. Consul marks a TTL check as critical if the heartbeat is not received within the specified TTL duration.

Answer

After 60 seconds

Answer

Once the agent restarts

Answer

Immediately

Question 12

Which states can a health check report? (Select THREE)

Accepted Answer

passing. The three standard states are passing, warning, and critical.

Answer

terminated

Answer

pending

Question 13

When using the Consul KV store, what is the maximum size allowed for a single value in a key?

Accepted Answer

512 KB. Consul enforces a hard limit of 512 KB per KV entry value.

Answer

There is no limit.

Answer

128 KB

Answer

1 MB

Question 14

You need to ensure that a read operation from the KV store is strongly consistent. Which consistency mode should you specify?

Accepted Answer

consistent. The 'consistent' consistency mode forces the leader to verify its leadership with a quorum of peers, ensuring strong consistency.

Answer

default

Answer

quorum

Answer

stale

Question 15

When configuring a Service-specific health check, what is the impact of setting the 'expose' field to true?

Accepted Answer

The check status is exposed on the HTTP interface. Setting 'expose' to true allows the service to expose its health checks via the local agent's HTTP interface, enabling external access to the health check status.

Answer

The service is automatically registered with a Load Balancer

Answer

The check is bypassed

Answer

The agent automatically upgrades the check to HTTP

Question 16

Which THREE of the following are required to successfully acquire a lock on a KV key?

Accepted Answer

A valid session ID. To acquire a lock, you need a session, the key itself, and the acquire parameter in the API call.

Answer

A 'write' ACL policy

Answer

A 'wait' parameter

Question 17

Which THREE of the following represent potential bottlenecks for Consul KV performance?

Accepted Answer

Very large number of keys. High update frequency, massive key counts, and large value sizes all impact KV performance.

Answer

High read frequency

Answer

Using HTTP instead of RPC

Question 18

Which TWO of the following accurately describe Consul's WAN gossip protocol behavior?

Accepted Answer

It involves only the server nodes of each datacenter.. WAN gossip is designed for high latency links and involves only server nodes, not all cluster nodes.

Answer

It relies on a central hub-and-spoke architecture.

Answer

It includes all client nodes in the gossip pool.

Answer

It is mandatory for service discovery.

Question 19

Which actions can you perform on a TTL check? (Select TWO)

Accepted Answer

pass. You can tell Consul that the check passed or is in a warning state.

Answer

restart

Answer

suspend

Answer

fail

Question 20

What is the default value for the Consul KV flags field if not provided during a write?

Accepted Answer

0. The default value for flags is 0.

Answer

1

Answer

null

Answer

-1