Consul 1.15 Service Discovery Practice Test 2 — 15 Questions

Question 1

When multiple agents are in a cluster, how does Consul ensure that service discovery information is consistent across all nodes?

Accepted Answer

Via the Raft consensus protocol for catalog changes.. The Gossip Protocol (serf) and Raft consensus maintain state across nodes.

Answer

Using a centralized database like PostgreSQL.

Answer

By polling the leader every second.

Answer

By broadcasting all service updates to every node.

Question 2

Which of the following best describes the 'consul agent -dev' mode in relation to service discovery?

Accepted Answer

It provides a single-node Consul environment for testing.. Dev mode is for testing and has ephemeral storage.

Answer

It disables DNS interfaces.

Answer

It forces the service catalog to be stored in Redis.

Answer

It is suitable for production clusters.

Question 3

What is the impact of setting 'enable_tag_override' to true in a service definition?

Accepted Answer

It allows tags to be modified via the API without updating the config file.. It allows external systems to modify service tags without updating the service definition file.

Answer

It ignores all tags in the catalog.

Answer

It forces all nodes to update their tags.

Answer

It prevents tags from being used in DNS lookups.

Question 4

Which interface would you use to register a service dynamically using standard tools like 'curl'?

Accepted Answer

HTTP API. The Consul HTTP API is the standard interface for dynamic registration.

Answer

DNS interface

Answer

Gossip protocol

Answer

CLI agent command

Question 5

What is the effect of changing the 'interval' parameter in a service health check?

Accepted Answer

It changes the frequency at which the check runs.. The interval defines how often the health check executes.

Answer

It changes the DNS TTL.

Answer

It changes the weight of the service.

Answer

It changes the timeout of the check.

Question 6

You need to ensure a service instance is removed from the catalog immediately after the service process terminates. Which setting helps?

Accepted Answer

Set 'deregister_critical_service_after' to a short duration.. The 'deregister_critical_service_after' setting defines the timeout before cleanup.

Answer

Use a 'pre-stop' script.

Answer

Enable 'auto_cleanup' in the agent config.

Answer

Set 'ttl' to 0.

Question 7

How does Consul handle service discovery when using the 'prepared query' feature?

Accepted Answer

By pre-compiling the service discovery logic.. Prepared queries allow for complex, pre-defined discovery logic including failover.

Answer

By automatically creating new services.

Answer

By disabling health checks.

Answer

By caching all DNS records in memory.

Question 8

You are querying the Consul DNS interface for a service. How can you exclude specific tags from the results?

Accepted Answer

Consul DNS does not support tag exclusion; you must filter via the HTTP API.. Consul DNS queries do not support tag exclusion directly in the query string; you filter by including only the desired tags.

Answer

Use the '!' character before the tag name.

Answer

Add a 'not' parameter to the query.

Answer

Use regex in the service name.

Question 9

Which file format is primarily used for defining services in Consul?

Accepted Answer

JSON. Consul supports JSON or HCL.

Answer

YAML

Answer

TOML

Answer

XML

Question 10

You need to verify if a node has successfully joined the cluster for service discovery. Which tool confirms this?

Accepted Answer

consul members. 'consul members' lists the nodes in the cluster.

Answer

consul catalog nodes

Answer

consul info

Answer

consul services

Question 11

When a service check transitions to 'critical', what does Consul do with the service's DNS entry?

Accepted Answer

It removes the instance from the DNS response.. Consul removes the service instance from DNS results when its health check is critical.

Answer

It marks the record as 'stale'.

Answer

It returns the IP but with a low TTL.

Answer

It returns a 503 status code.

Question 12

What command displays the currently registered services in the local agent?

Accepted Answer

consul catalog services. 'consul catalog services' is the standard way to list services.

Answer

consul show

Answer

consul agent services

Answer

consul services list

Question 13

Which THREE of the following are valid check types in Consul?

Accepted Answer

TCP. Consul supports HTTP, TCP, and Script (external) health checks.

Answer

SSH

Answer

FTP

Question 14

Which TWO of the following can be used to filter services during a DNS query?

Accepted Answer

Datacenter. DNS queries allow filtering by tags and datacenters.

Answer

IP Address

Answer

Metadata

Answer

Node Name

Question 15

Which THREE of the following are key components of a service definition?

Accepted Answer

Check/Health Check. Service definitions include the name, port, and health check requirements.

Answer

Secret Key

Answer

Node BIOS version