194 questions total · 3pages · All types, answers revealed
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Which THREE of the following are components of a Consul Connect service definition?
The proxy block defines sidecar settings.
Why this answer
Connect services typically use 'proxy', 'upstreams', and 'connect' blocks to define their behavior in the mesh.
You notice that the KV store is not consistent across datacenters. What is the cause?
Consul's KV store is not replicated globally between DCs automatically.
Why this answer
Consul does not natively replicate the entire KV store across datacenters by default; it requires separate configuration or manual syncing for state consistency.
Which command line tool can you use to manually trigger a TTL check update for a specific service?
This is the documented API call to pass a TTL check.
Why this answer
The 'consul monitor' is for logs, but to update a check via CLI, one typically interacts with the HTTP API or uses the 'consul kv' command if applicable, but specifically for TTL, the HTTP API endpoint '/v1/agent/check/pass' is the standard method.
Which TWO of the following are true regarding the behavior of the Consul KV store?
Stale consistency mode permits non-leader reads.
Why this answer
KV values are stored as base64 encoded strings in the API, and they are eventually consistent for stale reads.
Which configuration file format is preferred by Consul for defining service health checks?
JSON is a native configuration format for Consul.
Why this answer
Consul supports both JSON and HCL, but JSON is the most common format for service definitions.
Which protocol is used for the control plane communication between the Consul agent and the sidecar proxy?
Consul uses the gRPC-based xDS API to push configuration to Envoy.
Why this answer
The Consul agent communicates with the sidecar proxy (Envoy) using the Envoy xDS API.
Which of the following is a valid method to update a TTL health check?
This is the standard way to update TTL checks.
Why this answer
The agent exposes an HTTP API endpoint to update the status of a TTL check manually.
You need to retrieve the session information for a specific session ID. Which endpoint should you query?
This endpoint retrieves session metadata.
Why this answer
The /v1/session/info/:id endpoint returns the details of a specific session.
When using multiple datacenters, what is the primary role of the 'consul-template' tool?
This is the primary function of consul-template.
Why this answer
Consul-template is often used to watch for changes in the Consul catalog and update application configurations, which can be useful when reflecting cross-DC service information.
If you are running Consul Enterprise, what feature simplifies the management of cross-datacenter secrets?
ACL replication is a core Enterprise feature for secrets consistency.
Why this answer
Consul Enterprise supports cross-datacenter secret replication for specific ACL tokens and KV pairs, often utilized with the 'enterprise_license_path' features.
Which command is used to check the status of a registered service?
The 'consul health service' command shows the status of specific instances.
Why this answer
'consul catalog' or 'consul health' commands are used for status inspection.
You are troubleshooting a health check that seems to be hanging. Which flag, if available, would provide more information about the check's execution within the agent logs?
Debug level logs show detailed check activity.
Why this answer
Increasing the agent's log level to 'debug' provides detailed information about check execution and processing.
Which THREE of the following are key components of a service definition?
Critical for service discovery.
Why this answer
Service definitions include the name, port, and health check requirements.
You are querying the Consul DNS interface for a service. How can you exclude specific tags from the results?
DNS queries are limited; complex filtering requires the HTTP API.
Why this answer
Consul DNS queries do not support tag exclusion directly in the query string; you filter by including only the desired tags.
You are troubleshooting why a service registered via HTTP API is not showing up in the catalog. Which tool provides the most immediate insight into the registration status?
This command lists all services currently registered in the catalog.
Why this answer
The 'consul catalog' CLI command allows direct inspection of the catalog state.
What is the recommended number of Consul servers per datacenter to ensure high availability?
3 is the minimum recommended for quorum and HA.
Why this answer
The recommended number for a consensus-based system like Consul is 3 or 5, to tolerate n/2-1 failures.
Which protocol do Consul servers use to maintain the WAN gossip pool?
Consul uses Serf/SWIM for membership and gossip.
Why this answer
Consul uses the Serf library, which implements the SWIM-based gossip protocol for both LAN and WAN communication.
Which agent configuration allows you to specify the local address that the Consul agent binds to for performing health checks?
Used by the agent for internal and health check traffic.
Why this answer
The 'bind_addr' configuration defines the address the agent binds to, which is used for health check traffic initiated by that agent.
What is the function of the 'consul connect envoy' command?
This command runs the Envoy process with the correct Consul configuration.
Why this answer
This command bootstraps and manages the lifecycle of the Envoy sidecar process.
When using the HTTP health check type, how can you verify that a specific header is included in the health check request?
The 'header' field is used for this purpose.
Why this answer
The 'header' field within the HTTP check configuration allows specifying custom HTTP headers for the check request.
What is the effect of changing the 'interval' parameter in a service health check?
Interval determines the check frequency.
Why this answer
The interval defines how often the health check executes.
Which THREE of the following are benefits of using the Consul DNS interface?
DNS is a standard protocol.
Why this answer
Ease of use, platform-agnostic, and no application changes are benefits.
When troubleshooting a service that fails to start its Envoy proxy, which service definition field should you check for incorrect configuration?
Errors here directly impact proxy startup.
Why this answer
The 'proxy' configuration block is where all Envoy-specific settings, including ports and upstreams, are defined.
What components can affect the outcome of a health check? (Select THREE)
Blocks check traffic.
Why this answer
Network, agent configuration, and application responsiveness all affect health check outcomes.
Which TWO of the following are true regarding intentions?
This is their core purpose.
Why this answer
Intentions are managed via API/CLI and define allowed communication patterns between services.
Which feature allows you to define a health check that depends on the health of another service?
Custom logic must be handled via script.
Why this answer
Consul does not support direct service-to-service health check dependencies; instead, you would implement this logic within your application or use a custom script.
You want to perform a list operation on a KV prefix to see all keys, but you don't want the values returned. Which API parameter helps reduce payload size?
The keys parameter returns only the list of keys.
Why this answer
The 'keys' parameter can be used with a prefix to return only the list of key names, not their contents.
Which Consul feature allows you to observe the KV store for changes and run a command in response?
Watches trigger actions upon data changes.
Why this answer
Consul Watches are the built-in mechanism for reacting to changes in the KV store.
Which THREE of the following are supported as sidecar proxy types in Consul?
Supported as an alternative proxy.
Why this answer
Consul natively supports Envoy, and has legacy or plugin support for others like HAProxy.
What is the purpose of the 'check' field inside a 'service' object in a Consul configuration file?
It associates a health check with the lifecycle of the service.
Why this answer
The 'check' field is used to define health checks specifically associated with the service instance, ensuring the service is marked critical if the check fails.
Which THREE of the following are required to successfully acquire a lock on a KV key?
The session ID is required to identify the locker.
Why this answer
To acquire a lock, you need a session, the key itself, and the acquire parameter in the API call.
What is the consequence of having a service with no health checks registered?
Services without checks are considered healthy.
Why this answer
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.
Which file path is standard for storing the Consul server configuration, including WAN settings?
This is the conventional location for configs.
Why this answer
The '/etc/consul.d' directory is the standard location for Consul configuration files on Linux systems.
What happens if a service proxy loses its connection to the local Consul agent?
Envoy retains the last received xDS configuration.
Why this answer
The proxy will be unable to receive configuration updates and health status, potentially leading to service disruption.
Which of the following conditions can cause a health check to transition to the 'critical' state? (Select TWO)
Timeout indicates failure.
Why this answer
A check transitions to critical if the service fails to respond (timeout) or returns a non-success code (e.g., 500).
What happens if you do not specify an 'interval' for a health check in the configuration?
Interval is a mandatory field.
Why this answer
The 'interval' is a required field for periodic health checks; the agent will fail to load the configuration without it.
An administrator wants to register a service using a JSON file. Where should this file be placed on a standard Consul agent installation to ensure automatic loading?
The default configuration directory for Consul is typically /etc/consul.d/.
Why this answer
The Consul agent watches the directory defined by the '-config-dir' flag.
Which TWO of the following are common use cases for the Consul KV store?
This is a core use case.
Why this answer
KV is primarily used for configuration management and distributed locking.
Which CLI command would you use to check the status of a Connect-enabled service?
This displays the health of the service and its sidecars.
Why this answer
The 'consul catalog services' or 'consul health service' command shows the status, including Connect capabilities.
What is the 'Consul Connect proxy' kind used for?
This 'kind' identifies the resource as a proxy.
Why this answer
It defines a service that is explicitly a sidecar proxy.
Which THREE of the following are valid Consul health check statuses?
Degraded state.
Why this answer
Passing, Warning, and Critical are the three standard states.
Which TWO of the following accurately describe Consul's WAN gossip protocol behavior?
Only servers participate.
Why this answer
WAN gossip is designed for high latency links and involves only server nodes, not all cluster nodes.
Requires the application to send heartbeat signals to the agent.
Why this answer
The TTL (Time-To-Live) check requires the application to actively report its health status to the Consul agent, making it the correct choice for applications that cannot be polled externally.
You are configuring a sidecar proxy for a service named 'web'. Which configuration stanza in the service definition correctly defines the proxy's inbound port for Connect traffic?
The local_bind_port correctly specifies where the proxy listens for local traffic.
Why this answer
The 'proxy' configuration block within the service definition allows for the 'local_bind_port' and 'config' keys to define proxy behavior.
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Practice Consul 1.15 by domain
Target a specific domain to shore up weak areas.