consul

Display help

$ consul --help

$ consul [subcommand] --help

$ consul --version

consul [options]

agent
    Runs the Consul agent, which is the core process of Consul. It handles service discovery, health checks, and more.

connect
    Subcommands related to Consul Connect, for secure service-to-service communication.

config
    Subcommands related to managing Consul's configuration.

debug
    Prints debugging information.

dns
    Starts a local DNS server that resolves service names to addresses.

exec
    Executes a command on a remote Consul agent.

kv
    Commands for interacting with Consul's key/value store.

maint
    Commands for placing nodes or services into maintenance mode.

monitor
    Streams log output from the local Consul agent.

operator
    Commands for operational tasks like Raft management.

plugin
    Commands for managing Consul plugins.

query
    Commands for managing prepared queries.

reload
    Reloads the Consul agent's configuration.

rpc
    Executes a remote procedure call on a Consul agent.

services
    Lists the services registered with Consul.

snapshot
    Commands for creating and restoring Consul snapshots.

tls
    Commands for generating TLS certificates.

version
    Prints the Consul version.

-h, --help
    Displays help information.

Consul is a distributed, highly available, and data center aware solution for service discovery, configuration, and orchestration. It is used to manage the configuration of services, discover services, and enable secure service-to-service communication. Consul leverages a distributed consensus protocol (Raft) for high availability and consistency. It provides a central repository for services to register themselves and allows other services to discover them based on their name or tags. Consul is often used in cloud environments and microservices architectures to manage the dynamic nature of services and their dependencies. It includes features like health checking, key/value storage, and secure service communication through mTLS.

Consul requires proper configuration and network connectivity between agents to function correctly. Securing Consul with TLS and access control lists (ACLs) is crucial for production environments. Understanding Raft consensus is important for operating and troubleshooting Consul clusters. Changes to the consul configuration need to be carefully tested before applying to production.

Consul agents can operate in two modes: server and client. Servers participate in the Raft consensus protocol and store the cluster state. Clients forward requests to the servers and do not store the full cluster state. It is common to run one or more Consul server instances. The official recommendation is to deploy 3 or 5 Consul server nodes in a cluster to avoid split-brain situations.
Client nodes are deployed on every machine with services that need to be registered, discover other services, or use the key/value store.

Consul allows you to define health checks for your services. These health checks can be simple HTTP requests, TCP connections, or shell scripts. Consul uses these health checks to determine whether a service is healthy and available. Unhealthy services are automatically removed from the service discovery catalog. Health checks are key to implementing resilient architectures.

Consul's key/value store provides a simple mechanism for storing and retrieving configuration data. It supports features like versioning and change notifications. The key/value store can be used to store things like database connection strings, API keys, or application settings. The Key/Value store can be used to store configurations that can be updated and distributed across all the consul agents in the cluster.
Data in the KV store is replicated across all the server nodes.

Consul was created by HashiCorp and first released in April 2014. It was designed to address the challenges of service discovery and configuration management in dynamic infrastructure environments. Its development was driven by the increasing adoption of microservices architectures and the need for a reliable and scalable solution for managing services and their dependencies. It rapidly became a popular tool for service discovery in cloud native environments. Over time, Consul has evolved to include features like Consul Connect for secure service-to-service communication and improvements to its key/value store.

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