# HashiCorp Consul — Service Discovery & Service Mesh > Consul is a distributed service networking platform providing service discovery, health checking, KV storage, and a full service mesh with mTLS for microservices. ## Install Save in your project root: ## Quick Use ```bash # Start a dev server docker run -d --name consul -p 8500:8500 -p 8600:8600/udp hashicorp/consul:latest agent -server -ui -bootstrap -client=0.0.0.0 ``` Open `http://localhost:8500/ui` — Consul Web UI is ready. ## Intro **Consul** is a distributed, highly available, and data center-aware service networking platform from HashiCorp. It provides service discovery, health checking, key-value storage, and a full service mesh with mTLS — enabling secure, reliable communication between microservices and infrastructure. With 29.8K+ GitHub stars and BSL license, Consul is a cornerstone of the HashiCorp stack, used by enterprises and startups alike to manage service connectivity in multi-cloud, multi-datacenter environments. ## What Consul Does - **Service Discovery**: Register services and discover them via DNS or HTTP API - **Health Checking**: Continuously monitor service health and remove unhealthy instances - **KV Store**: Distributed key-value storage for dynamic configuration - **Service Mesh**: Full mTLS service mesh with Envoy sidecar proxies - **Intentions**: Declarative access control between services - **Multi-Datacenter**: Federate Consul clusters across regions and clouds - **Network Segmentation**: Isolate services via Consul Namespaces and Admin Partitions - **ACL**: Fine-grained access control with tokens and policies - **Event System**: Trigger events across clusters for coordinated actions ## Architecture ``` ┌─────────────────────────────────────────────┐ │ Datacenter 1 │ │ ┌──────────┐ ┌──────────┐ ┌──────────┐ │ │ │ Consul │──│ Consul │──│ Consul │ │ │ │ Server 1 │ │ Server 2 │ │ Server 3 │ │ │ └──────────┘ └──────────┘ └──────────┘ │ │ ▲ ▲ ▲ │ │ │ Raft Consensus │ │ │ ┌────┴──────────────┴──────────┴────┐ │ │ │ │ │ │ │ ┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐ │ │ │ │ │Agent│ │Agent│ │Agent│ │Agent│ │ │ │ │ │ Web │ │ API │ │ DB │ │Cache│ │ │ │ │ └─────┘ └─────┘ └─────┘ └─────┘ │ │ │ │ Client Agents │ │ │ └────────────────────────────────────┘ │ └─────────────────────────────────────────────┘ │ WAN Federation ▼ ┌─────────────────────────────────────────────┐ │ Datacenter 2 (Another region/cloud) │ └─────────────────────────────────────────────┘ ``` ## Self-Hosting ### Docker Compose (Dev) ```yaml services: consul: image: hashicorp/consul:latest ports: - "8500:8500" # HTTP API / UI - "8600:8600/udp" # DNS - "8600:8600/tcp" command: agent -server -ui -bootstrap-expect=1 -client=0.0.0.0 volumes: - consul-data:/consul/data volumes: consul-data: ``` ### Production Cluster (3 Servers) ```yaml services: consul-server-1: image: hashicorp/consul:latest command: agent -server -ui -bootstrap-expect=3 -retry-join=consul-server-2 -retry-join=consul-server-3 -client=0.0.0.0 volumes: - consul-1:/consul/data consul-server-2: image: hashicorp/consul:latest command: agent -server -bootstrap-expect=3 -retry-join=consul-server-1 -retry-join=consul-server-3 -client=0.0.0.0 volumes: - consul-2:/consul/data consul-server-3: image: hashicorp/consul:latest command: agent -server -bootstrap-expect=3 -retry-join=consul-server-1 -retry-join=consul-server-2 -client=0.0.0.0 volumes: - consul-3:/consul/data volumes: consul-1: consul-2: consul-3: ``` ## Service Discovery ### Register a Service ```json { "service": { "name": "web", "id": "web-1", "address": "10.0.1.5", "port": 8080, "tags": ["primary", "v2"], "checks": [ { "http": "http://10.0.1.5:8080/health", "interval": "10s", "timeout": "5s" } ] } } ``` ```bash curl -X PUT -d @service.json http://localhost:8500/v1/agent/service/register ``` ### Discover Services ```bash # HTTP API curl http://localhost:8500/v1/catalog/service/web # DNS query (SRV record) dig @localhost -p 8600 web.service.consul SRV # Only healthy instances curl http://localhost:8500/v1/health/service/web?passing=true ``` ### Integration in Code ```go // Go example import "github.com/hashicorp/consul/api" config := api.DefaultConfig() client, _ := api.NewClient(config) // Find web service services, _, _ := client.Health().Service("web", "", true, nil) for _, entry := range services { fmt.Printf("%s:%d ", entry.Service.Address, entry.Service.Port) } ``` ## KV Store ```bash # Write curl -X PUT -d 'production' http://localhost:8500/v1/kv/config/app/environment curl -X PUT -d '5432' http://localhost:8500/v1/kv/config/db/port # Read curl http://localhost:8500/v1/kv/config/app/environment?raw # List keys curl http://localhost:8500/v1/kv/config/?keys # Watch for changes (long polling) curl "http://localhost:8500/v1/kv/config/app/environment?index=123&wait=5m" ``` ## Service Mesh (Connect) ### Enable Connect ```json { "service": { "name": "web", "port": 8080, "connect": { "sidecar_service": { "proxy": { "upstreams": [ { "destination_name": "database", "local_bind_port": 9191 } ] } } } } } ``` ### Intentions (Access Control) ```bash # Allow web service to access database consul intention create web database # Deny all except explicitly allowed consul intention create -deny "*" "*" consul intention create web database ``` ## Consul vs Alternatives | Feature | Consul | Etcd | Eureka | Istio | |---------|--------|------|--------|-------| | Service discovery | Yes | Kv only | Yes | Via K8s | | KV store | Yes | Yes | No | No | | Health checks | Yes | No | Yes | Yes | | Service mesh | Yes | No | No | Yes | | Multi-DC | Yes | Limited | Yes | Complex | | DNS interface | Yes | No | No | No | | Language | Go | Go | Java | Go | | Stack | Any | K8s native | Java focus | K8s focus | ## 常见问题 **Q: Consul 和 etcd 怎么选？** A: etcd 主要是分布式 KV 存储（K8s 用它存储集群状态）。Consul 是完整的服务网络平台，包含 KV + 服务发现 + 健康检查 + 服务网格。如果你只需要 KV 存储，etcd 更轻量。如果需要服务发现和健康检查，选 Consul。 **Q: Consul 和 Istio 怎么选？** A: Istio 是 Kubernetes 原生服务网格（只能在 K8s 上用）。Consul 既支持 K8s 也支持 VM 和混合环境。如果你的服务混合部署在 K8s 和传统 VM 上，选 Consul。纯 K8s 环境下 Istio 功能更丰富。 **Q: BSL 许可证影响使用吗？** A: BSL（Business Source License）允许自由使用和修改，限制是不能作为 Consul 的竞品商业产品。对于绝大多数用户（自托管、内部使用），BSL 等同于开源许可。 ## 来源与致谢 - GitHub: [hashicorp/consul](https://github.com/hashicorp/consul) — 29.8K+ ⭐ | BSL - 官网: [consul.io](https://consul.io) --- Source: https://tokrepo.com/en/workflows/931a6bb7-352f-11f1-9bc6-00163e2b0d79 Author: AI Open Source