Consul

Comprehensive HashiCorp Consul commands and workflows for service discovery, configuration management, and service mesh.

Installation & Setup

Command	Description
consul version	Show Consul version
consul agent -dev	Start development agent
consul agent -config-dir=/etc/consul.d	Start with configuration
consul members	List cluster members
consul info	Show agent information

Agent Management

Basic Agent Operations

Command	Description
consul agent -server -bootstrap-expect=3	Start server agent
consul agent -client=0.0.0.0	Start client agent
consul join 192.168.1.100	Join cluster
consul leave	Gracefully leave cluster
consul reload	Reload configuration

Agent Configuration

Command	Description
consul validate /etc/consul.d	Validate configuration
consul configtest	Test configuration

Service Discovery

Service Registration

Command	Description
consul services register service.json	Register service from file
consul services deregister service-id	Deregister service
consul catalog services	List all services
consul catalog nodes	List all nodes

Service Queries

Command	Description
consul catalog service web	List instances of service
consul catalog service web -tag production	Filter by tag
consul health service web	Health check status
consul health node node1	Node health status

DNS Interface

Command	Description
dig @127.0.0.1 -p 8600 web.service.consul	Query service via DNS
dig @127.0.0.1 -p 8600 web.service.dc1.consul	Query specific datacenter
dig @127.0.0.1 -p 8600 node1.node.consul	Query node via DNS

Key-Value Store

KV Operations

Command	Description
consul kv put config/database/url "postgresql://..."	Store key-value
consul kv get config/database/url	Retrieve value
consul kv get -recurse config/	Get all keys under prefix
consul kv delete config/database/url	Delete key
consul kv delete -recurse config/	Delete all keys under prefix

KV Advanced Operations

Command	Description
consul kv put -cas -modify-index=123 config/app/version "2.0"	Conditional update
consul kv get -detailed config/app/version	Get with metadata
consul kv export config/	Export keys
consul kv import @backup.json	Import keys

Health Checks

Health Check Management

Command	Description
consul health checks	List all health checks
consul health checks web	List checks for service
consul health state critical	List critical checks
consul health state passing	List passing checks

Access Control Lists (ACLs)

ACL Management

Command	Description
consul acl bootstrap	Bootstrap ACL system
consul acl token create -description="Web service token"	Create token
consul acl token list	List tokens
consul acl token delete TOKEN_ID	Delete token

ACL Policies

Command	Description
consul acl policy create -name web-policy -rules @policy.hcl	Create policy
consul acl policy list	List policies
consul acl policy read web-policy	Read policy
consul acl policy update -id POLICY_ID -rules @new-policy.hcl	Update policy

Connect (Service Mesh)

Connect Configuration

Command	Description
consul connect ca get-config	Get CA configuration
consul connect ca set-config -config-file ca.json	Set CA configuration
consul connect proxy -service web	Start Connect proxy

Intentions

Command	Description
consul intention create web db	Allow web to connect to db
consul intention create -deny web cache	Deny web to cache
consul intention list	List all intentions
consul intention delete web db	Delete intention

Configuration Entries

Service Configuration

Command	Description
consul config write service-defaults.hcl	Write service defaults
consul config write proxy-defaults.hcl	Write proxy defaults
consul config list -kind service-defaults	List configurations
consul config read -kind service-defaults -name web	Read configuration
consul config delete -kind service-defaults -name web	Delete configuration

Snapshots and Backups

Snapshot Operations

Command	Description
consul snapshot save backup.snap	Create snapshot
consul snapshot restore backup.snap	Restore snapshot
consul snapshot inspect backup.snap	Inspect snapshot

Monitoring and Debugging

Monitoring Commands

Command	Description
consul monitor	Stream logs
consul monitor -log-level=DEBUG	Debug level logs
consul debug	Collect debug information
consul operator raft list-peers	List Raft peers

Performance

Command	Description
consul operator autopilot get-config	Get autopilot config
consul operator autopilot set-config -cleanup-dead-servers=true	Set autopilot config

Configuration Examples

Server Configuration

datacenter = "dc1"
data_dir = "/opt/consul"
log_level = "INFO"
node_name = "consul-server-1"
server = true
bootstrap_expect = 3
retry_join = ["10.0.1.10", "10.0.1.11"]

bind_addr = "10.0.1.10"
client_addr = "0.0.0.0"

ui_config \\\\{
  enabled = true
\\\\}

connect \\\\{
  enabled = true
\\\\}

acl = \\\\{
  enabled = true
  default_policy = "deny"
  enable_token_persistence = true
\\\\}

Client Configuration

datacenter = "dc1"
data_dir = "/opt/consul"
log_level = "INFO"
node_name = "consul-client-1"
retry_join = ["10.0.1.10", "10.0.1.11", "10.0.1.12"]

bind_addr = "10.0.1.20"
client_addr = "127.0.0.1"

services \\\\{
  name = "web"
  port = 80
  tags = ["production", "v1.0"]

  check \\\\{
    http = "http://localhost:80/health"
    interval = "10s"
  \\\\}
\\\\}

Service Definition

\\\\{
  "service": \\\\{
    "name": "web",
    "port": 80,
    "tags": ["production"],
    "check": \\\\{
      "http": "http://localhost:80/health",
      "interval": "10s"
    \\\\},
    "connect": \\\\{
      "sidecar_service": \\\\{\\\\}
    \\\\}
  \\\\}
\\\\}

ACL Policy

node_prefix "" \\\\{
  policy = "read"
\\\\}

service_prefix "" \\\\{
  policy = "read"
\\\\}

service "web" \\\\{
  policy = "write"
\\\\}

key_prefix "config/web/" \\\\{
  policy = "write"
\\\\}

session_prefix "" \\\\{
  policy = "read"
\\\\}

Service Mesh Configuration

Proxy Defaults

Kind = "proxy-defaults"
Name = "global"

Config \\\\{
  protocol = "http"
\\\\}

MeshGateway \\\\{
  Mode = "local"
\\\\}

Service Defaults

Kind = "service-defaults"
Name = "web"

Protocol = "http"

MeshGateway \\\\{
  Mode = "local"
\\\\}

Expose \\\\{
  Checks = true
  Paths = [
    \\\\{
      Path = "/health"
      LocalPathPort = 8080
      ListenerPort = 21500
    \\\\}
  ]
\\\\}

Multi-Datacenter Setup

WAN Federation

Command	Description
consul join -wan 192.168.2.10	Join WAN
consul members -wan	List WAN members
consul catalog datacenters	List datacenters

Cross-DC Queries

Command	Description
consul catalog service web -datacenter dc2	Query service in DC2
dig @127.0.0.1 -p 8600 web.service.dc2.consul	DNS query to DC2

Troubleshooting

Common Issues

Command	Description
consul operator raft list-peers	Check Raft cluster state
consul debug -duration=30s	Collect debug info
consul validate /etc/consul.d	Validate configuration
consul members -detailed	Detailed member information

Log Analysis

Command	Description
consul monitor -log-level=TRACE	Trace level logging
journalctl -u consul -f	Follow systemd logs

Best Practices

Security

1. Enable ACLs: Always use ACLs in production
2. TLS Encryption: Enable TLS for all communication
3. Gossip Encryption: Use gossip encryption
4. Network Segmentation: Proper network security
5. Token Management: Rotate tokens regularly

Performance

1. Resource Allocation: Adequate CPU and memory
2. Network Latency: Minimize network latency
3. Disk I/O: Use fast storage for data directory
4. Cluster Size: Optimal cluster sizing
5. Monitoring: Comprehensive monitoring setup

Operations

1. Backup Strategy: Regular snapshots
2. Upgrade Planning: Careful upgrade procedures
3. Health Monitoring: Monitor service health
4. Capacity Planning: Plan for growth
5. Documentation: Document service topology

Development

1. Service Registration: Proper service definitions
2. Health Checks: Comprehensive health checks
3. Configuration Management: Use KV store effectively
4. Service Discovery: Implement proper discovery patterns
5. Testing: Test service mesh configurations