{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://www.envoyproxy.io/schemas/cluster",
  "title": "Envoy Cluster",
  "description": "An upstream cluster represents a group of logically similar upstream hosts that Envoy connects to. Clusters define how Envoy discovers, health checks, load balances, and connects to upstream services.",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Unique name for the cluster, used to reference it in route configurations and stats."
    },
    "type": {
      "type": "string",
      "description": "The service discovery type to use for resolving cluster member endpoints.",
      "enum": ["STATIC", "STRICT_DNS", "LOGICAL_DNS", "EDS", "ORIGINAL_DST"]
    },
    "connect_timeout": {
      "type": "string",
      "description": "Timeout for new network connections to upstream hosts (e.g., '5s').",
      "pattern": "^[0-9]+(\\.[0-9]+)?s$"
    },
    "lb_policy": {
      "type": "string",
      "description": "The load balancing algorithm used to select an upstream host.",
      "enum": ["ROUND_ROBIN", "LEAST_REQUEST", "RING_HASH", "RANDOM", "MAGLEV", "CLUSTER_PROVIDED"]
    },
    "load_assignment": {
      "type": "object",
      "description": "Endpoint assignment for STATIC and EDS clusters.",
      "properties": {
        "cluster_name": {
          "type": "string"
        },
        "endpoints": {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "locality": {
                "type": "object",
                "properties": {
                  "region": { "type": "string" },
                  "zone": { "type": "string" },
                  "sub_zone": { "type": "string" }
                }
              },
              "lb_endpoints": {
                "type": "array",
                "items": {
                  "type": "object",
                  "properties": {
                    "endpoint": {
                      "type": "object",
                      "properties": {
                        "address": {
                          "type": "object",
                          "properties": {
                            "socket_address": {
                              "type": "object",
                              "properties": {
                                "address": { "type": "string" },
                                "port_value": {
                                  "type": "integer",
                                  "minimum": 0,
                                  "maximum": 65535
                                }
                              },
                              "required": ["address", "port_value"]
                            }
                          }
                        }
                      }
                    },
                    "health_status": {
                      "type": "string",
                      "enum": ["UNKNOWN", "HEALTHY", "UNHEALTHY", "DRAINING", "TIMEOUT", "DEGRADED"]
                    },
                    "load_balancing_weight": {
                      "type": "integer",
                      "minimum": 1
                    }
                  }
                }
              },
              "priority": {
                "type": "integer",
                "minimum": 0
              }
            }
          }
        }
      }
    },
    "eds_cluster_config": {
      "type": "object",
      "description": "Configuration for using EDS to discover cluster members.",
      "properties": {
        "eds_config": {
          "type": "object",
          "properties": {
            "api_config_source": {
              "type": "object",
              "properties": {
                "api_type": {
                  "type": "string",
                  "enum": ["REST", "GRPC", "DELTA_GRPC"]
                },
                "grpc_services": {
                  "type": "array",
                  "items": {
                    "type": "object"
                  }
                },
                "cluster_names": {
                  "type": "array",
                  "items": { "type": "string" }
                }
              }
            },
            "ads": { "type": "object" },
            "path": { "type": "string" },
            "resource_api_version": {
              "type": "string",
              "enum": ["AUTO", "V2", "V3"]
            }
          }
        },
        "service_name": {
          "type": "string",
          "description": "Alternative service name used to look up endpoints via EDS."
        }
      }
    },
    "health_checks": {
      "type": "array",
      "description": "Health checking configuration for cluster members.",
      "items": {
        "type": "object",
        "properties": {
          "timeout": { "type": "string" },
          "interval": { "type": "string" },
          "unhealthy_threshold": { "type": "integer" },
          "healthy_threshold": { "type": "integer" },
          "http_health_check": {
            "type": "object",
            "properties": {
              "host": { "type": "string" },
              "path": { "type": "string" },
              "expected_statuses": {
                "type": "array",
                "items": {
                  "type": "object",
                  "properties": {
                    "start": { "type": "integer" },
                    "end": { "type": "integer" }
                  }
                }
              }
            }
          },
          "tcp_health_check": { "type": "object" },
          "grpc_health_check": {
            "type": "object",
            "properties": {
              "service_name": { "type": "string" }
            }
          }
        }
      }
    },
    "circuit_breakers": {
      "type": "object",
      "description": "Circuit breaking limits for the cluster.",
      "properties": {
        "thresholds": {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "priority": {
                "type": "string",
                "enum": ["DEFAULT", "HIGH"]
              },
              "max_connections": { "type": "integer" },
              "max_pending_requests": { "type": "integer" },
              "max_requests": { "type": "integer" },
              "max_retries": { "type": "integer" },
              "track_remaining": { "type": "boolean" }
            }
          }
        }
      }
    },
    "outlier_detection": {
      "type": "object",
      "description": "Outlier detection configuration for ejecting unhealthy hosts.",
      "properties": {
        "consecutive_5xx": {
          "type": "integer",
          "description": "Number of consecutive 5xx responses before ejection."
        },
        "consecutive_gateway_failure": {
          "type": "integer",
          "description": "Number of consecutive gateway failures before ejection."
        },
        "interval": {
          "type": "string",
          "description": "Time interval between ejection analysis sweeps."
        },
        "base_ejection_time": {
          "type": "string",
          "description": "Base time for which a host is ejected."
        },
        "max_ejection_percent": {
          "type": "integer",
          "description": "Maximum percentage of hosts in the cluster that can be ejected.",
          "minimum": 0,
          "maximum": 100
        },
        "enforcing_consecutive_5xx": {
          "type": "integer",
          "minimum": 0,
          "maximum": 100
        },
        "enforcing_success_rate": {
          "type": "integer",
          "minimum": 0,
          "maximum": 100
        },
        "success_rate_minimum_hosts": {
          "type": "integer"
        },
        "success_rate_request_volume": {
          "type": "integer"
        },
        "success_rate_stdev_factor": {
          "type": "integer"
        }
      }
    },
    "transport_socket": {
      "type": "object",
      "description": "Transport socket configuration for upstream connections (e.g., TLS).",
      "properties": {
        "name": {
          "type": "string",
          "description": "Name of the transport socket implementation."
        },
        "typed_config": {
          "type": "object",
          "description": "Transport socket specific configuration."
        }
      }
    },
    "dns_lookup_family": {
      "type": "string",
      "description": "DNS IP address resolution policy for STRICT_DNS and LOGICAL_DNS clusters.",
      "enum": ["AUTO", "V4_ONLY", "V6_ONLY", "V4_PREFERRED", "ALL"]
    },
    "dns_resolvers": {
      "type": "array",
      "description": "Custom DNS resolvers for the cluster.",
      "items": {
        "type": "object",
        "properties": {
          "socket_address": {
            "type": "object",
            "properties": {
              "address": { "type": "string" },
              "port_value": { "type": "integer" }
            }
          }
        }
      }
    },
    "respect_dns_ttl": {
      "type": "boolean",
      "description": "Whether to respect DNS TTL values for DNS-based clusters."
    },
    "dns_refresh_rate": {
      "type": "string",
      "description": "DNS refresh rate for DNS-based clusters."
    },
    "per_connection_buffer_limit_bytes": {
      "type": "integer",
      "description": "Soft limit on size of the cluster's connections read and write buffers."
    },
    "metadata": {
      "type": "object",
      "description": "Metadata for the cluster, used for stats, logging, and access control.",
      "additionalProperties": true
    },
    "common_lb_config": {
      "type": "object",
      "description": "Common configuration shared by all load balancer implementations.",
      "properties": {
        "healthy_panic_threshold": {
          "type": "object",
          "properties": {
            "value": {
              "type": "number",
              "minimum": 0,
              "maximum": 100
            }
          }
        },
        "locality_weighted_lb_config": {
          "type": "object"
        },
        "zone_aware_lb_config": {
          "type": "object",
          "properties": {
            "routing_enabled": {
              "type": "object",
              "properties": {
                "value": { "type": "number" }
              }
            },
            "min_cluster_size": {
              "type": "integer"
            }
          }
        }
      }
    }
  },
  "required": ["name", "type"]
}