{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://github.com/api-evangelist/apache-apisix/blob/main/json-schema/upstream.json",
  "title": "Apache APISIX Upstream",
  "description": "An Upstream is a virtual host abstraction that performs load balancing on a given set of service nodes according to configured rules.",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Human-readable name for the upstream."
    },
    "desc": {
      "type": "string",
      "description": "Description of the upstream."
    },
    "type": {
      "type": "string",
      "enum": ["roundrobin", "chash", "least_conn", "ewma"],
      "default": "roundrobin",
      "description": "Load balancing algorithm."
    },
    "nodes": {
      "oneOf": [
        {
          "type": "object",
          "additionalProperties": {
            "type": "integer"
          },
          "description": "Key-value pairs of address:port to weight."
        },
        {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "host": {
                "type": "string"
              },
              "port": {
                "type": "integer"
              },
              "weight": {
                "type": "integer"
              },
              "priority": {
                "type": "integer",
                "default": 0
              }
            }
          },
          "description": "List of node objects."
        }
      ],
      "description": "Backend service nodes."
    },
    "service_name": {
      "type": "string",
      "description": "Service name for service discovery."
    },
    "discovery_type": {
      "type": "string",
      "description": "Type of service discovery (e.g. dns, consul, nacos, eureka)."
    },
    "hash_on": {
      "type": "string",
      "enum": ["vars", "header", "cookie", "consumer", "vars_combinations"],
      "default": "vars",
      "description": "Hash input for consistent hashing load balancer."
    },
    "key": {
      "type": "string",
      "description": "Hash key when using chash load balancer."
    },
    "checks": {
      "type": "object",
      "description": "Health check configuration.",
      "properties": {
        "active": {
          "type": "object",
          "description": "Active health check configuration.",
          "properties": {
            "type": {
              "type": "string",
              "enum": ["http", "https", "tcp"],
              "default": "http"
            },
            "timeout": {
              "type": "number",
              "default": 1
            },
            "http_path": {
              "type": "string",
              "default": "/"
            },
            "host": {
              "type": "string"
            },
            "port": {
              "type": "integer"
            },
            "https_verify_certificate": {
              "type": "boolean",
              "default": true
            },
            "healthy": {
              "type": "object",
              "properties": {
                "interval": {
                  "type": "integer"
                },
                "successes": {
                  "type": "integer"
                }
              }
            },
            "unhealthy": {
              "type": "object",
              "properties": {
                "interval": {
                  "type": "integer"
                },
                "http_failures": {
                  "type": "integer"
                },
                "tcp_failures": {
                  "type": "integer"
                },
                "timeouts": {
                  "type": "integer"
                }
              }
            }
          }
        },
        "passive": {
          "type": "object",
          "description": "Passive health check configuration.",
          "properties": {
            "type": {
              "type": "string",
              "enum": ["http", "https", "tcp"],
              "default": "http"
            },
            "healthy": {
              "type": "object",
              "properties": {
                "http_statuses": {
                  "type": "array",
                  "items": {
                    "type": "integer"
                  }
                },
                "successes": {
                  "type": "integer"
                }
              }
            },
            "unhealthy": {
              "type": "object",
              "properties": {
                "http_statuses": {
                  "type": "array",
                  "items": {
                    "type": "integer"
                  }
                },
                "http_failures": {
                  "type": "integer"
                },
                "tcp_failures": {
                  "type": "integer"
                },
                "timeouts": {
                  "type": "integer"
                }
              }
            }
          }
        }
      }
    },
    "retries": {
      "type": "integer",
      "description": "Number of retries for failed requests."
    },
    "retry_timeout": {
      "type": "number",
      "description": "Timeout in seconds for retry requests."
    },
    "timeout": {
      "type": "object",
      "description": "Timeout settings for upstream connections.",
      "properties": {
        "connect": {
          "type": "number",
          "default": 60,
          "description": "Connection timeout in seconds."
        },
        "send": {
          "type": "number",
          "default": 60,
          "description": "Send timeout in seconds."
        },
        "read": {
          "type": "number",
          "default": 60,
          "description": "Read timeout in seconds."
        }
      }
    },
    "scheme": {
      "type": "string",
      "enum": ["http", "https", "grpc", "grpcs"],
      "default": "http",
      "description": "The scheme for communicating with the upstream."
    },
    "pass_host": {
      "type": "string",
      "enum": ["pass", "node", "rewrite"],
      "default": "pass",
      "description": "How to set the Host header when proxying to upstream."
    },
    "upstream_host": {
      "type": "string",
      "description": "Host to use when pass_host is set to rewrite."
    },
    "labels": {
      "type": "object",
      "additionalProperties": {
        "type": "string"
      },
      "description": "Key-value pairs for categorization."
    },
    "keepalive_pool": {
      "type": "object",
      "description": "Keepalive pool configuration.",
      "properties": {
        "size": {
          "type": "integer",
          "default": 320
        },
        "idle_timeout": {
          "type": "number",
          "default": 60
        },
        "requests": {
          "type": "integer",
          "default": 1000
        }
      }
    },
    "tls": {
      "type": "object",
      "description": "TLS configuration for upstream connections.",
      "properties": {
        "client_cert": {
          "type": "string",
          "description": "Client certificate for mTLS."
        },
        "client_key": {
          "type": "string",
          "description": "Client private key for mTLS."
        }
      }
    }
  }
}