Open Policy Agent

REST API Edit

This document is the authoritative specification of the OPA REST API. The API can be broken down into the following groups:

Policy API - manage policy loaded into the OPA instance.
Data API - evaluate rules and retrieve data.
Query API - execute adhoc queries.
Compile API - access Rego’s Partial Evaluation functionality.
Health API - access instance operational health information.
Config API - view instance configuration.
Status API - view instance status state.

The REST API is a common way to integrate with OPA. There are 18 OPA Ecosystem projects - many of which are open source - built on the REST API which might serve as inspiration. You may also want to review the integration documentation for other options to build on OPA by embedding functionality directly into your application.

Integrating with OPA from a programming language? You might find it easier to build your OPA integration using one of the language SDKs than working with the REST API directly.

Policy API

The Policy API exposes CRUD endpoints for managing policy modules. Policy modules can be added, removed, and modified at any time.

The identifiers given to policy modules are only used for management purposes. They are not used outside the Policy API.

List Policies

GET /v1/policies HTTP/1.1

List policy modules.

Status Codes

200 - no error
500 - server error

Example Request

GET /v1/policies HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": [
    {
      "id": "example2",
      "raw": "package opa.examples\n\nimport data.servers\n\nviolations[server] {\n\tserver = servers[_]\n\tserver.protocols[_] = \"http\"\n\tpublic_servers[server]\n}\n",
      "ast": {
        "package": {
          "path": [
            {
              "type": "var",
              "value": "data"
            },
            {
              "type": "string",
              "value": "opa"
            },
            {
              "type": "string",
              "value": "examples"
            }
          ]
        },
        "rules": [
          {
            "head": {
              "name": "violations",
              "key": {
                "type": "var",
                "value": "server"
              }
            },
            "body": [
              {
                "index": 0,
                "terms": [
                  {
                    "type": "string",
                    "value": "eq"
                  },
                  {
                    "type": "var",
                    "value": "server"
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "data"
                      },
                      {
                        "type": "string",
                        "value": "servers"
                      },
                      {
                        "type": "var",
                        "value": "$0"
                      }
                    ]
                  }
                ]
              },
              {
                "index": 1,
                "terms": [
                  {
                    "type": "string",
                    "value": "eq"
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "server"
                      },
                      {
                        "type": "string",
                        "value": "protocols"
                      },
                      {
                        "type": "var",
                        "value": "$1"
                      }
                    ]
                  },
                  {
                    "type": "string",
                    "value": "http"
                  }
                ]
              },
              {
                "index": 2,
                "terms": {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "data"
                    },
                    {
                      "type": "string",
                      "value": "opa"
                    },
                    {
                      "type": "string",
                      "value": "examples"
                    },
                    {
                      "type": "string",
                      "value": "public_servers"
                    },
                    {
                      "type": "var",
                      "value": "server"
                    }
                  ]
                }
              }
            ]
          }
        ]
      }
    },
    {
      "id": "example1",
      "raw": "package opa.examples\n\nimport data.servers\nimport data.networks\nimport data.ports\n\npublic_servers[server] {\n\tserver = servers[_]\n\tserver.ports[_] = ports[k].id\n\tports[k].networks[_] = networks[m].id\n\tnetworks[m].public = true\n}\n",
      "ast": {
        "package": {
          "path": [
            {
              "type": "var",
              "value": "data"
            },
            {
              "type": "string",
              "value": "opa"
            },
            {
              "type": "string",
              "value": "examples"
            }
          ]
        },
        "rules": [
          {
            "head": {
              "name": "public_servers",
              "key": {
                "type": "var",
                "value": "server"
              }
            },
            "body": [
              {
                "index": 0,
                "terms": [
                  {
                    "type": "string",
                    "value": "eq"
                  },
                  {
                    "type": "var",
                    "value": "server"
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "data"
                      },
                      {
                        "type": "string",
                        "value": "servers"
                      },
                      {
                        "type": "var",
                        "value": "$0"
                      }
                    ]
                  }
                ]
              },
              {
                "index": 1,
                "terms": [
                  {
                    "type": "string",
                    "value": "eq"
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "server"
                      },
                      {
                        "type": "string",
                        "value": "ports"
                      },
                      {
                        "type": "var",
                        "value": "$1"
                      }
                    ]
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "data"
                      },
                      {
                        "type": "string",
                        "value": "ports"
                      },
                      {
                        "type": "var",
                        "value": "k"
                      },
                      {
                        "type": "string",
                        "value": "id"
                      }
                    ]
                  }
                ]
              },
              {
                "index": 2,
                "terms": [
                  {
                    "type": "string",
                    "value": "eq"
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "data"
                      },
                      {
                        "type": "string",
                        "value": "ports"
                      },
                      {
                        "type": "var",
                        "value": "k"
                      },
                      {
                        "type": "string",
                        "value": "networks"
                      },
                      {
                        "type": "var",
                        "value": "$2"
                      }
                    ]
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "data"
                      },
                      {
                        "type": "string",
                        "value": "networks"
                      },
                      {
                        "type": "var",
                        "value": "m"
                      },
                      {
                        "type": "string",
                        "value": "id"
                      }
                    ]
                  }
                ]
              },
              {
                "index": 3,
                "terms": [
                  {
                    "type": "string",
                    "value": "eq"
                  },
                  {
                    "type": "ref",
                    "value": [
                      {
                        "type": "var",
                        "value": "data"
                      },
                      {
                        "type": "string",
                        "value": "networks"
                      },
                      {
                        "type": "var",
                        "value": "m"
                      },
                      {
                        "type": "string",
                        "value": "public"
                      }
                    ]
                  },
                  {
                    "type": "boolean",
                    "value": true
                  }
                ]
              }
            ]
          }
        ]
      }
    }
  ]
}

Get a Policy

GET /v1/policies/<id>

Get a policy module.

Query Parameters

pretty - If parameter is true, response will be formatted for humans.

Status Codes

200 - no error
404 - not found
500 - server error

Example Request

GET /v1/policies/example1 HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": {
    "id": "example1",
    "raw": "package opa.examples\n\nimport data.servers\nimport data.networks\nimport data.ports\n\npublic_servers[server] {\n\tserver = servers[_]\n\tserver.ports[_] = ports[k].id\n\tports[k].networks[_] = networks[m].id\n\tnetworks[m].public = true\n}\n",
    "ast": {
      "package": {
        "path": [
          {
            "type": "var",
            "value": "data"
          },
          {
            "type": "string",
            "value": "opa"
          },
          {
            "type": "string",
            "value": "examples"
          }
        ]
      },
      "rules": [
        {
          "head": {
            "name": "public_servers",
            "key": {
              "type": "var",
              "value": "server"
            }
          },
          "body": [
            {
              "index": 0,
              "terms": [
                {
                  "type": "string",
                  "value": "eq"
                },
                {
                  "type": "var",
                  "value": "server"
                },
                {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "data"
                    },
                    {
                      "type": "string",
                      "value": "servers"
                    },
                    {
                      "type": "var",
                      "value": "$0"
                    }
                  ]
                }
              ]
            },
            {
              "index": 1,
              "terms": [
                {
                  "type": "string",
                  "value": "eq"
                },
                {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "server"
                    },
                    {
                      "type": "string",
                      "value": "ports"
                    },
                    {
                      "type": "var",
                      "value": "$1"
                    }
                  ]
                },
                {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "data"
                    },
                    {
                      "type": "string",
                      "value": "ports"
                    },
                    {
                      "type": "var",
                      "value": "k"
                    },
                    {
                      "type": "string",
                      "value": "id"
                    }
                  ]
                }
              ]
            },
            {
              "index": 2,
              "terms": [
                {
                  "type": "string",
                  "value": "eq"
                },
                {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "data"
                    },
                    {
                      "type": "string",
                      "value": "ports"
                    },
                    {
                      "type": "var",
                      "value": "k"
                    },
                    {
                      "type": "string",
                      "value": "networks"
                    },
                    {
                      "type": "var",
                      "value": "$2"
                    }
                  ]
                },
                {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "data"
                    },
                    {
                      "type": "string",
                      "value": "networks"
                    },
                    {
                      "type": "var",
                      "value": "m"
                    },
                    {
                      "type": "string",
                      "value": "id"
                    }
                  ]
                }
              ]
            },
            {
              "index": 3,
              "terms": [
                {
                  "type": "string",
                  "value": "eq"
                },
                {
                  "type": "ref",
                  "value": [
                    {
                      "type": "var",
                      "value": "data"
                    },
                    {
                      "type": "string",
                      "value": "networks"
                    },
                    {
                      "type": "var",
                      "value": "m"
                    },
                    {
                      "type": "string",
                      "value": "public"
                    }
                  ]
                },
                {
                  "type": "boolean",
                  "value": true
                }
              ]
            }
          ]
        }
      ]
    }
  }
}

Create or Update a Policy

PUT /v1/policies/<id>
Content-Type: text/plain

Create or update a policy module.

If the policy module does not exist, it is created. If the policy module already exists, it is replaced.

Query Parameters

pretty - If parameter is true, response will be formatted for humans.
metrics - Return compiler performance metrics in addition to result. See Performance Metrics for more detail.

Status Codes

200 - no error
400 - bad request
500 - server error

Before accepting the request, the server will parse, compile, and install the policy module. If the policy module is invalid, one of these steps will fail and the server will respond with 400. The error message in the response will be set to indicate the source of the error.

Example Request

PUT /v1/policies/example1 HTTP/1.1
Content-Type: text/plain

package opa.examples

import rego.v1

import data.networks
import data.ports
import data.servers

public_servers contains server if {
	some k, m
	server := servers[_]
	server.ports[_] == ports[k].id
	ports[k].networks[_] == networks[m].id
	networks[m].public == true
}

cURL’s -d/--data flag removes newline characters from input files. Use the --data-binary flag instead.

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{}

Delete a Policy

DELETE /v1/policies/<id>

Delete a policy module.

Query Parameters

pretty - If parameter is true, response will be formatted for humans.
metrics - Return compiler performance metrics in addition to result. See Performance Metrics for more detail.

Status Codes

200 - no error
400 - bad request
404 - not found
500 - server error

If other policy modules in the same package depend on rules in the policy module to be deleted, the server will return 400.

Example Request

DELETE /v1/policies/example2 HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{}

Data API

The Data API exposes endpoints for reading and writing documents in OPA. For an explanation to the different types of documents in OPA see How Does OPA Work?

Get a Document

GET /v1/data/{path:.+}

Get a document.

The path separator is used to access values inside object and array documents. The server attempts to convert path segments to integers. If a path element cannot be converted to an integer, the server will use its string representation.

Query Parameters

input - Provide an input document. Format is a JSON value that will be used as the value for the input document.
pretty - If parameter is true, response will be formatted for humans.
provenance - If parameter is true, response will include build/version info in addition to the result. See Provenance for more detail.
explain - Return query explanation in addition to result. Values: notes, fails, full, debug.
metrics - Return query performance metrics in addition to result. See Performance Metrics for more detail.
instrument - Instrument query evaluation and return a superset of performance metrics in addition to result. See Performance Metrics for more detail.
strict-builtin-errors - Treat built-in function call errors as fatal and return an error immediately.

Request Headers

Accept-Encoding: gzip: Indicates the server should respond with a gzip encoded body. The server will send the compressed response only if its length is above server.encoding.gzip.min_length value. See the configuration section

Status Codes

200 - no error
400 - bad request
500 - server error

The server returns 400 if the input document is invalid (i.e. malformed JSON).

The server returns 200 if the path refers to an undefined document. In this case, the response will not contain a result property.

Response Message

result - The base or virtual document referred to by the URL path. If the path is undefined, this key will be omitted.
metrics - If query metrics are enabled, this field contains query performance metrics collected during the parse, compile, and evaluation steps.

decision_id - If decision logging is enabled, this field contains a string that uniquely identifies the decision. The identifier will be included in the decision log event for this decision. Callers can use the identifier for correlation purposes.

Example Request

GET /v1/data/opa/examples/public_servers HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": [
    {
      "id": "s1",
      "name": "app",
      "ports": [
        "p1",
        "p2",
        "p3"
      ],
      "protocols": [
        "https",
        "ssh"
      ]
    },
    {
      "id": "s4",
      "name": "dev",
      "ports": [
        "p1",
        "p2"
      ],
      "protocols": [
        "http"
      ]
    }
  ]
}

Get a Document (with Input)

POST /v1/data/{path:.+}
Content-Type: application/json

{
  "input": ...
}

Get a document that requires input.

The request body contains an object that specifies a value for The input Document.

Request Headers

Content-Type: application/yaml: Indicates the request body is a YAML encoded object.
Content-Encoding: gzip: Indicates the request body is a gzip encoded object.
Accept-Encoding: gzip: Indicates the server should respond with a gzip encoded body. The server will send the compressed response only if its length is above server.encoding.gzip.min_length value. See the configuration section

Query Parameters

pretty - If parameter is true, response will be formatted for humans.
provenance - If parameter is true, response will include build/version info in addition to the result. See Provenance for more detail.
explain - Return query explanation in addition to result. Values: notes, fails, full, debug.
metrics - Return query performance metrics in addition to result. See Performance Metrics for more detail.
instrument - Instrument query evaluation and return a superset of performance metrics in addition to result. See Performance Metrics for more detail.
strict-builtin-errors - Treat built-in function call errors as fatal and return an error immediately.

Status Codes

200 - no error
400 - bad request
500 - server error

The server returns 400 if the input document is invalid (i.e. malformed JSON).

The server returns 200 if the path refers to an undefined document. In this case, the response will not contain a result property.

Response Message

result - The base or virtual document referred to by the URL path. If the path is undefined, this key will be omitted.
metrics - If query metrics are enabled, this field contains query performance metrics collected during the parse, compile, and evaluation steps.

decision_id - If decision logging is enabled, this field contains a string that uniquely identifies the decision. The identifier will be included in the decision log event for this decision. Callers can use the identifier for correlation purposes.

The examples below assume the following policy:

package opa.examples

import rego.v1

import input.example.flag

allow_request if flag == true

Example Request

POST /v1/data/opa/examples/allow_request HTTP/1.1
Content-Type: application/json

{
  "input": {
    "example": {
      "flag": true
    }
  }
}

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": true
}

Example Request

POST /v1/data/opa/examples/allow_request HTTP/1.1
Content-Type: application/json

{
  "input": {
    "example": {
      "flag": false
    }
  }
}

Example Response

HTTP/1.1 200 OK

{}

Get a Document (Webhook)

POST /v0/data/{path:.+}
Content-Type: application/json

Get a document from a webhook.

Use this API if you are enforcing policy decisions via webhooks that have pre-defined request/response formats. Note, the API path prefix is /v0 instead of /v1.

The request message body defines the content of the input document. The request message body may be empty. The path separator is used to access values inside object and array documents.

Request Headers

Content-Type: application/yaml: Indicates the request body is a YAML encoded object.
Content-Encoding: gzip: Indicates the request body is a gzip encoded object.
Accept-Encoding: gzip: Indicates the server should respond with a gzip encoded body. The server will send the compressed response only if its length is above server.encoding.gzip.min_length value. See the configuration section

Query Parameters

pretty - If parameter is true, response will be formatted for humans.

Status Codes

200 - no error
400 - bad request
404 - not found
500 - server error

If the requested document is missing or undefined, the server will return 404 and the message body will contain an error object.

The examples below assume the following policy:

package opa.examples

import rego.v1

import input.example.flag

allow_request if flag == true

Example Request

POST /v0/data/opa/examples/allow_request HTTP/1.1
Content-Type: application/json

{
  "example": {
    "flag": true
  }
}

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

true

Create or Overwrite a Document

PUT /v1/data/{path:.+}
Content-Type: application/json

Create or overwrite a document.

If the path does not refer to an existing document, the server will attempt to create all the necessary containing documents. This behavior is similar in principle to the Unix command mkdir -p.

The server will respect the If-None-Match header if it is set to *. In this case, the server will not overwrite an existing document located at the path.

Query Parameters

metrics - Return performance metrics in addition to result. See Performance Metrics for more detail.

Status Codes

204 - no content (success)
304 - not modified
400 - bad request
404 - write conflict
500 - server error

If the path refers to a virtual document or a conflicting base document the server will respond with 404. A base document conflict will occur if the parent portion of the path refers to a non-object document.

Example Request To Initialize Document With If-None-Match

PUT /v1/data/us-west/servers HTTP/1.1
Content-Type: application/json
If-None-Match: *

{}

Example Response If Document Already Exists

HTTP/1.1 304 Not Modified

Example Response If Document Does Not Exist

HTTP/1.1 204 No Content

Patch a Document

PATCH /v1/data/{path:.+}
Content-Type: application/json-patch+json

Update a document.

The server accepts updates encoded as JSON Patch operations. The message body of the request should contain a JSON encoded array containing one or more JSON Patch operations. Each operation specifies the operation type, path, and an optional value. For more information on JSON Patch, see RFC 6902.

The effective path of the JSON Patch operation is obtained by joining the path portion of the URL with the path value from the operation(s) contained in the message body. In all cases, the parent of the effective path MUST refer to an existing document, otherwise the server returns 404. In the case of remove and replace operations, the effective path MUST refer to an existing document, otherwise the server returns 404.

Status Codes

204 - no content (success)
400 - bad request
404 - not found
500 - server error

Example Request

PATCH /v1/data/servers HTTP/1.1
Content-Type: application/json-patch+json

[
    {"op": "add",
     "path": "-",
     "value": {
         "id": "s5",
         "name": "job",
         "protocols": ["amqp"],
         "ports": ["p3"]
     }}
]

Example Response

HTTP/1.1 204 No Content

Delete a Document

DELETE /v1/data/{path:.+}

Delete a document.

The server processes the DELETE method as if the client had sent a PATCH request containing a single remove operation.

Query Parameters

metrics - Return performance metrics in addition to result. See Performance Metrics for more detail.

Status Codes

204 - no content (success)
404 - not found
500 - server error

If the path refers to a non-existent document, the server returns 404.

Example Request

DELETE /v1/data/servers HTTP/1.1

Example Response

HTTP/1.1 204 No Content

Query API

Execute a Simple Query

POST /
Content-Type: application/json

Execute a simple query.

OPA serves POST requests without a URL path by querying for the document at path /data/system/main by default. The content of that document defines the response entirely. This default can be overridden by the default_decision configuration. See the Configuration Reference for more information.

Request Headers

Content-Type: application/yaml: Indicates the request body is a YAML encoded object.

Query Parameters

pretty - If parameter is true, response will be formatted for humans.

Status Codes

200 - no error
400 - bad request
404 - not found
500 - server error

If the default decision (defaulting to /system/main) is undefined, the server returns 404.

The policy example below shows how to define a rule that will produce a value for the /data/system/main document. You can configure OPA to use a different URL path to serve these queries. See the Configuration Reference for more information.

The request message body is mapped to the Input Document.

PUT /v1/policies/example1 HTTP/1.1
Content-Type: text/plain

package system

import rego.v1

main := msg if {
	msg := sprintf("hello, %v", [input.user])
}

Example Request

POST /
Content-Type: application/json

{
  "user": ["alice"]
}

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

"hello, alice"

Execute an Ad-hoc Query

Execute an ad-hoc query and return bindings for variables found in the query.

GET /v1/query

Query Parameters

q - The ad-hoc query to execute. OPA will parse, compile, and execute the query represented by the parameter value. The value MUST be URL encoded. Only used in GET method. For POST method the query is sent as part of the request body and this parameter is not used.
pretty - If parameter is true, response will be formatted for humans.
explain - Return query explanation in addition to result. Values: notes, fails, full, debug.
metrics - Return query performance metrics in addition to result. See Performance Metrics for more detail.

Status Codes

200 - no error
400 - bad request
500 - server error
501 - streaming not implemented

For queries that have large JSON values it is recommended to use the POST method with the query included as the POST body:

POST /v1/query HTTP/1.1
Content-Type: application/json

{
  "query": "input.servers[i].ports[_] = \"p2\"; input.servers[i].name = name",
  "input": {
    "servers": [ ... ],
  }
}

Example Request

GET /v1/query?q=data.servers[i].ports[_] = "p2"; data.servers[i].name = name HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": [
    {
      "i": 3,
      "name": "dev"
    },
    {
      "i": 0,
      "name": "app"
    }
  ]
}

Compile API

Partially Evaluate a Query

POST /v1/compile
Content-Type: application/json

Partially evaluate a query.

The Compile API allows you to partially evaluate Rego queries and obtain a simplified version of the policy. This is most useful when building integrations where policy logic is to be translated and evaluated in another environment. For example, this post on the OPA blog shows how SQL can be generated based on Compile API output. For more details on Partial Evaluation in OPA, please refer to this blog post.

Request Body

Compile API requests contain the following fields:

Field	Type	Required	Description
`query`	`string`	Yes	The query to partially evaluate and compile.
`input`	`any`	No	The input document to use during partial evaluation (default: undefined).
`options`	`object[string, any]`	No	Additional options to use during partial evaluation. Only `disableInlining` option is supported. (default: undefined).
`unknowns`	`array[string]`	No	The terms to treat as unknown during partial evaluation (default: `["input"]`]).

Request Headers

Content-Encoding: gzip: Indicates the request body is a gzip encoded object.
Accept-Encoding: gzip: Indicates the server should respond with a gzip encoded body. The server will send the compressed response only if its length is above server.encoding.gzip.min_length value

Query Parameters

pretty - If parameter is true, response will be formatted for humans.
explain - Return query explanation in addition to result. Values: notes, fails, full, debug.
metrics - Return query performance metrics in addition to result. See Performance Metrics for more detail.
instrument - Instrument query evaluation and return a superset of performance metrics in addition to result. See Performance Metrics for more detail.

Status Codes

200 - no error
400 - bad request
500 - server error

The example below assumes that OPA has been given the following policy:

package example

import rego.v1

allow if {
	input.subject.clearance_level >= data.reports[_].clearance_level
}

Example Request

POST /v1/compile HTTP/1.1
Content-Type: application/json

{
  "query": "data.example.allow == true",
  "input": {
    "subject": {
      "clearance_level": 4
    }
  },
  "options": {
    "disableInlining": []
  },
  "unknowns": [
    "data.reports"
  ]
}

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": {
    "queries": [
      [
        {
          "index": 0,
          "terms": [
            {
              "type": "ref",
              "value": [
                {
                  "type": "var",
                  "value": "gte"
                }
              ]
            },
            {
              "type": "number",
              "value": 4
            },
            {
              "type": "ref",
              "value": [
                {
                  "type": "var",
                  "value": "data"
                },
                {
                  "type": "string",
                  "value": "reports"
                },
                {
                  "type": "var",
                  "value": "i1"
                },
                {
                  "type": "string",
                  "value": "clearance_level"
                }
              ]
            }
          ]
        }
      ]
    ]
  }
}

Unconditional Results from Partial Evaluation

When you partially evaluate a query with the Compile API, OPA returns a new set of queries and supporting policies. However, in some cases, the result of Partial Evaluation is a conclusive, unconditional answer.

For example, if you extend to policy above to include a “break glass” condition, the decision may be to allow all requests regardless of clearance level.

package example

import rego.v1

allow if {
	input.subject.clearance_level >= data.reports[_].clearance_level
}

allow if {
	data.break_glass = true
}

In this case, if data.break_glass is true then the query data.example.allow == true will always be true. If the query is always true, the "queries" value in the result will contain an empty array. The empty array indicates that your query can be satisfied without any further evaluation.

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": {
    "queries": [
      [],
      [
        {
          "index": 0,
          "terms": [
            {
              "type": "ref",
              "value": [
                {
                  "type": "var",
                  "value": "gte"
                }
              ]
            },
            {
              "type": "number",
              "value": 4
            },
            {
              "type": "ref",
              "value": [
                {
                  "type": "var",
                  "value": "data"
                },
                {
                  "type": "string",
                  "value": "reports"
                },
                {
                  "type": "var",
                  "value": "$02"
                },
                {
                  "type": "string",
                  "value": "clearance_level"
                }
              ]
            }
          ]
        }
      ]
    ]
  }
}

It is also possible for queries to never be true. For example, the original policy could be extended to require that users be granted an exception:

package example

import rego.v1

allow if {
	input.subject.clearance_level >= data.reports[_].clearance_level
	exceptions[input.subject.name]
}

exceptions contains "bob"
exceptions contains "alice"

In this case, if we execute query on behalf of a user that does not have an exception (e.g., "eve"), the OPA response will not contain a queries field at all. This indicates there are NO conditions that could make the query true.

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": {}
}

The following table summarizes the behavior for partial evaluation results.

Example Query	Unknowns	Result	Description
`input.x > 0`	`["input"]`	`{"result": {"queries": [[input.x > 0]]}}`	The query is partially evaluated and remaining conditions are returned.
`input.x > 0`	Not specified.	`{"result": {"queries": [[input.x > 0]]}}`	If the set of unknowns is not specified, it defaults to `["input"]`.
`input.x > 0`	`[]`	`{"result": {}}`	The query is false/undefined because there are no unknowns.
`1 > 0`	N/A	`{"result": {"queries": [[]]}}`	The query is always true.
`1 < 0`	N/A	`{"result": {}}`	The query is always false.

The partially evaluated queries are represented as strings in the table above. The actual API response contains the JSON AST representation.

Health API

The /health API endpoint executes a simple built-in policy query to verify that the server is operational. Optionally it can account for bundle activation as well (useful for “ready” checks at startup).

Query Parameters

bundles - Boolean parameter to account for bundle activation status in response. This includes any discovery bundles or bundles defined in the loaded discovery configuration.
plugins - Boolean parameter to account for plugin status in response.
exclude-plugin - String parameter to exclude a plugin from status checks. Can be added multiple times. Does nothing if plugins is not true. This parameter is useful for special use cases where a plugin depends on the server being fully initialized before it can fully initialize itself.

Status Codes

200 - OPA service is healthy. If the bundles option is specified then all configured bundles have been activated. If the plugins option is specified then all plugins are in an OK state.
500 - OPA service is not healthy. If the bundles option is specified this can mean any of the configured bundles have not yet been activated. If the plugins option is specified then at least one plugin is in a non-OK state.

The bundle activation check is only for initial bundle activation. Subsequent downloads will not affect the health check. The Status API should be used for more fine-grained bundle status monitoring.

Example Request

GET /health HTTP/1.1

Example Request (bundle activation)

GET /health?bundles HTTP/1.1

Example Request (plugin status)

GET /health?plugins HTTP/1.1

Example Request (plugin status with exclude)

GET /health?plugins&exclude-plugin=decision-logs&exclude-plugin=status HTTP/1.1

Healthy Response

HTTP/1.1 200 OK
Content-Type: application/json

{}

Unhealthy Response

HTTP/1.1 500 Internal Server Error
Content-Type: application/json

{
  "error": "not all plugins in OK state"
}

Other error messages include:

"unable to perform evaluation"
"not all configured bundles have been activated"

Custom Health Checks

The Health API includes support for “all or nothing” checks that verify configured bundles have activated and plugins are operational. In some cases, health checks may need to perform fine-grained checks on plugin state or other internal components. To support these cases, use the policy-based Health API.

By convention, the /health/live and /health/ready API endpoints allow you to use Rego to evaluate the current state of the server and its plugins to determine “liveness” (when OPA is capable of receiving traffic) and “readiness” (when OPA is ready to receive traffic). Policy for the live and ready rules is defined under package system.health.

The “liveness” and “readiness” check convention comes from Kubernetes but they are just conventions. You can implement your own check endpoints under the system.health package as needed. Any rules implemented inside system.health will be exposed at /health/<rule-name>.

Policy Examples

Here is a basic health policy for liveness and readiness. In this example, OPA is live once it is able to process the live rule. OPA is ready once all plugins have entered the OK state at least once.

package system.health

import rego.v1

# opa is live if it can process this rule
default live := true

# by default, opa is not ready
default ready := false

# opa is ready once all plugins have reported OK at least once
ready if {
	input.plugins_ready
}

Note that once input.plugins_ready is true, it stays true. If you want to fail the ready check when specific a plugin leaves the OK state, try this:

package system.health

import rego.v1

default live := true

default ready := false

# opa is ready once all plugins have reported OK at least once AND
# the bundle plugin is currently in an OK state
ready if {
	input.plugins_ready
	input.plugin_state.bundle == "OK"
}

See the following section for all the inputs available to use in health policy.

Policy Inputs

input.plugins_ready: Will be false until all registered plugins have started and are reporting an OK state, at which point it will be true. Once true, it will stay true until the process ends.
input.plugin_state.<plugin_name>: Shows the current state of a plugin, where <plugin_name> is replaced with the name of the plugin, e.g. bundle, status.

Status Codes

200 - OPA service is healthy.
500 - OPA service is not healthy because policy has not evaluated to true, or is missing.

Example Requests

GET /health/ready HTTP/1.1

GET /health/live HTTP/1.1

Healthy Response

HTTP/1.1 200 OK
Content-Type: application/json

{}

Unhealthy Response

HTTP/1.1 500 Internal Server Error
Content-Type: application/json

{
  "error": "health policy was not true at data.system.health.<rule_name>"
}

Other error messages include:

"health policy was undefined at data.system.health.<rule_name>"

Config API

The /config API endpoint returns OPA’s active configuration. When the discovery feature is enabled, this API can be used to fetch the discovered configuration in the last evaluated discovery bundle. The credentials field in the Services configuration and the private_key and key fields in the Keys configuration will be omitted from the API response.

Get Config

GET /v1/config HTTP/1.1

Query Parameters

pretty - If parameter is true, response will be formatted for humans.

Status Codes

200 - no error
500 - server error

Example Request

GET /v1/config HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": {
    "services": {
      "acmecorp": {
        "url": "https://example.com/control-plane-api/v1"
      }
    },
    "labels": {
      "id": "test-id",
      "version": "0.27.0"
    },
    "keys": {
      "global_key": {
        "scope": "read"
      }
    },
    "decision_logs": {
      "service": "acmecorp"
    },
    "status": {
      "service": "acmecorp"
    },
    "bundles": {
      "authz": {
        "service": "acmecorp"
      }
    },
    "default_authorization_decision": "/system/authz/allow",
    "default_decision": "/system/main"
  }
}

Status API

The /status endpoint exposes a pull-based API for accessing OPA Status information. Normally this information is pushed by OPA to a remote service via HTTP, console, or custom plugins. However, in some cases, callers may wish to poll OPA and fetch the information.

Get Status

GET /v1/status HTTP/1.1

Query Parameters

pretty - If parameter is true, response will be formatted for humans.

Status Codes

200 - no error
500 - server error

Example Request

GET /v1/status HTTP/1.1

Example Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": {
    "labels": {
      "id": "7da62ac6-42e0-4b3c-b6d5-199239ad436e",
      "version": "99.9.9-dev"
    },
    "bundles": {
      "play": {
        "name": "play",
        "active_revision": "b3BlbnBvbGljeWFnZW50Lm9yZw==",
        "last_successful_activation": "2021-12-08T01:36:14.201927Z",
        "last_successful_download": "2021-12-08T01:36:14.20038Z",
        "last_successful_request": "2021-12-08T01:36:23.131346Z",
        "last_request": "2021-12-08T01:36:23.131346Z",
        "metrics": {
          "timer_bundle_request_ns": 168273779
        }
      }
    },
    "metrics": {
      "prometheus": {
<------------------8<------------------>
      }
    },
    "plugins": {
      "bundle": {
        "state": "OK"
      },
      "decision_logs": {
        "state": "OK"
      },
      "discovery": {
        "state": "OK"
      },
      "status": {
        "state": "OK"
      }
    }
  }
}

Authentication

The API is secured via HTTPS, Authentication, and Authorization.

Bearer Tokens

When OPA is started with the --authentication=token command line flag, clients MUST provide a Bearer token in the HTTP Authorization header:

GET /v1/data/exempli-gratia HTTP/1.1
Authorization: Bearer my-secret-token

Bearer tokens must be represented with a valid HTTP header value character sequence.

OPA will extract the Bearer token value (which is set to my-secret-token above) and provide it to the authorization component inside OPA that will (i) validate the token and (ii) execute the authorization policy configured by the admin.

Errors

All the API endpoints use standard HTTP status codes to indicate success or failure of an API call. If an API call fails, the response will contain a JSON encoded object that provides more detail. The errors and location fields are optional:

{
  "code": "invalid_parameter",
  "message": "error(s) occurred while compiling module(s)",
  "errors": [
    {
      "code": "rego_unsafe_var_error",
      "message": "var x is unsafe",
      "location": {
        "file": "example",
        "row": 3,
        "col": 1
      }
    }
  ]
}

Method not Allowed

OPA will respond with a 405 Error (Method Not Allowed) if the method used to access the URL is not supported. For example, if a client uses the HEAD method to access any path within “/v1/data/{path:.*}”, a 405 will be returned.

Explanations

OPA supports query explanations that describe (in detail) the steps taken to produce query results.

Explanations can be requested for:

Data API GET queries
Query API queries

Explanations are requested by setting the explain query parameter to one of the following values:

off - do not return any trace.
full - returns a full query trace containing every step in the query evaluation process.
debug - returns a full query trace including debug info.
notes - returns only note events and their context.
fails - returns only fail events and their context.

By default, explanations are represented in a machine-friendly format. Set the pretty parameter to request a human-friendly format for debugging purposes.

Trace Events

When the explain query parameter is set to anything except off, the response contains an array of Trace Event objects.

Trace Event objects contain the following fields:

op - identifies the kind of Trace Event. Values: “Enter”, “Exit”, “Eval”, “Fail”, “Redo”.
query_id - uniquely identifies the query that the Trace Event was emitted for.
parent_id - identifies the parent query.
type - indicates the type of the node field. Values: “expr”, “rule”, “body”.
node - contains the AST element associated with the evaluation step.
locals - contains the term bindings from the query at the time when the Trace Event was emitted.

Query IDs

Queries often reference rules or contain comprehensions. In both cases, query evaluation involves evaluation of one or more other queries, e.g., the body of the rule or comprehension.

Trace Events from different queries can be distinguished by the query_id field.

Trace Events from related queries can be identified by the parent_id field.

For example, if query A references a rule R, Trace Events emitted as part of evaluating rule R’s body will have the parent_id field set to query A’s query_id.

Types of Events

Each Trace Event represents a step in the query evaluation process. Trace Events are emitted at the following points:

enter - before a body or rule is evaluated.
exit - after a body or rule has evaluated successfully.
eval - before an expression is evaluated.
fail - after an expression has evaluated to false.
redo - before evaluation restarts from a body, rule, or expression.

By default, OPA searches for all sets of term bindings that make all expressions in the query evaluate to true. Because there may be multiple answers, the search can restart when OPA determines the query is true or false. When the search restarts, a Redo Trace Event is emitted.

Example Trace Event

{
  "op": "eval",
  "query_id": 20,
  "parent_id": 0,
  "type": "expr",
  "node": {
    "index": 1,
    "terms": [
      {
        "type": "var",
        "value": "eq"
      },
      {
        "type": "var",
        "value": "x"
      },
      {
        "type": "var",
        "value": "y"
      }
    ]
  },
  "locals": [
    {
      "key": {
        "type": "var",
        "value": "x"
      },
      "value": {
        "type": "string",
        "value": "hello"
      }
    }
  ]
}

Performance Metrics

OPA can report detailed performance metrics at runtime. Performance metrics can be requested on individual API calls and are returned inline with the API response. To enable performance metric collection on an API call, specify the metrics=true query parameter when executing the API call. Performance metrics are currently supported for the following APIs:

Policy API (PUT and DELETE)
Data API (GET, POST, PUT, and DELETE)
Query API (all methods)
Compile API (POST)

For example:

POST /v1/data/example?metrics=true HTTP/1.1

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "metrics": {
    "timer_rego_query_compile_ns": 69994,
    "timer_rego_query_eval_ns": 48425,
    "timer_rego_query_parse_ns": 4096
  },
  "result": {
    "some_strings": [
      "hello",
      "world"
    ]
  }
}

OPA currently supports the following query performance metrics:

timer_rego_input_parse_ns: time taken (in nanoseconds) to parse the input
timer_rego_query_parse_ns: time taken (in nanoseconds) to parse the query.
timer_rego_query_compile_ns: time taken (in nanoseconds) to compile the query.
timer_rego_query_eval_ns: time taken (in nanoseconds) to evaluate the query.
timer_rego_module_parse_ns: time taken (in nanoseconds) to parse the input policy module.
timer_rego_module_compile_ns: time taken (in nanoseconds) to compile the loaded policy modules.
timer_server_handler_ns: time take (in nanoseconds) to handle the API request.
counter_server_query_cache_hit: number of cache hits for the query.

The counter_server_query_cache_hit counter gives an indication about whether OPA creates a new Rego query or it uses a pre-processed query which holds some prepared state to serve the API request. A pre-processed query will be faster to evaluate since OPA will not have to re-parse or compile it. Hence, when the query is served from the cache timer_rego_query_parse_ns and timer_rego_query_compile_ns timers will be omitted from the reported performance metrics.

OPA also supports query instrumentation. To enable query instrumentation, specify the instrument=true query parameter when executing the API call. Query instrumentation can help diagnose performance problems, however, it can add significant overhead to query evaluation. We recommend leaving query instrumentation off unless you are debugging a performance problem.

When instrumentation is enabled there are several additional performance metrics for the compilation stages. They follow the format of timer_compile_stage_*_ns and timer_query_compile_stage_*_ns for the query and module compilation stages.

Provenance

OPA can report provenance information at runtime. Provenance information can be requested on individual API calls and are returned inline with the API response. To obtain provenance information on an API call, specify the provenance=true query parameter when executing the API call. Provenance information is currently supported for the following APIs:

Data API (GET and POST)

For example:

POST /v1/data/example?provenance=true HTTP/1.1

Response:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "provenance": {
    "build_commit": "1955fc4d",
    "build_host": "foo.com",
    "build_timestamp": "2019-04-29T23:42:04Z",
    "bundles": {
      "authz": {
        "revision": "ID-b1298a6c-6ad8-11e9-a26f-d38b5ceadad5"
      }
    },
    "version": "0.10.8-dev"
  },
  "result": true
}

OPA currently supports the following query provenance information:

version: The version of this OPA instance.
build_commit: The git commit id of this OPA build.
build_timestamp: The timestamp when this instance was built.
build_host: The hostname where this instance was built.
revision: (Deprecated) The revision string included in a .manifest file (if present) within a bundle. Omitted when bundles are configured.
bundles: A set of key-value pairs describing each bundle activated on the server. Includes the revision field which is the revision string included in a .manifest file (if present) within a bundle

Ecosystem Projects

OPA’s REST API has already been used by many projects in the OPA Ecosystem to support a variety of use cases.

The 18 ecosystem projects related to this page can be found in the corresponding OPA Ecosystem section.

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