Proxy Options

Reverse proxy configuration for NpgsqlRest endpoints. When an endpoint is marked as a proxy, incoming HTTP requests are forwarded to an upstream service, and the response can either be returned directly to the client (passthrough mode) or processed by the PostgreSQL function (transform mode).

Overview

{
  "NpgsqlRest": {
    "ProxyOptions": {
      "Enabled": false,
      "Host": null,
      "DefaultTimeout": "00:00:30",
      "ForwardHeaders": true,
      "ExcludeHeaders": ["Host", "Content-Length", "Transfer-Encoding"],
      "ForwardResponseHeaders": true,
      "ExcludeResponseHeaders": ["Transfer-Encoding", "Content-Length"],
      "ResponseStatusCodeParameter": "_proxy_status_code",
      "ResponseBodyParameter": "_proxy_body",
      "ResponseHeadersParameter": "_proxy_headers",
      "ResponseContentTypeParameter": "_proxy_content_type",
      "ResponseSuccessParameter": "_proxy_success",
      "ResponseErrorMessageParameter": "_proxy_error_message",
      "ForwardUploadContent": false
    }
  }
}

Settings Reference

Setting	Type	Default	Description
Enabled	bool	false	Enable proxy functionality for endpoints with proxy annotations.
Host	string	null	Default upstream host URL. Can be overridden per endpoint with annotation.
DefaultTimeout	string	"00:00:30"	Default timeout for proxy requests. Format: "HH:MM:SS" or interval format (e.g., "30s").
ForwardHeaders	bool	true	Forward request headers to upstream service.
ExcludeHeaders	array	["Host", "Content-Length", "Transfer-Encoding"]	Request headers to exclude from forwarding.
ForwardResponseHeaders	bool	true	Forward response headers from upstream to client.
ExcludeResponseHeaders	array	["Transfer-Encoding", "Content-Length"]	Response headers to exclude from forwarding.
ForwardUploadContent	bool	false	Forward raw multipart/form-data to upstream instead of processing locally.

Response Parameter Names

These settings configure which parameter names receive proxy response data:

Setting	Type	Default	Description
ResponseStatusCodeParameter	string	"_proxy_status_code"	Parameter name for HTTP status code from upstream.
ResponseBodyParameter	string	"_proxy_body"	Parameter name for response body content.
ResponseHeadersParameter	string	"_proxy_headers"	Parameter name for response headers as JSON.
ResponseContentTypeParameter	string	"_proxy_content_type"	Parameter name for Content-Type header value.
ResponseSuccessParameter	string	"_proxy_success"	Parameter name for success indicator (true for 2xx status).
ResponseErrorMessageParameter	string	"_proxy_error_message"	Parameter name for error message if request failed.

Proxy Modes

Passthrough Mode

When the PostgreSQL function has no proxy response parameters, the upstream response is returned directly to the client without opening a database connection:

create function get_external_data()
returns void
language sql as 'select';

comment on function get_external_data() is 'HTTP GET
@proxy https://api.example.com/data';

Transform Mode

When the PostgreSQL function has parameters matching the configured response parameter names, the proxy response is passed to the function for processing:

create function get_and_transform(
    _proxy_status_code int default null,
    _proxy_body text default null,
    _proxy_headers json default null,
    _proxy_content_type text default null,
    _proxy_success boolean default null,
    _proxy_error_message text default null
)
returns json
language plpgsql as $$
begin
    if not _proxy_success then
        return json_build_object('error', _proxy_error_message);
    end if;
    return json_build_object(
        'status', _proxy_status_code,
        'data', _proxy_body::json
    );
end;
$$;

comment on function get_and_transform(int, text, json, text, boolean, text) is 'HTTP GET
@proxy https://api.example.com/data';

Response Parameters

When the PostgreSQL function has parameters matching these names, the proxy response data is passed to the function:

Parameter Name	Type	Description
_proxy_status_code	int	HTTP status code from upstream (e.g., 200, 404).
_proxy_body	text	Response body content.
_proxy_headers	json	Response headers as JSON object.
_proxy_content_type	text	Content-Type header value.
_proxy_success	boolean	True for 2xx status codes.
_proxy_error_message	text	Error message if request failed.

User Claims Forwarding

Query Parameters (user_params)

When user_params is enabled on the endpoint, user claim values are forwarded to the upstream proxy as query string parameters:

create function proxy_with_claims(
    _user_id text default null,        -- Forwarded as ?userId=...
    _user_name text default null,      -- Forwarded as ?userName=...
    _ip_address text default null,     -- Forwarded as ?ipAddress=...
    _user_claims json default null,    -- Forwarded as ?userClaims=...
    _proxy_status_code int default null,
    _proxy_body text default null
)
returns json language plpgsql as $$
begin
    return json_build_object('user', _user_id, 'data', _proxy_body);
end;
$$;

comment on function proxy_with_claims(text, text, text, json, int, text) is 'HTTP GET
@authorize
@user_params
@proxy https://api.example.com/data';

HTTP Headers (user_context)

When user_context is enabled, user context values are forwarded as HTTP headers to the upstream proxy:

create function proxy_with_context(
    _proxy_status_code int default null,
    _proxy_body text default null
)
returns json language plpgsql as $$
begin
    return json_build_object('status', _proxy_status_code);
end;
$$;

comment on function proxy_with_context(int, text) is 'HTTP GET
@authorize
@user_context
@proxy https://api.example.com/data';
-- Headers forwarded: request.user_id, request.user_name, request.user_roles
-- (configurable via ContextKeyClaimsMapping)

Upload Forwarding

For upload endpoints with proxy, configure whether to process uploads locally or forward raw multipart data:

{
  "NpgsqlRest": {
    "ProxyOptions": {
      "ForwardUploadContent": false
    }
  }
}

Value	Description
false (default)	Uploads are processed locally; proxy receives parsed data.
true	Raw multipart/form-data is streamed directly to upstream (memory-efficient for large files).

Key Features

• Passthrough mode: No database connection opened when function has no proxy response parameters
• Transform mode: Process upstream response in PostgreSQL before returning to client
• User claims forwarding: Authenticated user claims passed as query parameters to upstream
• User context headers: User context values passed as HTTP headers to upstream
• Streaming uploads: Memory-efficient streaming for large file uploads when ForwardUploadContent is enabled
• Timeout handling: Configurable per-request timeout with proper 504 Gateway Timeout responses
• Header forwarding: Configurable request/response header forwarding with exclusion lists

Complete Example

Production configuration with proxy enabled:

{
  "NpgsqlRest": {
    "ProxyOptions": {
      "Enabled": true,
      "Host": "https://api.internal.example.com",
      "DefaultTimeout": "00:00:30",
      "ForwardHeaders": true,
      "ExcludeHeaders": ["Host", "Content-Length", "Transfer-Encoding", "Authorization"],
      "ForwardResponseHeaders": true,
      "ExcludeResponseHeaders": ["Transfer-Encoding", "Content-Length"],
      "ForwardUploadContent": false
    }
  }
}

Related

• proxy annotation - Enable proxy for specific endpoints
• user_context annotation - Enable user context forwarding
• user_parameters annotation - Enable user parameters forwarding
• Comment Annotations Guide - How annotations work
• Configuration Guide - How configuration works

Next Steps

• HTTP Client - HTTP Types for external API calls from PostgreSQL functions
• NpgsqlRest Options - Configure general NpgsqlRest settings
• Authentication - Configure authentication methods