servotron

Haiku

A deliverance -
an app server for Postgres
without O/R-M.

Why

Although it may seem trite to say it, Object/Relational Mapping is the Vietnam of Computer Science. It represents a quagmire which starts well, gets more complicated as time passes, and before long entraps its users in a commitment that has no clear demarcation point, no clear win conditions, and no clear exit strategy.

https://www.odbms.org/wp-content/uploads/2013/11/031.01-Neward-The-Vietnam-of-Computer-Science-June-2006.pdf

How

• SQL.
• Prepared statements provide authorization and API endpoints. PostgreSQL's row level security is also available.
• Authorization queries must return a boolean value indicating whether the request is authorized for the user.
• API queries return JSON (via PostgreSQL's JSON functions).
• User info is set on a per-request basis.
• For GET and DELETE requests, arguments parsed from the route and query string are passed in the order they appear in the route specification.
• For POST and PUT requests, the request body JSON is the first argument. The JSON string can be transformed into a record or recordset (for bulk inserts) via PostgreSQL's JSON functions. The data returned from the INSERT and UPDATE queries should contain the fields required of the associated SELECT for the resource.
• Service routes are proxied to associated service URLs.

Diagram

Dependencies

go

Install

git clone
go build
go install

Configuration

{
	"SQLRoot":"example/api",
	"FileServers":{
		"/assets":"example/www",
		"/lib":"example/www"
	},
	"TemplateServers":{
		"/":"example/template"
	},
	"AppUserAuth":{
		"ParseFrom":"Header",
		"Field":"Authorization",
		"Type":"JWT"
	},
	"AppUserLocalParams":{
		"info":"example/api/select/app_user/self.sql",
		"id":"example/api/select/app_user/id.sql"
	},
	"ListenPort":"80"
	"ManagementPort":"9000",
	"DBConnString":"postgresql://servotron@localhost:5432/postgres",
	"DBPoolSize":4,
	"DBNotifyChannels":["public_default"],
	"Debug":true
}

Directories

File paths specified with tilde will resolve to the user home dir.
Can be relative to current dir.
This can cause errors when running with sudo.

App User Auth

Used to extract identifying info for authorization from request.
Value is set in the app_user.auth parameter and available via current_setting function during request.
Can be parsed from Header or Cookie.
If ParseFrom is Header, then specify Field and Type (JWT or String). If Type is JWT, then specify Claim. If Claim is not present, then the entire JWT payload is set.
If ParseFrom is Cookie, then specify Name. If Name is not present, then all cookies are set as a JSON object of key-value pairs.

App User Local Params

Used to set parameters for the duration of the request.
Can also be used for sensible defaults in table definitions.
The result of the specified query is set in the app_user.[key] parameter for the duration of the request.
Value is available via the current_setting function.

File Servers

Static content such as HTML.

Template Servers

Templates written in the go text/template style.
Useful for server side includes.
Useful for altering content based on user roles/permissions.
Server passes the result of app user query to the template.

Management Port

For admin functionality such as route loading.

Pool Size

If not specified, this defaults to the number of CPUs.

Notify Channels

Likely to be removed.
Intended to enqueue messages.
This functionality can be achieved by writing specialized agent listeners.

Debug

If true, server writes error message responses to client.

Route Types

type	HTTP	SQL
create	POST	INSERT
read	GET	SELECT
update	PUT	UPDATE
delete	DELETE	DELETE
transaction	POST	PUT
service	*	null

Service route type is proxied to the service URL.

Example

Prerequisites

psql -f example/schema/app/public.sql

Run

servotron --config example/config.cookie.json

Load Routes

curl localhost:9000/routes -d @example/routes.json

Request

curl -b 'email_address=user_a@app.com' localhost:8000/api/buckets
[{"bucket_id":1,"name":"bucket_a","active":true}]

curl -b 'email_address=user_a@app.com' localhost:8000/api/bucket -XPOST -d '[{"name":"New Bucket"}]'
[{"bucket_id":3,"name":"New Bucket","active":true}]

curl -b 'email_address=user_a@app.com' localhost:8000/api/buckets
[{"bucket_id":1,"name":"bucket_a","active":true},
 {"bucket_id":3,"name":"New Bucket","active":true}]

curl -b 'email_address=user_a@app.com' localhost:8000/api/bucket/3
{"bucket_id":3,"name":"New Bucket","active":true}

curl -b 'email_address=user_a@app.com' localhost:8000/api/bucket -XPUT -d '{"bucket_id":3,"name":"Newish Bucket"}'
[{"bucket_id":3,"name":"Newish Bucket","active":true}]

curl -b 'email_address=user_a@app.com' localhost:8000/api/buckets
[{"bucket_id":1,"name":"bucket_a","active":true},
 {"bucket_id":3,"name":"Newish Bucket","active":true}]

curl -b 'email_address=user_a@app.com' localhost:8000/api/bucket/3 -XDELETE

curl -b 'email_address=user_a@app.com' localhost:8000/api/buckets
[{"bucket_id":1,"name":"bucket_a","active":true}]

curl -b 'email_address=user_a@app.com' localhost:8000/api/buckets?active=false
[{"bucket_id":3,"name":"Newish Bucket","active":false}]