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Sqlite To Rest

Koa routing middleware allowing you to expose a sqlite database via RESTful CRUD

Table of Contents

Why build it?

Mostly because I wanted to dig deeper into node web server code, but also because I haven't jumped onto the NoSQL bandwagon and think that web APIs are extremely useful. The result is a modest attempt at automating the CRUD boilerplate that every developer hates, while following the specs to make API consumption intuitive. I chose sqlite to keep the database side of things simple, with the intent that the API isn't serving heavy loads.

Features

  • Spec compliant CRUD RESTful API to an existing database's tables and views
  • GET utilizes JSONStream so the entire response is not held in memory, allowing for arbitrarily large responses.
  • Range requests with the custom range unit 'rows' can be used to GET specific rows. While compliant with rfc7233, the syntax and semantics were kept extremely similar to byte-ranges.
  • The server can configure a maximum request range per table since the amount of data per row will vary per-table.
  • The server can also configure whether to send the content-range header in a HEAD request. This allows the author to save the server from unnecessarily calculating the count on a table that is known to be very large.
  • Custom request header 'order' and conditional response header 'accept-order' exposes row sorting by column with optional ascending and descending specifiers
  • The API enforces correct usage, while sending developer-friendly error messages upon 4xx errors.
  • Comes with a friendly CLI to create a bare-bones koa server to get you up and running quickly.

Limitations

  • All tables must use primary keys. The next limitation explains why.
  • In effort to mitigate damage, unsafe methods only allow modification of single rows. This is enforced by matching the query parameters with the 'primary key' columns - friendly errors will tell you if called called an unsafe method incorrectly.
  • No built-in API key management. The library as-is can only serve trusted consumers.
  • It's sqlite. This library is not meant for clustering or large workloads. See 'Situations Where A Client/Server RDBMS May Work Better' for details.
  • This is my foray into reading rfc's and working with web server libraries (koa and middleware in general). I have tests and feel confident in my comprehension of the concepts, but the code is not the prettiest.
  • No friendly data validation currently. Right now contextless 500 statuses are returned if data doesn't pass constraints, and I don't have tests ensuring consistent behavior around data validation.

Tutorial

This tutorial will walk you through

  1. Creating an initial database
  2. Using sqlite-to-rest's CLI to create a bare-bones koa server
  3. Walk you through some curl commands to test the server's CRUD RESTful api.

CLI

By installing this library globally, you receive access to sqlite-to-rest.

The CLI currently contains one command generate-skeleton which creates an initial bare-bones koa server from an existing sqlite database. This should help you get started.

See sqlite-to-rest --help for more info.

API

require('sqlite-to-rest') returns an object with two properties.

  • generateSkeleton: madonna-function -> promise(undefined)
    This will usually be called from the CLI but is also made available via the js API. Its purpose is to generate a barebones koa server to get you up and running. In the directory it will:

    1. Run npm init -f if a package.json doesn't exist
    2. Output the generated koa server named 'skeleton.js'
    3. Install and save the dependencies required to run the server

    It takes two properties

    // example
sqliteToRest
  .generateSkeleton({
    dir: beerApiDir,
    dbPath: 'path/to/your/db.sqlite3',
  })
  .then(() => {
    /* skeleton.js is ready to be ran */
  })

  • getSqliteRouter: madonna-function -> promise(koa-router)
    This function generates the RESTful CRUD routing and returns the modified koa-router instance.

    It takes two properties

    // example
const app = new require('koa')(),
  dbPath = 'path/to/your/db.sqlite3'

getSqliteRouter({ dbPath }).then((router) => {
  app.use(router.routes())
  // ...
})

RESTful CRUD Operations

The following is a list of the available crud operations made available by the RESTful API in the form of pseudo examples. All assume a beer table with two columns id INTEGER PRIMARY KEY and name which is nullable.

As noted in limitations, Be aware that unsafe methods (DELETE and POST) can only affect one row at a time.

  • GET This allows for the most variation. Click here for all available query operators. Keep in mind the following examples ignore proper query encoding

    Headers may be specified right below urls

    • /beer
      Requests for all rows

    • /beer?id=1
      Where id = 1

    • /beer
      range: rows=0-2
      First three rows

    • /beer
      range: rows=-5
      Last five rows

    • /beer
      range: rows=0-
      As many rows as the server is able to provide, which in practice will be the smaller of maxRange and total row count.

    • /beer
      range: rows=1-
      As many rows as the server is able to provide, starting from row 1.

    • /beer
      order: name
      Ordered by name ascending

    • /beer
      order: name desc
      Ordered by name descending

    • /beer
      order: name desc,id
      Contrived, but orders first by name descending, and in the case of a tie by id ascending.

    • /beer?id>1
      Where id > 1

    • /beer?id>=2&id<5
      Where id >= 2 and id < 5

    • /beer?name_NOTNULL
      Where name is not null

    • /beer?name_ISNULL
      Where name is null

    • /beer?id!=5&name_LIKE'Spotted%'
      Where id != 5 and name is LIKE "Spotted%" (ignore quotes)

    • /beer?id>=1&id<10&name_LIKE'Avery%'
      order: name desc,id range: rows=2-4
      Contrived for sake of example.
      Get beer with ids between 1 and 9 inclusive, with name like "Avery%", ordered first by name descending then by id ascending, getting the third through 5th rows of the result. Or in SQL:

      SELECT *
FROM beer
WHERE id >= 1
  AND id <10
  AND name LIKE 'Avery%'
ORDER BY name desc, id
LIMIT 3 OFFSET 2

  • DELETE Requires a query string with all primary keys set equal to a value. This enforces a maximum deletion of a single row.

    • /beer?id=1
      Deletes beer with id=1

    if the beer table instead had a composite primary key of both id and name

    • /beer?id=1&name='Avery IPA'

  • POST create
    Must not pass a query string. If a query string is passed, then POST update is assumed. All POST requests must pass the header content-type: application/json.

    Keep in mind the body must contain all non-nullable and non INTEGER PRIMARY KEY columns. A 400 response will be sent otherwise indicating what fields were missed. Nullable columns will default to null and INTEGER PRIMARY KEY columns will automatically increment per sqlite3 specifications.

    Json data will be specified right below urls

    • /beer
      {"id":1,"name":"Serendipity"}
      Creates a beer with id = 1 and name = 'Serendipity'

    • /beer
      {"id":1}
      Creates a beer with id = 1 and name = NULL

    • /beer
      {"name":"Serendipity"}
      Creates a beer with id set to the next incremented value per sqlite3 INTEGER PRIMARY KEY specifications

    • /beer
      {}
      Creates a beer with id incremented, and name set to NULL

  • POST update
    Must contain a query string. Without a query string, POST create is assumed. As with POST create, the header content-type: application/json is mandatory.

    The query string must contain all primary keys to ensure only a single row gets updated. If incorrect values are passed, a 400 will be returned listing the offending keys.

    The request body must contain a non-empty object and must contain valid keys corresponding to column names.

    Json data will be specified right below urls

    • /beer?id=1
      {"id":2}
      Updates beer with id of 1 setting it to two.

    • /beer?id=1
      {"name":"Two Women"}
      Updates beer with id of 1 setting its name to Two Women.

    if the beer table instead had a composite primary key of both id and name

    • /beer?id=1&name=Two Women
      {"name":"Moon Man"}
      Updates beer where id is one and name is Two Women, setting name to Moon Man

Reference

isSqliteFile

  • Just checks the first 16 bytes of the file to see if it equals 'sqlite format 3' followed by a null byte.

isDirectory

isFile

GET query operators

Query conditions must be delimited by ampersands e.g. id>5&name!=Spotted Cow

Binary operators (require a value after)
=
!=
>=
<=
>
<
_LIKE

  • _LIKE is special in that it must have opening and closing single quotes. If not, a 400 error will be thrown showing where the parsing was unable to complete and what was expected. See RESTful CRUD Operations for examples.

Unary operators (must follow a column name)
_ISNULL
_NOTNULL

Router config object

isLadenPlainObject
The purpose of this object is to provide generic configuration for the sqlite router. The following properties are allowed:

  • prefix: isLadenString The string passed to koa-router's prefix constructor option. For example, the skeleton server doesn't specify a prefix, allowing the beer api to be hit directly from the domain root http://localhost:8085/beer. If you set prefix to '/api', then you would instead send requests to http://localhost:8085/api/beer.

  • allTablesAndViews: A tabular configuration object
    The configurations specified in this object will apply for all tables and views, optionally overridden by the tablesAndViews property.

  • tablesAndViews: isLadenPlainObject The object passed must have keys matching the database column or view names. If not, a friendly error message will be thrown. The values for each table and view must be a tabular configuration object

Tabular config object

isLadenPlainObject This object represents configurations that can be set for either views or tables. It allows the following properties:

  • maxRange: isPositiveNumber
    Application default: 1000
    This is the maximum range your server will allow requests for. If a GET request comes in with no range header, the spec assumes they want the entire resource. If the number of rows resulting in that GET is greater than maxRange, then a 416 status is returned with the custom header max-range. The application default is purposefully conservative in hopes that authors will set maxRange according to their needs.
    Note that 'Infinity' is a valid positive number.

  • flags: isLadenArray
    Currently the only flag accepted is the string 'sendContentRangeInHEAD'. When set, HEAD requests will return the available content range in the form content-range: */<max-range>. The reason it's configurable is that calculating max-range may be more work than its worth, depending on the load of the server and the size of your tables.

Custom Headers

Request

  • order: This header is only defined for GET, and can be thought of as the sql ORDER BY equivalent. It must contain a comma-delimited column names, each optionally followed by a space and the strings 'asc' or 'desc'. If incorrect order values are sent, a 400 response will indicate which ones.

Response

These aren't all necessarily custom, but all their usage falls outside what's defined in the spec and thus need clarification.

  • GET

    • max-range: This header is returned when the requested number of rows surpasses the configured maxRange. Note the request might not specify the range header, but the number of rows resulting in that resource will still be checked.

    • content-range: rfc7233 states

      only the 206 (Partial Content) and 416 (Range Not Satisfiable) status codes describe a meaning for Content-Range.

      When sqlite-to-rest responds with a 200 status code, the content-range header is sent with the 206 format of <row start>-<row end>/<row count>.

      When a request is sent without a range header and the number of resulting rows surpasses maxRange, a 400 is returned with content-range set in the 416 format of */<row count>

      Note this header may be returned in a HEAD response.

    • accept-order: This will be returned if the request header order had bad syntax or specified incorrect column names. For details, refer to HEAD -> accept-order below.

  • HEAD

    • accept-order: accept-order is just a comma-delimited list of the requested table columns, intended to tell the client the valid columns able to be used in the request header order.

    • max-range: The configured maxRange of the requested table.

    • content-range: This header will only be sent if the table has been configured with the flag sendContentRangeInHEAD. In that case, content-range is set to the 416 format of */<row count>

Test

npm test