165 lines
6.9 KiB
Markdown
165 lines
6.9 KiB
Markdown
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[](https://circleci.com/gh/begriffs/postgrest/tree/master)
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<a href="https://heroku.com/deploy?template=https://github.com/begriffs/postgrest">
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<img src="static/heroku.png" alt="Deploy">
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</a>
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PostgREST serves a fully RESTful API from any existing PostgreSQL
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database. It provides a cleaner, more standards-compliant, faster
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API than you are likely to write from scratch.
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### Demo [postgrest.herokuapp.com](https://postgrest.herokuapp.com) | Watch [Video](http://begriffs.com/posts/2014-12-30-intro-to-postgrest.html)
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Try making requests to the live demo server with an HTTP client
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such as [postman](http://www.getpostman.com/). The structure of the
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demo database is defined by
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[begriffs/postgrest-example](https://github.com/begriffs/postgrest-example).
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You can use it as inspiration for test-driven server migrations in
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your own projects.
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### Usage
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Download the binary ([OS X](http://bin.begriffs.com/dbapi/osx/postgrest-0.2.7.0.tar.xz) / [Linux](http://bin.begriffs.com/dbapi/heroku/postgrest-0.2.7.0.tar.xz)) and invoke like so:
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```bash
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postgrest --db-host localhost --db-port 5432 \
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--db-name my_db --db-user postgres \
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--db-pass foobar --db-pool 200 \
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--anonymous postgres --port 3000 \
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--v1schema public
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```
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In production include the `--secure` option which redirects all
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requests to HTTPS. Note that PostgREST does not handle the SSL
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internally and must be put behind another server that does (such
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as nginx or the Heroku load balancer).
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### Performance
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TLDR; subsecond response times for up to 2000 requests/sec on Heroku free tier. ([see the load test](https://github.com/begriffs/postgrest/wiki/Performance-and-Scaling))
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If you're used to servers written in interpreted languages (or named
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after precious gems), prepare to be pleasantly surprised by PostgREST
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performance.
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Three factors contribute to the speed. First the server is written
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in [Haskell](https://new-www.haskell.org/) using the
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[Warp](http://www.yesodweb.com/blog/2011/03/preliminary-warp-cross-language-benchmarks)
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HTTP server (aka a compiled language with lightweight threads).
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Next it delegates as much calculation as possible to the database
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including
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* Serializing JSON responses directly in SQL
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* Data validation
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* Authorization
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* Combined row counting and retrieval
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* Data post in single command (`returning *`)
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Finally it uses the database efficiently with the
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[Hasql](https://nikita-volkov.github.io/hasql-benchmarks/) library
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by
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* Reusing prepared statements
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* Keeping a pool of db connections
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* Using the Postgres binary protocol
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* Being stateless to allow horizontal scaling
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Ultimately the server (when load balanced) is constrained by database
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performance. This may make it inappropriate for very large traffic
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load. To learn more about scaling with Heroku and Amazon RDS see
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the [performance guide](https://github.com/begriffs/postgrest/wiki/Performance-and-Scaling).
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Other optimizations are possible, and some are outlined in the
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[Future Features](#future-features).
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### Security
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PostgREST handles authentication (HTTP Basic over SSL) and delegates
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authorization to the role information defined in the database. This
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ensures there is a single declarative source of truth for security.
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When dealing with the database the server assumes the identity of
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the currently authenticated user, and for the duration of the
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connection cannot do anything the user themselves couldn't.
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Postgres 9.5 will soon support true [row-level
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security](http://michael.otacoo.com/postgresql-2/postgres-9-5-feature-highlight-row-level-security/).
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In the meantime what isn't yet implemented can be simulated with
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triggers and security-barrier views. Because the possible queries
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to the database are limited to certain templates using
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[leakproof](http://blog.2ndquadrant.com/how-do-postgresql-security_barrier-views-work/)
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functions, the trigger workaround does not compromise row-level
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security.
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For example security patterns see the [security
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guide](https://github.com/begriffs/postgrest/wiki/Security-and-Permissions).
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### Versioning
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A robust long-lived API needs the freedom to exist in multiple
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versions. PostgREST supports versioning through HTTP content
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negotiation. Requests for a certain version translate into switching
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which database schema to search for tables. PostgreSQL schema search
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paths allow tables from earlier versions to be reused verbatim in
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later versions.
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To learn more, see the [guide to versioning](https://github.com/begriffs/postgrest/wiki/API-Versioning).
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### Self-documention
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Rather than writing and maintaining separate docs yourself let the
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API explain its own affordances using HTTP. All PostgREST endpoints
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respond to the OPTIONS verb and explain what they support as well
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as the data format of their JSON payload.
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The number of rows returned by an endpoint is reported by - and
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limited with - range headers. More about
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[that](http://begriffs.com/posts/2014-03-06-beyond-http-header-links.html).
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There are more opportunities for self-documentation listed in [Future
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Features](#future-features).
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### Data Integrity
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Rather than relying on an Object Relational Mapper and custom
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imperative coding, this system requires you put declarative constraints
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directly into your database. Hence no application can corrupt your
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data (including your API server).
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The PostgREST exposes HTTP interface with safeguards to prevent
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surprises, such as enforcing idempotent PUT requests, and
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See examples of [Postgres
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constraints](http://www.tutorialspoint.com/postgresql/postgresql_constraints.htm)
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and the [guide to routing](https://github.com/begriffs/postgrest/wiki/Routing).
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### Future Features
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* Watching endpoint changes with sockets and Postgres pubsub
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* Specifying per-view HTTP caching
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* Inferring good default caching policies from the Postgres stats collector
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* Generating mock data for test clients
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* Maintaining separate connection pools per role to avoid "set/reset
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role" performance penalty
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* Describe more relationships with Link headers
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* Depending on accept headers, render OPTIONS as [RAML](http://raml.org/) or a
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relational diagram
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* Add two-legged auth with OAuth 1.0a(?)
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* ... the other [issues](https://github.com/begriffs/postgrest/issues)
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### Guides
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* [Routing](https://github.com/begriffs/postgrest/wiki/Routing)
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* [Versioning](https://github.com/begriffs/postgrest/wiki/API-Versioning)
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* [Performance](https://github.com/begriffs/postgrest/wiki/Performance-and-Scaling)
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* [Security](https://github.com/begriffs/postgrest/wiki/Security-and-Permissions)
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### Thanks
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* [Adam Baker](https://github.com/adambaker) for code
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contributions and many fundamental design discussions
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* [Nikita Volkov](https://github.com/nikita-volkov) for writing the
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wonderful [Hasql](https://github.com/nikita-volkov/hasql) library
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and helping me use it
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* [Mikey Casalaina](https://github.com/casalaina) for the cool logo
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