NAME
Plack::App::dbi2http - Export DBI database as HTTP API (Riap::HTTP)
VERSION
This document describes version 0.07 of Plack::App::dbi2http (from Perl
distribution Plack-App-dbi2http), released on 2017-07-11.
SYNOPSIS
Prepare and edit a config file:
% cp share/sample-config/dbi2http.conf.yaml ~
% emacs ~/dbi2http.conf.yaml; # edit log path and supply DBI dsn/user/password
Run service:
% cd share/www
% plackup dbi2http.psgi
HTTP::Server::PSGI: Accepting connections at http://0:5000/
From another console, access HTTP API via, e.g. curl:
% curl http://localhost:5000/list_tables
countries
continents
% curl http://localhost:5000/list_columns?table=countries
id
ind_name
eng_name
tags
% curl 'http://localhost:5000/list_columns?table=countries&detail=1&-riap-fmt=json-pretty'
[
200,
"OK",
[
{
"pos" : 1,
"name" : "id",
"type" : "text"
},
{
"name" : "ind_name",
"pos" : 2,
"type" : "text"
},
{
"type" : "text",
"name" : "eng_name",
"pos" : 3
},
{
"pos" : 4,
"name" : "tags",
"type" : "text"
}
]
]
% curl 'http://localhost:5000/list_rows?table=countries'
China cn Cina panda
Indonesia id Indonesia bali,tropical
Singapore sg Singapura tropical
United States of America us Amerika Serikat
% curl 'http://localhost:5000/list_rows?table=countries&-riap-fmt=text-pretty'
.-----------------------------------------------------------------.
| eng_name id ind_name tags |
| |
| China cn Cina panda |
| Indonesia id Indonesia bali,tropical |
| Singapore sg Singapura tropical |
| United States of America us Amerika Serikat |
`-----------------------------------------------------------------'
Or use App::riap, a client shell for Riap (with filesystem-like API
browsing and shell tab completion):
% riap http://localhost:5000/
riap /> ls
list_columns
list_rows
list_tables
riap /> list_tables
countries
continents
riap /> list_columns --table countries --detail
riap /> list_rows --table countries
DESCRIPTION
This module provides a sample Plack application, which you can
customize, to export a DBI database as a HTTP API service.
I was reading Yanick's blog entry today,
<http://techblog.babyl.ca/entry/waack>, titled *Instant REST API for Any
Databases* and I thought I'd quickly cobble up something similar using a
different toolbox. Granted, the resulting HTTP API is not REST (read:
it's better :-) and at 0.01 the API functions are somewhat limited
(DBIx::FunctionalAPI) but this demonstrates how easy it is to create
something usable.
The tools and frameworks are: DBIx::FunctionalAPI which provides a set
of functions: "list_tables", "list_columns", "list_rows",
"create_table", "create_row", "rename_table", etc. These are normal Perl
functions that accept "dbh", "table" arguments and so on.
Next we have Perinci::Access::HTTP::Server, a set of Plack middlewares
that let you access Perl functions over HTTP using the Riap::HTTP
protocol. We compose the middlewares in a PSGI application called
"dbi2http.psgi".
All you need to do now is just run the PSGI application with Plack,
using one of the many available PSGI servers. There is a configuration
file required, to be put in the home directory, and can be copied from
the provided sample config. All you need to set is basically just path
to log file and the DBI connection information (db_dsn, db_user,
db_password) and you're good to go.
After the PSGI application is running, you can connect using a plain
HTTP client like curl. Riap::HTTP exposes Perl modules and functions
directly as URL paths. For example, you can just request the root URL
first, and a help message is returned:
% curl http://localhost:5000/
function list_columns
function list_rows
function list_tables
Tips:
* To call a function, try:
http://localhost:5000/api/list_tables
* Function arguments can be given via GET/POST params or JSON hash in req body
* To find out which arguments a function supports, try:
http://localhost:5000/api/list_tables?-riap-action=meta
* To find out all available actions on an entity, try:
http://localhost:5000/api/list_columns?-riap-action=actions
* This server uses Riap protocol for great autodiscoverability, for more info:
https://metacpan.org/module/Riap
We can see there are 3 top-level functions available. Let's call the
"list_tables" function to, well, list available tables.
% curl http://localhost:5000/list_tables
"main"."continents"
"main"."countries"
"main"."sqlite_master"
"temp"."sqlite_temp_master"
"main"."continents"
"main"."countries"
Functions usually return data structure and the PSGI application formats
it as a presentable text to the client. To get the raw data, use the
"-riap-fmt" special argument:
% curl http://localhost:5000/list_tables?-riap-fmt=json-pretty
[
200,
"OK",
[
"\"main\".\"continents\"",
"\"main\".\"countries\"",
"\"main\".\"sqlite_master\"",
"\"temp\".\"sqlite_temp_master\"",
"\"main\".\"continents\"",
"\"main\".\"countries\""
]
]
Actually, Riap provides more than just RPC (function call). It can also
expose function metadata so the protocol is super-self-discoverable. For
example, instead of the default "call" action, let's call the "meta"
action to request the function metadata:
% curl 'http://localhost:5000/list_tables?-riap-action=meta&-riap-fmt=json-pretty'
[
200,
"OK (meta action)",
{
"entity_v" : "0.01",
"result_naked" : "0",
"entity_date" : "2014-06-15",
"features" : {},
"summary": "List available tables",
"x.perinci.sub.wrapper.logs" : [
{
"normalize_schema" : "1",
"validate_args" : "1",
"validate_result" : "1"
}
],
"args_as" : "hash",
"v" : "1.1",
"args" : {}
}
]
Let's check the metadata of another function:
% curl 'http://localhost:5000/list_columns?-riap-action=meta&-riap-fmt=json-pretty'
[
200,
"OK (meta action)",
{
"summary": "List columns of a table",
"args" : {
"detail" : {
"summary" : "Whether to return detailed records instead of just items/strings",
"schema" : [
"bool",
{},
{}
]
},
"table" : {
"schema" : [
"str",
{
"req" : 1
},
{}
],
"req" : 1,
"summary" : "Table name"
}
},
"args_as" : "hash",
"v" : 1.1,
"result_naked" : 0,
"x.perinci.sub.wrapper.logs" : [
{
"validate_args" : "1",
"validate_result" : "1",
"normalize_schema" : "1"
}
],
"features" : {},
"entity_date" : "2014-06-15",
"entity_v" : "0.01"
}
]
We can see from the above that the "list_columns" function accepts
arguments "table" (a string, required) and "detail" (bool).
For the full specification of the metadata format, see Rinci.
Aside from using a low-level HTTP client, we can also use App::riap, a
Riap client (just to note that Riap can also be accessed via transport
protocol other than HTTP, but it's another subject matter). The client
is a command-line shell with some conveniences like filesystem-like
browsing of API tree, tab completion, debugging, command history, and
others. Let's install the client and try it out:
% cpanm -n App::riap
% riap http://localhost:5000/
riap />
We are first presented with a prompt. Let's try listing what's available
in the top-level directory:
riap /> ls -l
.-------------------------.
| type uri |
| |
| function list_columns |
| function list_rows |
| function list_tables |
`-------------------------'
We see that there are three functions available. To call a function, you
can run it like a running a program:
riap /> list_tables
.-----------------------------------------------------------.
| "main"."continents" "temp"."sqlite_temp_master" |
| "main"."countries" "main"."continents" |
| "main"."sqlite_master" "main"."countries" |
`-----------------------------------------------------------'
Note that you can do completion on the command-line. You can even call
with "--help" option like a normal program:
riap /> list_columns --help
Usage
/list_columns --help (or -h, -?) [--verbose]
/list_columns [options]
Options
--[no]detail
Whether to return detailed records instead of just items/strings.
--help, -h, -?
Display this help message.
--table=s [str] (required)
Table name.
This help message is generated from the metadata (so in the background,
the client performs a "meta" request and converts it to a formatted help
message).
To add HTTP authentication (or do any other customization), you can just
add a Plack middleware to the PSGI application.
Last word, exporting a database as a public API service is usually not a
good idea. In case you don't realize that ;-)
HOMEPAGE
Please visit the project's homepage at
<https://metacpan.org/release/Plack-App-dbi2http>.
SOURCE
Source repository is at
<https://github.com/perlancar/perl-Plack-App-dbi2http>.
BUGS
Please report any bugs or feature requests on the bugtracker website
<https://rt.cpan.org/Public/Dist/Display.html?Name=Plack-App-dbi2http>
When submitting a bug or request, please include a test-file or a patch
to an existing test-file that illustrates the bug or desired feature.
SEE ALSO
Rinci, Riap, Riap::HTTP, DBIx::FunctionalAPI, App::riap
AUTHOR
perlancar <perlancar@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2017, 2015, 2014 by perlancar@cpan.org.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.