by Lin Jen-Shin (godfat)
Lin Jen-Shin had given a talk about rest-core on RubyConf Taiwan 2011. The slide is in English, but the talk is in Mandarin. There's another talk about The Promise of rest-core
LINKS:
DESCRIPTION:
Various rest-builder middleware for building REST clients.
Checkout rest-more for pre-built clients.
FEATURES:
- Modular interface for REST clients similar to WSGI/Rack for servers via rest-builder.
- Concurrent requests with synchronous or asynchronous interfaces with threads via promise_pool.
WHY?
Build your own API clients for less dependencies, less codes, less memory, less conflicts, and run faster.
REQUIREMENTS:
Mandatory:
- Tested with MRI (official CRuby) and JRuby.
- gem rest-builder
- gem promise_pool
- gem timers
- gem httpclient
- gem mime-types
Optional:
- gem json or yajl-ruby, or multi_json (if
JsonResponse
orJsonRequest
middleware is used)
INSTALLATION:
gem install rest-core
Or if you want development version, put this in Gemfile:
gem 'rest-core', :git => 'git://github.com/godfat/rest-core.git',
:submodules => true
If you just want to use Facebook or Twitter clients, please take a look at [rest-more][] which has a lot of clients built with rest-core.
Build Your Own Clients:
You can use RestCore::Builder
to build your own dedicated clients.
Note that RC
is an alias of RestCore
require 'rest-core'
YourClient = RC::Builder.client do
use RC::DefaultSite , 'https://api.github.com/users/'
use RC::JsonResponse, true
use RC::CommonLogger, method(:puts)
use RC::Cache , nil, 3600 # :expires_in if cache store supports
end
Basic Usage:
And use it with per-instance basis (clients could have different configuration, e.g. different cache time or timeout time):
client = YourClient.new(:cache => {})
client.get('godfat') # cache miss
client.get('godfat') # cache hit
client.site = 'https://github.com/api/v2/json/user/show/'
client.get('godfat') # cache miss
client.get('godfat') # cache hit
Concurrent Requests with Futures:
You can also make concurrent requests easily: (see "Advanced Concurrent HTTP Requests -- Embrace the Future" for detail)
a = [client.get('godfat'), client.get('cardinalblue')]
puts "It's not blocking... but doing concurrent requests underneath"
p a.map{ |r| r['name'] } # here we want the values, so it blocks here
puts "DONE"
Exception Handling for Futures:
Note that since the API call would only block whenever you're looking at the response, it won't raise any exception at the time the API was called. So if you want to block and handle the exception at the time API was called, you would do something like this:
begin
response = client.get('bad-user').tap{} # .tap{} is the point
do_the_work(response)
rescue => e
puts "Got an exception: #{e}"
end
The trick here is forcing the future immediately give you the exact response,
so that rest-core could see the response and raise the exception. You can
call whatever methods on the future to force this behaviour, but since tap{}
is a method from Kernel
(which is included in Object
), it's always
available and would return the original value, so it is the easiest method
to be remembered and used.
If you know the response must be a string, then you can also use to_s
.
Like this:
begin
response = client.get('bad-user').to_s
do_the_work(response)
rescue => e
puts "Got an exception: #{e}"
end
Or you can also do this:
begin
response = client.get('bad-user')
response.class # simply force it to load
do_the_work(response)
rescue => e
puts "Got an exception: #{e}"
end
The point is simply making a method call to force it load, whatever method should work.
Concurrent Requests with Callbacks:
On the other hand, callback mode also available:
client.get('godfat'){ |v| p v }
puts "It's not blocking... but doing concurrent requests underneath"
client.wait # we block here to wait for the request done
puts "DONE"
Exception Handling for Callbacks:
What about exception handling in callback mode? You know that we cannot raise any exception in the case of using a callback. So rest-core would pass the exception object into your callback. You can handle the exception like this:
client.get('bad-user') do |response|
if response.kind_of?(Exception)
puts "Got an exception: #{response}"
else
do_the_work(response)
end
end
puts "It's not blocking... but doing concurrent requests underneath"
client.wait # we block here to wait for the request done
puts "DONE"
Thread Pool / Connection Pool
Underneath, rest-core would spawn a thread for each request, freeing you from blocking. However, occasionally we would not want this behaviour, giving that we might have limited resource and cannot maximize performance.
For example, maybe we could not afford so many threads running concurrently, or the target server cannot accept so many concurrent connections. In those cases, we would want to have limited concurrent threads or connections.
YourClient.pool_size = 10
YourClient.pool_idle_time = 60
This could set the thread pool size to 10, having a maximum of 10 threads running together, growing from requests. Each threads idled more than 60 seconds would be shut down automatically.
Note that pool_size
should at least be larger than 4, or it might be
very likely to have deadlock if you're using nested callbacks and having
a large number of concurrent calls.
Also, setting pool_size
to -1
would mean we want to make blocking
requests, without spawning any threads. This might be useful for debugging.
Gracefully shutdown
To shutdown gracefully, consider shutdown the thread pool (if we're using it),
and wait for all requests for a given client. For example, suppose we're using
RC::Universal
, we'll do this when we're shutting down:
RC::Universal.shutdown
We could put them in at_exit
callback like this:
at_exit do
RC::Universal.shutdown
end
If you're using unicorn, you probably want to put that in the config.
Random Asynchronous Tasks
Occasionally we might want to do some asynchronous tasks which could take
the advantage of the concurrency facilities inside rest-core, for example,
using wait
and shutdown
. You could do this with defer
for a particular
client. Still take RC::Universal
as an example:
RC::Universal.defer do
sleep(1)
puts "Slow task done"
end
RC::Universal.wait
Persistent connections (keep-alive connections)
Since we're using httpclient by default now, we would reuse connections, making it much faster for hitting the same host repeatedly.
Streaming Requests
Suppose we want to POST a file, instead of trying to read all the contents in memory and send them, we could stream it from the file system directly.
client.post('path', File.open('README.md'))
Basically, payloads could be any IO object. Check out RC::Payload for more information.
Streaming Responses
This one is much harder then streaming requests, since all built-in middleware actually assume the responses should be blocking and buffered. Say, some JSON parser could not really parse from streams.
We solve this issue similarly to the way Rack solves it. That is, we hijack the socket. This would be how we're doing:
sock = client.get('path', {}, RC::HIJACK => true)
p sock.read(10)
p sock.read(10)
p sock.read(10)
Of course, if we don't want to block in order to get the socket, we could always use the callback form:
client.get('path', {}, RC::HIJACK => true) do |sock|
p sock.read(10)
p sock.read(10)
p sock.read(10)
end
Note that since the socket would be put inside RC::RESPONSE_SOCKET
instead of RC::RESPONSE_BODY
, not all middleware would handle the socket.
In the case of hijacking, RC::RESPONSE_BODY
would always be mapped to an
empty string, as it does not make sense to store the response in this case.
SSE (Server-Sent Events)
Not only JavaScript could receive server-sent events, any languages could. Doing so would establish a keep-alive connection to the server, and receive data periodically. We'll take Firebase as an example:
If you are using Firebase, please consider rest-firebase instead.
require 'rest-core'
# Streaming over 'users/tom.json'
cl = RC::Universal.new(:site => 'https://SampleChat.firebaseIO-demo.com/')
es = cl.event_source('users/tom.json', {}, # this is query, none here
:headers => {'Accept' => 'text/event-stream'})
@reconnect = true
es.onopen { |sock| p sock } # Called when connected
es.onmessage{ |event, data, sock| p event, data } # Called for each message
es.onerror { |error, sock| p error } # Called whenever there's an error
# Extra: If we return true in onreconnect callback, it would automatically
# reconnect the node for us if disconnected.
es.onreconnect{ |error, sock| p error; @reconnect }
# Start making the request
es.start
# Try to close the connection and see it reconnects automatically
es.close
# Update users/tom.json
p cl.put('users/tom.json', RC::Json.encode(:some => 'data'))
p cl.post('users/tom.json', RC::Json.encode(:some => 'other'))
p cl.get('users/tom.json')
p cl.delete('users/tom.json')
# Need to tell onreconnect stops reconnecting, or even if we close
# the connection manually, it would still try to reconnect again.
@reconnect = false
# Close the connection to gracefully shut it down.
es.close
Those callbacks would be called in a separate background thread,
so we don't have to worry about blocking it. If we want to wait for
the connection to be closed, we could call wait
:
es.wait # This would block until the connection is closed
More Control with request_full
:
You can also use request_full
to retrieve everything including response
status, response headers, and also other rest-core options. But since using
this interface is like using Rack directly, you have to build the env
manually. To help you build the env manually, everything has a default,
including the path.
client.request_full({})[RC::RESPONSE_BODY] # {"message"=>"Not Found"}
# This would print something like this:
# RestCore: spent 1.135713 Requested GET https://api.github.com/users/
client.request_full(RC::REQUEST_PATH => 'godfat')[RC::RESPONSE_STATUS]
client.request_full(RC::REQUEST_PATH => 'godfat')[RC::RESPONSE_HEADERS]
# Headers are normalized with all upper cases and
# dashes are replaced by underscores.
# To make POST (or any other request methods) request:
client.request_full(RC::REQUEST_PATH => 'godfat',
RC::REQUEST_METHOD => :post)[RC::RESPONSE_STATUS] # 404
Examples:
Runnable example is at: example/simple.rb. Please see [rest-more][] for more complex examples to build clients, and slides from rubyconf.tw/2011 for concepts.
Playing Around:
You can also play around with RC::Universal
client, which has installed
all reasonable middleware built-in rest-core. So the above example could
also be achieved by:
require 'rest-core'
client = RC::Universal.new(:site => 'https://api.github.com/users/',
:json_response => true,
:log_method => method(:puts))
client.get('godfat')
RC::Universal
is defined as:
module RestCore
Universal = Builder.client do
use Timeout , 0
use DefaultSite , nil
use DefaultHeaders, {}
use DefaultQuery , {}
use DefaultPayload, {}
use JsonRequest , false
use AuthBasic , nil, nil
use CommonLogger , method(:puts)
use ErrorHandler , nil
use ErrorDetectorHttp
use SmashResponse , false
use ClashResponse , false
use JsonResponse , false
use QueryResponse , false
use Cache , {}, 600 # default :expires_in 600 but the default
# cache {} didn't support it
use FollowRedirect, 10
end
end
If you have both rib and [rest-more][] installed, you can also play around with an interactive shell, like this:
rib rest-core
And you will be entering a rib shell, which self
is an instance of
RC::Universal
you can play:
rest-core>> get 'https://api.github.com/users/godfat'
will print out the response from Github. You can also do this to make calling Github easier:
rest-core>> self.site = 'https://api.github.com/users/'
rest-core>> self.json_response = true
Then it would do exactly like the original example:
rest-core>> get 'godfat' # you get a nice parsed hash
This is mostly for fun and experimenting, so it's only included in [rest-more][] and rib. Please make sure you have both of them installed before trying this.
List of built-in Middleware:
use RC::Cache, cache, expires_in
where cache
is the cache store which the cache data would be storing to.
expires_in
would be passed to
cache.store(key, value :expires_in => expires_in)
if store
method is
available and its arity should be at least 3. The interface to the cache
could be referenced from moneta, namely:
- (required)
[](key)
- (required)
[]=(key, value)
- (optional, required if :expires_in is needed)
store(key, value, options)
Note that {:expires_in => seconds}
would be passed as the options in
store(key, value, options)
, and a plain old Ruby hash {}
satisfies
the mandatory requirements: [](key)
and []=(key, value)
, but not the
last one for :expires_in
because the store
method for Hash did not take
the third argument. That means we could use {}
as the cache but it would
simply ignore :expires_in
.
Advanced Concurrent HTTP Requests -- Embrace the Future
The Interface
There are a number of different ways to make concurrent requests in rest-core. They could be roughly categorized to two different forms. One is using the well known callbacks, while the other one is using through a technique called future. Basically, it means it would return you a promise, which would eventually become the real value (response here) you were asking for whenever you really want it. Otherwise, the program keeps running until the value is evaluated, and blocks there if the computation (response) hasn't been done yet. If the computation is already done, then it would simply return you the result.
Here's a very simple example for using futures:
require 'rest-core'
YourClient = RC::Builder.client do
use RC::DefaultSite , 'https://api.github.com/users/'
use RC::JsonResponse, true
use RC::CommonLogger, method(:puts)
end
client = YourClient.new
puts "httpclient with threads doing concurrent requests"
a = [client.get('godfat'), client.get('cardinalblue')]
puts "It's not blocking... but doing concurrent requests underneath"
p a.map{ |r| r['name'] } # here we want the values, so it blocks here
puts "DONE"
And here's a corresponded version for using callbacks:
require 'rest-core'
YourClient = RC::Builder.client do
use RC::DefaultSite , 'https://api.github.com/users/'
use RC::JsonResponse, true
use RC::CommonLogger, method(:puts)
end
client = YourClient.new
puts "httpclient with threads doing concurrent requests"
client.get('godfat'){ |v|
p v['name']
}.
get('cardinalblue'){ |v|
p v['name']
}
puts "It's not blocking... but doing concurrent requests underneath"
client.wait # until all requests are done
puts "DONE"
You can pick whatever works for you.
A full runnable example is at: example/simple.rb. If you want to know all the possible use cases, you can also see: example/use-cases.rb. It's also served as a test for each possible combinations, so it's quite complex and complete.
Configure the underlying HTTP engine
Occasionally we might want to configure the underlying HTTP engine, which for now is httpclient. For example, we might not want to decompress gzip automatically, (rest-core configures httpclient to request and decompress gzip automatically). or we might want to skip verifying SSL in some situation. (e.g. making requests against a self-signed testing server)
In such cases, we could use config_engine
option to configure the underlying
engine. This could be set with request based, client instance based, or
client class based. Please refer to:
How We Pick the Default Value,
except that there's no middleware for config_engine
.
Here are some examples:
require 'rest-core'
YourClient = RC::Builder.client
# class based:
def YourClient.default_config_engine
lambda do |engine|
# disable auto-gzip:
engine.transparent_gzip_decompression = false
# disable verifying SSL
engine.ssl_config.verify_mode = OpenSSL::SSL::VERIFY_NONE
end
end
# instance based:
client = YourClient.new(:config_engine => lambda do |engine|
# disable auto-gzip:
engine.transparent_gzip_decompression = false
# disable verifying SSL
engine.ssl_config.verify_mode = OpenSSL::SSL::VERIFY_NONE
end)
# request based:
client.get('http://example.com/', {}, :config_engine => lambda do |engine|
# disable auto-gzip:
engine.transparent_gzip_decompression = false
# disable verifying SSL
engine.ssl_config.verify_mode = OpenSSL::SSL::VERIFY_NONE
end)
As we stated in How We Pick the Default Value, the priority here is:
- request based
- instance based
- class based
rest-core users:
- rest-firebase
- [rest-more][]
- rest-more-yahoo_buy
- s2sync
- s2sync_web
- topcoder
Powered sites:
CHANGES:
CONTRIBUTORS:
- Andrew Liu (@eggegg)
- andy (@coopsite)
- Barnabas Debreczeni (@keo)
- Bruce Chu (@bruchu)
- Ethan Czahor (@ethanz5)
- Florent Vaucelle (@florent)
- Jaime Cham (@jcham)
- Joe Chen (@joe1chen)
- John Fan (@johnfan)
- khoa nguyen (@khoan)
- Lin Jen-Shin (@godfat)
- lulalala (@lulalala)
- Man Vuong (@kidlab)
- Mariusz Pruszynski (@snicky)
- Mr. Big Cat (@miaout17)
- Nicolas Fouché (@nfo)
- Robert Balousek (@volksport)
- Szu-Kai Hsu (@brucehsu)
LICENSE:
Apache License 2.0 (Apache-2.0)
Copyright (c) 2011-2023, Lin Jen-Shin (godfat)
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
https://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.