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https://github.com/local-ch/lhc
🚀 Advanced HTTP Client for Ruby. Fueled with interceptors.
https://github.com/local-ch/lhc
http http-client interceptors ruby
Last synced: 14 days ago
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🚀 Advanced HTTP Client for Ruby. Fueled with interceptors.
- Host: GitHub
- URL: https://github.com/local-ch/lhc
- Owner: local-ch
- License: gpl-3.0
- Created: 2014-10-07T07:09:50.000Z (about 10 years ago)
- Default Branch: master
- Last Pushed: 2022-11-01T12:48:28.000Z (about 2 years ago)
- Last Synced: 2024-10-22T09:51:06.376Z (23 days ago)
- Topics: http, http-client, interceptors, ruby
- Language: Ruby
- Homepage:
- Size: 687 KB
- Stars: 43
- Watchers: 45
- Forks: 1
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
LHC is an extended/advanced HTTP client. Implementing basic http-communication enhancements like interceptors, exception handling, format handling, accessing response data, configuring endpoints and placeholders and fully compatible, RFC-compliant URL-template support.
LHC uses [typhoeus](https://github.com/typhoeus/typhoeus) for low level http communication.
See [LHS](https://github.com/local-ch/LHS), if you are searching for something more **high level** that can query webservices easily and provides an ActiveRecord like interface.
## Quick start guide
```ruby
gem install lhc
```
or add it to your Gemfile:
```ruby
gem 'lhc'
```
use it like:
```ruby
response = LHC.get('http://datastore/v2/feedbacks')
response.data.items[0]
response.data.items[0].recommended
response.body
response.headers
```
## Table of contents
* [Quick start guide](#quick-start-guide)
* [Basic methods](#basic-methods)
* [Request](#request)
* [Formats](#formats)
* [Default format](#default-format)
* [Unformatted requests](#unformatted-requests)
* [Upload with LHC](#upload-with-lhc)
* [Parallel requests](#parallel-requests)
* [Follow redirects](#follow-redirects)
* [Transfer data through the request body](#transfer-data-through-the-request-body)
* [Request parameters](#request-parameters)
* [Array Parameter Encoding](#array-parameter-encoding)
* [Request URL encoding](#request-url-encoding)
* [Request URL-Templates](#request-url-templates)
* [Request timeout](#request-timeout)
* [Request Agent](#request-agent)
* [Response](#response)
* [Accessing response data](#accessing-response-data)
* [Exceptions](#exceptions)
* [Custom error handling (rescue)](#custom-error-handling-rescue)
* [Ignore certain errors](#ignore-certain-errors)
* [Configuration](#configuration)
* [Configuring endpoints](#configuring-endpoints)
* [Configuring placeholders](#configuring-placeholders)
* [Configuring scrubs](#configuring-scrubs)
* [Interceptors](#interceptors)
* [Quick start: Configure/Enable Interceptors](#quick-start-configureenable-interceptors)
* [Interceptors on local request level](#interceptors-on-local-request-level)
* [Core Interceptors](#core-interceptors)
* [Authentication Interceptor](#authentication-interceptor)
* [Bearer Authentication](#bearer-authentication)
* [Basic Authentication](#basic-authentication)
* [Body Authentication](#body-authentication)
* [Reauthenticate](#reauthenticate)
* [Bearer Authentication with client access token](#bearer-authentication-with-client-access-token)
* [Caching Interceptor](#caching-interceptor)
* [Options](#options)
* [Default Timeout Interceptor](#default-timeout-interceptor)
* [Overwrite defaults](#overwrite-defaults)
* [Logging Interceptor](#logging-interceptor)
* [Installation](#installation)
* [What and how it logs](#what-and-how-it-logs)
* [Configure](#configure)
* [Monitoring Interceptor](#monitoring-interceptor)
* [Installation](#installation-1)
* [Environment](#environment)
* [What it tracks](#what-it-tracks)
* [Before and after request tracking](#before-and-after-request-tracking)
* [Response tracking](#response-tracking)
* [Timeout tracking](#timeout-tracking)
* [Caching tracking](#caching-tracking)
* [Configure](#configure-1)
* [Prometheus Interceptor](#prometheus-interceptor)
* [Retry Interceptor](#retry-interceptor)
* [Limit the amount of retries while making the request](#limit-the-amount-of-retries-while-making-the-request)
* [Change the default maximum of retries of the retry interceptor](#change-the-default-maximum-of-retries-of-the-retry-interceptor)
* [Retry all requests](#retry-all-requests)
* [Do not retry certain response codes](#do-not-retry-certain-response-codes)
* [Rollbar Interceptor](#rollbar-interceptor)
* [Forward additional parameters](#forward-additional-parameters)
* [Throttle](#throttle)
* [Zipkin](#zipkin)
* [Create an interceptor from scratch](#create-an-interceptor-from-scratch)
* [Interceptor callbacks](#interceptor-callbacks)
* [Interceptor request/response](#interceptor-requestresponse)
* [Provide a response replacement through an interceptor](#provide-a-response-replacement-through-an-interceptor)
* [Testing](#testing)
* [License](#license)
## Basic methods
Available are `get`, `post`, `put` & `delete`.
Other methods are available using `LHC.request(options)`.
## Request
The request class handles the http request, implements the interceptor pattern, loads configured endpoints, generates urls from url-templates and raises [exceptions](#exceptions) for any response code that is not indicating success (2xx).
```ruby
response = LHC.request(url: 'http://local.ch', method: :options)
response.request.response # the associated response.
response.request.options # the options used for creating the request.
response.request.params # access request params
response.request.headers # access request headers
response.request.url # URL that is used for doing the request
response.request.method # provides the used http-method
```
### Formats
You can use any of the basic methods in combination with a format like `json`:
```ruby
LHC.json.get(options)
```
Currently supported formats: `json`, `multipart`, `plain` (for no formatting)
If formats are used, headers for `Content-Type` and `Accept` are enforced by LHC, but also http bodies are translated by LHC, so you can pass bodies as ruby objects:
```ruby
LHC.json.post('http://slack', body: { text: 'Hi there' })
# Content-Type: application/json
# Accept: application/json
# Translates body to "{\"text\":\"Hi there\"}" before sending
```
#### Default format
If you use LHC's basic methods `LHC.get`, `LHC.post` etc. without any explicit format, `JSON` will be chosen as the default format.
#### Unformatted requests
In case you need to send requests without LHC formatting headers or the body, use `plain`:
```ruby
LHC.plain.post('http://endpoint', body: { weird: 'format%s2xX' })
```
##### Upload with LHC
If you want to upload data with LHC, it's recommended to use the `multipart` format:
```ruby
response = LHC.multipart.post('http://upload', body: { file })
response.headers['Location']
# Content-Type: multipart/form-data
# Leaves body unformatted
```
### Parallel requests
If you pass an array of requests to `LHC.request`, it will perform those requests in parallel.
You will get back an array of LHC::Response objects in the same order of the passed requests.
```ruby
options = []
options << { url: 'http://datastore/v2/feedbacks' }
options << { url: 'http://datastore/v2/content-ads/123/feedbacks' }
responses = LHC.request(options)
```
```ruby
LHC.request([request1, request2, request3])
# returns [response1, response2, response3]
```
### Follow redirects
```ruby
LHC.get('http://local.ch', followlocation: true)
```
### Transfer data through the request body
Data that is transfered using the HTTP request body is transfered using the selected format, or the default `json`, so you need to provide it as a ruby object.
Also consider setting the http header for content-type or use one of the provided [formats](#formats), like `LHC.json`.
```ruby
LHC.post('http://datastore/v2/feedbacks',
body: feedback,
headers: { 'Content-Type' => 'application/json' }
)
```
### Request parameters
When using LHC, try to pass params via `params` option. It's not recommended to build a url and attach the parameters yourself:
DO
```ruby
LHC.get('http://local.ch', params: { q: 'Restaurant' })
```
DON'T
```ruby
LHC.get('http://local.ch?q=Restaurant')
```
#### Array Parameter Encoding
LHC can encode array parameters in URLs in two ways. The default is `:rack` which generates URL parameters compatible with Rack and Rails.
```ruby
LHC.get('http://local.ch', params: { q: [1, 2] })
# http://local.ch?q[]=1&q[]=2
```
Some Java-based apps expect their arrays in the `:multi` format:
```ruby
LHC.get('http://local.ch', params: { q: [1, 2] }, params_encoding: :multi)
# http://local.ch?q=1&q=2
```
### Request URL encoding
LHC, by default, encodes urls:
```ruby
LHC.get('http://local.ch?q=some space')
# http://local.ch?q=some%20space
LHC.get('http://local.ch', params: { q: 'some space' })
# http://local.ch?q=some%20space
```
which can be disabled:
```ruby
LHC.get('http://local.ch?q=some space', url_encoding: false)
# http://local.ch?q=some space
```
### Request URL-Templates
Instead of using concrete urls you can also use url-templates that contain placeholders.
This is especially handy for configuring an endpoint once and generate the url from the params when doing the request.
Since version `7.0` url templates follow the [RFC 6750](https://tools.ietf.org/html/rfc6570).
```ruby
LHC.get('http://datastore/v2/feedbacks/{id}', params:{ id: 123 })
# GET http://datastore/v2/feedbacks/123
```
You can also use URL templates, when [configuring endpoints](#configuring-endpoints):
```ruby
LHC.configure do |c|
c.endpoint(:find_feedback, 'http://datastore/v2/feedbacks/{id}')
end
LHC.get(:find_feedback, params:{ id: 123 }) # GET http://datastore/v2/feedbacks/123
```
If you miss to provide a parameter that is part of the url-template, it will raise an exception.
### Request timeout
Working and configuring timeouts is important, to ensure your app stays alive when services you depend on start to get really slow...
LHC forwards two timeout options directly to typhoeus:
`timeout` (in seconds) - The maximum time in seconds that you allow the libcurl transfer operation to take. Normally, name lookups can take a considerable time and limiting operations to less than a few seconds risk aborting perfectly normal operations. This option may cause libcurl to use the SIGALRM signal to timeout system calls.
`connecttimeout` (in seconds) - It should contain the maximum time in seconds that you allow the connection phase to the server to take. This only limits the connection phase, it has no impact once it has connected. Set to zero to switch to the default built-in connection timeout - 300 seconds.
```ruby
LHC.get('http://local.ch', timeout: 5, connecttimeout: 1)
```
LHC provides a [timeout interceptor](#default-timeout-interceptor) that lets you apply default timeout values to all the requests that you are performig in your application.
### Request Agent
LHC identifies itself towards outher services, using the `User-Agent` header.
```
User-Agent LHC (9.4.2) [https://github.com/local-ch/lhc]
```
If LHC is used in an Rails Application context, also the application name is added to the `User-Agent` header.
```
User-Agent LHC (9.4.2; MyRailsApplicationName) [https://github.com/local-ch/lhc]
```
## Response
```ruby
response.request # the associated request.
response.data # in case response body contains parsable JSON.
response.data.something.nested
response.body #
response.code #
response.headers #
response.time # Provides response time in ms.
response.timeout? #true|false
```
### Accessing response data
The response data can be access with dot-notation and square-bracket notation. You can convert response data to open structs or json (if the response format is json).
```ruby
response = LHC.request(url: 'http://datastore/entry/1')
response.data.as_open_struct #
response.data.as_json # { name: 'local.ch' }
response.data.name # 'local.ch'
response.data[:name] # 'local.ch'
```
You can also access response data directly through the response object (with square bracket notation only):
```ruby
LHC.json.get(url: 'http://datastore/entry/1')[:name]
```
## Exceptions
Anything but a response code indicating success (2xx) raises an exception.
```ruby
LHC.get('localhost') # UnknownError: 0
LHC.get('http://localhost:3000') # LHC::Timeout: 0
```
You can access the response object that was causing the error.
```ruby
LHC.get('local.ch')
rescue => e
e.response #
e.response.code # 403
e.response.timeout? # false
Rails.logger.error e
# LHC::UnknownError: get http://local.cac
# Params: {:url=>"http://local.cac", :method=>:get}
# Response Code: 0
#
```
All errors that are raise by LHC inherit from `LHC::Error`.
They are divided into `LHC::ClientError`, `LHC::ServerError`, `LHC::Timeout` and `LHC::UnkownError` and mapped according to the following status code.
```ruby
400 => LHC::BadRequest
401 => LHC::Unauthorized
402 => LHC::PaymentRequired
403 => LHC::Forbidden
403 => LHC::Forbidden
404 => LHC::NotFound
405 => LHC::MethodNotAllowed
406 => LHC::NotAcceptable
407 => LHC::ProxyAuthenticationRequired
408 => LHC::RequestTimeout
409 => LHC::Conflict
410 => LHC::Gone
411 => LHC::LengthRequired
412 => LHC::PreconditionFailed
413 => LHC::RequestEntityTooLarge
414 => LHC::RequestUriToLong
415 => LHC::UnsupportedMediaType
416 => LHC::RequestedRangeNotSatisfiable
417 => LHC::ExpectationFailed
422 => LHC::UnprocessableEntity
423 => LHC::Locked
424 => LHC::FailedDependency
426 => LHC::UpgradeRequired
500 => LHC::InternalServerError
501 => LHC::NotImplemented
502 => LHC::BadGateway
503 => LHC::ServiceUnavailable
504 => LHC::GatewayTimeout
505 => LHC::HttpVersionNotSupported
507 => LHC::InsufficientStorage
510 => LHC::NotExtended
timeout? => LHC::Timeout
anything_else => LHC::UnknownError
```
### Custom error handling (rescue)
You can provide custom error handlers to handle errors happening during the request.
If a error handler is provided nothing is raised.
If your error handler returns anything else but `nil` it replaces the response body.
```ruby
handler = ->(response){ do_something_with_response; return {name: 'unknown'} }
response = LHC.get('http://something', rescue: handler)
response.data.name # 'unknown'
```
### Ignore certain errors
As it's discouraged to rescue errors and then don't handle them (ruby styleguide)[https://github.com/bbatsov/ruby-style-guide#dont-hide-exceptions],
but you often want to continue working with `nil`, LHC provides the `ignore` option.
Errors listed in this option will not be raised and will leave the `response.body` and `response.data` to stay `nil`.
You can either pass the LHC error class you want to be ignored or an array of LHC error classes.
```ruby
response = LHC.get('http://something', ignore: LHC::NotFound)
response.body # nil
response.data # nil
response.error_ignored? # true
response.request.error_ignored? # true
```
## Configuration
If you want to configure LHC, do it on initialization (like in a Rails initializer, `environment.rb` or `application.rb`), otherwise you could run into the problem that certain configurations can only be set once.
You can use `LHC.configure` to prevent the initialization problem.
Take care that you only use `LHC.configure` once, because it is actually reseting previously made configurations and applies the new once.
```ruby
LHC.configure do |c|
c.placeholder :datastore, 'http://datastore'
c.endpoint :feedbacks, '{+datastore}/feedbacks', params: { has_reviews: true }
c.interceptors = [CachingInterceptor, MonitorInterceptor, TrackingIdInterceptor]
end
```
### Configuring endpoints
You can configure endpoints, for later use, by giving them a name, a url and some parameters (optional).
```ruby
LHC.configure do |c|
c.endpoint(:feedbacks, 'http://datastore/v2/feedbacks', params: { has_reviews: true })
c.endpoint(:find_feedback, 'http://datastore/v2/feedbacks/{id}')
end
LHC.get(:feedbacks) # GET http://datastore/v2/feedbacks
LHC.get(:find_feedback, params:{ id: 123 }) # GET http://datastore/v2/feedbacks/123
```
Explicit request options override configured options.
```ruby
LHC.get(:feedbacks, params: { has_reviews: false }) # Overrides configured params
```
### Configuring placeholders
You can configure global placeholders, that are used when generating urls from url-templates.
```ruby
LHC.configure do |c|
c.placeholder(:datastore, 'http://datastore')
c.endpoint(:feedbacks, '{+datastore}/feedbacks', { params: { has_reviews: true } })
end
LHC.get(:feedbacks) # http://datastore/v2/feedbacks
```
### Configuring scrubs
You can filter out sensitive request data from your log files and rollbar by appending them to `LHS.config.scrubs`. These values will be marked `[FILTERED]` in the log and on rollbar. Also nested parameters are being filtered.
The scrubbing configuration affects all request done by LHC independent of the endpoint. You can scrub any attribute within `:params`, `:headers` or `:body`. For `:auth` you either can choose `:bearer` or `:basic` (default is both).
LHS scrubs per default:
- Bearer Token within the Request Header
- Basic Auth `username` and `password` within the Request Header
- `password` and `password_confirmation` within the Request Body
Enhance the default scrubbing by pushing the name of the parameter, which should be scrubbed, as string to the existing configuration.
You can also add multiple parameters at once by pushing multiple strings.
Example:
```ruby
LHC.configure do |c|
c.scrubs[:params] << 'api_key'
c.scrubs[:body].push('user_token', 'secret_key')
end
```
For disabling scrubbing, add following configuration:
```ruby
LHC.configure do |c|
c.scrubs = {}
end
```
If you want to turn off `:bearer` or `:basic` scrubbing, then just overwrite the `:auth` configuration.
Example:
```ruby
LHC.configure do |c|
c.scrubs[:auth] = [:bearer]
end
```
If your app has a different authentication strategy than Bearer Authentication or Basic Authentication then you can filter the data by scrubbing the whole header:
```ruby
LHC.configure do |c|
c.scrubs[:headers] << 'Authorization'
end
```
## Interceptors
To monitor and manipulate the HTTP communication done with LHC, you can define interceptors that follow the (Inteceptor Pattern)[https://en.wikipedia.org/wiki/Interceptor_pattern].
There are some interceptors that are part of LHC already, so called [Core Interceptors](#core-interceptors), that cover some basic usecases.
### Quick start: Configure/Enable Interceptors
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Auth, LHC::Caching, LHC::DefaultTimeout, LHC::Logging, LHC::Monitoring, LHC::Prometheus, LHC::Retry, LHC::Rollbar, LHC::Zipkin]
end
```
You can only set the list of global interceptors once and you can not alter it after you set it.
### Interceptors on local request level
You can override the global list of interceptors on local request level:
```ruby
interceptors = LHC.config.interceptors
interceptors -= [LHC::Caching] # remove caching
interceptors += [LHC::Retry] # add retry
LHC.request({url: 'http://local.ch', retry: 2, interceptors: interceptors})
LHC.request({url: 'http://local.ch', interceptors: []}) # no interceptor for this request at all
```
### Core Interceptors
#### Authentication Interceptor
Add the auth interceptor to your basic set of LHC interceptors.
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Auth]
end
```
##### Bearer Authentication
```ruby
LHC.get('http://local.ch', auth: { bearer: -> { access_token } })
```
Adds the following header to the request:
```
'Authorization': 'Bearer 123456'
```
Assuming the method `access_token` responds on runtime of the request with `123456`.
##### Basic Authentication
```ruby
LHC.get('http://local.ch', auth: { basic: { username: 'steve', password: 'can' } })
```
Adds the following header to the request:
```
'Authorization': 'Basic c3RldmU6Y2Fu'
```
Which is the base64 encoded credentials "username:password".
##### Body Authentication
```ruby
LHC.post('http://local.ch', auth: { body: { userToken: 'dheur5hrk3' } })
```
Adds the following to body of all requests:
```
{
"userToken": "dheur5hrk3"
}
```
##### Reauthenticate
The current implementation offers only reauthentication for _client access tokens_.
Make sure that your interceptors contain `LHC::Auth` and `LHC::Retry`, whereas `LHC::Retry` comes _after_ `LHC::Auth` in the chain.
Provide the refresh token as following:
```ruby
LHC.get('http://local.ch', auth: { bearer: -> { access_token }, refresh_client_token: -> { TokenRefreshUtil.client_access_token(true) })
```
Where `TokenRefreshUtil.client_access_token(true)` forces a refresh of the token and returns the new token. It is also expected that this implementation will handle invalidating caches if necessary.
You can also set a global `refresh_client_token`. This is not recommended for apps with multiple endpoint and different access tokens.
```ruby
LHC::Auth.refresh_client_token = -> { TokenRefreshUtil.client_access_token(true) }
```
Reauthentication will be initiated if:
* setup is correct
* `response.success?` is false and an `LHC::Unauthorized` was observed
* reauthentication wasn't already attempted once
If this is the case, this happens:
* refresh the client token, by calling `refresh_client_token`
* the authentication header will be updated with the new token
* `LHC::Retry` will be triggered by adding `retry: { max: 1 }` to the request options
#### Caching Interceptor
Add the cache interceptor to your basic set of LHC interceptors.
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Caching]
end
```
You can configure your own cache (default Rails.cache) and logger (default Rails.logger):
```ruby
LHC::Caching.cache = ActiveSupport::Cache::MemoryStore.new
```
Caching is not enabled by default, although you added it to your basic set of interceptors.
If you want to have requests served/stored and stored in/from cache, you have to enable it by request.
```ruby
LHC.get('http://local.ch', cache: true)
```
You can also enable caching when configuring an endpoint in LHS.
```ruby
class Feedbacks < LHS::Service
endpoint '{+datastore}/v2/feedbacks', cache: true
end
```
Only GET requests are cached by default. If you want to cache any other request method, just configure it:
```ruby
LHC.get('http://local.ch', cache: { methods: [:get] })
```
Responses served from cache are marked as served from cache:
```ruby
response = LHC.get('http://local.ch', cache: true)
response.from_cache? # true
```
You can also use a central http cache to be used by the `LHC::Caching` interceptor.
If you configure a local and a central cache, LHC will perform multi-level-caching.
LHC will try to retrieve cached information first from the central, in case of a miss from the local cache, while writing back into both.
```ruby
LHC::Caching.central = {
read: 'redis://[email protected]:6379/0',
write: 'redis://[email protected]:6379/0'
}
```
##### Options
```ruby
LHC.get('http://local.ch', cache: { key: 'key' expires_in: 1.day, race_condition_ttl: 15.seconds, use: ActiveSupport::Cache::MemoryStore.new })
```
`expires_in` - lets the cache expires every X seconds.
`key` - Set the key that is used for caching by using the option. Every key is prefixed with `LHC_CACHE(v1): `.
`race_condition_ttl` - very useful in situations where a cache entry is used very frequently and is under heavy load.
If a cache expires and due to heavy load several different processes will try to read data natively and then they all will try to write to cache.
To avoid that case the first process to find an expired cache entry will bump the cache expiration time by the value set in `race_condition_ttl`.
`use` - Set an explicit cache to be used for this request. If this option is missing `LHC::Caching.cache` is used.
#### Default Timeout Interceptor
Applies default timeout values to all requests made in an application, that uses LHC.
```ruby
LHC.configure do |c|
c.interceptors = [LHC::DefaultTimeout]
end
```
`timeout` default: 15 seconds
`connecttimeout` default: 2 seconds
##### Overwrite defaults
```ruby
LHC::DefaultTimeout.timeout = 5 # seconds
LHC::DefaultTimeout.connecttimeout = 3 # seconds
```
#### Logging Interceptor
The logging interceptor logs all requests done with LHC to the Rails logs.
##### Installation
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Logging]
end
LHC::Logging.logger = Rails.logger
```
##### What and how it logs
The logging Interceptor logs basic information about the request and the response:
```ruby
LHC.get('http://local.ch')
# Before LHC request<70128730317500> GET http://local.ch at 2018-05-23T07:53:19+02:00 Params={} Headers={\"User-Agent\"=>\"Typhoeus - https://github.com/typhoeus/typhoeus\", \"Expect\"=>\"\"}
# After LHC response for request<70128730317500>: GET http://local.ch at 2018-05-23T07:53:28+02:00 Time=0ms URL=http://local.ch:80/
```
##### Configure
You can configure the logger beeing used by the logging interceptor:
```ruby
LHC::Logging.logger = Another::Logger
```
#### Monitoring Interceptor
The monitoring interceptor reports all requests done with LHC to a given StatsD instance.
##### Installation
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Monitoring]
end
```
You also have to configure statsd in order to have the monitoring interceptor report.
```ruby
LHC::Monitoring.statsd =
```
##### Environment
By default, the monitoring interceptor uses Rails.env to determine the environment. In case you want to configure that, use:
```ruby
LHC::Monitoring.env = ENV['DEPLOYMENT_TYPE'] || Rails.env
```
##### What it tracks
It tracks request attempts with `before_request` and `after_request` (counts).
In case your workers/processes are getting killed due limited time constraints,
you are able to detect deltas with relying on "before_request", and "after_request" counts:
###### Before and after request tracking
```ruby
"lhc.....before_request", 1
"lhc.....after_request", 1
```
###### Response tracking
In case of a successful response it reports the response code with a count and the response time with a gauge value.
```ruby
LHC.get('http://local.ch')
"lhc.....count", 1
"lhc.....200", 1
"lhc.....time", 43
```
In case of a unsuccessful response it reports the response code with a count but no time:
```ruby
LHC.get('http://local.ch')
"lhc.....count", 1
"lhc.....500", 1
```
###### Timeout tracking
Timeouts are also reported:
```ruby
"lhc.....timeout", 1
```
All the dots in the host are getting replaced with underscore, because dot is the default separator in graphite.
###### Caching tracking
When you want to track caching stats please make sure you have enabled the `LHC::Caching` and the `LHC::Monitoring` interceptor.
Make sure that the `LHC::Caching` is listed before `LHC::Monitoring` interceptor when configuring interceptors:
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Caching, LHC::Monitoring]
end
```
If a response was served from cache it tracks:
```ruby
"lhc.....cache.hit", 1
```
If a response was not served from cache it tracks:
```ruby
"lhc.....cache.miss", 1
```
##### Configure
It is possible to set the key for Monitoring Interceptor on per request basis:
```ruby
LHC.get('http://local.ch', monitoring_key: 'local_website')
"local_website.count", 1
"local_website.200", 1
"local_website.time", 43
```
If you use this approach you need to add all namespaces (app, environment etc.) to the key on your own.
#### Prometheus Interceptor
Logs basic request/response information to prometheus.
```ruby
require 'prometheus/client'
LHC.configure do |c|
c.interceptors = [LHC::Prometheus]
end
LHC::Prometheus.client = Prometheus::Client
LHC::Prometheus.namespace = 'web_location_app'
```
```ruby
LHC.get('http://local.ch')
```
- Creates a prometheus counter that receives additional meta information for: `:code`, `:success` and `:timeout`.
- Creates a prometheus histogram for response times in milliseconds.
#### Retry Interceptor
If you enable the retry interceptor, you can have LHC retry requests for you:
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Retry]
end
response = LHC.get('http://local.ch', retry: true)
```
It will try to retry the request up to 3 times (default) internally, before it passes the last response back, or raises an error for the last response.
Consider, that all other interceptors will run for every single retry.
##### Limit the amount of retries while making the request
```ruby
LHC.get('http://local.ch', retry: { max: 1 })
```
##### Change the default maximum of retries of the retry interceptor
```ruby
LHC::Retry.max = 3
```
##### Retry all requests
If you want to retry all requests made from your application, you just need to configure it globally:
```ruby
LHC::Retry.all = true
configuration.interceptors = [LHC::Retry]
```
##### Do not retry certain response codes
If you do not want to retry based on certain response codes, use retry in combination with explicit `ignore`:
```ruby
LHC.get('http://local.ch', ignore: LHC::NotFound, retry: { max: 1 })
```
Or if you use `LHC::Retry.all`:
```ruby
LHC.get('http://local.ch', ignore: LHC::NotFound)
```
#### Rollbar Interceptor
Forward errors to rollbar when exceptions occur during http requests.
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Rollbar]
end
```
```ruby
LHC.get('http://local.ch')
```
If it raises, it forwards the request and response object to rollbar, which contain all necessary data.
##### Forward additional parameters
```ruby
LHC.get('http://local.ch', rollbar: { tracking_key: 'this particular request' })
```
#### Throttle
The throttle interceptor allows you to raise an exception if a predefined quota of a provider request limit is reached in advance.
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Throttle]
end
```
```ruby
options = {
throttle: {
track: true,
break: '80%',
provider: 'local.ch',
limit: { header: 'Rate-Limit-Limit' },
remaining: { header: 'Rate-Limit-Remaining' },
expires: { header: 'Rate-Limit-Reset' }
}
}
LHC.get('http://local.ch', options)
# { headers: { 'Rate-Limit-Limit' => 100, 'Rate-Limit-Remaining' => 19 } }
LHC.get('http://local.ch', options)
# raises LHC::Throttle::OutOfQuota: Reached predefined quota for local.ch
```
**Options Description**
* `track`: enables tracking of current limit/remaining requests of rate-limiting
* `break`: quota in percent after which errors are raised. Percentage symbol is optional, values will be converted to integer (e.g. '23.5' will become 23)
* `provider`: name of the provider under which throttling tracking is aggregated,
* `limit`:
* a hard-coded integer
* a hash pointing at the response header containing the limit value
* a proc that receives the response as argument and returns the limit value
* `remaining`:
* a hash pointing at the response header containing the current amount of remaining requests
* a proc that receives the response as argument and returns the current amount of remaining requests
* `expires`:
* a hash pointing at the response header containing the timestamp when the quota will reset
* a proc that receives the response as argument and returns the timestamp when the quota will reset
#### Zipkin
** Zipkin 0.33 breaks our current implementation of the Zipkin interceptor **
Zipkin is a distributed tracing system. It helps gather timing data needed to troubleshoot latency problems in microservice architectures [Zipkin Distributed Tracing](https://zipkin.io/).
Add the zipkin interceptor to your basic set of LHC interceptors.
```ruby
LHC.configure do |c|
c.interceptors = [LHC::Zipkin]
end
```
The following configuration needs to happen in the application that wants to run this interceptor:
1. Add `gem 'zipkin-tracer', '< 0.33.0'` to your Gemfile.
2. Add the necessary Rack middleware and configuration
```ruby
config.middleware.use ZipkinTracer::RackHandler, {
service_name: 'service-name', # name your service will be known as in zipkin
service_port: 80, # the port information that is sent along the trace
json_api_host: 'http://zipkin-collector', # the zipkin endpoint
sample_rate: 1 # sample rate, where 1 = 100% of all requests, and 0.1 is 10% of all requests
}
```
### Create an interceptor from scratch
```ruby
class TrackingIdInterceptor < LHC::Interceptor
def before_request
request.params[:tid] = 123
end
end
```
```ruby
LHC.configure do |c|
c.interceptors = [TrackingIdInterceptor]
end
```
#### Interceptor callbacks
`before_raw_request` is called before the raw typhoeus request is prepared/created.
`before_request` is called when the request is prepared and about to be executed.
`after_request` is called after request was started.
`before_response` is called when response started to arrive.
`after_response` is called after the response arrived completely.
#### Interceptor request/response
Every interceptor can directly access their instance [request](#request) or [response](#response).
#### Provide a response replacement through an interceptor
Inside an interceptor, you are able to provide a response, rather then doing a real request.
This is useful for implementing e.g. caching.
```ruby
class LHC::Cache < LHC::Interceptor
def before_request(request)
cached_response = Rails.cache.fetch(request.url)
return LHC::Response.new(cached_response) if cached_response
end
end
```
Take care that having more than one interceptor trying to return a response will cause an exception.
You can access the request.response to identify if a response was already provided by another interceptor.
```ruby
class RemoteCacheInterceptor < LHC::Interceptor
def before_request(request)
return unless request.response.nil?
return LHC::Response.new(remote_cache)
end
end
```
## Testing
When writing tests for your application when using LHC, please make sure you require the lhc rspec test helper:
```ruby
# spec/spec_helper.rb
require 'lhc/rspec'
```
## License
[GNU General Public License Version 3.](https://www.gnu.org/licenses/gpl-3.0.en.html)