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 for low level http communication.
See LHS, if you are searching for something more high level that can query webservices easily and provides an ActiveRecord like interface.
Quick start guide
gem install lhc
or add it to your Gemfile:
gem 'lhc'
use it like:
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
- Basic methods
- Request
- Response
- Exceptions
- Configuration
- Interceptors
- Quick start: Configure/Enable Interceptors
- Interceptors on local request level
- Core Interceptors
- Create an interceptor from scratch
- Testing
- 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 for any response code that is not indicating success (2xx).
response = LHC.request(url: 'http://local.ch', method: :options)
response.request.response #<LHC::Response> the associated response.
response.request. #<Hash> the options used for creating the request.
response.request.params # access request params
response.request.headers # access request headers
response.request.url #<String> URL that is used for doing the request
response.request.method #<Symbol> provides the used http-method
Formats
You can use any of the basic methods in combination with a format like json
:
LHC.json.get()
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:
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
:
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:
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.
= []
<< { url: 'http://datastore/v2/feedbacks' }
<< { url: 'http://datastore/v2/content-ads/123/feedbacks' }
responses = LHC.request()
LHC.request([request1, request2, request3])
# returns [response1, response2, response3]
Follow redirects
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, like LHC.json
.
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
LHC.get('http://local.ch', params: { q: 'Restaurant' })
DON'T
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.
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:
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:
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:
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.
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:
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.
LHC.get('http://local.ch', timeout: 5, connecttimeout: 1)
LHC provides a 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
response.request #<LHC::Request> the associated request.
response.data #<OpenStruct> in case response body contains parsable JSON.
response.data.something.nested
response.body #<String>
response.code #<Fixnum>
response.headers #<Hash>
response.time #<Fixnum> 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).
response = LHC.request(url: 'http://datastore/entry/1')
response.data.as_open_struct #<OpenStruct name='local.ch'>
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):
LHC.json.get(url: 'http://datastore/entry/1')[:name]
Exceptions
Anything but a response code indicating success (2xx) raises an exception.
LHC.get('localhost') # UnknownError: 0
LHC.get('http://localhost:3000') # LHC::Timeout: 0
You can access the response object that was causing the error.
LHC.get('local.ch')
rescue => e
e.response #<LHC: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
# <Response Body>
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.
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.
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.
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.
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).
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.
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.
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
andpassword
within the Request Header password
andpassword_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:
LHC.configure do |c|
c.scrubs[:params] << 'api_key'
c.scrubs[:body].push('user_token', 'secret_key')
end
For disabling scrubbing, add following configuration:
LHC.configure do |c|
c.scrubs = {}
end
If you want to turn off :bearer
or :basic
scrubbing, then just overwrite the :auth
configuration.
Example:
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:
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, that cover some basic usecases.
Quick start: Configure/Enable Interceptors
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:
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.
LHC.configure do |c|
c.interceptors = [LHC::Auth]
end
Bearer Authentication
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
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
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:
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.
LHC::Auth.refresh_client_token = -> { TokenRefreshUtil.client_access_token(true) }
Reauthentication will be initiated if:
- setup is correct
response.success?
is false and anLHC::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 addingretry: { max: 1 }
to the request options
Caching Interceptor
Add the cache interceptor to your basic set of LHC interceptors.
LHC.configure do |c|
c.interceptors = [LHC::Caching]
end
You can configure your own cache (default Rails.cache) and logger (default Rails.logger):
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.
LHC.get('http://local.ch', cache: true)
You can also enable caching when configuring an endpoint in LHS.
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:
LHC.get('http://local.ch', cache: { methods: [:get] })
Responses served from cache are marked as served from cache:
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.
LHC::Caching.central = {
read: 'redis://[email protected]:6379/0',
write: 'redis://[email protected]:6379/0'
}
Options
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.
LHC.configure do |c|
c.interceptors = [LHC::DefaultTimeout]
end
timeout
default: 15 seconds
connecttimeout
default: 2 seconds
Overwrite defaults
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
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:
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:
LHC::Logging.logger = Another::Logger
Monitoring Interceptor
The monitoring interceptor reports all requests done with LHC to a given StatsD instance.
Installation
LHC.configure do |c|
c.interceptors = [LHC::Monitoring]
end
You also have to configure statsd in order to have the monitoring interceptor report.
LHC::Monitoring.statsd = <your-instance-of-statsd>
Environment
By default, the monitoring interceptor uses Rails.env to determine the environment. In case you want to configure that, use:
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
"lhc.<app_name>.<env>.<host>.<http_method>.before_request", 1
"lhc.<app_name>.<env>.<host>.<http_method>.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.
LHC.get('http://local.ch')
"lhc.<app_name>.<env>.<host>.<http_method>.count", 1
"lhc.<app_name>.<env>.<host>.<http_method>.200", 1
"lhc.<app_name>.<env>.<host>.<http_method>.time", 43
In case of a unsuccessful response it reports the response code with a count but no time:
LHC.get('http://local.ch')
"lhc.<app_name>.<env>.<host>.<http_method>.count", 1
"lhc.<app_name>.<env>.<host>.<http_method>.500", 1
Timeout tracking
Timeouts are also reported:
"lhc.<app_name>.<env>.<host>.<http_method>.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:
LHC.configure do |c|
c.interceptors = [LHC::Caching, LHC::Monitoring]
end
If a response was served from cache it tracks:
"lhc.<app_name>.<env>.<host>.<http_method>.cache.hit", 1
If a response was not served from cache it tracks:
"lhc.<app_name>.<env>.<host>.<http_method>.cache.miss", 1
Configure
It is possible to set the key for Monitoring Interceptor on per request basis:
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.
require 'prometheus/client'
LHC.configure do |c|
c.interceptors = [LHC::Prometheus]
end
LHC::Prometheus.client = Prometheus::Client
LHC::Prometheus.namespace = 'web_location_app'
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:
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
LHC.get('http://local.ch', retry: { max: 1 })
Change the default maximum of retries of the retry interceptor
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:
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
:
LHC.get('http://local.ch', ignore: LHC::NotFound, retry: { max: 1 })
Or if you use LHC::Retry.all
:
LHC.get('http://local.ch', ignore: LHC::NotFound)
Rollbar Interceptor
Forward errors to rollbar when exceptions occur during http requests.
LHC.configure do |c|
c.interceptors = [LHC::Rollbar]
end
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
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.
LHC.configure do |c|
c.interceptors = [LHC::Throttle]
end
= {
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', )
# { headers: { 'Rate-Limit-Limit' => 100, 'Rate-Limit-Remaining' => 19 } }
LHC.get('http://local.ch', )
# raises LHC::Throttle::OutOfQuota: Reached predefined quota for local.ch
Options Description
track
: enables tracking of current limit/remaining requests of rate-limitingbreak
: 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.
Add the zipkin interceptor to your basic set of LHC interceptors.
LHC.configure do |c|
c.interceptors = [LHC::Zipkin]
end
The following configuration needs to happen in the application that wants to run this interceptor:
- Add
gem 'zipkin-tracer', '< 0.33.0'
to your Gemfile. - Add the necessary Rack middleware and configuration
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
class TrackingIdInterceptor < LHC::Interceptor
def before_request
request.params[:tid] = 123
end
end
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 or 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.
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.
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:
# spec/spec_helper.rb
require 'lhc/rspec'