package pipeline
import (
"context"
"net"
"net/http"
"os"
"time"
)
// The Factory interface represents an object that can create its Policy object. Each HTTP request sent
// requires that this Factory create a new instance of its Policy object.
type Factory interface {
New(next Policy, po *PolicyOptions) Policy
}
// FactoryFunc is an adapter that allows the use of an ordinary function as a Factory interface.
type FactoryFunc func(next Policy, po *PolicyOptions) PolicyFunc
// New calls f(next,po).
func (f FactoryFunc) New(next Policy, po *PolicyOptions) Policy {
return f(next, po)
}
// The Policy interface represents a mutable Policy object created by a Factory. The object can mutate/process
// the HTTP request and then forward it on to the next Policy object in the linked-list. The returned
// Response goes backward through the linked-list for additional processing.
// NOTE: Request is passed by value so changes do not change the caller's version of
// the request. However, Request has some fields that reference mutable objects (not strings).
// These references are copied; a deep copy is not performed. Specifically, this means that
// you should avoid modifying the objects referred to by these fields: URL, Header, Body,
// GetBody, TransferEncoding, Form, MultipartForm, Trailer, TLS, Cancel, and Response.
type Policy interface {
Do(ctx context.Context, request Request) (Response, error)
}
// PolicyFunc is an adapter that allows the use of an ordinary function as a Policy interface.
type PolicyFunc func(ctx context.Context, request Request) (Response, error)
// Do calls f(ctx, request).
func (f PolicyFunc) Do(ctx context.Context, request Request) (Response, error) {
return f(ctx, request)
}
// Options configures a Pipeline's behavior.
type Options struct {
HTTPSender Factory // If sender is nil, then the pipeline's default client is used to send the HTTP requests.
Log LogOptions
}
// LogLevel tells a logger the minimum level to log. When code reports a log entry,
// the LogLevel indicates the level of the log entry. The logger only records entries
// whose level is at least the level it was told to log. See the Log* constants.
// For example, if a logger is configured with LogError, then LogError, LogPanic,
// and LogFatal entries will be logged; lower level entries are ignored.
type LogLevel uint32
const (
// LogNone tells a logger not to log any entries passed to it.
LogNone LogLevel = iota
// LogFatal tells a logger to log all LogFatal entries passed to it.
LogFatal
// LogPanic tells a logger to log all LogPanic and LogFatal entries passed to it.
LogPanic
// LogError tells a logger to log all LogError, LogPanic and LogFatal entries passed to it.
LogError
// LogWarning tells a logger to log all LogWarning, LogError, LogPanic and LogFatal entries passed to it.
LogWarning
// LogInfo tells a logger to log all LogInfo, LogWarning, LogError, LogPanic and LogFatal entries passed to it.
LogInfo
// LogDebug tells a logger to log all LogDebug, LogInfo, LogWarning, LogError, LogPanic and LogFatal entries passed to it.
LogDebug
)
// LogOptions configures the pipeline's logging mechanism & level filtering.
type LogOptions struct {
Log func(level LogLevel, message string)
// ShouldLog is called periodically allowing you to return whether the specified LogLevel should be logged or not.
// An application can return different values over the its lifetime; this allows the application to dynamically
// alter what is logged. NOTE: This method can be called by multiple goroutines simultaneously so make sure
// you implement it in a goroutine-safe way. If nil, nothing is logged (the equivalent of returning LogNone).
// Usually, the function will be implemented simply like this: return level <= LogWarning
ShouldLog func(level LogLevel) bool
}
type pipeline struct {
factories []Factory
options Options
}
// The Pipeline interface represents an ordered list of Factory objects and an object implementing the HTTPSender interface.
// You construct a Pipeline by calling the pipeline.NewPipeline function. To send an HTTP request, call pipeline.NewRequest
// and then call Pipeline's Do method passing a context, the request, and a method-specific Factory (or nil). Passing a
// method-specific Factory allows this one call to Do to inject a Policy into the linked-list. The policy is injected where
// the MethodFactoryMarker (see the pipeline.MethodFactoryMarker function) is in the slice of Factory objects.
//
// When Do is called, the Pipeline object asks each Factory object to construct its Policy object and adds each Policy to a linked-list.
// THen, Do sends the Context and Request through all the Policy objects. The final Policy object sends the request over the network
// (via the HTTPSender object passed to NewPipeline) and the response is returned backwards through all the Policy objects.
// Since Pipeline and Factory objects are goroutine-safe, you typically create 1 Pipeline object and reuse it to make many HTTP requests.
type Pipeline interface {
Do(ctx context.Context, methodFactory Factory, request Request) (Response, error)
}
// NewPipeline creates a new goroutine-safe Pipeline object from the slice of Factory objects and the specified options.
func NewPipeline(factories []Factory, o Options) Pipeline {
if o.HTTPSender == nil {
o.HTTPSender = newDefaultHTTPClientFactory()
}
if o.Log.Log == nil {
o.Log.Log = func(LogLevel, string) {} // No-op logger
}
return &pipeline{factories: factories, options: o}
}
// Do is called for each and every HTTP request. It tells each Factory to create its own (mutable) Policy object
// replacing a MethodFactoryMarker factory (if it exists) with the methodFactory passed in. Then, the Context and Request
// are sent through the pipeline of Policy objects (which can transform the Request's URL/query parameters/headers) and
// ultimately sends the transformed HTTP request over the network.
func (p *pipeline) Do(ctx context.Context, methodFactory Factory, request Request) (Response, error) {
response, err := p.newPolicies(methodFactory).Do(ctx, request)
request.close()
return response, err
}
func (p *pipeline) newPolicies(methodFactory Factory) Policy {
// The last Policy is the one that actually sends the request over the wire and gets the response.
// It is overridable via the Options' HTTPSender field.
po := &PolicyOptions{pipeline: p} // One object shared by all policy objects
next := p.options.HTTPSender.New(nil, po)
// Walk over the slice of Factory objects in reverse (from wire to API)
markers := 0
for i := len(p.factories) - 1; i >= 0; i-- {
factory := p.factories[i]
if _, ok := factory.(methodFactoryMarker); ok {
markers++
if markers > 1 {
panic("MethodFactoryMarker can only appear once in the pipeline")
}
if methodFactory != nil {
// Replace MethodFactoryMarker with passed-in methodFactory
next = methodFactory.New(next, po)
}
} else {
// Use the slice's Factory to construct its Policy
next = factory.New(next, po)
}
}
// Each Factory has created its Policy
if markers == 0 && methodFactory != nil {
panic("Non-nil methodFactory requires MethodFactoryMarker in the pipeline")
}
return next // Return head of the Policy object linked-list
}
// A PolicyOptions represents optional information that can be used by a node in the
// linked-list of Policy objects. A PolicyOptions is passed to the Factory's New method
// which passes it (if desired) to the Policy object it creates. Today, the Policy object
// uses the options to perform logging. But, in the future, this could be used for more.
type PolicyOptions struct {
pipeline *pipeline
}
// ShouldLog returns true if the specified log level should be logged.
func (po *PolicyOptions) ShouldLog(level LogLevel) bool {
if po.pipeline.options.Log.ShouldLog != nil {
return po.pipeline.options.Log.ShouldLog(level)
}
return false
}
// Log logs a string to the Pipeline's Logger.
func (po *PolicyOptions) Log(level LogLevel, msg string) {
if !po.ShouldLog(level) {
return // Short circuit message formatting if we're not logging it
}
// We are logging it, ensure trailing newline
if len(msg) == 0 || msg[len(msg)-1] != '\n' {
msg += "\n" // Ensure trailing newline
}
po.pipeline.options.Log.Log(level, msg)
// If logger doesn't handle fatal/panic, we'll do it here.
if level == LogFatal {
os.Exit(1)
} else if level == LogPanic {
panic(msg)
}
}
var pipelineHTTPClient = newDefaultHTTPClient()
func newDefaultHTTPClient() *http.Client {
// We want the Transport to have a large connection pool
return &http.Client{
Transport: &http.Transport{
Proxy: http.ProxyFromEnvironment,
// We use Dial instead of DialContext as DialContext has been reported to cause slower performance.
Dial /*Context*/ : (&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
DualStack: true,
}).Dial, /*Context*/
MaxIdleConns: 0, // No limit
MaxIdleConnsPerHost: 100,
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: 10 * time.Second,
ExpectContinueTimeout: 1 * time.Second,
DisableKeepAlives: false,
DisableCompression: false,
MaxResponseHeaderBytes: 0,
//ResponseHeaderTimeout: time.Duration{},
//ExpectContinueTimeout: time.Duration{},
},
}
}
// newDefaultHTTPClientFactory creates a DefaultHTTPClientPolicyFactory object that sends HTTP requests to a Go's default http.Client.
func newDefaultHTTPClientFactory() Factory {
return FactoryFunc(func(next Policy, po *PolicyOptions) PolicyFunc {
return func(ctx context.Context, request Request) (Response, error) {
r, err := pipelineHTTPClient.Do(request.WithContext(ctx))
if err != nil {
err = NewError(err, "HTTP request failed")
}
return NewHTTPResponse(r), err
}
})
}
var mfm = methodFactoryMarker{} // Singleton
// MethodFactoryMarker returns a special marker Factory object. When Pipeline's Do method is called, any
// MethodMarkerFactory object is replaced with the specified methodFactory object. If nil is passed fro Do's
// methodFactory parameter, then the MethodFactoryMarker is ignored as the linked-list of Policy objects is created.
func MethodFactoryMarker() Factory {
return mfm
}
type methodFactoryMarker struct {
}
func (methodFactoryMarker) New(next Policy, po *PolicyOptions) Policy {
panic("methodFactoryMarker policy should have been replaced with a method policy")
}
