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Request buffering middleware

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Łukasz Harasimowicz 2018-01-31 15:32:04 +01:00 • committed by Traefiker
parent d426126a92
commit a81171d5f1
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vendor/github.com/mailgun/multibuf/buffer.go generated vendored Normal file
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// package multibuf implements buffer optimized for streaming large chunks of data,
// multiple reads and optional partial buffering to disk.
package multibuf
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"os"
)
// MultiReader provides Read, Close, Seek and Size methods. In addition to that it supports WriterTo interface
// to provide efficient writing schemes, as functions like io.Copy use WriterTo when it's available.
type MultiReader interface {
io.Reader
io.Seeker
io.Closer
io.WriterTo
// Size calculates and returns the total size of the reader and not the length remaining.
Size() (int64, error)
}
// WriterOnce implements write once, read many times writer. Create a WriterOnce and write to it, once Reader() function has been
// called, the internal data is transferred to MultiReader and this instance of WriterOnce should be no longer used.
type WriterOnce interface {
// Write implements io.Writer
Write(p []byte) (int, error)
// Reader transfers all data written to this writer to MultiReader. If there was no data written it retuns an error
Reader() (MultiReader, error)
// WriterOnce owns the data before Reader has been called, so Close will close all the underlying files if Reader has not been called.
Close() error
}
// MaxBytes, ignored if set to value >=, if request exceeds the specified limit, the reader will return error,
// by default buffer is not limited, negative values mean no limit
func MaxBytes(m int64) optionSetter {
return func(o *options) error {
o.maxBytes = m
return nil
}
}
// MemBytes specifies the largest buffer to hold in RAM before writing to disk, default is 1MB
func MemBytes(m int64) optionSetter {
return func(o *options) error {
if m < 0 {
return fmt.Errorf("MemBytes should be >= 0")
}
o.memBytes = m
return nil
}
}
// NewWriterOnce returns io.ReadWrite compatible object that can limit the size of the buffer and persist large buffers to disk.
// WriterOnce implements write once, read many times writer. Create a WriterOnce and write to it, once Reader() function has been
// called, the internal data is transferred to MultiReader and this instance of WriterOnce should be no longer used.
// By default NewWriterOnce returns unbound buffer that will allow to write up to 1MB in RAM and will start buffering to disk
// It supports multiple functional optional arguments:
//
// // Buffer up to 1MB in RAM and limit max buffer size to 20MB
// multibuf.NewWriterOnce(r, multibuf.MemBytes(1024 * 1024), multibuf.MaxBytes(1024 * 1024 * 20))
//
//
func NewWriterOnce(setters ...optionSetter) (WriterOnce, error) {
o := options{
memBytes: DefaultMemBytes,
maxBytes: DefaultMaxBytes,
}
if o.memBytes == 0 {
o.memBytes = DefaultMemBytes
}
for _, s := range setters {
if err := s(&o); err != nil {
return nil, err
}
}
return &writerOnce{o: o}, nil
}
// New returns MultiReader that can limit the size of the buffer and persist large buffers to disk.
// By default New returns unbound buffer that will read up to 1MB in RAM and will start buffering to disk
// It supports multiple functional optional arguments:
//
// // Buffer up to 1MB in RAM and limit max buffer size to 20MB
// multibuf.New(r, multibuf.MemBytes(1024 * 1024), multibuf.MaxBytes(1024 * 1024 * 20))
//
//
func New(input io.Reader, setters ...optionSetter) (MultiReader, error) {
o := options{
memBytes: DefaultMemBytes,
maxBytes: DefaultMaxBytes,
}
for _, s := range setters {
if err := s(&o); err != nil {
return nil, err
}
}
if o.memBytes == 0 {
o.memBytes = DefaultMemBytes
}
if o.maxBytes > 0 && o.maxBytes < o.memBytes {
o.memBytes = o.maxBytes
}
memReader := &io.LimitedReader{
R: input, // Read from this reader
N: o.memBytes, // Maximum amount of data to read
}
readers := make([]io.ReadSeeker, 0, 2)
buffer, err := ioutil.ReadAll(memReader)
if err != nil {
return nil, err
}
readers = append(readers, bytes.NewReader(buffer))
var file *os.File
// This means that we have exceeded all the memory capacity and we will start buffering the body to disk.
totalBytes := int64(len(buffer))
if memReader.N <= 0 {
file, err = ioutil.TempFile("", tempFilePrefix)
if err != nil {
return nil, err
}
os.Remove(file.Name())
readSrc := input
if o.maxBytes > 0 {
readSrc = &maxReader{R: input, Max: o.maxBytes - o.memBytes}
}
writtenBytes, err := io.Copy(file, readSrc)
if err != nil {
return nil, err
}
totalBytes += writtenBytes
file.Seek(0, 0)
readers = append(readers, file)
}
var cleanupFn cleanupFunc
if file != nil {
cleanupFn = func() error {
file.Close()
return nil
}
}
return newBuf(totalBytes, cleanupFn, readers...), nil
}
// MaxSizeReachedError is returned when the maximum allowed buffer size is reached when reading
type MaxSizeReachedError struct {
MaxSize int64
}
func (e *MaxSizeReachedError) Error() string {
return fmt.Sprintf("Maximum size %d was reached", e)
}
const (
DefaultMemBytes = 1048576
DefaultMaxBytes = -1
// Equivalent of bytes.MinRead used in ioutil.ReadAll
DefaultBufferBytes = 512
)
// Constraints:
// - Implements io.Reader
// - Implements Seek(0, 0)
// - Designed for Write once, Read many times.
type multiReaderSeek struct {
length int64
readers []io.ReadSeeker
mr io.Reader
cleanup cleanupFunc
}
type cleanupFunc func() error
func newBuf(length int64, cleanup cleanupFunc, readers ...io.ReadSeeker) *multiReaderSeek {
converted := make([]io.Reader, len(readers))
for i, r := range readers {
// This conversion is safe as ReadSeeker includes Reader
converted[i] = r.(io.Reader)
}
return &multiReaderSeek{
length: length,
readers: readers,
mr: io.MultiReader(converted...),
cleanup: cleanup,
}
}
func (mr *multiReaderSeek) Close() (err error) {
if mr.cleanup != nil {
return mr.cleanup()
}
return nil
}
func (mr *multiReaderSeek) WriteTo(w io.Writer) (int64, error) {
b := make([]byte, DefaultBufferBytes)
var total int64
for {
n, err := mr.mr.Read(b)
// Recommended way is to always handle non 0 reads despite the errors
if n > 0 {
nw, errw := w.Write(b[:n])
total += int64(nw)
// Write must return a non-nil error if it returns nw < n
if nw != n || errw != nil {
return total, errw
}
}
if err != nil {
if err == io.EOF {
return total, nil
}
return total, err
}
}
}
func (mr *multiReaderSeek) Read(p []byte) (n int, err error) {
return mr.mr.Read(p)
}
func (mr *multiReaderSeek) Size() (int64, error) {
return mr.length, nil
}
func (mr *multiReaderSeek) Seek(offset int64, whence int) (int64, error) {
// TODO: implement other whence
// TODO: implement real offsets
if whence != 0 {
return 0, fmt.Errorf("multiReaderSeek: unsupported whence")
}
if offset != 0 {
return 0, fmt.Errorf("multiReaderSeek: unsupported offset")
}
for _, seeker := range mr.readers {
seeker.Seek(0, 0)
}
ior := make([]io.Reader, len(mr.readers))
for i, arg := range mr.readers {
ior[i] = arg.(io.Reader)
}
mr.mr = io.MultiReader(ior...)
return 0, nil
}
type options struct {
// MemBufferBytes sets up the size of the memory buffer for this request.
// If the data size exceeds the limit, the remaining request part will be saved on the file system.
memBytes int64
maxBytes int64
}
type optionSetter func(o *options) error
// MaxReader does not allow to read more than Max bytes and returns error if this limit has been exceeded.
type maxReader struct {
R io.Reader // underlying reader
N int64 // bytes read
Max int64 // max bytes to read
}
func (r *maxReader) Read(p []byte) (int, error) {
readBytes, err := r.R.Read(p)
if err != nil && err != io.EOF {
return readBytes, err
}
r.N += int64(readBytes)
if r.N > r.Max {
return readBytes, &MaxSizeReachedError{MaxSize: r.Max}
}
return readBytes, err
}
const (
writerInit = iota
writerMem
writerFile
writerCalledRead
writerErr
)
type writerOnce struct {
o options
err error
state int
mem *bytes.Buffer
file *os.File
total int64
cleanupFn cleanupFunc
}
// how many bytes we can still write to memory
func (w *writerOnce) writeToMem(p []byte) int {
left := w.o.memBytes - w.total
if left <= 0 {
return 0
}
bufLen := len(p)
if int64(bufLen) < left {
return bufLen
}
return int(left)
}
func (w *writerOnce) Write(p []byte) (int, error) {
out, err := w.write(p)
return out, err
}
func (w *writerOnce) Close() error {
if w.file != nil {
return w.file.Close()
}
return nil
}
func (w *writerOnce) write(p []byte) (int, error) {
if w.o.maxBytes > 0 && int64(len(p))+w.total > w.o.maxBytes {
return 0, fmt.Errorf("total size of %d exceeded allowed %d", int64(len(p))+w.total, w.o.maxBytes)
}
switch w.state {
case writerCalledRead:
return 0, fmt.Errorf("can not write after reader has been called")
case writerInit:
w.mem = &bytes.Buffer{}
w.state = writerMem
fallthrough
case writerMem:
writeToMem := w.writeToMem(p)
if writeToMem > 0 {
wrote, err := w.mem.Write(p[:writeToMem])
w.total += int64(wrote)
if err != nil {
return wrote, err
}
}
left := len(p) - writeToMem
if left <= 0 {
return len(p), nil
}
// we can't write to memory any more, switch to file
if err := w.initFile(); err != nil {
return int(writeToMem), err
}
w.state = writerFile
wrote, err := w.file.Write(p[writeToMem:])
w.total += int64(wrote)
return len(p), err
case writerFile:
wrote, err := w.file.Write(p)
w.total += int64(wrote)
return wrote, err
}
return 0, fmt.Errorf("unsupported state: %d", w.state)
}
func (w *writerOnce) initFile() error {
file, err := ioutil.TempFile("", tempFilePrefix)
if err != nil {
return err
}
w.file = file
w.cleanupFn = func() error {
file.Close()
os.Remove(file.Name())
return nil
}
return nil
}
func (w *writerOnce) Reader() (MultiReader, error) {
switch w.state {
case writerInit:
return nil, fmt.Errorf("no data ready")
case writerCalledRead:
return nil, fmt.Errorf("reader has been called")
case writerMem:
w.state = writerCalledRead
return newBuf(w.total, nil, bytes.NewReader(w.mem.Bytes())), nil
case writerFile:
_, err := w.file.Seek(0, 0)
if err != nil {
return nil, err
}
// we are not responsible for file and buffer any more
w.state = writerCalledRead
br, fr := bytes.NewReader(w.mem.Bytes()), w.file
w.file = nil
w.mem = nil
return newBuf(w.total, w.cleanupFn, br, fr), nil
}
return nil, fmt.Errorf("unsupported state: %d\n", w.state)
}
const tempFilePrefix = "temp-multibuf-"

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/*
Package buffer provides http.Handler middleware that solves several problems when dealing with http requests:
Reads the entire request and response into buffer, optionally buffering it to disk for large requests.
Checks the limits for the requests and responses, rejecting in case if the limit was exceeded.
Changes request content-transfer-encoding from chunked and provides total size to the handlers.
Examples of a buffering middleware:
// sample HTTP handler
handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
w.Write([]byte("hello"))
})
// Buffer will read the body in buffer before passing the request to the handler
// calculate total size of the request and transform it from chunked encoding
// before passing to the server
buffer.New(handler)
// This version will buffer up to 2MB in memory and will serialize any extra
// to a temporary file, if the request size exceeds 10MB it will reject the request
buffer.New(handler,
buffer.MemRequestBodyBytes(2 * 1024 * 1024),
buffer.MaxRequestBodyBytes(10 * 1024 * 1024))
// Will do the same as above, but with responses
buffer.New(handler,
buffer.MemResponseBodyBytes(2 * 1024 * 1024),
buffer.MaxResponseBodyBytes(10 * 1024 * 1024))
// Buffer will replay the request if the handler returns error at least 3 times
// before returning the response
buffer.New(handler, buffer.Retry(`IsNetworkError() && Attempts() <= 2`))
*/
package buffer
import (
"fmt"
"io"
"io/ioutil"
"net/http"
"bufio"
"net"
"reflect"
"github.com/mailgun/multibuf"
log "github.com/sirupsen/logrus"
"github.com/vulcand/oxy/utils"
)
const (
// DefaultMemBodyBytes Store up to 1MB in RAM
DefaultMemBodyBytes = 1048576
// DefaultMaxBodyBytes No limit by default
DefaultMaxBodyBytes = -1
// DefaultMaxRetryAttempts Maximum retry attempts
DefaultMaxRetryAttempts = 10
)
var errHandler utils.ErrorHandler = &SizeErrHandler{}
// Buffer is responsible for buffering requests and responses
// It buffers large requests and responses to disk,
type Buffer struct {
maxRequestBodyBytes int64
memRequestBodyBytes int64
maxResponseBodyBytes int64
memResponseBodyBytes int64
retryPredicate hpredicate
next http.Handler
errHandler utils.ErrorHandler
}
// New returns a new buffer middleware. New() function supports optional functional arguments
func New(next http.Handler, setters ...optSetter) (*Buffer, error) {
strm := &Buffer{
next: next,
maxRequestBodyBytes: DefaultMaxBodyBytes,
memRequestBodyBytes: DefaultMemBodyBytes,
maxResponseBodyBytes: DefaultMaxBodyBytes,
memResponseBodyBytes: DefaultMemBodyBytes,
}
for _, s := range setters {
if err := s(strm); err != nil {
return nil, err
}
}
if strm.errHandler == nil {
strm.errHandler = errHandler
}
return strm, nil
}
type optSetter func(s *Buffer) error
// Retry provides a predicate that allows buffer middleware to replay the request
// if it matches certain condition, e.g. returns special error code. Available functions are:
//
// Attempts() - limits the amount of retry attempts
// ResponseCode() - returns http response code
// IsNetworkError() - tests if response code is related to networking error
//
// Example of the predicate:
//
// `Attempts() <= 2 && ResponseCode() == 502`
//
func Retry(predicate string) optSetter {
return func(s *Buffer) error {
p, err := parseExpression(predicate)
if err != nil {
return err
}
s.retryPredicate = p
return nil
}
}
// ErrorHandler sets error handler of the server
func ErrorHandler(h utils.ErrorHandler) optSetter {
return func(s *Buffer) error {
s.errHandler = h
return nil
}
}
// MaxRequestBodyBytes sets the maximum request body size in bytes
func MaxRequestBodyBytes(m int64) optSetter {
return func(s *Buffer) error {
if m < 0 {
return fmt.Errorf("max bytes should be >= 0 got %d", m)
}
s.maxRequestBodyBytes = m
return nil
}
}
// MaxRequestBody bytes sets the maximum request body to be stored in memory
// buffer middleware will serialize the excess to disk.
func MemRequestBodyBytes(m int64) optSetter {
return func(s *Buffer) error {
if m < 0 {
return fmt.Errorf("mem bytes should be >= 0 got %d", m)
}
s.memRequestBodyBytes = m
return nil
}
}
// MaxResponseBodyBytes sets the maximum request body size in bytes
func MaxResponseBodyBytes(m int64) optSetter {
return func(s *Buffer) error {
if m < 0 {
return fmt.Errorf("max bytes should be >= 0 got %d", m)
}
s.maxResponseBodyBytes = m
return nil
}
}
// MemResponseBodyBytes sets the maximum request body to be stored in memory
// buffer middleware will serialize the excess to disk.
func MemResponseBodyBytes(m int64) optSetter {
return func(s *Buffer) error {
if m < 0 {
return fmt.Errorf("mem bytes should be >= 0 got %d", m)
}
s.memResponseBodyBytes = m
return nil
}
}
// Wrap sets the next handler to be called by buffer handler.
func (s *Buffer) Wrap(next http.Handler) error {
s.next = next
return nil
}
func (s *Buffer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
if log.GetLevel() >= log.DebugLevel {
logEntry := log.WithField("Request", utils.DumpHttpRequest(req))
logEntry.Debug("vulcand/oxy/buffer: begin ServeHttp on request")
defer logEntry.Debug("vulcand/oxy/buffer: competed ServeHttp on request")
}
if err := s.checkLimit(req); err != nil {
log.Errorf("vulcand/oxy/buffer: request body over limit, err: %v", err)
s.errHandler.ServeHTTP(w, req, err)
return
}
// Read the body while keeping limits in mind. This reader controls the maximum bytes
// to read into memory and disk. This reader returns an error if the total request size exceeds the
// prefefined MaxSizeBytes. This can occur if we got chunked request, in this case ContentLength would be set to -1
// and the reader would be unbounded bufio in the http.Server
body, err := multibuf.New(req.Body, multibuf.MaxBytes(s.maxRequestBodyBytes), multibuf.MemBytes(s.memRequestBodyBytes))
if err != nil || body == nil {
log.Errorf("vulcand/oxy/buffer: error when reading request body, err: %v", err)
s.errHandler.ServeHTTP(w, req, err)
return
}
// Set request body to buffered reader that can replay the read and execute Seek
// Note that we don't change the original request body as it's handled by the http server
// and we don'w want to mess with standard library
defer func() {
if body != nil {
errClose := body.Close()
if errClose != nil {
log.Errorf("vulcand/oxy/buffer: failed to close body, err: %v", errClose)
}
}
}()
// We need to set ContentLength based on known request size. The incoming request may have been
// set without content length or using chunked TransferEncoding
totalSize, err := body.Size()
if err != nil {
log.Errorf("vulcand/oxy/buffer: failed to get request size, err: %v", err)
s.errHandler.ServeHTTP(w, req, err)
return
}
if totalSize == 0 {
body = nil
}
outreq := s.copyRequest(req, body, totalSize)
attempt := 1
for {
// We create a special writer that will limit the response size, buffer it to disk if necessary
writer, err := multibuf.NewWriterOnce(multibuf.MaxBytes(s.maxResponseBodyBytes), multibuf.MemBytes(s.memResponseBodyBytes))
if err != nil {
log.Errorf("vulcand/oxy/buffer: failed create response writer, err: %v", err)
s.errHandler.ServeHTTP(w, req, err)
return
}
// We are mimicking http.ResponseWriter to replace writer with our special writer
b := &bufferWriter{
header: make(http.Header),
buffer: writer,
responseWriter: w,
}
defer b.Close()
s.next.ServeHTTP(b, outreq)
if b.hijacked {
log.Infof("vulcand/oxy/buffer: connection was hijacked downstream. Not taking any action in buffer.")
return
}
var reader multibuf.MultiReader
if b.expectBody(outreq) {
rdr, err := writer.Reader()
if err != nil {
log.Errorf("vulcand/oxy/buffer: failed to read response, err: %v", err)
s.errHandler.ServeHTTP(w, req, err)
return
}
defer rdr.Close()
reader = rdr
}
if (s.retryPredicate == nil || attempt > DefaultMaxRetryAttempts) ||
!s.retryPredicate(&context{r: req, attempt: attempt, responseCode: b.code}) {
utils.CopyHeaders(w.Header(), b.Header())
w.WriteHeader(b.code)
if reader != nil {
io.Copy(w, reader)
}
return
}
attempt += 1
if body != nil {
if _, err := body.Seek(0, 0); err != nil {
log.Errorf("vulcand/oxy/buffer: failed to rewind response body, err: %v", err)
s.errHandler.ServeHTTP(w, req, err)
return
}
}
outreq = s.copyRequest(req, body, totalSize)
log.Infof("vulcand/oxy/buffer: retry Request(%v %v) attempt %v", req.Method, req.URL, attempt)
}
}
func (s *Buffer) copyRequest(req *http.Request, body io.ReadCloser, bodySize int64) *http.Request {
o := *req
o.URL = utils.CopyURL(req.URL)
o.Header = make(http.Header)
utils.CopyHeaders(o.Header, req.Header)
o.ContentLength = bodySize
// remove TransferEncoding that could have been previously set because we have transformed the request from chunked encoding
o.TransferEncoding = []string{}
// http.Transport will close the request body on any error, we are controlling the close process ourselves, so we override the closer here
if body == nil {
o.Body = nil
} else {
o.Body = ioutil.NopCloser(body.(io.Reader))
}
return &o
}
func (s *Buffer) checkLimit(req *http.Request) error {
if s.maxRequestBodyBytes <= 0 {
return nil
}
if req.ContentLength > s.maxRequestBodyBytes {
return &multibuf.MaxSizeReachedError{MaxSize: s.maxRequestBodyBytes}
}
return nil
}
type bufferWriter struct {
header http.Header
code int
buffer multibuf.WriterOnce
responseWriter http.ResponseWriter
hijacked bool
}
// RFC2616 #4.4
func (b *bufferWriter) expectBody(r *http.Request) bool {
if r.Method == "HEAD" {
return false
}
if (b.code >= 100 && b.code < 200) || b.code == 204 || b.code == 304 {
return false
}
if b.header.Get("Content-Length") == "" && b.header.Get("Transfer-Encoding") == "" {
return false
}
if b.header.Get("Content-Length") == "0" {
return false
}
return true
}
func (b *bufferWriter) Close() error {
return b.buffer.Close()
}
func (b *bufferWriter) Header() http.Header {
return b.header
}
func (b *bufferWriter) Write(buf []byte) (int, error) {
return b.buffer.Write(buf)
}
// WriteHeader sets rw.Code.
func (b *bufferWriter) WriteHeader(code int) {
b.code = code
}
//CloseNotifier interface - this allows downstream connections to be terminated when the client terminates.
func (b *bufferWriter) CloseNotify() <-chan bool {
if cn, ok := b.responseWriter.(http.CloseNotifier); ok {
return cn.CloseNotify()
}
log.Warningf("Upstream ResponseWriter of type %v does not implement http.CloseNotifier. Returning dummy channel.", reflect.TypeOf(b.responseWriter))
return make(<-chan bool)
}
//This allows connections to be hijacked for websockets for instance.
func (b *bufferWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
if hi, ok := b.responseWriter.(http.Hijacker); ok {
conn, rw, err := hi.Hijack()
if err != nil {
b.hijacked = true
}
return conn, rw, err
}
log.Warningf("Upstream ResponseWriter of type %v does not implement http.Hijacker. Returning dummy channel.", reflect.TypeOf(b.responseWriter))
return nil, nil, fmt.Errorf("The response writer that was wrapped in this proxy, does not implement http.Hijacker. It is of type: %v", reflect.TypeOf(b.responseWriter))
}
type SizeErrHandler struct {
}
func (e *SizeErrHandler) ServeHTTP(w http.ResponseWriter, req *http.Request, err error) {
if _, ok := err.(*multibuf.MaxSizeReachedError); ok {
w.WriteHeader(http.StatusRequestEntityTooLarge)
w.Write([]byte(http.StatusText(http.StatusRequestEntityTooLarge)))
return
}
utils.DefaultHandler.ServeHTTP(w, req, err)
}

225
vendor/github.com/vulcand/oxy/buffer/threshold.go generated vendored Normal file
View file

@ -0,0 +1,225 @@
package buffer
import (
"fmt"
"net/http"
"github.com/vulcand/predicate"
)
func IsValidExpression(expr string) bool {
_, err := parseExpression(expr)
return err == nil
}
type context struct {
r *http.Request
attempt int
responseCode int
}
type hpredicate func(*context) bool
// Parses expression in the go language into Failover predicates
func parseExpression(in string) (hpredicate, error) {
p, err := predicate.NewParser(predicate.Def{
Operators: predicate.Operators{
AND: and,
OR: or,
EQ: eq,
NEQ: neq,
LT: lt,
GT: gt,
LE: le,
GE: ge,
},
Functions: map[string]interface{}{
"RequestMethod": requestMethod,
"IsNetworkError": isNetworkError,
"Attempts": attempts,
"ResponseCode": responseCode,
},
})
if err != nil {
return nil, err
}
out, err := p.Parse(in)
if err != nil {
return nil, err
}
pr, ok := out.(hpredicate)
if !ok {
return nil, fmt.Errorf("expected predicate, got %T", out)
}
return pr, nil
}
type toString func(c *context) string
type toInt func(c *context) int
// RequestMethod returns mapper of the request to its method e.g. POST
func requestMethod() toString {
return func(c *context) string {
return c.r.Method
}
}
// Attempts returns mapper of the request to the number of proxy attempts
func attempts() toInt {
return func(c *context) int {
return c.attempt
}
}
// ResponseCode returns mapper of the request to the last response code, returns 0 if there was no response code.
func responseCode() toInt {
return func(c *context) int {
return c.responseCode
}
}
// IsNetworkError returns a predicate that returns true if last attempt ended with network error.
func isNetworkError() hpredicate {
return func(c *context) bool {
return c.responseCode == http.StatusBadGateway || c.responseCode == http.StatusGatewayTimeout
}
}
// and returns predicate by joining the passed predicates with logical 'and'
func and(fns ...hpredicate) hpredicate {
return func(c *context) bool {
for _, fn := range fns {
if !fn(c) {
return false
}
}
return true
}
}
// or returns predicate by joining the passed predicates with logical 'or'
func or(fns ...hpredicate) hpredicate {
return func(c *context) bool {
for _, fn := range fns {
if fn(c) {
return true
}
}
return false
}
}
// not creates negation of the passed predicate
func not(p hpredicate) hpredicate {
return func(c *context) bool {
return !p(c)
}
}
// eq returns predicate that tests for equality of the value of the mapper and the constant
func eq(m interface{}, value interface{}) (hpredicate, error) {
switch mapper := m.(type) {
case toString:
return stringEQ(mapper, value)
case toInt:
return intEQ(mapper, value)
}
return nil, fmt.Errorf("unsupported argument: %T", m)
}
// neq returns predicate that tests for inequality of the value of the mapper and the constant
func neq(m interface{}, value interface{}) (hpredicate, error) {
p, err := eq(m, value)
if err != nil {
return nil, err
}
return not(p), nil
}
// lt returns predicate that tests that value of the mapper function is less than the constant
func lt(m interface{}, value interface{}) (hpredicate, error) {
switch mapper := m.(type) {
case toInt:
return intLT(mapper, value)
}
return nil, fmt.Errorf("unsupported argument: %T", m)
}
// le returns predicate that tests that value of the mapper function is less or equal than the constant
func le(m interface{}, value interface{}) (hpredicate, error) {
l, err := lt(m, value)
if err != nil {
return nil, err
}
e, err := eq(m, value)
if err != nil {
return nil, err
}
return func(c *context) bool {
return l(c) || e(c)
}, nil
}
// gt returns predicate that tests that value of the mapper function is greater than the constant
func gt(m interface{}, value interface{}) (hpredicate, error) {
switch mapper := m.(type) {
case toInt:
return intGT(mapper, value)
}
return nil, fmt.Errorf("unsupported argument: %T", m)
}
// ge returns predicate that tests that value of the mapper function is less or equal than the constant
func ge(m interface{}, value interface{}) (hpredicate, error) {
g, err := gt(m, value)
if err != nil {
return nil, err
}
e, err := eq(m, value)
if err != nil {
return nil, err
}
return func(c *context) bool {
return g(c) || e(c)
}, nil
}
func stringEQ(m toString, val interface{}) (hpredicate, error) {
value, ok := val.(string)
if !ok {
return nil, fmt.Errorf("expected string, got %T", val)
}
return func(c *context) bool {
return m(c) == value
}, nil
}
func intEQ(m toInt, val interface{}) (hpredicate, error) {
value, ok := val.(int)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *context) bool {
return m(c) == value
}, nil
}
func intLT(m toInt, val interface{}) (hpredicate, error) {
value, ok := val.(int)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *context) bool {
return m(c) < value
}, nil
}
func intGT(m toInt, val interface{}) (hpredicate, error) {
value, ok := val.(int)
if !ok {
return nil, fmt.Errorf("expected int, got %T", val)
}
return func(c *context) bool {
return m(c) > value
}, nil
}