Improve HTTP caching layer
- make thread-safe - only cache GET, HEAD, and GraphQL requests - only cache non-5xx, non-403 responses - include `Accept` and `Authorization` headers in cache key
This commit is contained in:
Mislav Marohnić
parent
f7a82a216b
commit
7663acdc29
2 changed files with 119 additions and 36 deletions
105
api/cache.go
105
api/cache.go
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@ -11,6 +11,8 @@ import (
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"net/http"
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"os"
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"path/filepath"
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"strings"
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"sync"
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"time"
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)
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@ -21,39 +23,79 @@ func makeCachedClient(httpClient *http.Client, cacheTTL time.Duration) *http.Cli
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}
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}
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func isCacheableRequest(req *http.Request) bool {
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if strings.EqualFold(req.Method, "GET") || strings.EqualFold(req.Method, "HEAD") {
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return true
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}
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if strings.EqualFold(req.Method, "POST") && (req.URL.Path == "/graphql" || req.URL.Path == "/api/graphql") {
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return true
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}
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return false
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}
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func isCacheableResponse(res *http.Response) bool {
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return res.StatusCode < 500 && res.StatusCode != 403
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}
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// CacheReponse produces a RoundTripper that caches HTTP responses to disk for a specified amount of time
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func CacheReponse(ttl time.Duration, dir string) ClientOption {
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fs := fileStorage{
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dir: dir,
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ttl: ttl,
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mu: &sync.RWMutex{},
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}
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return func(tr http.RoundTripper) http.RoundTripper {
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return &funcTripper{roundTrip: func(req *http.Request) (*http.Response, error) {
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if !isCacheableRequest(req) {
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return tr.RoundTrip(req)
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}
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key, keyErr := cacheKey(req)
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cacheFile := filepath.Join(dir, key)
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if keyErr == nil {
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// TODO: make thread-safe
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if res, err := readCache(ttl, cacheFile, req); err == nil {
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if res, err := fs.read(key); err == nil {
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res.Request = req
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return res, nil
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}
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}
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res, err := tr.RoundTrip(req)
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if err == nil && keyErr == nil {
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// TODO: make thread-safe
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_ = writeCache(cacheFile, res)
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if err == nil && keyErr == nil && isCacheableResponse(res) {
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_ = fs.store(key, res)
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}
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return res, err
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}}
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}
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}
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func copyStream(r io.ReadCloser) (io.ReadCloser, io.ReadCloser) {
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b := &bytes.Buffer{}
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nr := io.TeeReader(r, b)
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return ioutil.NopCloser(b), &readCloser{
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Reader: nr,
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Closer: r,
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}
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}
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type readCloser struct {
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io.Reader
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io.Closer
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}
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func cacheKey(req *http.Request) (string, error) {
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h := sha256.New()
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fmt.Fprintf(h, "%s:", req.Method)
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fmt.Fprintf(h, "%s:", req.URL.String())
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fmt.Fprintf(h, "%s:", req.Header.Get("Accept"))
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fmt.Fprintf(h, "%s:", req.Header.Get("Authorization"))
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if req.Body != nil {
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bodyCopy := &bytes.Buffer{}
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defer req.Body.Close()
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_, err := io.Copy(h, io.TeeReader(req.Body, bodyCopy))
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req.Body = ioutil.NopCloser(bodyCopy)
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if err != nil {
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var bodyCopy io.ReadCloser
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req.Body, bodyCopy = copyStream(req.Body)
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defer bodyCopy.Close()
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if _, err := io.Copy(h, bodyCopy); err != nil {
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return "", err
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}
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}
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@ -62,20 +104,38 @@ func cacheKey(req *http.Request) (string, error) {
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return fmt.Sprintf("%x", digest), nil
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}
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func readCache(ttl time.Duration, cacheFile string, req *http.Request) (*http.Response, error) {
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type fileStorage struct {
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dir string
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ttl time.Duration
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mu *sync.RWMutex
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}
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func (fs *fileStorage) filePath(key string) string {
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if len(key) >= 6 {
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return filepath.Join(fs.dir, key[0:2], key[2:4], key[4:])
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}
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return filepath.Join(fs.dir, key)
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}
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func (fs *fileStorage) read(key string) (*http.Response, error) {
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cacheFile := fs.filePath(key)
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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f, err := os.Open(cacheFile)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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fs, err := f.Stat()
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stat, err := f.Stat()
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if err != nil {
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return nil, err
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}
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age := time.Since(fs.ModTime())
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if age > ttl {
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age := time.Since(stat.ModTime())
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if age > fs.ttl {
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return nil, errors.New("cache expired")
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}
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@ -85,11 +145,16 @@ func readCache(ttl time.Duration, cacheFile string, req *http.Request) (*http.Re
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return nil, err
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}
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res, err := http.ReadResponse(bufio.NewReader(body), req)
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res, err := http.ReadResponse(bufio.NewReader(body), nil)
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return res, err
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}
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func writeCache(cacheFile string, res *http.Response) error {
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func (fs *fileStorage) store(key string, res *http.Response) error {
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cacheFile := fs.filePath(key)
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fs.mu.Lock()
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defer fs.mu.Unlock()
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err := os.MkdirAll(filepath.Dir(cacheFile), 0755)
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if err != nil {
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return err
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@ -101,10 +166,10 @@ func writeCache(cacheFile string, res *http.Response) error {
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}
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defer f.Close()
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bodyCopy := &bytes.Buffer{}
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var origBody io.ReadCloser
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origBody, res.Body = copyStream(res.Body)
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defer res.Body.Close()
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res.Body = ioutil.NopCloser(io.TeeReader(res.Body, bodyCopy))
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err = res.Write(f)
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res.Body = ioutil.NopCloser(bodyCopy)
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res.Body = origBody
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return err
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}
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@ -20,8 +20,12 @@ func Test_CacheReponse(t *testing.T) {
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roundTrip: func(req *http.Request) (*http.Response, error) {
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counter += 1
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body := fmt.Sprintf("%d: %s %s", counter, req.Method, req.URL.String())
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status := 200
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if req.URL.Path == "/error" {
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status = 500
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}
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return &http.Response{
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StatusCode: 200,
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StatusCode: status,
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Body: ioutil.NopCloser(bytes.NewBufferString(body)),
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}, nil
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},
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@ -47,25 +51,39 @@ func Test_CacheReponse(t *testing.T) {
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return string(resBody), err
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}
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res1, err := do("GET", "http://example.com/path", nil)
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require.NoError(t, err)
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assert.Equal(t, "1: GET http://example.com/path", res1)
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res2, err := do("GET", "http://example.com/path", nil)
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require.NoError(t, err)
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assert.Equal(t, "1: GET http://example.com/path", res2)
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var res string
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var err error
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res3, err := do("GET", "http://example.com/path2", nil)
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res, err = do("GET", "http://example.com/path", nil)
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require.NoError(t, err)
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assert.Equal(t, "2: GET http://example.com/path2", res3)
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assert.Equal(t, "1: GET http://example.com/path", res)
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res, err = do("GET", "http://example.com/path", nil)
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require.NoError(t, err)
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assert.Equal(t, "1: GET http://example.com/path", res)
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res4, err := do("POST", "http://example.com/path", bytes.NewBufferString(`hello`))
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res, err = do("GET", "http://example.com/path2", nil)
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require.NoError(t, err)
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assert.Equal(t, "3: POST http://example.com/path", res4)
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res5, err := do("POST", "http://example.com/path", bytes.NewBufferString(`hello`))
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require.NoError(t, err)
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assert.Equal(t, "3: POST http://example.com/path", res5)
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assert.Equal(t, "2: GET http://example.com/path2", res)
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res6, err := do("POST", "http://example.com/path", bytes.NewBufferString(`hello2`))
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res, err = do("POST", "http://example.com/path2", nil)
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require.NoError(t, err)
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assert.Equal(t, "4: POST http://example.com/path", res6)
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assert.Equal(t, "3: POST http://example.com/path2", res)
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res, err = do("POST", "http://example.com/graphql", bytes.NewBufferString(`hello`))
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require.NoError(t, err)
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assert.Equal(t, "4: POST http://example.com/graphql", res)
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res, err = do("POST", "http://example.com/graphql", bytes.NewBufferString(`hello`))
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require.NoError(t, err)
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assert.Equal(t, "4: POST http://example.com/graphql", res)
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res, err = do("POST", "http://example.com/graphql", bytes.NewBufferString(`hello2`))
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require.NoError(t, err)
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assert.Equal(t, "5: POST http://example.com/graphql", res)
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res, err = do("GET", "http://example.com/error", nil)
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require.NoError(t, err)
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assert.Equal(t, "6: GET http://example.com/error", res)
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res, err = do("GET", "http://example.com/error", nil)
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require.NoError(t, err)
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assert.Equal(t, "7: GET http://example.com/error", res)
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}
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