Merge pull request #114 from c4milo/fetch-url-refactor
refactor(datastore/fetch): Makes more failure proof fetching user-data files.
This commit is contained in:
Jonathan Boulle
commit
04fcd3935f
@ -1,53 +1,104 @@
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package datasource
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import (
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"errors"
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"fmt"
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"io/ioutil"
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"log"
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"math"
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"net"
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"net/http"
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neturl "net/url"
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"strings"
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"time"
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)
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const maxTimeout = time.Second * 5
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const (
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HTTP_2xx = 2
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HTTP_4xx = 4
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maxTimeout = time.Second * 5
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maxRetries = 15
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)
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type Datasource interface {
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Fetch() ([]byte, error)
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Type() string
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}
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func fetchURL(url string) ([]byte, error) {
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resp, err := getWithExponentialBackoff(url)
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if err != nil {
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return []byte{}, err
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}
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defer resp.Body.Close()
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// HTTP client timeout
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// This one is low since exponential backoff will kick off too.
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var timeout = time.Duration(2) * time.Second
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respBytes, err := ioutil.ReadAll(resp.Body)
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func dialTimeout(network, addr string) (net.Conn, error) {
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deadline := time.Now().Add(timeout)
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c, err := net.DialTimeout(network, addr, timeout)
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if err != nil {
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return nil, err
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}
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c.SetDeadline(deadline)
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return c, nil
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}
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// Fetches user-data url with support for exponential backoff and maximum retries
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func fetchURL(rawurl string) ([]byte, error) {
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if rawurl == "" {
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return nil, errors.New("user-data URL is empty. Skipping.")
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}
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url, err := neturl.Parse(rawurl)
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if err != nil {
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return nil, err
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}
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return respBytes, nil
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}
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// Unfortunately, url.Parse is too generic to throw errors if a URL does not
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// have a valid HTTP scheme. So, we have to do this extra validation
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if !strings.HasPrefix(url.Scheme, "http") {
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return nil, fmt.Errorf("user-data URL %s does not have a valid HTTP scheme. Skipping.", rawurl)
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}
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// getWithExponentialBackoff issues a GET to the specified URL. If the
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// response is a non-2xx or produces an error, retry the GET forever using
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// an exponential backoff.
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func getWithExponentialBackoff(url string) (*http.Response, error) {
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var err error
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var resp *http.Response
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for i := 0; ; i++ {
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resp, err = http.Get(url)
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if err == nil && resp.StatusCode/100 == 2 {
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return resp, nil
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userdataURL := url.String()
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// We need to create our own client in order to add timeout support.
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// TODO(c4milo) Replace it once Go 1.3 is officially used by CoreOS
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// More info: https://code.google.com/p/go/source/detail?r=ada6f2d5f99f
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transport := &http.Transport{
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Dial: dialTimeout,
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}
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client := &http.Client{
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Transport: transport,
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}
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for retry := 1; retry <= maxRetries; retry++ {
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log.Printf("Fetching user-data from %s. Attempt #%d", userdataURL, retry)
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resp, err := client.Get(userdataURL)
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if err == nil {
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defer resp.Body.Close()
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status := resp.StatusCode / 100
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if status == HTTP_2xx {
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return ioutil.ReadAll(resp.Body)
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}
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if status == HTTP_4xx {
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return nil, fmt.Errorf("user-data not found. HTTP status code: %d", resp.StatusCode)
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}
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log.Printf("user-data not found. HTTP status code: %d", resp.StatusCode)
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} else {
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log.Printf("unable to fetch user-data: %s", err.Error())
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}
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duration := time.Millisecond * time.Duration((math.Pow(float64(2), float64(i)) * 100))
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duration := time.Millisecond * time.Duration((math.Pow(float64(2), float64(retry)) * 100))
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if duration > maxTimeout {
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duration = maxTimeout
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}
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log.Printf("unable to fetch user-data from %s, try again in %s", url, duration)
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time.Sleep(duration)
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}
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return resp, err
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return nil, fmt.Errorf("unable to fetch user-data. Maximum retries reached: %d", maxRetries)
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}
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@ -17,7 +17,9 @@ var expBackoffTests = []struct {
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{2, "number of attempts: 2"},
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}
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func TestGetWithExponentialBackoff(t *testing.T) {
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// Test exponential backoff and that it continues retrying if a 5xx response is
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// received
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func TestFetchURLExpBackOff(t *testing.T) {
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for i, tt := range expBackoffTests {
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mux := http.NewServeMux()
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count := 0
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@ -31,15 +33,87 @@ func TestGetWithExponentialBackoff(t *testing.T) {
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})
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ts := httptest.NewServer(mux)
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defer ts.Close()
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data, err := fetchURL(ts.URL)
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if err != nil {
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t.Errorf("Test case %d produced error: %v", i, err)
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}
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if count != tt.count {
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t.Errorf("Test case %d failed: %d != %d", i, count, tt.count)
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}
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if string(data) != tt.body {
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t.Errorf("Test case %d failed: %s != %s", i, tt.body, data)
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}
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}
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}
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// Test that it stops retrying if a 4xx response comes back
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func TestFetchURL4xx(t *testing.T) {
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retries := 0
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ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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retries++
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http.Error(w, "", 404)
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}))
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defer ts.Close()
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_, err := fetchURL(ts.URL)
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if err == nil {
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t.Errorf("Incorrect result\ngot: %s\nwant: %s", err.Error(), "user-data not found. HTTP status code: 404")
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}
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if retries > 1 {
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t.Errorf("Number of retries:\n%d\nExpected number of retries:\n%s", retries, 1)
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}
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}
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// Test that it fetches and returns user-data just fine
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func TestFetchURL2xx(t *testing.T) {
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var cloudcfg = `
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#cloud-config
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coreos:
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oem:
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id: test
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name: CoreOS.box for Test
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version-id: %VERSION_ID%+%BUILD_ID%
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home-url: https://github.com/coreos/coreos-cloudinit
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bug-report-url: https://github.com/coreos/coreos-cloudinit
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update:
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reboot-strategy: best-effort
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`
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ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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fmt.Fprint(w, cloudcfg)
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}))
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defer ts.Close()
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data, err := fetchURL(ts.URL)
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if err != nil {
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t.Errorf("Incorrect result\ngot: %v\nwant: %v", err, nil)
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}
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if string(data) != cloudcfg {
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t.Errorf("Incorrect result\ngot: %s\nwant: %s", string(data), cloudcfg)
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}
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}
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// Test attempt to fetching using malformed URL
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func TestFetchURLMalformed(t *testing.T) {
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var tests = []struct {
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url string
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want string
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}{
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{"boo", "user-data URL boo does not have a valid HTTP scheme. Skipping."},
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{"mailto://boo", "user-data URL mailto://boo does not have a valid HTTP scheme. Skipping."},
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{"ftp://boo", "user-data URL ftp://boo does not have a valid HTTP scheme. Skipping."},
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{"", "user-data URL is empty. Skipping."},
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}
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for _, test := range tests {
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_, err := fetchURL(test.url)
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if err == nil || err.Error() != test.want {
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t.Errorf("Incorrect result\ngot: %v\nwant: %v", err, test.want)
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}
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}
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}
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