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source_url.go
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/
source_url.go
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// Copyright 2019 xgfone
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package gconf
import (
"fmt"
"io/ioutil"
"net/http"
neturl "net/url"
"strings"
"time"
)
var errNoContentType = fmt.Errorf("http response has no the header Content-Type")
// NewURLSource returns a url source to read the configuration data from the url
// by the stdlib http.Get(url).
//
// The header "Content-Type" indicates the data format, that's, it will split
// the value by "/" and use the last part, such as "application/json" represents
// the format "json". But you can set format to override it.
//
// It supports the watcher, which checks whether the data is changed once
// with interval time. If interval is 0, it is time.Minute by default.
func NewURLSource(url string, interval time.Duration, format ...string) Source {
if url == "" {
panic("the url must not be nil")
} else if _, err := neturl.Parse(url); err != nil {
panic(err)
}
var _format string
if len(format) > 0 && format[0] != "" {
_format = format[0]
}
if interval <= 0 {
interval = time.Minute
}
return urlSource{id: fmt.Sprintf("url:%s", url), url: url, format: _format, period: interval}
}
type urlSource struct {
id string
url string
format string
period time.Duration
}
func (u urlSource) Read() (DataSet, error) {
resp, err := http.Get(u.url)
if err != nil {
return DataSet{Source: u.id, Format: u.format}, err
}
defer resp.Body.Close()
format := u.format
if format == "" {
// Get the Content-Type as the format.
ct := strings.TrimSpace(resp.Header.Get("Content-Type"))
if index := strings.IndexByte(ct, ';'); index > 0 {
ct = strings.TrimSpace(ct[:index])
}
if index := strings.LastIndexByte(ct, '/'); index > 0 {
ct = ct[index+1:]
}
if ct == "" {
return DataSet{Source: u.id}, errNoContentType
}
format = ct
}
// Read the body of the response.
data, err := ioutil.ReadAll(resp.Body)
if err != nil {
return DataSet{Source: u.id, Format: format}, err
}
ds := DataSet{
Data: data,
Format: format,
Source: u.id,
Timestamp: time.Now(),
}
ds.Checksum = "md5:" + ds.Md5()
return ds, nil
}
func (u urlSource) Watch(load func(DataSet, error) bool, exit <-chan struct{}) {
go u.watchurl(load, exit)
}
func (u urlSource) watchurl(load func(DataSet, error) bool, exit <-chan struct{}) {
last := DataSet{}
first := true
for {
if first {
first = false
} else {
time.Sleep(u.period)
}
select {
case <-exit:
return
default:
}
if ds, err := u.Read(); err != nil {
load(ds, err)
} else if len(ds.Data) > 0 && ds.Checksum != last.Checksum {
if load(ds, nil) {
last = ds
}
}
}
}