86 lines
1.8 KiB
Go
86 lines
1.8 KiB
Go
package application
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import (
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"net/http"
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"time"
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)
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// Fetches data from remote endpoint, parses it and updates in storage.
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func (a *Application) fetch() {
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// Do not do anything if fetching is running.
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// ToDo: maybe another approach?
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a.fetchIsRunningMutex.RLock()
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// This is an optimization to avoid excessive waiting when using Lock().
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// Most of time application will wait between fetches.
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// nolint:ifshort
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isFetching := a.fetchIsRunning
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a.fetchIsRunningMutex.RUnlock()
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if isFetching {
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return
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}
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a.fetchIsRunningMutex.Lock()
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a.fetchIsRunning = true
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a.fetchIsRunningMutex.Unlock()
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a.logger.Infoln("Fetching data for", a.name)
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req, err := http.NewRequestWithContext(a.ctx, "GET", a.config.Endpoint, nil)
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if err != nil {
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a.logger.Infoln("Failed to create request for", a.name, "metrics:", err.Error())
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return
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}
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for header, value := range a.config.Headers {
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req.Header.Add(header, value)
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}
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resp, err := a.httpClient.Do(req)
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if err != nil {
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a.logger.Infoln("Failed to execute request for", a.name, "metrics:", err.Error())
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return
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}
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defer resp.Body.Close()
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data, err := a.parse(resp.Body)
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if err != nil {
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a.logger.Infoln("Failed to parse response body for", a.name, "metrics:", err.Error())
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return
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}
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a.storage.Put(data)
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a.fetchIsRunningMutex.Lock()
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a.fetchIsRunning = false
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a.fetchIsRunningMutex.Unlock()
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}
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// Configures and starts Prometheus data fetching goroutine.
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func (a *Application) startFetcher() {
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fetchTicker := time.NewTicker(a.config.TimeBetweenRequests)
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// nolint:exhaustivestruct
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a.httpClient = &http.Client{
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Timeout: time.Second * 5,
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}
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defer a.logger.Debugln("Fetcher for", a.name, "completed")
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// First fetch should be executed ASAP.
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a.fetch()
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for {
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select {
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case <-a.ctx.Done():
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return
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case <-fetchTicker.C:
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a.fetch()
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}
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}
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}
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