Reporter package (#116)

x/report/report.go

@@ -0,0 +1,207 @@
+// Package report provides functionality for collecting and sending reports.
+//
+// It defines the behavior of a report collector and provides implementations of the [Collector] interface.
+// It also defines a report type and a [HasSuccess] interface that is implemented by the report type.
+// The report type is used to represent a connectivity test report.
+// The [HasSuccess] interface is used to determine the success status of a report. This will be used to control [SamplingCollector] behavior.
+// The report package also defines a [BadRequestError] type that is used to represent an error that occurs when a sending the report to remote collector fails.
+package report
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"math/rand"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+// BadRequestError represents an error that occurs when a request fails.
+type BadRequestError struct {
+	Err error
+}
+
+// Error returns the error message associated with the [BadRequestError].
+func (e BadRequestError) Error() string {
+	return e.Err.Error()
+}
+
+// Unwrap returns the underlying error wrapped by the [BadRequestError].
+func (e BadRequestError) Unwrap() error {
+	return e.Err
+}
+
+// Report is an alias for any type of report.
+type Report any
+
+// HasSuccess is an interface that represents an object that has a success status.
+type HasSuccess interface {
+	IsSuccess() bool
+}
+
+// Collector is an interface that defines the behavior of a report collector.
+// Implementations of this interface should be able to collect a report in a given context.
+type Collector interface {
+	Collect(context.Context, Report) error
+}
+
+// RemoteCollector represents a collector that communicates with a remote endpoint.
+type RemoteCollector struct {
+	httpClient        *http.Client
+	collectorEndpoint *url.URL
+}
+
+// Collect sends the given report to the remote collector.
+// It marshals the report into JSON format and sends it using the [sendReport] method.
+// If there is an error encoding the JSON or sending the report, it returns the error.
+// Otherwise, it returns nil.
+func (c *RemoteCollector) Collect(ctx context.Context, report Report) error {
+	jsonData, err := json.Marshal(report)
+	if err != nil {
+		return fmt.Errorf("failed to marshal JSON: %w", err)
+	}
+	err = c.sendReport(ctx, jsonData)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// SamplingCollector represents a collector that randomly samples and collects a report.
+type SamplingCollector struct {
+	collector       Collector
+	successFraction float64
+	failureFraction float64
+}
+
+// Collect collects the given report based on the sampling rate defined in the [SamplingCollector].
+// It checks if the report implements the [HasSuccess] interface and determines the sampling rate based on the success status.
+// If the randomly generated number is less than the sampling rate, the report is collected using the underlying collector.
+// Otherwise, the report is not sent.
+// It returns an error if there is an issue collecting the report.
+// Sampling rate of 1.0 means report is always sent, and 0.0 means report is never sent.
+func (c *SamplingCollector) Collect(ctx context.Context, report Report) error {
+	var samplingRate float64
+	hs, ok := report.(HasSuccess)
+	if !ok {
+		return nil
+	}
+	if hs.IsSuccess() {
+		samplingRate = c.successFraction
+	} else {
+		samplingRate = c.failureFraction
+	}
+	// Generate a random float64 number between 0 and 1
+	random := rand.Float64()
+	if random < samplingRate {
+		err := c.collector.Collect(ctx, report)
+		if err != nil {
+			return err
+		}
+		return nil
+	} else {
+		return nil
+	}
+}
+
+// RetryCollector represents a collector that supports retrying failed operations.
+type RetryCollector struct {
+	collector    Collector
+	maxRetry     int
+	initialDelay time.Duration
+}
+
+// Collect collects the report by making multiple attempts with retries.
+// It uses the provided context and report to call the underlying collector's [Collect] method.
+// If a [BadRequestError] is encountered during the collection, it breaks the retry loop.
+// It sleeps for a specified duration between retries.
+// Returns an error if the maximum number of retries is exceeded.
+func (c *RetryCollector) Collect(ctx context.Context, report Report) error {
+	var e *BadRequestError
+	for i := 0; i < c.maxRetry; i++ {
+		err := c.collector.Collect(ctx, report)
+		if err != nil {
+			if errors.As(err, &e) {
+				break
+			} else {
+				time.Sleep(time.Duration(math.Pow(2, float64(i))) * c.initialDelay)
+			}
+		} else {
+			return nil
+		}
+	}
+	return errors.New("max retry exceeded")
+}
+
+// FallbackCollector is a type that represents a collector that falls back to multiple collectors.
+type FallbackCollector struct {
+	collectors []Collector
+}
+
+// Collect implements [Collector] interface on [FallbackCollector] type that collects a report using the provided context and report data.
+// It iterates over a list of collectors and attempts to collect the report using each collector.
+// If any of the collectors succeeds in collecting the report, operation aborts, and it returns nil.
+// If all collectors fail to collect the report, it returns an error indicating the failure.
+func (c *FallbackCollector) Collect(ctx context.Context, report Report) error {
+	for i := range c.collectors {
+		err := c.collectors[i].Collect(ctx, report)
+		if err == nil {
+			return nil
+		}
+	}
+	return errors.New("all collectors failed")
+}
+
+// sendReport sends a report to the remote collector.
+// It takes a context.Context object for cancellation and deadline propagation,
+// and a []byte containing the JSON data to be sent.
+// It returns an error if there was a problem sending the report or reading the response.
+func (c *RemoteCollector) sendReport(ctx context.Context, jsonData []byte) error {
+	// TODO: return status code of HTTP response
+	req, err := http.NewRequest("POST", c.collectorEndpoint.String(), bytes.NewReader(jsonData))
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Content-Type", "application/json; charset=utf-8")
+	resp, err := c.httpClient.Do(req.WithContext(ctx))
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	_, err = io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	if 400 <= resp.StatusCode && resp.StatusCode < 500 {
+		return &BadRequestError{
+			Err: fmt.Errorf("http request failed with status code %d", resp.StatusCode),
+		}
+	}
+	return nil
+}
+
+// WriteCollector represents a collector that writes the report to an io.Writer.
+type WriteCollector struct {
+	writer io.Writer
+}
+
+// Collect writes the report to the underlying io.Writer.
+// It returns an error if there was a problem writing the report.
+func (c *WriteCollector) Collect(ctx context.Context, report Report) error {
+	jsonData, err := json.Marshal(report)
+	if err != nil {
+		return fmt.Errorf("failed to marshal JSON: %w", err)
+	}
+	_, err = c.writer.Write(jsonData)
+	if err != nil {
+		return err
+	}
+	fmt.Println("Report written")
+	return nil
+}