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worker.go
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worker.go
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package service
import (
"bytes"
"context"
"encoding/base64"
"errors"
"fmt"
"io"
"net/http"
"strings"
"sync"
"time"
"github.com/Nitro/urlsign"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/s3"
"github.com/aws/aws-sdk-go/service/s3/s3iface"
"github.com/google/uuid"
"github.com/nitro/lazypdf/v2"
"github.com/rs/zerolog"
awstrace "gopkg.in/DataDog/dd-trace-go.v1/contrib/aws/aws-sdk-go/aws"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
ddTracer "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
)
// Worker used to fetch and process PDF files.
type Worker struct {
HTTPClient *http.Client
URLSigningSecret string
Logger zerolog.Logger
TraceExtractor func(context.Context, zerolog.Logger) (zerolog.Logger, error)
StorageBucketRegion map[string]string
getS3Client func(string) (s3iface.S3API, error)
s3Clients map[string]s3iface.S3API
mutex sync.Mutex
}
// Init worker internal state.
func (w *Worker) Init() error {
if w.HTTPClient == nil {
return errors.New("internal/service/Worker.HTTPClient can't be nil")
}
if w.URLSigningSecret == "" {
return errors.New("internal/service/Worker.URLSigningSecret can't be empty")
}
if w.TraceExtractor == nil {
return errors.New("internal/service/Worker.TraceExtractor can't be nil")
}
if len(w.StorageBucketRegion) == 0 {
return errors.New("internal/service/Worker.StorageBucketRegion can't be empty")
}
if w.getS3Client == nil {
w.getS3Client = w.getBucketS3Client
}
w.s3Clients = make(map[string]s3iface.S3API)
return nil
}
func (w *Worker) Process(
ctx context.Context, url, path string, page int, width int, scale float32, output io.Writer,
) (err error) {
span, ctx := w.startSpan(ctx, "Worker.Process")
defer func() { span.Finish(ddTracer.WithError(err)) }()
// This change is required because of historical reasons. The first page for the frontend is 1 and not zero.
page--
if page < 0 {
return newClientError(errors.New("invalid page"))
}
if width < 0 {
return newClientError(errors.New("invalid width"))
} else if width > 4096 {
return newClientError(errors.New("invalid width, can't be bigger than 4096"))
}
if scale < 0 {
return newClientError(errors.New("invalid scale"))
} else if scale > 3 {
return newClientError(errors.New("invalid scale, can't be bigger than 3"))
}
if !urlsign.IsValidSignature(w.URLSigningSecret, 8*time.Hour, time.Now(), url) {
return newClientError(errors.New("invalid token"))
}
payload, err := w.fetchFile(ctx, path)
if err != nil {
return fmt.Errorf("fail to fetch the file: %w", err)
}
storage := bytes.NewBuffer([]byte{})
err = lazypdf.SaveToPNG(ctx, uint16(page), uint16(width), scale, bytes.NewBuffer(payload), storage)
if err != nil {
return fmt.Errorf("fail to extract the PNG from the PDF: %w", err)
}
result := io.NopCloser(storage)
defer result.Close()
if _, err := io.Copy(output, result); err != nil {
return fmt.Errorf("fail write the result to the output: %w", err)
}
return nil
}
// Metadata is used to fetch the document metadata.
func (w *Worker) Metadata(ctx context.Context, url, path string) (_ string, _ int, err error) {
span, ctx := w.startSpan(ctx, "Worker.Metadata")
defer func() { span.Finish(ddTracer.WithError(err)) }()
if !urlsign.IsValidSignature(w.URLSigningSecret, 8*time.Hour, time.Now(), url) {
return "", 0, newClientError(errors.New("invalid token"))
}
payload, err := w.fetchFile(ctx, path)
if err != nil {
return "", 0, fmt.Errorf("fail to fetch the file: %w", err)
}
pageCount, err := lazypdf.PageCount(ctx, bytes.NewReader(payload))
if err != nil {
return "", 0, fmt.Errorf("fail to count the file pages: %w", err)
}
return w.generateFilename(), pageCount, nil
}
func (w *Worker) fetchFile(ctx context.Context, path string) (_ []byte, err error) {
span, ctx := ddTracer.StartSpanFromContext(ctx, "Worker.fetchFile")
defer func() { span.Finish(ddTracer.WithError(err)) }()
if strings.HasPrefix(path, "dropbox/") {
return w.fetchFileFromDropbox(ctx, path)
}
fragments := strings.Split(path, "/")
if len(fragments) < 2 {
return nil, newClientError(errors.New("invalid path"))
}
bucket := fragments[0]
s3Client, err := w.getS3Client(bucket)
if err != nil {
return nil, fmt.Errorf("fail to get the s3 bucket client: %w", err)
}
output, err := s3Client.GetObjectWithContext(ctx, &s3.GetObjectInput{
Bucket: &bucket,
Key: aws.String(strings.Join(fragments[1:], "/")),
})
if err != nil {
if awsErr, ok := err.(awserr.Error); ok && (awsErr.Code() == s3.ErrCodeNoSuchKey) {
return nil, newNotFoundError(err)
}
return nil, fmt.Errorf("fail to get object: %w", err)
}
defer output.Body.Close()
payload, err := io.ReadAll(output.Body)
if err != nil {
return nil, fmt.Errorf("fail to read the reader: %w", err)
}
span.SetTag("fileSize", len(payload))
return payload, nil
}
func (w *Worker) fetchFileFromDropbox(ctx context.Context, path string) (_ []byte, err error) {
span, ctx := ddTracer.StartSpanFromContext(ctx, "Worker.fetchFileFromDropbox")
defer func() { span.Finish(ddTracer.WithError(err)) }()
fileURL, err := base64.RawURLEncoding.DecodeString(strings.TrimPrefix(path, "dropbox/"))
if err != nil {
return nil, newClientError(fmt.Errorf("fail to decode base64 path: %w", err))
}
req, err := http.NewRequestWithContext(ctx, http.MethodGet, string(fileURL), nil)
if err != nil {
return nil, fmt.Errorf("fail to create the HTTP request: %w", err)
}
resp, err := w.HTTPClient.Do(req)
if err != nil {
return nil, fmt.Errorf("fail to download file: %w", err)
}
defer resp.Body.Close()
if resp.StatusCode == http.StatusNotFound {
return nil, newNotFoundError(errors.New("dropbox returned 404"))
} else if resp.StatusCode < 200 || resp.StatusCode >= 300 {
return nil, fmt.Errorf("invalid status code '%d'", resp.StatusCode)
}
payload, err := io.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("fail to read the body response: %w", err)
}
return payload, nil
}
func (*Worker) generateFilename() string {
id := uuid.New()
return id.String() + "/document.pdf"
}
func (*Worker) startSpan(ctx context.Context, operation string) (ddtrace.Span, context.Context) {
return ddTracer.StartSpanFromContext(ctx, "internal/service/"+operation)
}
func (w *Worker) getBucketS3Client(bucket string) (s3iface.S3API, error) {
region, ok := w.StorageBucketRegion[bucket]
if !ok {
return nil, fmt.Errorf("can't find the bucket '%s' region", bucket)
}
w.mutex.Lock()
defer w.mutex.Unlock()
client, ok := w.s3Clients[region]
if ok {
return client, nil
}
sess, err := session.NewSession(&aws.Config{HTTPClient: w.HTTPClient, Region: ®ion})
if err != nil {
return nil, fmt.Errorf("fail to start a session on region '%s': %w", region, err)
}
sess = awstrace.WrapSession(sess)
client = s3.New(sess, &aws.Config{HTTPClient: w.HTTPClient})
w.s3Clients[region] = client
return client, nil
}