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Add instrumentation to signature fetcher #17

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38 changes: 38 additions & 0 deletions modules/openads/signatures/fetcher.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,11 +4,14 @@ import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"net"
"net/http"
"time"

"github.com/golang/glog"
)

type Signature struct {
Expand Down Expand Up @@ -70,12 +73,21 @@ func (f *httpFetcher) Fetch(ctx context.Context, body []byte) ([]SignatureWrappe

req.Header.Set("Content-Type", "application/json")

start := time.Now()
resp, err := f.client.Do(req)
elapsed := time.Since(start)

if err != nil {
logFetchError(ctx, err, elapsed)
return nil, fmt.Errorf("failed to execute request: %w", err)
}
defer resp.Body.Close()

// Log slow but successful requests (near-misses)
if elapsed > 40*time.Millisecond {
glog.Warningf("SIS fetch slow: elapsed=%v, status=%d", elapsed, resp.StatusCode)
}

if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
}
Expand All @@ -96,3 +108,29 @@ func (f *httpFetcher) Fetch(ctx context.Context, body []byte) ([]SignatureWrappe

return signatures, nil
}

func logFetchError(ctx context.Context, err error, elapsed time.Duration) {
ctxErr := ctx.Err()
ctxStatus := "active"
if ctxErr != nil {
if errors.Is(ctxErr, context.DeadlineExceeded) {
ctxStatus = "deadline_exceeded"
} else if errors.Is(ctxErr, context.Canceled) {
ctxStatus = "canceled"
}
}

errType := fmt.Sprintf("%T", err)

// Unwrap to get the root cause
var netErr *net.OpError
var rootCause string
if errors.As(err, &netErr) {
rootCause = fmt.Sprintf("op=%s, net=%s, addr=%v, err=%v", netErr.Op, netErr.Net, netErr.Addr, netErr.Err)
} else {
rootCause = err.Error()
}

glog.Warningf("SIS fetch failed: type=%s, elapsed=%v, ctx=%s, cause=%s",
errType, elapsed, ctxStatus, rootCause)
}
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