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feat(tracing): add snapshot spans and propagator setup #309

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42 changes: 40 additions & 2 deletions internal/snapshot/snapshot.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,11 +10,18 @@ import (
"time"

"github.com/alecthomas/errors"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/codes"
"go.opentelemetry.io/otel/trace"

"github.com/block/cachew/client"
"github.com/block/cachew/internal/cache"
)

//nolint:gochecknoglobals // OTel tracer instances are package-scoped by convention
var tracer = otel.Tracer("github.com/block/cachew/internal/snapshot")

// Create archives a directory using tar with zstd compression, then uploads to the cache.
//
// The archive preserves all file permissions, ownership, and symlinks.
Expand All @@ -34,7 +41,24 @@ func Create(ctx context.Context, remote cache.Cache, key cache.Key, directory st
// Each entry in includePaths is archived relative to baseDir and must exist.
// Exclude patterns use tar's --exclude syntax.
// threads controls zstd parallelism; 0 uses all available CPU cores.
func CreatePaths(ctx context.Context, remote cache.Cache, key cache.Key, baseDir, archiveName string, includePaths []string, ttl time.Duration, excludePatterns []string, threads int, extraHeaders ...http.Header) error {
func CreatePaths(ctx context.Context, remote cache.Cache, key cache.Key, baseDir, archiveName string, includePaths []string, ttl time.Duration, excludePatterns []string, threads int, extraHeaders ...http.Header) (returnErr error) {
ctx, span := tracer.Start(ctx, "cachew.snapshot.create",
trace.WithAttributes(
attribute.String("cache.key", key.String()),
attribute.String("snapshot.archive_name", archiveName),
attribute.Int("snapshot.include_paths", len(includePaths)),
attribute.Int("snapshot.exclude_patterns", len(excludePatterns)),
attribute.Int("snapshot.threads", threads),
),
)
defer func() {
if returnErr != nil {
span.RecordError(returnErr)
span.SetStatus(codes.Error, returnErr.Error())
}
span.End()
}()

headers := make(http.Header)
headers.Set("Content-Type", "application/zstd")
headers.Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", archiveName+".tar.zst"))
Expand Down Expand Up @@ -71,7 +95,21 @@ func StreamTo(ctx context.Context, w io.Writer, directory string, excludePattern
// all file permissions, ownership, and symlinks.
// The operation is fully streaming - no temporary files are created.
// threads controls zstd parallelism; 0 uses all available CPU cores.
func Restore(ctx context.Context, remote cache.Cache, key cache.Key, directory string, threads int) error {
func Restore(ctx context.Context, remote cache.Cache, key cache.Key, directory string, threads int) (returnErr error) {
ctx, span := tracer.Start(ctx, "cachew.snapshot.restore",
trace.WithAttributes(
attribute.String("cache.key", key.String()),
attribute.Int("snapshot.threads", threads),
),
)
defer func() {
if returnErr != nil {
span.RecordError(returnErr)
span.SetStatus(codes.Error, returnErr.Error())
}
span.End()
}()

rc, _, err := remote.Open(ctx, key)
if err != nil {
return errors.Wrap(err, "failed to open object")
Expand Down
9 changes: 9 additions & 0 deletions internal/tracing/tracing.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ import (
"github.com/alecthomas/errors"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
"go.opentelemetry.io/otel/propagation"
"go.opentelemetry.io/otel/sdk/trace"
)

Expand Down Expand Up @@ -41,6 +42,14 @@ func New(ctx context.Context, cfg Config) (stop func(), err error) {
provider := trace.NewTracerProvider(trace.WithBatcher(exporter))
otel.SetTracerProvider(provider)

// Register a W3C trace context + baggage propagator so trace IDs
// flow across HTTP boundaries (otelhttp/otelconnect use the global
// propagator). Without this, every service starts a new trace.
otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
propagation.TraceContext{},
propagation.Baggage{},
))

return func() {
_ = provider.Shutdown(context.Background()) //nolint:errcheck // shutdown errors are not actionable
}, nil
Expand Down