kubo/core/corehttp/gateway_handler_car.go
Gus Eggert f855bfe6ef
feat: add basic gateway tracing (#8595)
* add deprecation warning when tracer plugins are loaded
* add response format attribute to span in gateway handler
* add note about tracing's experimental status in godoc
* add nil check for TTL when adding name span attrs
* add basic sharness test for integration with otel collector
* add nil check in UnixFSAPI.processLink
* test: sharness check all json objs for swarm span
* add env var docs to docs/environment-variables.md
* chore: pin the otel collector version
* add tracing spans per response type (#8841)
* docs: tracing with jaeger-ui

Co-authored-by: Marcin Rataj <lidel@lidel.org>
2022-04-04 19:24:05 +02:00

93 lines
3.3 KiB
Go

package corehttp
import (
"context"
"fmt"
"net/http"
"time"
blocks "github.com/ipfs/go-block-format"
cid "github.com/ipfs/go-cid"
"github.com/ipfs/go-ipfs/tracing"
coreiface "github.com/ipfs/interface-go-ipfs-core"
ipath "github.com/ipfs/interface-go-ipfs-core/path"
gocar "github.com/ipld/go-car"
selectorparse "github.com/ipld/go-ipld-prime/traversal/selector/parse"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/trace"
)
// serveCar returns a CAR stream for specific DAG+selector
func (i *gatewayHandler) serveCar(w http.ResponseWriter, r *http.Request, resolvedPath ipath.Resolved, contentPath ipath.Path, carVersion string, begin time.Time) {
ctx, span := tracing.Span(r.Context(), "Gateway", "ServeCar", trace.WithAttributes(attribute.String("path", resolvedPath.String())))
defer span.End()
ctx, cancel := context.WithCancel(ctx)
defer cancel()
switch carVersion {
case "": // noop, client does not care about version
case "1": // noop, we support this
default:
err := fmt.Errorf("only version=1 is supported")
webError(w, "unsupported CAR version", err, http.StatusBadRequest)
return
}
rootCid := resolvedPath.Cid()
// Set Content-Disposition
name := rootCid.String() + ".car"
setContentDispositionHeader(w, name, "attachment")
// Weak Etag W/ because we can't guarantee byte-for-byte identical responses
// (CAR is streamed, and in theory, blocks may arrive from datastore in non-deterministic order)
etag := `W/` + getEtag(r, rootCid)
w.Header().Set("Etag", etag)
// Finish early if Etag match
if r.Header.Get("If-None-Match") == etag {
w.WriteHeader(http.StatusNotModified)
return
}
// Make it clear we don't support range-requests over a car stream
// Partial downloads and resumes should be handled using
// IPLD selectors: https://github.com/ipfs/go-ipfs/issues/8769
w.Header().Set("Accept-Ranges", "none")
// Explicit Cache-Control to ensure fresh stream on retry.
// CAR stream could be interrupted, and client should be able to resume and get full response, not the truncated one
w.Header().Set("Cache-Control", "no-cache, no-transform")
w.Header().Set("Content-Type", "application/vnd.ipld.car; version=1")
w.Header().Set("X-Content-Type-Options", "nosniff") // no funny business in the browsers :^)
// Same go-car settings as dag.export command
store := dagStore{dag: i.api.Dag(), ctx: ctx}
// TODO: support selectors passed as request param: https://github.com/ipfs/go-ipfs/issues/8769
dag := gocar.Dag{Root: rootCid, Selector: selectorparse.CommonSelector_ExploreAllRecursively}
car := gocar.NewSelectiveCar(ctx, store, []gocar.Dag{dag}, gocar.TraverseLinksOnlyOnce())
if err := car.Write(w); err != nil {
// We return error as a trailer, however it is not something browsers can access
// (https://github.com/mdn/browser-compat-data/issues/14703)
// Due to this, we suggest client always verify that
// the received CAR stream response is matching requested DAG selector
w.Header().Set("X-Stream-Error", err.Error())
return
}
// Update metrics
i.carStreamGetMetric.WithLabelValues(contentPath.Namespace()).Observe(time.Since(begin).Seconds())
}
type dagStore struct {
dag coreiface.APIDagService
ctx context.Context
}
func (ds dagStore) Get(c cid.Cid) (blocks.Block, error) {
obj, err := ds.dag.Get(ds.ctx, c)
return obj, err
}