blockservice: remove session embeding in context

This brings us to a state before #549 back then I also did cleanup in this session code, that I have kept, I only removed the sessions in context feature.

Author: Jorropo

CHANGELOG.md

@@ -16,7 +16,6 @@ The following emojis are used to highlight certain changes:
 
 ### Added
 
-- `blockservice` now has `ContextWithSession` and `EmbedSessionInContext` functions, which allows to embed a session in a context. Future calls to `BlockGetter.GetBlock`, `BlockGetter.GetBlocks` and `NewSession` will use the session in the context.
 - `blockservice.NewWritethrough` deprecated function has been removed, instead you can do `blockservice.New(..., ..., WriteThrough())` like previously.
 - `gateway`: a new header configuration middleware has been added to replace the existing header configuration, which can be used more generically.
 - `namesys` now has a `WithMaxCacheTTL` option, which allows you to define a maximum TTL that will be used for caching IPNS entries.

blockservice/blockservice.go

@@ -140,16 +140,6 @@ func (s *blockService) Allowlist() verifcid.Allowlist {
 // directly.
 // Sessions are lazily setup, this is cheap.
 func NewSession(ctx context.Context, bs BlockService) *Session {
-	ses := grabSessionFromContext(ctx, bs)
-	if ses != nil {
-		return ses
-	}
-
-	return newSession(ctx, bs)
-}
-
-// newSession is like [NewSession] but it does not attempt to reuse session from the existing context.
-func newSession(ctx context.Context, bs BlockService) *Session {
 	return &Session{bs: bs, sesctx: ctx}
 }
 
@@ -232,10 +222,6 @@ func (s *blockService) AddBlocks(ctx context.Context, bs []blocks.Block) error {
 // GetBlock retrieves a particular block from the service,
 // Getting it from the datastore using the key (hash).
 func (s *blockService) GetBlock(ctx context.Context, c cid.Cid) (blocks.Block, error) {
-	if ses := grabSessionFromContext(ctx, s); ses != nil {
-		return ses.GetBlock(ctx, c)
-	}
-
 	ctx, span := internal.StartSpan(ctx, "blockService.GetBlock", trace.WithAttributes(attribute.Stringer("CID", c)))
 	defer span.End()
 
@@ -295,10 +281,6 @@ func getBlock(ctx context.Context, c cid.Cid, bs BlockService, fetchFactory func
 // the returned channel.
 // NB: No guarantees are made about order.
 func (s *blockService) GetBlocks(ctx context.Context, ks []cid.Cid) <-chan blocks.Block {
-	if ses := grabSessionFromContext(ctx, s); ses != nil {
-		return ses.GetBlocks(ctx, ks)
-	}
-
 	ctx, span := internal.StartSpan(ctx, "blockService.GetBlocks")
 	defer span.End()
 
@@ -474,43 +456,6 @@ func (s *Session) GetBlocks(ctx context.Context, ks []cid.Cid) <-chan blocks.Blo
 
 var _ BlockGetter = (*Session)(nil)
 
-// ContextWithSession is a helper which creates a context with an embded session,
-// future calls to [BlockGetter.GetBlock], [BlockGetter.GetBlocks] and [NewSession] with the same [BlockService]
-// will be redirected to this same session instead.
-// Sessions are lazily setup, this is cheap.
-// It wont make a new session if one exists already in the context.
-func ContextWithSession(ctx context.Context, bs BlockService) context.Context {
-	if grabSessionFromContext(ctx, bs) != nil {
-		return ctx
-	}
-	return EmbedSessionInContext(ctx, NewSession(ctx, bs))
-}
-
-// EmbedSessionInContext is like [ContextWithSession] but it allows to embed an existing session.
-func EmbedSessionInContext(ctx context.Context, ses *Session) context.Context {
-	// use ses.bs as a key, so if multiple blockservices use embeded sessions it gets dispatched to the matching blockservice.
-	return context.WithValue(ctx, ses.bs, ses)
-}
-
-// grabSessionFromContext returns nil if the session was not found
-// This is a private API on purposes, I dislike when consumers tradeoff compiletime typesafety with runtime typesafety,
-// if this API is public it is too easy to forget to pass a [BlockService] or [Session] object around in your app.
-// By having this private we allow consumers to follow the trace of where the blockservice is passed and used.
-func grabSessionFromContext(ctx context.Context, bs BlockService) *Session {
-	s := ctx.Value(bs)
-	if s == nil {
-		return nil
-	}
-
-	ss, ok := s.(*Session)
-	if !ok {
-		// idk what to do here, that kinda sucks, giveup
-		return nil
-	}
-
-	return ss
-}
-
 // grabAllowlistFromBlockservice never returns nil
 func grabAllowlistFromBlockservice(bs BlockService) verifcid.Allowlist {
 	if bbs, ok := bs.(BoundedBlockService); ok {

blockservice/blockservice_test.go

@@ -288,68 +288,3 @@ func TestAllowlist(t *testing.T) {
 	check(blockservice.GetBlock)
 	check(NewSession(ctx, blockservice).GetBlock)
 }
-
-type fakeIsNewSessionCreateExchange struct {
-	ses                 exchange.Fetcher
-	newSessionWasCalled bool
-}
-
-var _ exchange.SessionExchange = (*fakeIsNewSessionCreateExchange)(nil)
-
-func (*fakeIsNewSessionCreateExchange) Close() error {
-	return nil
-}
-
-func (*fakeIsNewSessionCreateExchange) GetBlock(context.Context, cid.Cid) (blocks.Block, error) {
-	panic("should call on the session")
-}
-
-func (*fakeIsNewSessionCreateExchange) GetBlocks(context.Context, []cid.Cid) (<-chan blocks.Block, error) {
-	panic("should call on the session")
-}
-
-func (f *fakeIsNewSessionCreateExchange) NewSession(context.Context) exchange.Fetcher {
-	f.newSessionWasCalled = true
-	return f.ses
-}
-
-func (*fakeIsNewSessionCreateExchange) NotifyNewBlocks(context.Context, ...blocks.Block) error {
-	return nil
-}
-
-func TestContextSession(t *testing.T) {
-	t.Parallel()
-	a := assert.New(t)
-
-	ctx, cancel := context.WithCancel(context.Background())
-	defer cancel()
-
-	bgen := butil.NewBlockGenerator()
-	block1 := bgen.Next()
-	block2 := bgen.Next()
-
-	bs := blockstore.NewBlockstore(ds.NewMapDatastore())
-	a.NoError(bs.Put(ctx, block1))
-	a.NoError(bs.Put(ctx, block2))
-	sesEx := &fakeIsNewSessionCreateExchange{ses: offline.Exchange(bs)}
-
-	service := New(blockstore.NewBlockstore(ds.NewMapDatastore()), sesEx)
-
-	ctx = ContextWithSession(ctx, service)
-
-	b, err := service.GetBlock(ctx, block1.Cid())
-	a.NoError(err)
-	a.Equal(b.RawData(), block1.RawData())
-	a.True(sesEx.newSessionWasCalled, "new session from context should be created")
-	sesEx.newSessionWasCalled = false
-
-	bchan := service.GetBlocks(ctx, []cid.Cid{block2.Cid()})
-	a.Equal((<-bchan).RawData(), block2.RawData())
-	a.False(sesEx.newSessionWasCalled, "session should be reused in context")
-
-	a.Equal(
-		NewSession(ctx, service),
-		NewSession(ContextWithSession(ctx, service), service),
-		"session must be deduped in all invocations on the same context",
-	)
-}

gateway/blocks_backend.go

@@ -689,12 +689,6 @@ func (bb *BlocksBackend) IsCached(ctx context.Context, p path.Path) bool {
 	return has
 }
 
-var _ WithContextHint = (*BlocksBackend)(nil)
-
-func (bb *BlocksBackend) WrapContextForRequest(ctx context.Context) context.Context {
-	return blockservice.ContextWithSession(ctx, bb.blockService)
-}
-
 func (bb *BlocksBackend) ResolvePath(ctx context.Context, path path.ImmutablePath) (ContentPathMetadata, error) {
 	roots, lastSeg, remainder, err := bb.getPathRoots(ctx, path)
 	if err != nil {