services/syncbase/server/interfaces/sync.vdl

// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package interfaces

import (
	wire "v.io/v23/services/syncbase"
	"v.io/v23/security/access"
)

// Sync defines methods for data exchange between Syncbases.
// TODO(hpucha): Flesh this out further.
type Sync interface {
	// GetTime returns metadata related to the Syncbase virtual clock, including
	// system clock values, last NTP timestamp, num reboots, etc.
	GetTime(req TimeReq, initiator string) (TimeResp | error)

	// GetDeltas returns the responder's current generation vectors and all
	// the missing log records when compared to the initiator's generation
	// vectors for one Database for either syncgroup metadata or data.
	// The final result (in DeltaFinalResp) currently includes the
	// syncgroup priorities for blob ownership for the server.
	GetDeltas(req DeltaReq, initiator string) stream<_, DeltaResp> (DeltaFinalResp | error) {access.Read}

	// Syncgroup-related methods.

	// PublishSyncgroup is invoked on the syncgroup name (typically served
	// by a "central" peer) to publish the syncgroup.  It takes the name of
	// Syncbase doing the publishing (the publisher) and returns the name
	// of the Syncbase where the syncgroup is published (the publishee).
	// This allows the publisher and the publishee to learn of each other.
	// When a syncgroup is published, the publishee is given the syncgroup
	// metadata, its current version at the publisher, and the current
	// syncgroup generation vector.  The generation vector serves as a
	// checkpoint at the time of publishing.  The publishing proceeds
	// asynchronously, and the publishee learns the syncgroup history
	// through the routine p2p sync process and determines when it has
	// caught up to the level of knowledge at the time of publishing using
	// the checkpointed generation vector.  Until that point, the publishee
	// locally deems the syncgroup to be in a pending state and does not
	// mutate it.  Thus it locally rejects syncgroup joins or updates to
	// its spec until it is caught up on the syncgroup history.
	PublishSyncgroup(publisher string, sg Syncgroup, version string, genvec GenVector) (string | error) {access.Write}

	// JoinSyncgroupAtAdmin is invoked by a prospective syncgroup member's
	// Syncbase on a syncgroup admin. It checks whether the requestor is
	// allowed to join the named syncgroup, and if so, adds the requestor to
	// the syncgroup.  It returns a copy of the updated syncgroup metadata,
	// its version, and the syncgroup generation vector at the time of the
	// join.  Similar to the PublishSyncgroup scenario, the joiner at that
	// point does not have the syncgroup history and locally deems it to be
	// in a pending state and does not mutate it.  This means it rejects
	// local updates to the syncgroup spec or, if it were also an admin on
	// the syncgroup, it would reject syncgroup joins until it is caught up
	// on the syncgroup history through p2p sync.
	JoinSyncgroupAtAdmin(dbId wire.Id, sgId wire.Id, joinerName string, myInfo wire.SyncgroupMemberInfo) (sg Syncgroup, version string, genvec GenVector | error) {access.Read}

	// BlobSync methods.

	// HaveBlob verifies that the peer has the requested blob, and if
	// present, returns its size.  Otherwise, it returns -1, and the location
	// hints (the Signpost) that the peer has for the blob, filtered to
	// include only data the caller is permitted to see:
	// + Device D reveals a syncgroup SG to the caller C iff
	//   - D is in SG, and
	//   - SG is in the Signpost, and
	//   - at least one of:
	//     - SG is not private, or
	//     - C has permission to join SG.
	// + Device D reveals a location hint L to caller C iff
	//   there is a syncgroup SG such that
	//   - D is in SG, and
	//   - SG is in the Signpost, and
	//   - L is in SG, and
	//   - at least one of:
	//     - SG is not private, or
	//     - C has permission to join SG, or
	//     - L is a blob server in SG.
	HaveBlob(br wire.BlobRef) (size int64, signpost Signpost | error)

	// FetchBlob fetches the requested blob.
	// It returns a number of blob ownership shares that the server hopes
	// the client will accept using the AcceptedBlobOwnership() call.
	FetchBlob(br wire.BlobRef, mySgPriorities SgPriorities) stream<_, []byte> (shares BlobSharesBySyncgroup | error)

	// Methods for incremental blob transfer. The transfer starts with the
	// receiver making a FetchBlobRecipe call to the sender for a given
	// BlobRef. The sender, in turn, sends the chunk hashes of all the
	// chunks that make up the requested blob (blob recipe). The receiver
	// looks up the chunk hashes in its local blob store, and identifies the
	// missing ones. The receiver then fetches the missing chunks using a
	// FetchChunks call from the sender. Finally, the receiver finishes the
	// blob fetch by combining the chunks obtained over the network with the
	// already available local chunks as per the blob recipe.
	// callerName is the syncbase Id of the caller, expressed as a string.
	// FetchBlobRecipe returns a number of blob ownership shares that the
	// server hopes the client will accept for each syncgroup using the
	// AcceptedBlobOwnership() call.
	FetchBlobRecipe(br wire.BlobRef, callerName string, mySgPriorities SgPriorities) stream<_, ChunkHash> (shares BlobSharesBySyncgroup | error)
	FetchChunks() stream<ChunkHash, ChunkData> error

	// RequestTakeBlob indicates that the caller wishes the server to take
	// some blob ownership shares for various syncgroups for the specified blob.
	// If the server chooses to act on the request, it may call FetchBlob/FetchBlobRecipe,
	// and ultimately AcceptedBlobOwnership().
	// callerName is the syncbase Id of the caller, expressed as a string.
	RequestTakeBlob(br wire.BlobRef, callerName string, shares BlobSharesBySyncgroup) error

	// AcceptedBlobOwnership tells the server that the client callerName (a
	// syncbase Id expressed as a string) has accepted blob ownership of a
	// specified number of shares for blob br.  The server may decrement
	// its share count by up to this number.  It is safe for the server to
	// decrement its share count by fewer than the number of shares another
	// device has taken responsibility for, but unsafe to decrement it by
	// more than that that number.  It returns a hint as to whether the
	// server is likely to keep the blob itself, plus its syncbase Id
	// expressed as a string.
	AcceptedBlobOwnership(br wire.BlobRef, callerName string, shares BlobSharesBySyncgroup) (serverName string, keepingBlob bool | error)
}

// TODO(ivanpi): Some methods are missing additional parameter handling ({:_}).
error (
	DupSyncgroupPublish(sgId wire.Id) {"en": "duplicate publish on syncgroup: {sgId}"}
	ConnFail() {"en": "connection to peer failed{:_}"}
	BrokenCrConnection() {"en": "CrConnection stream to client does not exist or is broken"}
	DbOffline(dbId wire.Id) {"en": "database {dbId} is offline and cannot be synced{:_}"}
	GetTimeFailed() {"en": "GetTime failed{:_}"}
	NotAdmin() {"en": "not an admin of the syncgroup"}
)