joiningsource.go

// Copyright 2019 dfuse Platform Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package bstream

import (
	"errors"
	"fmt"
	"sync"

	pbbstream "github.com/streamingfast/bstream/pb/sf/bstream/v1"

	"github.com/streamingfast/shutter"
	"go.uber.org/zap"
)

var stopSourceOnJoin = errors.New("stopping source on join")

// JoiningSource joins an irreversible-only source (file) to a fork-aware source close to HEAD (live)
// 1) it tries to get the source from LiveSourceFactory (using startblock or cursor)
// 2) if it can't, it will ask the FileSourceFactory for a source of those blocks.
// 3) when it receives blocks from Filesource, it looks at LiveSource
// the JoiningSource will instantiate and run an 'initialSource' until it can bridge the gap
type JoiningSource struct {
	*shutter.Shutter

	fileSourceFactory ForkableSourceFactory
	liveSourceFactory ForkableSourceFactory

	lowestLiveBlockNum uint64
	liveSource         Source
	sourcesLock        sync.Mutex

	handler Handler

	lastBlockProcessed *pbbstream.Block

	startBlockNum  uint64 // overriden by cursor if it exists, unless we are in cursorIsTarget mode
	cursor         *Cursor
	cursorIsTarget bool

	logger *zap.Logger
}

func NewJoiningSource(
	fileSourceFactory,
	liveSourceFactory ForkableSourceFactory,
	h Handler,
	startBlockNum uint64,
	cursor *Cursor,
	cursorIsTarget bool,
	logger *zap.Logger) *JoiningSource {
	logger.Info("creating new joining source", zap.Stringer("cursor", cursor), zap.Uint64("start_block_num", startBlockNum))

	s := &JoiningSource{
		Shutter:           shutter.New(),
		fileSourceFactory: fileSourceFactory,
		liveSourceFactory: liveSourceFactory,
		handler:           h,
		startBlockNum:     startBlockNum,
		cursor:            cursor,
		cursorIsTarget:    cursorIsTarget,
		logger:            logger,
	}

	return s
}

func (s *JoiningSource) Run() {
	s.Shutdown(s.run())
}

func (s *JoiningSource) run() error {

	// if liveSource works, no need for fileSource or wrapped handler
	if src := s.tryGetSource(s.handler, s.liveSourceFactory); src != nil {
		s.liveSource = src

		s.OnTerminating(s.liveSource.Shutdown)
		s.liveSource.Run()
		return s.liveSource.Err()
	}
	if lowestBlockGetter, ok := s.liveSourceFactory.(LowSourceLimitGetter); ok {
		s.lowestLiveBlockNum = lowestBlockGetter.LowestBlockNum()
	}

	fileSrc := s.tryGetSource(HandlerFunc(s.fileSourceHandler), s.fileSourceFactory)

	if fileSrc == nil {
		return fmt.Errorf("cannot run joining_source: start_block %d (cursor %s) not found",
			s.startBlockNum,
			s.cursor.String())
	}

	s.OnTerminating(fileSrc.Shutdown)
	fileSrc.Run()

	if s.liveSource == nil { // got stopped before joining
		return fileSrc.Err()
	}

	s.OnTerminating(s.liveSource.Shutdown)
	s.liveSource.Run()
	return s.liveSource.Err()

}

func (s *JoiningSource) tryGetSource(handler Handler, factory ForkableSourceFactory) Source {
	if s.cursor != nil {
		if s.cursorIsTarget {
			return factory.SourceThroughCursor(s.startBlockNum, s.cursor, handler)
		}
		return factory.SourceFromCursor(s.cursor, handler)
	}
	return factory.SourceFromBlockNum(s.startBlockNum, handler)
}

func (s *JoiningSource) fileSourceHandler(blk *pbbstream.Block, obj interface{}) error {
	if s.liveSource != nil { // we should be already shutdown anyway
		return nil
	}

	if blk.Number >= s.lowestLiveBlockNum {
		if s.cursorIsTarget {
			if src := s.liveSourceFactory.SourceThroughCursor(blk.Number, s.cursor, s.handler); src != nil {
				s.liveSource = src
				return stopSourceOnJoin
			}
		} else {
			if src := s.liveSourceFactory.SourceFromBlockNum(blk.Number, s.handler); src != nil {
				s.liveSource = src
				return stopSourceOnJoin
			}
		}
		if lowestBlockGetter, ok := s.liveSourceFactory.(LowSourceLimitGetter); ok {
			s.lowestLiveBlockNum = lowestBlockGetter.LowestBlockNum()
		}
	}

	return s.handler.ProcessBlock(blk, obj)
}