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subscription.go
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// 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 hub
import (
"fmt"
"github.com/streamingfast/bstream"
"github.com/streamingfast/shutter"
)
// Subscription is a bstream.Source and has the following guarantees:
type Subscription struct {
*shutter.Shutter
handler bstream.Handler
blocks chan *bstream.PreprocessedBlock
}
// s.hub.unsubscribe(sub)
func NewSubscription(handler bstream.Handler, chanSize int) *Subscription {
sub := &Subscription{
Shutter: shutter.New(),
handler: handler,
blocks: make(chan *bstream.PreprocessedBlock, chanSize),
}
return sub
}
func (s *Subscription) push(ppblk *bstream.PreprocessedBlock) error {
if len(s.blocks) == cap(s.blocks) {
return fmt.Errorf("subscription channel at max capacity")
}
s.blocks <- ppblk
return nil
}
func (s *Subscription) run() error {
for {
select {
case ppblk := <-s.blocks:
if s.IsTerminating() { // deal with non-predictibility of select
return nil
}
if err := s.handler.ProcessBlock(ppblk.Block, ppblk.Obj); err != nil {
return err
}
case <-s.Terminating():
return nil
}
}
}
func (s *Subscription) Run() {
s.Shutdown(s.run())
}