Distributed Services with Go: Chapter 3 suggestions

Page 28: It implements io.ReaderAt on the store type.

• Sorry if it’s a dumb question but was the io.ReaderAt supposed to be io.ReadAt?

Page 29:
func (s *store) Close() error {
s.mu.Lock()
defer s.mu.Unlock()
err := s.buf.Flush()
if err != nil {
return err
}

• Possibly:
  if err := s.buf.Flush(); err != nil {
  return err
  }

Page 31: At the end of store_test.go

• Could you please include instructions/Makefile to execute the tests?
• I finally managed to run them by cd’ing into internal/log and running ‘go test -v’ but this was after a bunch of failed attempts at running them.

Page 30-50: I would suggest running the tests after each of the Store, Index, and Segment would help people stay more engaged? Otherwise it seems too much (25 pages) code reading without interactivity.

Page 34: an ungraceful shutdown

• Does ‘forceful’ shutdown sound more appealing than ‘ungraceful’?

Page 37: type Config struct {

• I was trying to execute index_test.go and index.go and was trying to figure out what the unresolved Config was. Would it help to move this definition ahead of usage?

Page 36: Then we verify that the index and scanner error when

• that the index and scanner ‘throw an error’ when?

Page 37: We need the next and base offsets to know…

• This isn’t clear. Could you please consider drawing a simple picture to clarify this better?

Page 39: func (s *segment) Append(record *api.Record) (offset uint64, err error) {

• Please consider forward declaring the definition of Record to make compilation and execution possible.

Page 41: import (
“fmt”
“os”
“path”

"github.com/gogo/protobuf/proto"
api "github.com/travisjeffery/proglog/api/v1"

)

• Errors: go: finding github.com/travisjeffery/proglog/api latest
  segment.go:9:2: no matching versions for query “latest”
• Something’s really not working here, it would help to have specific instructions to get the test running.
• Modified:
• api “github.com/travisjeffery/proglog/api/v1”

• api “github.com/travisjeffery/proglog/WriteALogPackage/api/v1”
  resulting in error: go: finding github.com/travisjeffery/proglog latest
  segment.go:9:2: module github.com/travisjeffery/proglog@latest found (v0.0.0-20201127042147-f6dae5fb8cb4), but does not contain package github.com/travisjeffery/proglog/WriteALogPackage/api/v1

• Some other modifications threw: go: github.com/travisjeffery/proglog/WriteALogPackage/internal/log imports
  github.com/travisjeffery/proglog/WriteALogPackage/api/v1: github.com/travisjeffery/proglog/WriteALogPackage@v0.0.0-20201127042147-f6dae5fb8cb4: parsing go.mod:
  module declares its path as: github.com/travisjeffery/proglog
  but was required as: github.com/travisjeffery/proglog/WriteALogPackage
• And lo, finally ran successfully with:
• api “github.com/travisjeffery/proglog/api/v1”

• api “github.com/travisjeffery/proglog/StructureDataWithProtobuf/api/v1”

Page 43: api “github.com/travisjeffery/proglog/api/v1”

• Needed: api “github.com/travisjeffery/proglog/StructureDataWithProtobuf/api/v1”

Page 43: Next, add the this setup() method below NewLog()

• Next, add ‘this’ setup() method below NewLog()

Page 48: api “github.com/travisjeffery/proglog/api/v1”

• Needed: api “github.com/travisjeffery/proglog/StructureDataWithProtobuf/api/v1”

Page 51: testReader(*testing.T, *log.Log) tests that we can read the full, raw log as it’s stored on disk so that on, when we can snapshot

• so that on ‘startup’?, when we can snapshot - something is off here