depot/go/trains/darwin/darwingest/darwingest.go

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2021-11-18 22:24:20 +00:00
package darwingest
import (
"bytes"
"compress/gzip"
"context"
"encoding/xml"
"fmt"
"io"
"log"
"strings"
"time"
"github.com/cenkalti/backoff/v4"
"github.com/go-stomp/stomp/v3"
"github.com/jlaffaye/ftp"
"gocloud.dev/blob"
"hg.lukegb.com/lukegb/depot/go/trains/darwin"
"hg.lukegb.com/lukegb/depot/go/trains/darwin/darwingest/darwingestftp"
"hg.lukegb.com/lukegb/depot/go/trains/darwin/darwingest/darwingests3"
)
func degzip(b []byte) ([]byte, error) {
gzr, err := gzip.NewReader(bytes.NewBuffer(b))
if err != nil {
return nil, fmt.Errorf("gzip.NewReader: %w", err)
}
d, err := io.ReadAll(gzr)
if err != nil {
return nil, fmt.Errorf("io.ReadAll: %w", err)
}
return d, nil
}
func unmarshalGzipPushPort(m []byte) (*darwin.PushPort, error) {
d, err := degzip(m)
if err != nil {
return nil, fmt.Errorf("degzip: %w", err)
}
var pp darwin.PushPort
if err := xml.Unmarshal(d, &pp); err != nil {
return nil, fmt.Errorf("xml.Unmarshal(%q): %w", string(d), err)
}
return &pp, nil
}
func ridToDate(rid string) (time.Time, error) {
t, err := time.ParseInLocation("20060102", rid[0:8], darwin.London)
if err != nil {
return time.Time{}, err
}
if t.Hour() < 2 || (t.Hour() == 2 && t.Minute() < 45) {
t = t.AddDate(0, 0, -1)
}
return t, nil
}
type Config struct {
Verbose bool
DialStomp func(ctx context.Context) (*stomp.Conn, error)
StompSubscribe func(ctx context.Context, sc *stomp.Conn) (*stomp.Subscription, error)
DialFTP func(ctx context.Context) (*ftp.ServerConn, error)
Message func(pp *darwin.PushPort) error
MessageCatchUp func(pp *darwin.PushPort) error
Timetable func(ppt *darwin.PushPortTimetable) error
ReferenceData func(pprd *darwin.PushPortReferenceData) error
CatchUpComplete func(ctx context.Context) error
}
func Start(ctx context.Context, bucket *blob.Bucket, cfg Config) error {
return run(ctx, bucket, cfg, false)
}
func CatchUpAndStart(ctx context.Context, bucket *blob.Bucket, cfg Config) error {
return run(ctx, bucket, cfg, true)
}
func run(ctx context.Context, bucket *blob.Bucket, cfg Config, runCatchup bool) error {
handleMsg := func(cb func(*darwin.PushPort) error) func(*darwin.PushPort) error {
return func(pp *darwin.PushPort) error {
for _, ttid := range pp.TimeTableID {
fn := strings.TrimSpace(ttid.Filename)
if fn != "" {
log.Printf("informed that there's a new timetable at %q", fn)
ppt, err := darwingests3.LoadTimetable(ctx, bucket, fn)
if err == darwingests3.ErrBadVersion {
continue
}
if err != nil {
return fmt.Errorf("LoadTimetable(%q): %w", fn, err)
}
if err := cfg.Timetable(ppt); err != nil {
return fmt.Errorf("Timetable(%q): %w", fn, err)
}
}
fn = strings.TrimSpace(ttid.ReferenceFilename)
if fn != "" {
log.Printf("informed that there's a new refsheet at %q", fn)
rd, err := darwingests3.LoadReferenceData(ctx, bucket, fn)
if err == darwingests3.ErrBadVersion {
continue
}
if err != nil {
return fmt.Errorf("LoadReferenceData(%q): %w", fn, err)
}
if err := cfg.ReferenceData(rd); err != nil {
return fmt.Errorf("cfg.ReferenceData(%q): %w", fn, err)
}
}
}
return cb(pp)
}
}
if runCatchup {
// Load the latest reference data.
rd, err := darwingests3.LoadLatestReferenceData(ctx, bucket)
if err != nil {
return fmt.Errorf("LoadLatestReferenceData: %w", err)
}
if err := cfg.ReferenceData(rd); err != nil {
return fmt.Errorf("cfg.ReferenceData: %w", err)
}
}
stompBackoff := backoff.NewExponentialBackOff()
stompBackoff.MaxElapsedTime = 24 * time.Hour
stompConn, err := cfg.DialStomp(ctx)
if err != nil {
return fmt.Errorf("DialStomp: %w", err)
}
defer stompConn.Disconnect()
sub, err := cfg.StompSubscribe(ctx, stompConn)
if err != nil {
return fmt.Errorf("StompSubscribe: %w", err)
}
defer sub.Unsubscribe()
drainConnection := func() {
if sub == nil {
return
}
go sub.Unsubscribe()
for m := range sub.C {
stompConn.Nack(m)
}
}
if runCatchup {
if err := func() error {
log.Println("awaiting first message to find replay timestamp")
// Find the start timestamp we need to replay up to.
m := <-sub.C
defer stompConn.Nack(m)
d, err := unmarshalGzipPushPort(m.Body)
if err != nil {
return fmt.Errorf("unmarshalGzipPushPort: %w", err)
}
log.Printf("first message is at %v", d.Time)
// Don't handle the message just yet.
rids := d.AffectedRIDs()
var timetableDate time.Time
if len(rids) == 0 {
log.Printf("no affected RIDs in first message! falling back to time.Now...")
timetableDate = time.Now()
} else {
timetableDate, err = ridToDate(rids[0])
if err != nil {
log.Printf("couldn't parse RID %q to date, falling back to time.Now: %v", rids[0], err)
timetableDate = time.Now()
}
}
// Load the timetable first.
log.Println("loading initial timetable")
ppt, err := darwingests3.LoadTimetableForDate(ctx, bucket, timetableDate)
if err != nil {
return fmt.Errorf("LoadTimetableForDate: %w", err)
}
log.Println("feeding timetable to database")
if err := cfg.Timetable(ppt); err != nil {
return fmt.Errorf("Timetable: %w", err)
}
log.Println("connecting to FTP")
sc, err := cfg.DialFTP(ctx)
if err != nil {
return fmt.Errorf("DialFTP: %w", err)
}
defer sc.Quit()
// Grab the full snapshot dump
log.Println("loading snapshot")
lw, _, err := darwingestftp.LoadSnapshot(ctx, sc, handleMsg(cfg.MessageCatchUp))
if err != nil {
return fmt.Errorf("LoadSnapshot: %w", err)
}
// Now try to "catch it up" using the push-port logs to the start timestamp of the message...
log.Println("loading logs")
if err := darwingestftp.LoadLogs(ctx, sc, lw, d.Time, handleMsg(cfg.MessageCatchUp)); err != nil {
return fmt.Errorf("LoadLogs: %w", err)
}
log.Println("marking catchup complete")
if err := cfg.CatchUpComplete(ctx); err != nil {
return fmt.Errorf("CatchUpComplete callback: %w", err)
}
log.Println("we think we've caught up! let's go...")
if err := handleMsg(cfg.Message)(d); err != nil {
return fmt.Errorf("replaying first pushport message: %w", err)
}
if err := stompConn.Ack(m); err != nil {
return fmt.Errorf("acking first pushport message: %w", err)
}
return nil
}(); err != nil {
drainConnection()
return err
}
} else {
if err := cfg.CatchUpComplete(ctx); err != nil {
return fmt.Errorf("CatchUpComplete callback: %w", err)
}
}
mustReconnect := false
for {
if sub == nil {
mustReconnect = true
}
if mustReconnect {
duration := stompBackoff.NextBackOff()
if duration == backoff.Stop {
drainConnection()
return fmt.Errorf("exceeded stomp reconnection retries")
}
log.Printf("subscription appears to have closed, retrying after %v...", duration)
if err := darwin.Sleep(ctx, duration); err != nil {
drainConnection()
return err
}
var err error
log.Printf("resubscribing...")
if stompConn != nil {
sub, err = cfg.StompSubscribe(ctx, stompConn)
} else {
err = fmt.Errorf("no stompConn")
}
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if err != nil {
log.Printf("StompSubscribe while resubscribing: %v", err)
// Force close the server connection and dial again.
if stompConn != nil {
stompConn.MustDisconnect()
}
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stompConn, err = cfg.DialStomp(ctx)
if err != nil {
log.Printf("DialStomp failed as well :(")
// Try again later.
continue
}
defer stompConn.Disconnect()
sub, err = cfg.StompSubscribe(ctx, stompConn)
if err != nil {
log.Printf("StompSubscribe with new connection failed: %v", err)
// Try again later.
continue
}
}
defer sub.Unsubscribe()
mustReconnect = false
}
select {
case <-ctx.Done():
return ctx.Err()
case m, ok := <-sub.C:
if !ok {
mustReconnect = true
continue
}
d, err := unmarshalGzipPushPort(m.Body)
if err != nil {
log.Printf("unmarshalGzipPushPort: %v", err)
if err := stompConn.Nack(m); err != nil {
log.Printf("attempting to nack unparsable message: %v", err)
}
continue
}
if err := handleMsg(cfg.Message)(d); err != nil {
log.Printf("Message: %v", err)
if err := stompConn.Nack(m); err != nil {
log.Printf("attempting to nack unhandled message: %v", err)
}
continue
}
if err := stompConn.Ack(m); err != nil {
log.Printf("attempting to ack handled message: %v", err)
continue
}
stompBackoff.Reset()
}
}
}