// NewLedgerClosePump starts a background proc that continually watches the
// history database provided. The watch is stopped after the provided context
// is cancelled.
//
// Every second, the proc spawned by calling this func will check to see
// if a new ledger has been imported (by ruby-horizon as of 2015-04-30, but
// should eventually end up being in this project). If a new ledger is seen
// the the channel returned by this function emits
func NewLedgerClosePump(ctx context.Context, db *sql.DB) <-chan time.Time {
result := make(chan time.Time)
go func() {
var lastSeenLedger int32
for {
select {
case <-time.After(1 * time.Second):
var latestLedger int32
row := db.QueryRow("SELECT MAX(sequence) FROM history_ledgers")
err := row.Scan(&latestLedger)
if err != nil {
log.Warn(ctx, "Failed to check latest ledger", err)
break
}
if latestLedger > lastSeenLedger {
log.Debugf(ctx, "saw new ledger: %d, prev: %d", latestLedger, lastSeenLedger)
lastSeenLedger = latestLedger
result <- time.Now()
}
case <-ctx.Done():
log.Info(ctx, "canceling ledger pump")
return
}
}
}()
return result
}
// clearSliceIfPossible is a utility function that clears a slice if the
// provided interface wraps one. In the event that `dest` is not a pointer to a
// slice this func will fail with a warning, this allowing the forthcoming db
// select fail more concretely due to an incompatible destination.
func (r *Repo) clearSliceIfPossible(dest interface{}) {
v := reflect.ValueOf(dest)
vt := v.Type()
if vt.Kind() != reflect.Ptr {
log.Warn("cannot clear slice: dest is not pointer")
return
}
if vt.Elem().Kind() != reflect.Slice {
log.Warn("cannot clear slice: dest is a pointer, but not to a slice")
return
}
reflect.Indirect(v).SetLen(0)
}
// NewLedgerClosePump starts a background proc that continually watches the
// history database provided. The watch is stopped after the provided context
// is cancelled.
//
// Every second, the proc spawned by calling this func will check to see
// if a new ledger has been imported (by ruby-horizon as of 2015-04-30, but
// should eventually end up being in this project). If a new ledger is seen
// the the channel returned by this function emits
func NewLedgerClosePump(ctx context.Context, db *sqlx.DB) <-chan struct{} {
result := make(chan struct{})
go func() {
var lastSeenLedger int32
for {
select {
case <-time.After(1 * time.Second):
var latestLedger int32
row := db.QueryRow(MaxHistoryLedger)
err := row.Scan(&latestLedger)
if err != nil {
log.Warn(ctx, "Failed to check latest ledger", err)
break
}
if latestLedger > lastSeenLedger {
log.Debugf(ctx, "saw new ledger: %d, prev: %d", latestLedger, lastSeenLedger)
select {
case result <- struct{}{}:
lastSeenLedger = latestLedger
default:
log.Debug(ctx, "ledger pump channel is blocked. waiting...")
}
} else if latestLedger < lastSeenLedger {
log.Warn(ctx, "latest ledger went backwards! reseting ledger pump")
lastSeenLedger = 0
}
case <-ctx.Done():
log.Info(ctx, "canceling ledger pump")
close(result)
return
}
}
}()
return result
}
// NewLedgerClosePump starts a background proc that continually watches the
// history database provided. The watch is stopped after the provided context
// is cancelled.
//
// Every second, the proc spawned by calling this func will check to see
// if a new ledger has been imported (by ruby-horizon as of 2015-04-30, but
// should eventually end up being in this project). If a new ledger is seen
// the the channel returned by this function emits
func NewLedgerClosePump(ctx context.Context, q *history.Q) <-chan struct{} {
result := make(chan struct{})
go func() {
var lastSeenLedger int32
for {
select {
case <-time.After(1 * time.Second):
var latestLedger int32
err := q.LatestLedger(&latestLedger)
if err != nil {
log.Warn("Failed to check latest ledger", err)
continue
}
if latestLedger > lastSeenLedger {
log.Debugf("saw new ledger: %d, prev: %d", latestLedger, lastSeenLedger)
select {
case result <- struct{}{}:
lastSeenLedger = latestLedger
default:
log.Debug("ledger pump channel is blocked. waiting...")
}
} else if latestLedger < lastSeenLedger {
log.Warn("latest ledger went backwards! reseting ledger pump")
lastSeenLedger = 0
}
case <-ctx.Done():
log.Info("canceling ledger pump")
close(result)
return
}
}
}()
return result
}