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// Package state provides cross-process state tracking for hakurei container instances.
package state
import (
"strconv"
"hakurei.app/container/check"
"hakurei.app/hst"
"hakurei.app/internal/lockedfile"
"hakurei.app/message"
)
/* this provides an implementation of Store on top of the improved state tracking to ease in the changes */
type Store interface {
// Do calls f exactly once and ensures store exclusivity until f returns.
// Returns whether f is called and any errors during the locking process.
// Cursor provided to f becomes invalid as soon as f returns.
Do(identity int, f func(c Cursor)) (ok bool, err error)
// List queries the store and returns a list of identities known to the store.
// Note that some or all returned identities might not have any active apps.
List() (identities []int, err error)
}
// NewMulti returns an instance of the multi-file store.
func NewMulti(msg message.Msg, prefix *check.Absolute) Store {
store := &stateStore{msg: msg, base: prefix.Append("state")}
store.fileMu = lockedfile.MutexAt(store.base.Append(storeMutexName).String())
return store
}
// Cursor provides access to the store of an identity.
type Cursor interface {
Save(state *hst.State) error
Destroy(id hst.ID) error
Load() (map[hst.ID]*hst.State, error)
Len() (int, error)
}
// do implements stateStore.Do on storeHandle.
func (h *storeHandle) do(f func(c Cursor)) (bool, error) {
if unlock, err := h.fileMu.Lock(); err != nil {
return false, &hst.AppError{Step: "acquire lock on store segment " + strconv.Itoa(h.identity), Err: err}
} else {
defer unlock()
}
f(h)
return true, nil
}
/* these compatibility methods must only be called while fileMu is held */
func (h *storeHandle) Save(state *hst.State) error {
return (&stateEntryHandle{nil, h.path.Append(state.ID.String()), state.ID}).save(state)
}
func (h *storeHandle) Destroy(id hst.ID) error {
return (&stateEntryHandle{nil, h.path.Append(id.String()), id}).destroy()
}
func (h *storeHandle) Load() (map[hst.ID]*hst.State, error) {
entries, n, err := h.entries()
if err != nil {
return nil, err
}
r := make(map[hst.ID]*hst.State, n)
for eh := range entries {
if eh.decodeErr != nil {
err = eh.decodeErr
break
}
var s hst.State
if _, err = eh.load(&s); err != nil {
break
}
r[eh.ID] = &s
}
return r, err
}
func (h *storeHandle) Len() (int, error) {
entries, _, err := h.entries()
if err != nil {
return -1, err
}
var n int
for eh := range entries {
if eh.decodeErr != nil {
err = eh.decodeErr
}
n++
}
return n, err
}
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