/
statemanager.go
175 lines (159 loc) · 4.8 KB
/
statemanager.go
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// Copyright 2020 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.
package relation
import (
"fmt"
"sync"
"github.com/juju/collections/set"
"github.com/juju/errors"
"github.com/juju/names/v5"
"github.com/kr/pretty"
"gopkg.in/yaml.v2"
"github.com/juju/juju/rpc/params"
)
// NewStateManager creates a new StateManager instance.
func NewStateManager(rw UnitStateReadWriter, logger Logger) (StateManager, error) {
mgr := &stateManager{unitStateRW: rw, logger: logger}
return mgr, mgr.initialize()
}
type stateManager struct {
unitStateRW UnitStateReadWriter
relationState map[int]State
logger Logger
mu sync.Mutex
}
// Relation returns a copy of the relation state for
// the given id. Returns NotFound.
func (m *stateManager) Relation(id int) (*State, error) {
m.mu.Lock()
defer m.mu.Unlock()
if s, ok := m.relationState[id]; ok {
return s.copy(), nil
}
return nil, errors.NotFoundf("relation %d", id)
}
// RemoveRelation removes the state for the given id from the
// manager. The change to the manager is only made when the
// data is successfully saved.
func (m *stateManager) RemoveRelation(id int, unitGetter UnitGetter, knownUnits map[string]bool) error {
m.mu.Lock()
defer m.mu.Unlock()
st, ok := m.relationState[id]
if !ok {
return errors.NotFoundf("relation %d", id)
}
// Check that the member unit exists - if not we ignore it.
// Cache the known member units so we only do any look up once per unit.
knownMembers := set.NewStrings()
for unitName := range st.Members {
unitExists, ok := knownUnits[unitName]
if !ok {
_, err := unitGetter.Unit(names.NewUnitTag(unitName))
if err != nil && !params.IsCodeNotFoundOrCodeUnauthorized(err) {
return errors.Trace(err)
}
unitExists = err == nil
knownUnits[unitName] = unitExists
}
if !unitExists {
m.logger.Warningf("unit %v in relation %d no longer exists", unitName, id)
continue
}
knownMembers.Add(unitName)
}
if knownMembers.Size() != 0 {
return errors.New(fmt.Sprintf("cannot remove persisted state, relation %d has members: %v", id, knownMembers.SortedValues()))
}
if err := m.remove(id); err != nil {
return err
}
delete(m.relationState, id)
return nil
}
// KnownIDs returns a slice of relation ids, known to the
// state manager.
func (m *stateManager) KnownIDs() []int {
m.mu.Lock()
defer m.mu.Unlock()
ids := make([]int, len(m.relationState))
// 0 is a valid id, and it's the initial value of an int
// ensure the only 0 is the slice should be there.
i := 0
for k := range m.relationState {
ids[i] = k
i += 1
}
return ids
}
// SetRelation persists the given state, overwriting the previous
// state for a given id or creating state at a new id. The change to
// the manager is only made when the data is successfully saved.
func (m *stateManager) SetRelation(st *State) error {
m.mu.Lock()
defer m.mu.Unlock()
if err := m.write(st); err != nil {
return errors.Annotatef(err, "could not persist relation %d state", st.RelationId)
}
m.relationState[st.RelationId] = *st
return nil
}
// RelationFound returns true if the state manager has a
// state for the given id.
func (m *stateManager) RelationFound(id int) bool {
m.mu.Lock()
defer m.mu.Unlock()
_, ok := m.relationState[id]
return ok
}
// initialize loads the current state into the manager.
func (m *stateManager) initialize() error {
unitState, err := m.unitStateRW.State()
if err != nil && !errors.IsNotFound(err) {
return errors.Trace(err)
}
m.relationState = make(map[int]State, len(unitState.RelationState))
if m.logger.IsTraceEnabled() {
m.logger.Tracef("initialising state manager: %# v", pretty.Formatter(unitState.RelationState))
}
for k, v := range unitState.RelationState {
var state State
if err = yaml.Unmarshal([]byte(v), &state); err != nil {
return errors.Annotatef(err, "cannot unmarshall relation %d state", k)
}
m.relationState[k] = state
}
return nil
}
func (m *stateManager) write(st *State) error {
newSt, err := m.stateToPersist()
if err != nil {
return errors.Trace(err)
}
str, err := st.YamlString()
if err != nil {
return errors.Trace(err)
}
newSt[st.RelationId] = str
return m.unitStateRW.SetState(params.SetUnitStateArg{RelationState: &newSt})
}
func (m *stateManager) remove(id int) error {
newSt, err := m.stateToPersist()
if err != nil {
return errors.Trace(err)
}
delete(newSt, id)
return m.unitStateRW.SetState(params.SetUnitStateArg{RelationState: &newSt})
}
// stateToPersist transforms the relationState of this manager
// into a form used for UnitStateReadWriter SetState.
func (m *stateManager) stateToPersist() (map[int]string, error) {
newSt := make(map[int]string, len(m.relationState))
for k, v := range m.relationState {
str, err := v.YamlString()
if err != nil {
return newSt, errors.Trace(err)
}
newSt[k] = str
}
return newSt, nil
}