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import { AgedCompareFunc, compareAscending, IAgedValue } from '../queue/IAgedQueue';
import { Logger } from '../shared/Logger';
import { IDisposable } from '../shared/IDisposable';
import {
IStorageHierarchy,
StorageHierarchyUpdatePolicy,
IStorageHierarchyWrite,
} from './IStorageHierarchy';
import {
StorageProviderUpdateHandler,
isISubscribableStorageProvider,
} from './ISubscribableStorageProvider';
type SubscriberUpdateHandler<TKey, TValue> = (
key: TKey,
value?: IAgedValue<TValue>
) => Promise<boolean>;
/**
* The default storage hierarchy implementation relying on IStorageProvider for actual data access
*/
export class StorageHierarchy<TKey, TValue>
implements IStorageHierarchy<TKey, TValue>, IDisposable
{
readonly totalLevels = this.levels.length;
readonly isPersistable = this.levels[this.totalLevels - 1].isPersistable;
private readonly logger = Logger.get(StorageHierarchy.name);
private readonly storageChangedHandlers = new Map<
number,
StorageProviderUpdateHandler<TKey, TValue>
>();
private readonly pendingUpdates: Set<Promise<void>> = new Set();
private readonly topLevel = this.levels[this.totalLevels - 1];
private readonly publishLevel?: number;
/**
* @param levels The levels in the hierarchy with index 0 being the lowest level (first to read)
* @param updatePolicy How updates from subscribed higher level storage providers should be handled
*/
constructor(
private readonly levels: IStorageProvider<TKey, TValue>[],
private readonly updatePolicy: StorageHierarchyUpdatePolicy = StorageHierarchyUpdatePolicy.OnlyIfKeyExist,
private readonly ageCompareFunc: AgedCompareFunc = compareAscending
) {
Iif (levels.length < 2) {
throw new Error('StorageHierarchy must have at least 2 storage provider');
}
this.logger.info(`Created storage hierarchy with levels: ${this.totalLevels}`);
this.publishLevel = this.subscribeAtLevel(this.totalLevels - 1);
}
/**
* Clean up the object when it's no longer used. After a dispose(), an object
* is no longer guaranteed to be usable.
*/
public dispose(): Promise<void> {
this.storageChangedHandlers.forEach((handler, level) => {
const currentLevel = this.levels[level];
if (isISubscribableStorageProvider(currentLevel)) {
currentLevel.unsubscribe(handler);
}
this.storageChangedHandlers.delete(level);
});
return Promise.all(this.pendingUpdates).then(() => undefined);
}
/**
* @param key The key to retrieve
* @param level The level at which to retrieve the key
* @param isAscending To go up the hierarchy (true) or down (false) from level
* @returns The value if it's in the hierarchy from the level going up/down or null
*/
public getAtLevel(
key: TKey,
level?: number,
isAscending = true
): Promise<IAgedValue<TValue> | null> {
const rLevel = this.getCurrentLevelOrNull(isAscending, level);
if (rLevel === null) {
return Promise.resolve(null);
}
return this.levels[rLevel]
.get(key)
.then(agedValue => {
if (agedValue) {
return agedValue;
} else {
this.logger.debug(`Cache miss: level=${rLevel}, key=${key}`);
return this.getAtLevel(key, isAscending ? rLevel + 1 : rLevel - 1, isAscending);
}
})
.catch(error => {
this.logger.debug(`Failed to Get: level=${rLevel}, key=${key}, error=${error}`);
return this.getAtLevel(key, isAscending ? rLevel + 1 : rLevel - 1, isAscending);
});
}
/**
* @param key The key to set
* @param value The value to set
* @param level The level at which to set the key
* @param isAscending To go up the hierarchy (true) or down (false) from level
* @returns If the write succeeded to all levels going up/down or the error condition
*/
public setAtLevel(
key: TKey,
value: IAgedValue<TValue>,
level?: number,
isAscending = false
): Promise<IStorageHierarchyWrite<TValue>> {
const rLevel = this.getCurrentLevelOrNull(isAscending, level);
if (rLevel === null) {
return Promise.resolve(this.getFullWriteStatus(value));
}
return this.levels[rLevel]
.set(key, value)
.then(valueWritten => {
if (valueWritten !== null) {
return this.setAtLevel(
key,
valueWritten,
isAscending ? rLevel + 1 : rLevel - 1,
isAscending
);
}
return this.getPartialWriteStatus(isAscending, rLevel, value);
})
.catch(error => {
this.logger.warn(`Error setting: level=${rLevel}, key=${key}, error=${error}`);
return this.getPartialWriteStatus(isAscending, rLevel, value);
});
}
/**
* @param key The key to delete
* @param level The level at which to delete the key
* @param isAscending To go up the hierarchy (true) or down (false) from level
* @returns If the write succeeded to all levels going up/down or the error condition
*/
public deleteAtLevel(
key: TKey,
level?: number,
isAscending = false,
writtenValue?: IAgedValue<TValue>
): Promise<IStorageHierarchyWrite<TValue>> {
const rLevel = this.getCurrentLevelOrNull(isAscending, level);
if (rLevel === null) {
return Promise.resolve(this.getFullWriteStatus(writtenValue));
}
return this.levels[rLevel]
.delete(key)
.then(isSuccessful => {
if (isSuccessful) {
return this.deleteAtLevel(key, isAscending ? rLevel + 1 : rLevel - 1, isAscending);
}
return this.getPartialWriteStatus(isAscending, rLevel, writtenValue);
})
.catch(error => {
this.logger.warn(`Error deleting: level=${rLevel}, key=${key}, error=${error}`);
return this.getPartialWriteStatus(isAscending, rLevel, writtenValue);
});
}
/**
* @param level The level at which to search
* @return The number of keys at the specified level
*/
public getSizeAtLevel(level: number): Promise<number> {
return this.levels[level].size();
}
/**
* @returns The keys a the top level (should be all keys across the entire hierarchy)
*/
public getKeysAtTopLevel(): Promise<TKey[]> {
return this.topLevel.keys();
}
/**
* @param key The key to retrieve
* @returns The value at the top level only or null
*/
public getValueAtTopLevel(key: TKey): Promise<IAgedValue<TValue> | null> {
return this.getAtLevel(key, this.totalLevels - 1);
}
/**
* @param key The key to retrieve
* @returns The value at the bottom level only or null
*/
public getValueAtBottomLevel(key: TKey): Promise<IAgedValue<TValue> | null> {
return this.getAtLevel(key, 0, false);
}
/**
* Set only the levels below the top level (for refresing from the top level for instance)
* @param key The key to set
* @param value The value to set
* @returns If the write succeeded to all levels going up/down or the error condition
*/
public setBelowTopLevel(
key: TKey,
value: IAgedValue<TValue>
): Promise<IStorageHierarchyWrite<TValue>> {
return this.setAtLevel(key, value, this.totalLevels - 2);
}
private subscribeAtLevel(level: number, publishLevel?: number): number | undefined {
if (level <= 0) {
return publishLevel;
}
const nextLevel = level - 1;
const currentLevel = this.levels[level];
if (isISubscribableStorageProvider(currentLevel)) {
this.logger.debug(`subscribe to level: ${level}`);
let handler = this.getUpdateHandlerAlways(nextLevel);
if (this.updatePolicy === StorageHierarchyUpdatePolicy.OnlyIfKeyExist) {
handler = this.getUpdateHandlerOnlyIfKeyExist(nextLevel, handler);
}
const wrappedHandler = this.getManagedPromiseSubscribe(handler);
currentLevel.subscribe(wrappedHandler);
this.storageChangedHandlers.set(level, wrappedHandler);
if (!publishLevel) {
publishLevel = level;
}
}
return this.subscribeAtLevel(nextLevel, publishLevel);
}
private getCurrentLevelOrNull(isAscending: boolean, level?: number): number | null {
level = level === undefined ? (isAscending ? 0 : this.totalLevels - 1) : level;
if (isAscending && level >= this.totalLevels) {
return null;
} else if (!isAscending && level < 0) {
return null;
} else {
return level;
}
}
private getUpdateHandlerAlways(updateLevel: number) {
return (key: TKey, value?: IAgedValue<TValue>): Promise<boolean> => {
if (value) {
return this.setAtLevel(key, value, updateLevel).then(
s => s.writtenLevels === this.totalLevels
);
} else {
return this.deleteAtLevel(key, updateLevel).then(s => s.writtenLevels === this.totalLevels);
}
};
}
private getUpdateHandlerOnlyIfKeyExist(
updateLevel: number,
updateUnconditionally: SubscriberUpdateHandler<TKey, TValue>
) {
return (key: TKey, value?: IAgedValue<TValue>): Promise<boolean> => {
return this.getAtLevel(key, updateLevel, false).then(agedValue => {
if (agedValue) {
Iif (value !== undefined && this.ageCompareFunc(agedValue.age, value.age) >= 0) {
return Promise.resolve(true);
}
return updateUnconditionally(key, value);
}
this.logger.debug(`Key doesn't exist, ignoring subscribed update: ${key}`);
return Promise.resolve(false);
});
};
}
private getManagedPromiseSubscribe(func: SubscriberUpdateHandler<TKey, TValue>) {
return (key: TKey, value?: IAgedValue<TValue>): void => {
const promise = func(key, value).then(() => {
this.pendingUpdates.delete(promise);
});
this.pendingUpdates.add(promise);
};
}
private getPartialWriteStatus(
isAscending: boolean,
level: number,
value?: IAgedValue<TValue>
): IStorageHierarchyWrite<TValue> {
const writtenLevels = isAscending ? level : this.totalLevels - level - 1;
return {
isPersisted: !isAscending && level <= this.totalLevels - 2 && this.topLevel.isPersistable,
isPublished:
this.publishLevel !== undefined &&
(isAscending ? level > this.publishLevel : level < this.publishLevel),
writtenLevels,
writtenValue: writtenLevels !== 0 ? value : undefined,
};
}
private getFullWriteStatus(value?: IAgedValue<TValue>): IStorageHierarchyWrite<TValue> {
return {
isPersisted: this.topLevel.isPersistable,
isPublished: this.publishLevel !== undefined,
writtenLevels: this.totalLevels,
writtenValue: value,
};
}
}
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