pip-services3-components-node/obj/src/cache/MemoryCache.js

Component definitions for Pip.Services in Node.js

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.MemoryCache = void 0;
const CacheEntry_1 = require("./CacheEntry");
/**
 * Cache that stores values in the process memory.
 *
 * Remember: This implementation is not suitable for synchronization of distributed processes.
 *
 * ### Configuration parameters ###
 *
 * __options:__
 * - timeout:               default caching timeout in milliseconds (default: 1 minute)
 * - max_size:              maximum number of values stored in this cache (default: 1000)
 *
 * @see [[ICache]]
 *
 * ### Example ###
 *
 *     let cache = new MemoryCache();
 *
 *     cache.store("123", "key1", "ABC", (err) => {
 *         cache.store("123", "key1", (err, value) => {
 *             // Result: "ABC"
 *         });
 *     });
 *
 */
class MemoryCache {
    /**
     * Creates a new instance of the cache.
     */
    constructor() {
        this._cache = {};
        this._count = 0;
        this._timeout = 60000;
        this._maxSize = 1000;
    }
    /**
     * Configures component by passing configuration parameters.
     *
     * @param config    configuration parameters to be set.
     */
    configure(config) {
        this._timeout = config.getAsLongWithDefault("options.timeout", this._timeout);
        this._maxSize = config.getAsLongWithDefault("options.max_size", this._maxSize);
    }
    /**
     * Clears component state.
     *
     * @param correlationId 	(optional) transaction id to trace execution through call chain.
     * @param callback 			callback function that receives error or null no errors occured.
     */
    cleanup() {
        let oldest = null;
        let now = new Date().getTime();
        this._count = 0;
        // Cleanup obsolete entries and find the oldest
        for (var prop in this._cache) {
            let entry = this._cache[prop];
            // Remove obsolete entry
            if (entry.isExpired()) {
                delete this._cache[prop];
            }
            // Count the remaining entry 
            else {
                this._count++;
                if (oldest == null || oldest.getExpiration() > entry.getExpiration())
                    oldest = entry;
            }
        }
        // Remove the oldest if cache size exceeded maximum
        if (this._count > this._maxSize && oldest != null) {
            delete this._cache[oldest.getKey()];
            this._count--;
        }
    }
    /**
     * Retrieves cached value from the cache using its key.
     * If value is missing in the cache or expired it returns null.
     *
     * @param correlationId     (optional) transaction id to trace execution through call chain.
     * @param key               a unique value key.
     * @param callback          callback function that receives cached value or error.
     */
    retrieve(correlationId, key, callback) {
        if (key == null) {
            let err = new Error('Key cannot be null');
            callback(err, null);
            return;
        }
        // Get entry from the cache
        let entry = this._cache[key];
        // Cache has nothing
        if (entry == null) {
            callback(null, null);
            return;
        }
        // Remove entry if expiration set and entry is expired
        if (this._timeout > 0 && entry.isExpired()) {
            delete this._cache[key];
            this._count--;
            callback(null, null);
            return;
        }
        callback(null, entry.getValue());
    }
    /**
     * Stores value in the cache with expiration time.
     *
     * @param correlationId     (optional) transaction id to trace execution through call chain.
     * @param key               a unique value key.
     * @param value             a value to store.
     * @param timeout           expiration timeout in milliseconds.
     * @param callback          (optional) callback function that receives an error or null for success
     */
    store(correlationId, key, value, timeout, callback) {
        if (key == null) {
            let err = new Error('Key cannot be null');
            if (callback)
                callback(err, null);
            return;
        }
        // Get the entry
        let entry = this._cache[key];
        // Shortcut to remove entry from the cache
        if (value == null) {
            if (entry != null) {
                delete this._cache[key];
                this._count--;
            }
            if (callback)
                callback(null, value);
            return;
        }
        timeout = timeout != null && timeout > 0 ? timeout : this._timeout;
        // Update the entry
        if (entry) {
            entry.setValue(value, timeout);
        }
        // Or create a new entry 
        else {
            entry = new CacheEntry_1.CacheEntry(key, value, timeout);
            this._cache[key] = entry;
            this._count++;
        }
        // Clean up the cache
        if (this._maxSize > 0 && this._count > this._maxSize)
            this.cleanup();
        if (callback)
            callback(null, value);
    }
    /**
     * Removes a value from the cache by its key.
     *
     * @param correlationId     (optional) transaction id to trace execution through call chain.
     * @param key               a unique value key.
     * @param callback          (optional) callback function that receives an error or null for success
     */
    remove(correlationId, key, callback) {
        if (key == null) {
            let err = new Error('Key cannot be null');
            if (callback)
                callback(err);
            return;
        }
        // Get the entry
        let entry = this._cache[key];
        // Remove entry from the cache
        if (entry != null) {
            delete this._cache[key];
            this._count--;
        }
        if (callback)
            callback(null);
    }
}
exports.MemoryCache = MemoryCache;
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