add caching for topic content db calls (Postgres only)

[websub-hub] / src / db / postgres / index.js

diff --git a/src/db/postgres/index.js b/src/db/postgres/index.js
index d02d98165360f33819e220b195e3af0d18c26cd2..e6b5f5b391b9fbb29992b834b6a6a6ad6dde1bd5 100644 (file)
--- a/src/db/postgres/index.js
+++ b/src/db/postgres/index.js
@@ -10,6 +10,7 @@ const pgp = require('pg-promise')(pgpInitOptions);
 const svh = require('../schema-version-helper');
 const Database = require('../base');
 const DBErrors = require('../errors');
+const Listener = require('./listener');
 const common = require('../../common');
 
 const _fileScope = common.fileScope(__filename);
@@ -43,10 +44,23 @@ class DatabasePostgres extends Database {
     // Suppress QF warnings when running tests
     this.noWarnings = options.db.noWarnings;
 
+    if (options.db.cacheEnabled) {
+      this.listener = new Listener(logger, this.db, Object.assign({}, options.db.listener, {
+        channel: 'topic_changed',
+        dataCallback: this._topicChanged.bind(this),
+        connectionEstablishedCallback: this._listenerEstablished.bind(this),
+        connectionLostCallback: this._listenerLost.bind(this),
+      }));
+    }
+
     // Log queries
     const queryLogLevel = options.db.queryLogLevel;
     if (queryLogLevel) {
       pgpInitOptions.query = (event) => {
+        // Quell outgoing pings
+        if (event && event.query && event.query.startsWith('NOTIFY')) {
+          return;
+        }
         this.logger[queryLogLevel](_fileScope('pgp:query'), '', { ...common.pick(event, ['query', 'params']) });
       };
     }
@@ -69,6 +83,10 @@ class DatabasePostgres extends Database {
         }
       }
       if (queryLogLevel) {
+        // Quell outgoing pings
+        if (result && result.command === 'NOTIFY') {
+          return;
+        }
         // Omitting .rows
         const resultLog = common.pick(result, ['command', 'rowCount', 'duration']);
         this.logger[queryLogLevel](_fileScope('pgp:result'), '', { query: event.query, ...resultLog });
@@ -86,6 +104,7 @@ class DatabasePostgres extends Database {
   _queryFileHelper(_pgp) {
     return (file) => {
       const _scope = _fileScope('_queryFile');
+      /* istanbul ignore next */
       const qfParams = {
         minify: true,
         ...(this.noWarnings && { noWarnings: this.noWarnings }),
@@ -107,6 +126,9 @@ class DatabasePostgres extends Database {
       await this._initTables();
     }
     await super.initialize();
+    if (this.listener) {
+      await this.listener.start();
+    }
   }
 
 
@@ -173,6 +195,9 @@ class DatabasePostgres extends Database {
   async _closeConnection() {
     const _scope = _fileScope('_closeConnection');
     try {
+      if (this.listener) {
+        await this.listener.stop();
+      }
       await this._pgp.end();
     } catch (e) {
       this.logger.error(_scope, 'failed', { error: e });
@@ -181,6 +206,7 @@ class DatabasePostgres extends Database {
   }
 
   
+  /* istanbul ignore next */
   async _purgeTables(really = false) {
     const _scope = _fileScope('_purgeTables');
     try {
@@ -219,6 +245,77 @@ class DatabasePostgres extends Database {
   }
 
 
+  /**
+   * Receive notices when topic entry is updated.
+   * Clear relevant cache entry.
+   * @param {String} payload
+   */
+  _topicChanged(payload) {
+    const _scope = _fileScope('_topicChanged');
+    if (payload !== 'ping') {
+      this.logger.debug(_scope, 'called', { payload });
+      this.cache.delete(payload);
+    }
+  }
+
+
+  /**
+   * Called when a listener connection is opened.
+   * Enable cache.
+   */
+  _listenerEstablished() {
+    const _scope = _fileScope('_listenerEstablished');
+    this.logger.debug(_scope, 'called', {});
+    this.cache = new Map();
+  }
+
+
+  /**
+   * Called when a listener connection is closed.
+   * Disable cache.
+   */
+  _listenerLost() {
+    const _scope = _fileScope('_listenerLost');
+    this.logger.debug(_scope, 'called', {});
+    delete this.cache;
+  }
+
+
+  /**
+   * Return a cached entry, if available.
+   * @param {*} key
+   */
+  _cacheGet(key) {
+    const _scope = _fileScope('_cacheGet');
+    if (this.cache && this.cache.has(key)) {
+      const cacheEntry = this.cache.get(key);
+      this.logger.debug(_scope, 'found cache entry', { key, ...common.pick(cacheEntry, ['added', 'hits', 'lastHit']) });
+      cacheEntry.hits += 1;
+      cacheEntry.lastHit = new Date();
+      return cacheEntry.data;
+    }
+  }
+
+
+  /**
+   * Store an entry in cache, if available.
+   * @param {*} key
+   * @param {*} data
+   */
+  _cacheSet(key, data) {
+    const _scope = _fileScope('_cacheSet');
+    if (this.cache) {
+      this.cache.set(key, {
+        added: new Date(),
+        hits: 0,
+        lastHit: undefined,
+        data,
+      });
+      this.logger.debug(_scope, 'added cache entry', { key });
+    }
+  }
+
+
   async context(fn) {
     return this.db.task(async (t) => fn(t));
   }
@@ -692,8 +789,14 @@ class DatabasePostgres extends Database {
 
     let topic;
     try {
+      topic = this._cacheGet(topicId);
+      if (topic) {
+        return topic;
+      }
       topic = await dbCtx.oneOrNone(this.statement.topicGetContentById, { topicId });
-      return this._topicDefaults(topic);
+      const topicWithDefaults = this._topicDefaults(topic);
+      this._cacheSet(topicId, topicWithDefaults);
+      return topicWithDefaults;
     } catch (e) {
       this.logger.error(_scope, 'failed', { error: e, topic, topicId });
       throw e;