Add option to cycle between multiple postgres instances

src/config.ts

@@ -1,7 +1,7 @@
 import fs from "fs";
 import { SBSConfig } from "./types/config.model";
 import packageJson from "../package.json";
-import { isBoolean, isNumber } from "lodash";
+import { isNumber } from "lodash";
 
 const isTestMode = process.env.npm_lifecycle_script === packageJson.scripts.test;
 const configFile = process.env.TEST_POSTGRES ? "ci.json"
@@ -81,6 +81,17 @@ addDefaults(config, {
             rejectUnauthorized: false
         }
     },
+    postgresReadOnly: {
+        enabled: false,
+        weight: 1,
+        user: "",
+        host: "",
+        password: "",
+        port: 5432,
+        ssl: {
+            rejectUnauthorized: false
+        }
+    },
     dumpDatabase: {
         enabled: false,
         minTimeBetweenMs: 180000,

src/databases/Postgres.ts

@@ -3,6 +3,7 @@ import { IDatabase, QueryType } from "./IDatabase";
 import { Client, Pool, PoolClient, types } from "pg";
 
 import fs from "fs";
+import { CustomPostgresConfig, CustomPostgresReadOnlyConfig } from "../types/config.model";
 
 // return numeric (pg_type oid=1700) as float
 types.setTypeParser(1700, function(val) {
@@ -14,16 +15,33 @@ types.setTypeParser(20, function(val) {
     return parseInt(val, 10);
 });
 
+export interface DatabaseConfig {
+    dbSchemaFileName: string,
+    dbSchemaFolder: string,
+    fileNamePrefix: string,
+    readOnly: boolean,
+    createDbIfNotExists: boolean,
+    postgres: CustomPostgresConfig,
+    postgresReadOnly: CustomPostgresReadOnlyConfig
+}
+
 export class Postgres implements IDatabase {
     private pool: Pool;
+    private poolRead: Pool;
 
-    constructor(private config: Record<string, any>) {}
+    constructor(private config: DatabaseConfig) {}
 
     async init(): Promise<void> {
         this.pool = new Pool(this.config.postgres);
-        this.pool.on("error", (err) => {
+        const errorHandler = (err: Error) => {
             Logger.error(err.stack);
-        });
+        };
+        this.pool.on("error", errorHandler);
+
+        if (this.config.postgresReadOnly) {
+            this.poolRead = new Pool(this.config.postgresReadOnly);
+            this.poolRead.on("error", errorHandler);
+        }
 
         if (!this.config.readOnly) {
             if (this.config.createDbIfNotExists) {
@@ -60,7 +78,7 @@ export class Postgres implements IDatabase {
 
         let client: PoolClient;
         try {
-            client = await this.pool.connect();
+            client = await this.getClient(type);
             const queryResult = await client.query({ text: query, values: params });
 
             switch (type) {
@@ -85,6 +103,15 @@ export class Postgres implements IDatabase {
         }
     }
 
+    private getClient(type: string): Promise<PoolClient> {
+        if (this.poolRead && (type === "get" || type === "all")
+                && Math.random() > 1 / (this.config.postgresReadOnly.weight + 1)) {
+            return this.poolRead.connect();
+        } else {
+            return this.pool.connect();
+        }
+    }
+
     private async createDB() {
         const client = new Client({
             ...this.config.postgres,

src/databases/databases.ts

@@ -19,7 +19,11 @@ if (config.mysql) {
         postgres: {
             ...config.postgres,
             database: "sponsorTimes",
-        }
+        },
+        postgresReadOnly: config.postgresReadOnly ? {
+            ...config.postgresReadOnly,
+            database: "sponsorTimes"
+        } : null
     });
 
     privateDB = new Postgres({
@@ -31,7 +35,11 @@ if (config.mysql) {
         postgres: {
             ...config.postgres,
             database: "privateDB"
-        }
+        },
+        postgresReadOnly: config.postgresReadOnly ? {
+            ...config.postgresReadOnly,
+            database: "privateDB"
+        } : null
     });
 } else {
     db = new Sqlite({

src/types/config.model.ts

@@ -5,10 +5,14 @@ interface RedisConfig extends redis.RedisClientOptions {
     enabled: boolean;
 }
 
-interface CustomPostgresConfig extends PoolConfig {
+export interface CustomPostgresConfig extends PoolConfig {
     enabled: boolean;
 }
 
+export interface CustomPostgresReadOnlyConfig extends CustomPostgresConfig {
+    weight: number;
+}
+
 export interface SBSConfig {
     [index: string]: any
     port: number;
@@ -51,6 +55,7 @@ export interface SBSConfig {
     redis?: RedisConfig;
     maxRewardTimePerSegmentInSeconds?: number;
     postgres?: CustomPostgresConfig;
+    postgresReadOnly?: CustomPostgresReadOnlyConfig;
     dumpDatabase?: DumpDatabase;
     diskCacheURL: string;
     crons: CronJobOptions;