feat: add postgres pool error handler (typeorm#4474)

Add option to customize pool error handling. Users can decide to log these errors with higher level (eg. error), crash application or reconnect.

docs/connection-options.md

@@ -180,6 +180,8 @@ See [SSL options](https://github.com/mysqljs/mysql#ssl-options).
 
 * `uuidExtension` - The Postgres extension to use when generating UUIDs. Defaults to `uuid-ossp`. Can be changed to `pgcrypto` if the `uuid-ossp` extension is unavailable.
 
+* `poolErrorHandler` - A function that get's called when underlying pool emits `'error'` event. Takes single parameter (error instance) and defaults to logging with `warn` level.
+
 ## `sqlite` connection options
 
 * `database` - Database path. For example "./mydb.sql"
@@ -258,6 +260,8 @@ See [SSL options](https://github.com/mysqljs/mysql#ssl-options).
 * `pool.idleTimeoutMillis` -  the minimum amount of time that an object may sit idle in the pool before it is eligible for
  eviction due to idle time. Supersedes `softIdleTimeoutMillis`. Default: `30000`.
 
+ * `pool.errorHandler` - A function that get's called when underlying pool emits `'error'` event. Takes single parameter (error instance) and defaults to logging with `warn` level.
+
 * `options.fallbackToDefaultDb` - By default, if the database requestion by `options.database` cannot be accessed, the connection
  will fail with an error. However, if `options.fallbackToDefaultDb` is set to `true`, then the user's default database will
   be used instead (Default: `false`).

src/driver/cockroachdb/CockroachConnectionOptions.ts

@@ -33,4 +33,11 @@ export interface CockroachConnectionOptions extends BaseConnectionOptions, Cockr
 
     };
 
+
+    /*
+    * Function handling errors thrown by drivers pool.
+    * Defaults to logging error with `warn` level.
+     */
+    readonly poolErrorHandler?: (err: any) => any;
+
 }

src/driver/cockroachdb/CockroachDriver.ts

@@ -710,11 +710,14 @@ export class CockroachDriver implements Driver {
         // create a connection pool
         const pool = new this.postgres.Pool(connectionOptions);
         const { logger } = this.connection;
+
+        const poolErrorHandler = options.poolErrorHandler || ((error: any) => logger.log("warn", `Postgres pool raised an error. ${error}`));
+
         /*
           Attaching an error handler to pool errors is essential, as, otherwise, errors raised will go unhandled and
           cause the hosting app to crash.
          */
-        pool.on("error", (error: any) => logger.log("warn", `Postgres pool raised an error. ${error}`));
+        pool.on("error", poolErrorHandler);
 
         return new Promise((ok, fail) => {
             pool.connect((err: any, connection: any, release: Function) => {

src/driver/postgres/PostgresConnectionOptions.ts

@@ -39,4 +39,11 @@ export interface PostgresConnectionOptions extends BaseConnectionOptions, Postgr
      * If uuid-ossp is selected, TypeORM will use the uuid_generate_v4() function from this extension.
      */
     readonly uuidExtension?: "pgcrypto" | "uuid-ossp";
+
+
+    /*
+    * Function handling errors thrown by drivers pool.
+    * Defaults to logging error with `warn` level.
+     */
+    readonly poolErrorHandler?: (err: any) => any;
 }

src/driver/postgres/PostgresDriver.ts

@@ -894,11 +894,14 @@ export class PostgresDriver implements Driver {
         // create a connection pool
         const pool = new this.postgres.Pool(connectionOptions);
         const { logger } = this.connection;
+
+        const poolErrorHandler = options.poolErrorHandler || ((error: any) => logger.log("warn", `Postgres pool raised an error. ${error}`));
+
         /*
           Attaching an error handler to pool errors is essential, as, otherwise, errors raised will go unhandled and
           cause the hosting app to crash.
          */
-        pool.on("error", (error: any) => logger.log("warn", `Postgres pool raised an error. ${error}`));
+        pool.on("error", poolErrorHandler);
 
         return new Promise((ok, fail) => {
             pool.connect((err: any, connection: any, release: Function) => {

src/driver/sqlserver/SqlServerConnectionOptions.ts

@@ -106,6 +106,12 @@ export interface SqlServerConnectionOptions extends BaseConnectionOptions, SqlSe
          * to idle time. Supercedes softIdleTimeoutMillis Default: 30000
          */
         readonly idleTimeoutMillis?: number;
+
+        /*
+        * Function handling errors thrown by drivers pool.
+        * Defaults to logging error with `warn` level.
+         */
+        readonly errorHandler?: (err: any) => any;
     };
 
     /**
@@ -271,4 +277,5 @@ export interface SqlServerConnectionOptions extends BaseConnectionOptions, SqlSe
 
     };
 
+
 }

src/driver/sqlserver/SqlServerDriver.ts

@@ -749,11 +749,13 @@ export class SqlServerDriver implements Driver {
             const pool = new this.mssql.ConnectionPool(connectionOptions);
 
             const { logger } = this.connection;
+
+            const poolErrorHandler = (options.pool && options.pool.errorHandler) || ((error: any) => logger.log("warn", `MSSQL pool raised an error. ${error}`));
             /*
               Attaching an error handler to pool errors is essential, as, otherwise, errors raised will go unhandled and
               cause the hosting app to crash.
              */
-            pool.on("error", (error: any) => logger.log("warn", `MSSQL pool raised an error. ${error}`));
+            pool.on("error", poolErrorHandler);
 
             const connection = pool.connect((err: any) => {
                 if (err) return fail(err);