Make LoadBalancer purge connections

Purging moved from `RoutingDriver` to the `LoadBalancer` to keep one place
where we remove address from the routing table and purge all
connections to it.

Author: lutovich

src/v1/internal/connection-providers.js

@@ -67,6 +67,7 @@ export class LoadBalancer extends ConnectionProvider {
 
   forget(address) {
     this._routingTable.forget(address);
+    this._connectionPool.purge(address);
   }
 
   forgetWriter(address) {
@@ -115,6 +116,7 @@ export class LoadBalancer extends ConnectionProvider {
       });
     }, Promise.resolve(null));
 
+    // todo: who removes the final router when all routers fail?
     return refreshedTablePromise.then(newRoutingTable => {
       if (newRoutingTable && !newRoutingTable.writers.isEmpty()) {
         this._updateRoutingTable(newRoutingTable);

src/v1/routing-driver.js

@@ -39,10 +39,10 @@ class RoutingDriver extends Driver {
     return new RoutingSession(connectionPromise, (error, conn) => {
       if (error.code === SERVICE_UNAVAILABLE || error.code === SESSION_EXPIRED) {
         if (conn) {
-          this._forget(conn.url)
+          this._connectionProvider.forget(conn.url);
         } else {
           connectionPromise.then((conn) => {
-            this._forget(conn.url);
+            this._connectionProvider.forget(conn.url);
           }).catch(() => {/*ignore*/});
         }
         return error;
@@ -63,11 +63,6 @@ class RoutingDriver extends Driver {
     });
   }
 
-  _forget(url) {
-    this._connectionProvider.forget(url);
-    this._pool.purge(url);
-  }
-
   static _validateConfig(config) {
     if(config.trust === 'TRUST_ON_FIRST_USE') {
       throw newError('The chosen trust mode is not compatible with a routing driver');

test/internal/connection-providers.test.js

@@ -77,6 +77,28 @@ describe('LoadBalancer', () => {
     );
   });
 
+  it('purges connections when address is forgotten', () => {
+    const pool = newPool();
+
+    pool.acquire('server-1');
+    pool.acquire('server-3');
+    pool.acquire('server-5');
+    expectPoolToContain(pool, ['server-1', 'server-3', 'server-5']);
+
+    const loadBalancer = newLoadBalancer(
+      ['server-1', 'server-2'],
+      ['server-3', 'server-2'],
+      ['server-2', 'server-4'],
+      pool
+    );
+
+    loadBalancer.forget('server-1');
+    loadBalancer.forget('server-5');
+
+    expectPoolToContain(pool, ['server-3']);
+    expectPoolToNotContain(pool, ['server-1', 'server-5']);
+  });
+
   it('can forget writer address', () => {
     const loadBalancer = newLoadBalancer(
       ['server-1', 'server-2'],
@@ -550,6 +572,12 @@ function expectRoutingTable(loadBalancer, routers, readers, writers) {
   expect(loadBalancer._routingTable.writers.toArray()).toEqual(writers);
 }
 
+function expectPoolToContain(pool, addresses) {
+  addresses.forEach(address => {
+    expect(pool.has(address)).toBeTruthy();
+  });
+}
+
 function expectPoolToNotContain(pool, addresses) {
   addresses.forEach(address => {
     expect(pool.has(address)).toBeFalsy();