Improve purge address of the Pool routine

packages/bolt-connection/src/pool/pool.js

@@ -300,16 +300,18 @@ class Pool {
   async _purgeKey (key) {
     const pool = this._pools[key] || []
     const poolState = this._poolState[key] || new PoolState()
+    const destructionList = []
     while (pool.length) {
       const resource = pool.pop()
       if (this._removeIdleObserver) {
         this._removeIdleObserver(resource)
       }
-      await this._destroy(resource)
+      destructionList.push(this._destroy(resource))
     }
     poolState.close()
     delete this._pools[key]
     delete this._poolState[key]
+    await Promise.all(destructionList)
   }
 
   _processPendingAcquireRequests (address) {

packages/bolt-connection/test/pool/pool.test.js

@@ -923,6 +923,43 @@ describe('#unit Pool', () => {
     expect(resource1.observer).toBeFalsy()
     expect(resource2.observer).toBeFalsy()
   })
+
+  it('should purge resources in parallel', async () => {
+    const address = ServerAddress.fromUrl('bolt://localhost:7687')
+    let resourceCount = 0
+    const resourcesReleased = []
+    let resolveRelease 
+    const releasePromise = new Promise((resolve) => {
+      resolveRelease = resolve
+    })
+
+    const pool = new Pool({
+      create: (server, release) => 
+        Promise.resolve(new Resource(server, resourceCount++, release)),
+      destroy: res => {
+        resourcesReleased.push(res)
+        resourceCount--
+        // Only destroy when the last resource
+        // get destroyed
+        if (resourceCount === 0) {
+          resolveRelease()
+        }
+        return releasePromise
+      },
+      validate: res => true,
+    })
+
+    const resource1 = await pool.acquire(address)
+    const resource2 = await pool.acquire(address)
+    await resource1.close()
+    await resource2.close()
+
+    await pool.purge(address)
+
+    expect(resourcesReleased).toEqual([
+      resource2, resource1
+    ])
+  })
 })
 
 function expectNoPendingAcquisitionRequests (pool) {