Merge branch '8784-dir-listings'

[arvados.git] / sdk / go / arvadosclient / pool.go

diff --git a/sdk/go/arvadosclient/pool.go b/sdk/go/arvadosclient/pool.go
index 87b67c39b67c6f3ee95a165f9cc50f83ba5be3a7..732080770b31bdbece62be480004b129c50cf4a4 100644 (file)
--- a/sdk/go/arvadosclient/pool.go
+++ b/sdk/go/arvadosclient/pool.go
@@ -1,3 +1,7 @@
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package arvadosclient
 
 import (
@@ -10,22 +14,32 @@ import (
 // credentials. See arvados-git-httpd for an example, and sync.Pool
 // for more information about garbage collection.
 type ClientPool struct {
-       sync.Pool
-       lastErr error
+       // Initialize new clients by coping this one.
+       Prototype *ArvadosClient
+
+       pool      *sync.Pool
+       lastErr   error
+       setupOnce sync.Once
 }
 
-// MakeClientPool returns a new empty ClientPool.
+// MakeClientPool returns a new empty ClientPool, using environment
+// variables to initialize the prototype.
 func MakeClientPool() *ClientPool {
-       p := &ClientPool{}
-       p.Pool = sync.Pool{New: func() interface{} {
-               arv, err := MakeArvadosClient()
-               if err != nil {
-                       p.lastErr = err
+       proto, err := MakeArvadosClient()
+       return &ClientPool{
+               Prototype: proto,
+               lastErr:   err,
+       }
+}
+
+func (p *ClientPool) setup() {
+       p.pool = &sync.Pool{New: func() interface{} {
+               if p.lastErr != nil {
                        return nil
                }
-               return &arv
+               c := *p.Prototype
+               return &c
        }}
-       return p
 }
 
 // Err returns the error that was encountered last time Get returned
@@ -39,7 +53,8 @@ func (p *ClientPool) Err() error {
 // (including its ApiToken) will be just as it was when it was Put
 // back in the pool.
 func (p *ClientPool) Get() *ArvadosClient {
-       c, ok := p.Pool.Get().(*ArvadosClient)
+       p.setupOnce.Do(p.setup)
+       c, ok := p.pool.Get().(*ArvadosClient)
        if !ok {
                return nil
        }
@@ -48,5 +63,6 @@ func (p *ClientPool) Get() *ArvadosClient {
 
 // Put puts an ArvadosClient back in the pool.
 func (p *ClientPool) Put(c *ArvadosClient) {
-       p.Pool.Put(c)
+       p.setupOnce.Do(p.setup)
+       p.pool.Put(c)
 }