X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/9f45d7dd8adfac9a2f690de6a0831498cff5512f..80a90301263f46ebb7b26297093763882f2cf582:/sdk/go/arvadosclient/pool.go

diff --git a/sdk/go/arvadosclient/pool.go b/sdk/go/arvadosclient/pool.go
index 1c5893aa31..bb7867aef7 100644
--- a/sdk/go/arvadosclient/pool.go
+++ b/sdk/go/arvadosclient/pool.go
@@ -1,39 +1,83 @@
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package arvadosclient
 
 import (
 	"sync"
+
+	"git.arvados.org/arvados.git/sdk/go/arvados"
 )
 
+// A ClientPool is a pool of ArvadosClients. This is useful for
+// applications that make API calls using a dynamic set of tokens,
+// like web services that pass through their own clients'
+// 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 copying this one.
+	Prototype *ArvadosClient
+
+	pool      *sync.Pool
+	lastErr   error
+	setupOnce sync.Once
 }
 
+// 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
+	return MakeClientPoolWith(nil)
+}
+
+// MakeClientPoolWith returns a new empty ClientPool with a previously
+// initialized arvados.Client.
+func MakeClientPoolWith(client *arvados.Client) *ClientPool {
+	var err error
+	var proto *ArvadosClient
+
+	if client == nil {
+		proto, err = MakeArvadosClient()
+	} else {
+		proto, err = New(client)
+	}
+	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
+// nil.
 func (p *ClientPool) Err() error {
 	return p.lastErr
 }
 
+// Get returns an ArvadosClient taken from the pool, or a new one if
+// the pool is empty. If an existing client is returned, its state
+// (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
 	}
 	return c
 }
 
+// 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)
 }