Merge branch 'patch-1' of https://github.com/mr-c/arvados into mr-c-patch-1

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

diff --git a/sdk/go/arvadosclient/pool.go b/sdk/go/arvadosclient/pool.go
index 1c5893aa319b82bcd5663d6bf22653c43c9afe6d..bb7867aef7e35d283c5e47adb68873492bda609c 100644 (file)
--- 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)
 }