switch to vendored singleflight (#1445)

go mod is nice and trims unused packages from large imports, so this is more
sensible to do now. we had one usage to switch to.

also removed THIRD_PARTY file, this was stale (now all 3 usages noted there
are no longer direct, either)... found this from grepping.

THIRD_PARTY

@@ -1,8 +0,0 @@
-This software uses third-party software.
-
-For: api/server/tree.go
-Copyright 2013 Julien Schmidt. All rights reserved. BSD-license
-
-For: api/server/internal/routecache/lru.go
-For: api/server/singleflight.go
-Copyright 2012 Google Inc. All rights reserved. Apache 2 license

api/agent/data_access.go

@@ -6,8 +6,8 @@ import (
 	"time"
 
 	"github.com/fnproject/fn/api/common"
-	"github.com/fnproject/fn/api/common/singleflight"
 	"github.com/fnproject/fn/api/models"
+	"github.com/golang/groupcache/singleflight"
 	"github.com/patrickmn/go-cache"
 )
 
@@ -58,7 +58,7 @@ type cachedDataAccess struct {
 	ReadDataAccess
 
 	cache        *cache.Cache
-	singleflight singleflight.SingleFlight
+	singleflight singleflight.Group
 }
 
 func NewCachedDataAccess(da ReadDataAccess) ReadDataAccess {

api/common/singleflight/singleflight.go

@@ -1,50 +0,0 @@
-package singleflight
-
-// TODO figure out how this differs?
-
-// Imported from https://github.com/golang/groupcache/blob/master/singleflight/singleflight.go
-
-import (
-	"sync"
-)
-
-// call is an in-flight or completed do call
-type call struct {
-	wg  sync.WaitGroup
-	val interface{}
-	err error
-}
-
-type SingleFlight struct {
-	mu sync.Mutex            // protects m
-	m  map[interface{}]*call // lazily initialized
-}
-
-// do executes and returns the results of the given function, making
-// sure that only one execution is in-flight for a given key at a
-// time. If a duplicate comes in, the duplicate caller waits for the
-// original to complete and receives the same results.
-func (g *SingleFlight) Do(key interface{}, fn func() (interface{}, error)) (interface{}, error) {
-	g.mu.Lock()
-	if g.m == nil {
-		g.m = make(map[interface{}]*call)
-	}
-	if c, ok := g.m[key]; ok {
-		g.mu.Unlock()
-		c.wg.Wait()
-		return c.val, c.err
-	}
-	c := new(call)
-	c.wg.Add(1)
-	g.m[key] = c
-	g.mu.Unlock()
-
-	c.val, c.err = fn()
-	c.wg.Done()
-
-	g.mu.Lock()
-	delete(g.m, key)
-	g.mu.Unlock()
-
-	return c.val, c.err
-}

go.mod

@@ -17,6 +17,7 @@ require (
 	github.com/gin-contrib/sse v0.0.0-20170109093832-22d885f9ecc7 // indirect
 	github.com/gin-gonic/gin v1.3.0
 	github.com/go-sql-driver/mysql v1.4.0
+	github.com/golang/groupcache v0.0.0-20180924190550-6f2cf27854a4
 	github.com/golang/protobuf v1.2.1-0.20190109072247-347cf4a86c1c
 	github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c
 	github.com/grpc-ecosystem/go-grpc-middleware v1.0.0

go.sum

@@ -83,6 +83,7 @@ github.com/gogo/protobuf v1.1.1 h1:72R+M5VuhED/KujmZVcIquuo8mBgX4oVda//DQb3PXo=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
+github.com/golang/groupcache v0.0.0-20180924190550-6f2cf27854a4 h1:6UVLWz0fIIrv0UVj6t0A7cL48n8IyAdLVQqAYzEfsKI=
 github.com/golang/groupcache v0.0.0-20180924190550-6f2cf27854a4/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
 github.com/golang/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:tluoj9z5200jBnyusfRPU2LqT6J+DAorxEvtC7LHB+E=
 github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=

vendor/github.com/golang/groupcache/LICENSE

@@ -0,0 +1,191 @@
+Apache License
+Version 2.0, January 2004
+http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
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+"Legal Entity" shall mean the union of the acting entity and all other entities
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+
+"You" (or "Your") shall mean an individual or Legal Entity exercising
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+"Object" form shall mean any form resulting from mechanical transformation or
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+5. Submission of Contributions.
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+Unless You explicitly state otherwise, any Contribution intentionally submitted
+for inclusion in the Work by You to the Licensor shall be under the terms and
+conditions of this License, without any additional terms or conditions.
+Notwithstanding the above, nothing herein shall supersede or modify the terms of
+any separate license agreement you may have executed with Licensor regarding
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+6. Trademarks.
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+This License does not grant permission to use the trade names, trademarks,
+service marks, or product names of the Licensor, except as required for
+reasonable and customary use in describing the origin of the Work and
+reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty.
+
+Unless required by applicable law or agreed to in writing, Licensor provides the
+Work (and each Contributor provides its Contributions) on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied,
+including, without limitation, any warranties or conditions of TITLE,
+NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are
+solely responsible for determining the appropriateness of using or
+redistributing the Work and assume any risks associated with Your exercise of
+permissions under this License.
+
+8. Limitation of Liability.
+
+In no event and under no legal theory, whether in tort (including negligence),
+contract, or otherwise, unless required by applicable law (such as deliberate
+and grossly negligent acts) or agreed to in writing, shall any Contributor be
+liable to You for damages, including any direct, indirect, special, incidental,
+or consequential damages of any character arising as a result of this License or
+out of the use or inability to use the Work (including but not limited to
+damages for loss of goodwill, work stoppage, computer failure or malfunction, or
+any and all other commercial damages or losses), even if such Contributor has
+been advised of the possibility of such damages.
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+9. Accepting Warranty or Additional Liability.
+
+While redistributing the Work or Derivative Works thereof, You may choose to
+offer, and charge a fee for, acceptance of support, warranty, indemnity, or
+other liability obligations and/or rights consistent with this License. However,
+in accepting such obligations, You may act only on Your own behalf and on Your
+sole responsibility, not on behalf of any other Contributor, and only if You
+agree to indemnify, defend, and hold each Contributor harmless for any liability
+incurred by, or claims asserted against, such Contributor by reason of your
+accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work
+
+To apply the Apache License to your work, attach the following boilerplate
+notice, with the fields enclosed by brackets "[]" replaced with your own
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+   Copyright [yyyy] [name of copyright owner]
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+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
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+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
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+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
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vendor/github.com/golang/groupcache/singleflight/singleflight.go

@@ -0,0 +1,64 @@
+/*
+Copyright 2012 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package singleflight provides a duplicate function call suppression
+// mechanism.
+package singleflight
+
+import "sync"
+
+// call is an in-flight or completed Do call
+type call struct {
+	wg  sync.WaitGroup
+	val interface{}
+	err error
+}
+
+// Group represents a class of work and forms a namespace in which
+// units of work can be executed with duplicate suppression.
+type Group struct {
+	mu sync.Mutex       // protects m
+	m  map[string]*call // lazily initialized
+}
+
+// Do executes and returns the results of the given function, making
+// sure that only one execution is in-flight for a given key at a
+// time. If a duplicate comes in, the duplicate caller waits for the
+// original to complete and receives the same results.
+func (g *Group) Do(key string, fn func() (interface{}, error)) (interface{}, error) {
+	g.mu.Lock()
+	if g.m == nil {
+		g.m = make(map[string]*call)
+	}
+	if c, ok := g.m[key]; ok {
+		g.mu.Unlock()
+		c.wg.Wait()
+		return c.val, c.err
+	}
+	c := new(call)
+	c.wg.Add(1)
+	g.m[key] = c
+	g.mu.Unlock()
+
+	c.val, c.err = fn()
+	c.wg.Done()
+
+	g.mu.Lock()
+	delete(g.m, key)
+	g.mu.Unlock()
+
+	return c.val, c.err
+}

vendor/modules.txt

@@ -103,6 +103,8 @@ github.com/go-ini/ini
 github.com/go-sql-driver/mysql
 # github.com/gogo/protobuf v1.1.1
 github.com/gogo/protobuf/proto
+# github.com/golang/groupcache v0.0.0-20180924190550-6f2cf27854a4
+github.com/golang/groupcache/singleflight
 # github.com/golang/protobuf v1.2.1-0.20190109072247-347cf4a86c1c
 github.com/golang/protobuf/ptypes/empty
 github.com/golang/protobuf/proto