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get-free-port: prevent duplicate ports on Linux (#564)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,84 +1,95 @@ | ||
| // The MIT License | ||
| // | ||
| // Copyright (c) 2022 Temporal Technologies Inc. All rights reserved. | ||
| // | ||
| // Copyright (c) 2020 Uber Technologies, Inc. | ||
| // | ||
| // Copyright (c) 2021 Datadog, Inc. | ||
| // | ||
| // Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| // of this software and associated documentation files (the "Software"), to deal | ||
| // in the Software without restriction, including without limitation the rights | ||
| // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| // copies of the Software, and to permit persons to whom the Software is | ||
| // furnished to do so, subject to the following conditions: | ||
| // | ||
| // The above copyright notice and this permission notice shall be included in | ||
| // all copies or substantial portions of the Software. | ||
| // | ||
| // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
| // THE SOFTWARE. | ||
|
|
||
| package devserver | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "net" | ||
| "runtime" | ||
| ) | ||
|
|
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| // Modified from https://github.com/phayes/freeport/blob/95f893ade6f232a5f1511d61735d89b1ae2df543/freeport.go | ||
|
|
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| func MustGetFreePort() int { | ||
| p := NewPortProvider() | ||
| defer p.Close() | ||
| return p.MustGetFreePort() | ||
| } | ||
|
|
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| func NewPortProvider() *PortProvider { | ||
| return &PortProvider{} | ||
| } | ||
|
|
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| type PortProvider struct { | ||
| listeners []*net.TCPListener | ||
| } | ||
|
|
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| // GetFreePort asks the kernel for a free open port that is ready to use. | ||
| func (p *PortProvider) GetFreePort() (int, error) { | ||
| addr, err := net.ResolveTCPAddr("tcp", "127.0.0.1:0") | ||
| // Returns a TCP port that is available to listen on, for the given (local) host. | ||
| // | ||
| // This works by binding a new TCP socket on port 0, which requests the OS to | ||
| // allocate a free port. There is no strict guarantee that the port will remain | ||
| // available after this function returns, but it should be safe to assume that | ||
| // a given port will not be allocated again to any process on this machine | ||
| // within a few seconds. | ||
| // | ||
| // On Unix-based systems, binding to the port returned by this function requires | ||
| // setting the `SO_REUSEADDR` socket option (Go already does that by default, | ||
| // but other languages may not); otherwise, the OS may fail with a message such | ||
| // as "address already in use". Windows default behavior is already appropriate | ||
| // in this regard; on that platform, `SO_REUSEADDR` has a different meaning and | ||
| // should not be set (setting it may have unpredictable consequences). | ||
| func GetFreePort(host string) (int, error) { | ||
| l, err := net.Listen("tcp", host+":0") | ||
| if err != nil { | ||
| if addr, err = net.ResolveTCPAddr("tcp6", "[::1]:0"); err != nil { | ||
| panic(fmt.Sprintf("temporal: failed to get free port: %v", err)) | ||
| } | ||
| return 0, fmt.Errorf("failed to assign a free port: %v", err) | ||
| } | ||
| defer l.Close() | ||
| port := l.Addr().(*net.TCPAddr).Port | ||
|
|
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| l, err := net.ListenTCP("tcp", addr) | ||
| if err != nil { | ||
| return 0, err | ||
| // On Linux and some BSD variants, ephemeral ports are randomized, and may | ||
| // consequently repeat within a short time frame after the listenning end | ||
| // has been closed. To avoid this, we make a connection to the port, then | ||
| // close that connection from the server's side (this is very important), | ||
| // which puts the connection in TIME_WAIT state for some time (by default, | ||
| // 60s on Linux). While it remains in that state, the OS will not reallocate | ||
| // that port number for bind(:0) syscalls, yet we are not prevented from | ||
| // explicitly binding to it (thanks to SO_REUSEADDR). | ||
| // | ||
| // On macOS and Windows, the above technique is not necessary, as the OS | ||
| // allocates ephemeral ports sequentially, meaning a port number will only | ||
| // be reused after the entire range has been exhausted. Quite the opposite, | ||
| // given that these OSes use a significantly smaller range for ephemeral | ||
| // ports, making an extra connection just to reserve a port might actually | ||
| // be harmful (by hastening ephemeral port exhaustion). | ||
| if runtime.GOOS != "darwin" && runtime.GOOS != "windows" { | ||
| r, err := net.DialTCP("tcp", nil, l.Addr().(*net.TCPAddr)) | ||
| if err != nil { | ||
| return 0, fmt.Errorf("failed to assign a free port: %v", err) | ||
| } | ||
| c, err := l.Accept() | ||
| if err != nil { | ||
| return 0, fmt.Errorf("failed to assign a free port: %v", err) | ||
| } | ||
| // Closing the socket from the server side | ||
| c.Close() | ||
| defer r.Close() | ||
| } | ||
|
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| p.listeners = append(p.listeners, l) | ||
|
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| return l.Addr().(*net.TCPAddr).Port, nil | ||
| return port, nil | ||
| } | ||
|
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| func (p *PortProvider) MustGetFreePort() int { | ||
| port, err := p.GetFreePort() | ||
| // Returns a TCP port that is available to listen on, for the given (local) | ||
| // host; panics if no port is available. | ||
| // | ||
| // This works by binding a new TCP socket on port 0, which requests the OS to | ||
| // allocate a free port. There is no strict guarantee that the port will remain | ||
| // available after this function returns, but it should be safe to assume that | ||
| // a given port will not be allocated again to any process on this machine | ||
| // within a few seconds. | ||
| // | ||
| // On Unix-based systems, binding to the port returned by this function requires | ||
| // setting the `SO_REUSEADDR` socket option (Go already does that by default, | ||
| // but other languages may not); otherwise, the OS may fail with a message such | ||
| // as "address already in use". Windows default behavior is already appropriate | ||
| // in this regard; on that platform, `SO_REUSEADDR` has a different meaning and | ||
| // should not be set (setting it may have unpredictable consequences). | ||
| func MustGetFreePort(host string) int { | ||
| port, err := GetFreePort(host) | ||
| if err != nil { | ||
| panic(err) | ||
| panic(fmt.Errorf("failed assigning ephemeral port: %w", err)) | ||
| } | ||
| return port | ||
| } | ||
|
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| func (p *PortProvider) Close() error { | ||
| for _, l := range p.listeners { | ||
| if err := l.Close(); err != nil { | ||
| return err | ||
| } | ||
| // Asserts that the given TCP port is available to listen on, for the given | ||
| // (local) host; return an error if it is not. | ||
| func CheckPortFree(host string, port int) error { | ||
| l, err := net.Listen("tcp", fmt.Sprintf("%s:%d", host, port)) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| l.Close() | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,69 @@ | ||
| package devserver_test | ||
|
|
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| import ( | ||
| "fmt" | ||
| "net" | ||
| "testing" | ||
|
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| "github.com/temporalio/cli/temporalcli/devserver" | ||
| ) | ||
|
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| func TestFreePort_NoDouble(t *testing.T) { | ||
| host := "127.0.0.1" | ||
| portSet := make(map[int]bool) | ||
|
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| for i := 0; i < 2000; i++ { | ||
| p, err := devserver.GetFreePort(host) | ||
| if err != nil { | ||
| t.Fatalf("Error: %s", err) | ||
| break | ||
| } | ||
|
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| if _, exists := portSet[p]; exists { | ||
| t.Fatalf("Port %d has been assigned more than once", p) | ||
| } | ||
|
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| // Add port to the set | ||
| portSet[p] = true | ||
| } | ||
| } | ||
|
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| func TestFreePort_CanBindImmediatelySameProcess(t *testing.T) { | ||
| host := "127.0.0.1" | ||
|
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| for i := 0; i < 500; i++ { | ||
| p, err := devserver.GetFreePort(host) | ||
| if err != nil { | ||
| t.Fatalf("Error: %s", err) | ||
| break | ||
| } | ||
| err = tryListenAndDialOn(host, p) | ||
| if err != nil { | ||
| t.Fatalf("Error: %s", err) | ||
| break | ||
| } | ||
| } | ||
| } | ||
|
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| // This function is used as part of unit tests, to ensure that the port | ||
| func tryListenAndDialOn(host string, port int) error { | ||
| l, err := net.Listen("tcp", fmt.Sprintf("%s:%d", host, port)) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer l.Close() | ||
|
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| r, err := net.DialTCP("tcp", nil, l.Addr().(*net.TCPAddr)) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| defer r.Close() | ||
|
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| c, err := l.Accept() | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| defer c.Close() | ||
|
|
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| return nil | ||
| } |
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