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117 lines
4.0 KiB
Markdown
117 lines
4.0 KiB
Markdown
# "pastebin" SDK Example
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This `pastebin` example is a minimal `zrok` SDK application that implements a wormhole that makes redirecting file contents between multiple `zrok` environments very easy.
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The `pastebin` example is split into two separate commands. The `copyto` command takes a copy buffer from standard input. You can use it like this:
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```
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$ echo "this is a pastebin test" | copyto
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access your pastebin using 'pastefrom b46p9j82z81f'
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```
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And then using another terminal window, you can access your pastebin data like this:
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```
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$ pastefrom b46p9j82z81f
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this is a pastebin test
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```
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## The `copyto` Implementation
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The `copyto` utility is an illustration of how to implement an application that creates a share and exposes it to the `zrok` network. Let's look at each section of the implementation:
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```go
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data, err := loadData()
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if err != nil {
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panic(err)
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}
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```
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This first block of code is responsible for calling the `loadData` function, which loads the pastebin with data from `os.Stdin`.
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All SDK applications need to load the user's "root" from the `environment` package, like this:
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```go
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root, err := environment.LoadRoot()
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if err != nil {
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panic(err)
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}
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```
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The `root` is a structure that contains all of the user's environment detail and allows the SDK application to access the `zrok` service instance and the underlying OpenZiti network.
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Next, `copyto` will create a `zrok` share:
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```go
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shr, err := sdk.CreateShare(root, &sdk.ShareRequest{
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BackendMode: sdk.TcpTunnelBackendMode,
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ShareMode: sdk.PrivateShareMode,
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Target: "pastebin",
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})
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if err != nil {
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panic(err)
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}
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fmt.Printf("access your pastebin using 'pastefrom %v'\n", shr.Token)
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```
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The `sdk.CreateShare` call uses the loaded `environment` root along with the details of the share request (`sdk.ShareRequest`) to create the share that will be used to access the `pastebin`.
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For the `pastebin` application, we're using a `sdk.TcpTunnelBackendMode` backend mode (we're just using a single network connection that implements a reliable byte stream, so TCP works great). Tunnel backends only work with `private` shares as of `zrok` `v0.4`, so we're using `sdk.PrivateShareMode`.
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We'll set the `Target` to be `pastebin`, as that's just metadata describing the application.
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Finally, we emit the share token so the user can access the `pastebin` using the `pastefrom` command.
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Next, we'll use the SDK to create a listener for this share:
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```go
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listener, err := sdk.NewListener(shr.Token, root)
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if err != nil {
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panic(err)
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}
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```
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The `sdk.NewListener` establishes a network listener for the newly created share. This listener works just like a `net.Listener`.
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Next, we're going to add a shutdown hook so that `copyto` will delete the share when the application is terminated using `^C`:
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```go
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c := make(chan os.Signal)
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signal.Notify(c, os.Interrupt, syscall.SIGTERM)
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go func() {
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<-c
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if err := sdk.DeleteShare(root, shr); err != nil {
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panic(err)
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}
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_ = listener.Close()
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os.Exit(0)
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}()
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```
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This anonymous function runs waiting for a signal to exit. When that is received, it runs the `sdk.DeleteShare` function to remove the share that was created. This is how ephemeral shares work for the `zrok share` commands as well.
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And finally, we run in an infinite loop waiting for requests for the `pastebin` data from the network:
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```go
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for {
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if conn, err := listener.Accept(); err == nil {
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go handle(conn, data)
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} else {
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panic(err)
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}
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}
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```
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## The "pastefrom" Implementation
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The `pastefrom` application works very similarly to `copyto`. The primary difference is that it "dials" the share through the SDK using `sdk.NewDialer`, which returns a `net.Conn`:
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```go
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conn, err := sdk.NewDialer(shrToken, root)
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if err != nil {
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panic(err)
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}
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```
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When this `sdk.NewDialer` function returns without an error, a bidirectional `net.Conn` has been established between the `copyto` "server" and the `pastefrom` "client". `pastefrom` then just reads the available data from the `net.Conn` and emits it to `os.Stdout`. |