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Merge pull request #4410 from Enrico204/restic-stdin-command
add --stdin-from-command flag to backup command
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,14 @@ | ||
| Enhancement: Support reading backup from a program's standard output | ||
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| When reading data from stdin, the `backup` command could not verify whether the | ||
| corresponding command completed successfully. | ||
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| The `backup` command now supports starting an arbitrary command and sourcing | ||
| the backup content from its standard output. This enables restic to verify that | ||
| the command completes with exit code zero. A non-zero exit code causes the | ||
| backup to fail. | ||
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| Example: `restic backup --stdin-from-command mysqldump [...]` | ||
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| https://github.com/restic/restic/issues/4251 | ||
| https://github.com/restic/restic/pull/4410 |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| package fs | ||
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| import ( | ||
| "bufio" | ||
| "context" | ||
| "fmt" | ||
| "io" | ||
| "os/exec" | ||
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| "github.com/restic/restic/internal/errors" | ||
| ) | ||
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| // CommandReader wrap a command such that its standard output can be read using | ||
| // a io.ReadCloser. Close() waits for the command to terminate, reporting | ||
| // any error back to the caller. | ||
| type CommandReader struct { | ||
| cmd *exec.Cmd | ||
| stdout io.ReadCloser | ||
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| // cmd.Wait() must only be called once. Prevent duplicate executions in | ||
| // Read() and Close(). | ||
| waitHandled bool | ||
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| // alreadyClosedReadErr is the error that we should return if we try to | ||
| // read the pipe again after closing. This works around a Read() call that | ||
| // is issued after a previous Read() with `io.EOF` (but some bytes were | ||
| // read in the past). | ||
| alreadyClosedReadErr error | ||
| } | ||
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| func NewCommandReader(ctx context.Context, args []string, logOutput io.Writer) (*CommandReader, error) { | ||
| // Prepare command and stdout | ||
| command := exec.CommandContext(ctx, args[0], args[1:]...) | ||
| stdout, err := command.StdoutPipe() | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to setup stdout pipe: %w", err) | ||
| } | ||
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| // Use a Go routine to handle the stderr to avoid deadlocks | ||
| stderr, err := command.StderrPipe() | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to setup stderr pipe: %w", err) | ||
| } | ||
| go func() { | ||
| sc := bufio.NewScanner(stderr) | ||
| for sc.Scan() { | ||
| _, _ = fmt.Fprintf(logOutput, "subprocess %v: %v\n", command.Args[0], sc.Text()) | ||
| } | ||
| }() | ||
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| if err := command.Start(); err != nil { | ||
| return nil, fmt.Errorf("failed to start command: %w", err) | ||
| } | ||
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| return &CommandReader{ | ||
| cmd: command, | ||
| stdout: stdout, | ||
| }, nil | ||
| } | ||
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| // Read populate the array with data from the process stdout. | ||
| func (fp *CommandReader) Read(p []byte) (int, error) { | ||
| if fp.alreadyClosedReadErr != nil { | ||
| return 0, fp.alreadyClosedReadErr | ||
| } | ||
| b, err := fp.stdout.Read(p) | ||
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| // If the error is io.EOF, the program terminated. We need to check the | ||
| // exit code here because, if the program terminated with no output, the | ||
| // error in `Close()` is ignored. | ||
| if errors.Is(err, io.EOF) { | ||
| fp.waitHandled = true | ||
| // check if the command terminated successfully, If not return the error. | ||
| if errw := fp.wait(); errw != nil { | ||
| err = errw | ||
| } | ||
| } | ||
| fp.alreadyClosedReadErr = err | ||
| return b, err | ||
| } | ||
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| func (fp *CommandReader) wait() error { | ||
| err := fp.cmd.Wait() | ||
| if err != nil { | ||
| // Use a fatal error to abort the snapshot. | ||
| return errors.Fatal(fmt.Errorf("command failed: %w", err).Error()) | ||
| } | ||
| return nil | ||
| } | ||
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| func (fp *CommandReader) Close() error { | ||
| if fp.waitHandled { | ||
| return nil | ||
| } | ||
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| return fp.wait() | ||
| } |
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