terraform/builtin/provisioners/local-exec/resource_provisioner.go

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package localexec
import (
"context"
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"fmt"
"io"
"os"
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"os/exec"
"runtime"
"github.com/armon/circbuf"
"github.com/hashicorp/terraform/helper/schema"
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"github.com/hashicorp/terraform/terraform"
"github.com/mitchellh/go-linereader"
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)
const (
// maxBufSize limits how much output we collect from a local
// invocation. This is to prevent TF memory usage from growing
// to an enormous amount due to a faulty process.
maxBufSize = 8 * 1024
)
func Provisioner() terraform.ResourceProvisioner {
return &schema.Provisioner{
Schema: map[string]*schema.Schema{
"command": &schema.Schema{
Type: schema.TypeString,
Required: true,
},
},
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ApplyFunc: applyFn,
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}
}
func applyFn(ctx context.Context) error {
data := ctx.Value(schema.ProvConfigDataKey).(*schema.ResourceData)
o := ctx.Value(schema.ProvOutputKey).(terraform.UIOutput)
command := data.Get("command").(string)
if command == "" {
return fmt.Errorf("local-exec provisioner command must be a non-empty string")
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}
// Execute the command using a shell
var shell, flag string
if runtime.GOOS == "windows" {
shell = "cmd"
flag = "/C"
} else {
shell = "/bin/sh"
flag = "-c"
}
// Setup the reader that will read the output from the command.
// We use an os.Pipe so that the *os.File can be passed directly to the
// process, and not rely on goroutines copying the data which may block.
// See golang.org/issue/18874
pr, pw, err := os.Pipe()
if err != nil {
return fmt.Errorf("failed to initialize pipe for output: %s", err)
}
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// Setup the command
cmd := exec.CommandContext(ctx, shell, flag, command)
cmd.Stderr = pw
cmd.Stdout = pw
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output, _ := circbuf.NewBuffer(maxBufSize)
// Write everything we read from the pipe to the output buffer too
tee := io.TeeReader(pr, output)
// copy the teed output to the UI output
copyDoneCh := make(chan struct{})
go copyOutput(o, tee, copyDoneCh)
// Output what we're about to run
o.Output(fmt.Sprintf(
"Executing: %s %s \"%s\"",
shell, flag, command))
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// Start the command
err = cmd.Start()
if err == nil {
err = cmd.Wait()
}
// Close the write-end of the pipe so that the goroutine mirroring output
// ends properly.
pw.Close()
// Cancelling the command may block the pipe reader if the file descriptor
// was passed to a child process which hasn't closed it. In this case the
// copyOutput goroutine will just hang out until exit.
select {
case <-copyDoneCh:
case <-ctx.Done():
}
if err != nil {
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return fmt.Errorf("Error running command '%s': %v. Output: %s",
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command, err, output.Bytes())
}
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return nil
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}
func copyOutput(o terraform.UIOutput, r io.Reader, doneCh chan<- struct{}) {
defer close(doneCh)
lr := linereader.New(r)
for line := range lr.Ch {
o.Output(line)
}
}