mirror of https://github.com/status-im/consul.git
89 lines
2.1 KiB
Go
89 lines
2.1 KiB
Go
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package agent
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import (
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"bytes"
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"encoding/json"
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"fmt"
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"io"
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"log"
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"os"
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"os/exec"
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"runtime"
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"strconv"
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"github.com/armon/circbuf"
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"github.com/hashicorp/consul/watch"
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)
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const (
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// Limit the size of a watch handlers's output to the
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// last WatchBufSize. Prevents an enormous buffer
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// from being captured
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WatchBufSize = 4 * 1024 // 4KB
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)
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// verifyWatchHandler does the pre-check for our handler configuration
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func verifyWatchHandler(params interface{}) error {
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if params == nil {
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return fmt.Errorf("Must provide watch handler")
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}
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_, ok := params.(string)
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if !ok {
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return fmt.Errorf("Watch handler must be a string")
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}
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return nil
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}
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// makeWatchHandler returns a handler for the given watch
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func makeWatchHandler(logOutput io.Writer, params interface{}) watch.HandlerFunc {
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script := params.(string)
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logger := log.New(logOutput, "", log.LstdFlags)
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fn := func(idx uint64, data interface{}) {
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// Determine the shell invocation based on OS
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var shell, flag string
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if runtime.GOOS == "windows" {
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shell = "cmd"
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flag = "/C"
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} else {
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shell = "/bin/sh"
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flag = "-c"
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}
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// Create the command
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cmd := exec.Command(shell, flag, script)
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cmd.Env = append(os.Environ(),
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"CONSUL_INDEX="+strconv.FormatUint(idx, 10),
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)
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// Collect the output
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output, _ := circbuf.NewBuffer(WatchBufSize)
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cmd.Stdout = output
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cmd.Stderr = output
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// Setup the input
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var inp bytes.Buffer
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enc := json.NewEncoder(&inp)
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if err := enc.Encode(data); err != nil {
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logger.Printf("[ERR] agent: Failed to encode data for watch '%s': %v", script, err)
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return
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}
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cmd.Stdin = &inp
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// Run the handler
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if err := cmd.Run(); err != nil {
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logger.Printf("[ERR] agent: Failed to invoke watch handler '%s': %v", script, err)
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}
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// Get the output, add a message about truncation
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outputStr := string(output.Bytes())
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if output.TotalWritten() > output.Size() {
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outputStr = fmt.Sprintf("Captured %d of %d bytes\n...\n%s",
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output.Size(), output.TotalWritten(), outputStr)
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}
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// Log the output
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logger.Printf("[DEBUG] agent: watch handler '%s' output: %s", script, outputStr)
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}
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return fn
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}
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