download.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package configstore abstracts interaction with the telemetry config server.
     6  // Telemetry config (golang.org/x/telemetry/config) is distributed as a go
     7  // module containing go.mod and config.json. Programs that upload collected
     8  // counters download the latest config using `go mod download`. This provides
     9  // verification of downloaded configuration and cacheability.
    10  package configstore
    11  
    12  import (
    13  	"bytes"
    14  	"encoding/json"
    15  	"fmt"
    16  	"os"
    17  	"os/exec"
    18  	"path/filepath"
    19  	"sync/atomic"
    20  
    21  	"golang.org/x/telemetry/internal/telemetry"
    22  )
    23  
    24  const (
    25  	ModulePath     = "golang.org/x/telemetry/config"
    26  	configFileName = "config.json"
    27  )
    28  
    29  // needNoConsole is used on windows to set the windows.CREATE_NO_WINDOW
    30  // creation flag.
    31  var needNoConsole = func(cmd *exec.Cmd) {}
    32  
    33  var downloads int64
    34  
    35  // Downloads reports, for testing purposes, the number of times [Download] has
    36  // been called.
    37  func Downloads() int64 {
    38  	return atomic.LoadInt64(&downloads)
    39  }
    40  
    41  // Download fetches the requested telemetry UploadConfig using "go mod
    42  // download". If envOverlay is provided, it is appended to the environment used
    43  // for invoking the go command.
    44  //
    45  // The second result is the canonical version of the requested configuration.
    46  func Download(version string, envOverlay []string) (*telemetry.UploadConfig, string, error) {
    47  	atomic.AddInt64(&downloads, 1)
    48  
    49  	if version == "" {
    50  		version = "latest"
    51  	}
    52  	modVer := ModulePath + "@" + version
    53  	var stdout, stderr bytes.Buffer
    54  	cmd := exec.Command("go", "mod", "download", "-json", modVer)
    55  	needNoConsole(cmd)
    56  	cmd.Env = append(os.Environ(), envOverlay...)
    57  	cmd.Stdout = &stdout
    58  	cmd.Stderr = &stderr
    59  	if err := cmd.Run(); err != nil {
    60  		var info struct {
    61  			Error string
    62  		}
    63  		if err := json.Unmarshal(stdout.Bytes(), &info); err == nil && info.Error != "" {
    64  			return nil, "", fmt.Errorf("failed to download config module: %v", info.Error)
    65  		}
    66  		return nil, "", fmt.Errorf("failed to download config module: %w\n%s", err, &stderr)
    67  	}
    68  
    69  	var info struct {
    70  		Dir     string
    71  		Version string
    72  		Error   string
    73  	}
    74  	if err := json.Unmarshal(stdout.Bytes(), &info); err != nil || info.Dir == "" {
    75  		return nil, "", fmt.Errorf("failed to download config module (invalid JSON): %w", err)
    76  	}
    77  	data, err := os.ReadFile(filepath.Join(info.Dir, configFileName))
    78  	if err != nil {
    79  		return nil, "", fmt.Errorf("invalid config module: %w", err)
    80  	}
    81  	cfg := new(telemetry.UploadConfig)
    82  	if err := json.Unmarshal(data, cfg); err != nil {
    83  		return nil, "", fmt.Errorf("invalid config: %w", err)
    84  	}
    85  	return cfg, info.Version, nil
    86  }
    87
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