PLT-7503: Create Message Export Scheduled Task and CLI Command (#7612)

* Created message export scheduled task

* Added CLI command to immediately kick off an export job

* Added email addresses for users joining and leaving the channel to the export

* Added support for both MySQL and PostgreSQL

* Fixing gofmt error

* Added a new ChannelMemberHistory store and associated tests

* Updating the ChannelMemberHistory channel as users create/join/leave channels

* Added user email to the message export object so it can be included in the actiance export xml

* Don't fail to log a leave event if a corresponding join event wasn't logged

* Adding copyright notices

* Adding message export settings to daily diagnostics report

* Added System Console integration for message export

* Cleaned up TODOs

* Made batch size configurable

* Added export from timestamp to CLI command

* Made ChannelMemberHistory table updates best effort

* Added a context-based timeout option to the message export CLI

* Minor PR updates/improvements

* Removed unnecessary fields from MessageExport object to reduce query overhead

* Removed JSON functions from the message export query in an effort to optimize performance

* Changed the way that channel member history queries and purges work to better account for edge cases

* Fixing a test I missed with the last refactor

* Added file copy functionality to file backend, improved config validation, added default config values

* Fixed file copy tests

* More concise use of the testing libraries

* Fixed context leak error

* Changed default export path to correctly place an 'export' directory under the 'data' directory

* Can't delete records from a read replica

* Fixed copy file tests

* Start job workers when license is applied, if configured to do so

* Suggestions from the PR

* Moar unit tests

* Fixed test imports

cmd/platform/message_export_test.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package main
+
+import (
+	"testing"
+
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/utils"
+	"github.com/stretchr/testify/require"
+)
+
+// There are no tests that actually run the Message Export job, because it can take a long time to complete depending
+// on the size of the database that the config is pointing to. As such, these tests just ensure that the CLI command
+// fails fast if invalid flags are supplied
+
+func TestMessageExportNotEnabled(t *testing.T) {
+	configPath := writeTempConfig(t, false)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because the feature isn't enabled
+	require.Error(t, runCommand(t, "--config", configPath, "export"))
+}
+
+func TestMessageExportInvalidFormat(t *testing.T) {
+	configPath := writeTempConfig(t, true)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because format isn't supported
+	require.Error(t, runCommand(t, "--config", configPath, "--format", "not_actiance", "export"))
+}
+
+func TestMessageExportNegativeExportFrom(t *testing.T) {
+	configPath := writeTempConfig(t, true)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because export from must be a valid timestamp
+	require.Error(t, runCommand(t, "--config", configPath, "--format", "actiance", "--exportFrom", "-1", "export"))
+}
+
+func TestMessageExportNegativeTimeoutSeconds(t *testing.T) {
+	configPath := writeTempConfig(t, true)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because timeout seconds must be a positive int
+	require.Error(t, runCommand(t, "--config", configPath, "--format", "actiance", "--exportFrom", "0", "--timeoutSeconds", "-1", "export"))
+}
+
+func writeTempConfig(t *testing.T, isMessageExportEnabled bool) string {
+	dir, err := ioutil.TempDir("", "")
+	require.NoError(t, err)
+
+	utils.TranslationsPreInit()
+	config := utils.LoadGlobalConfig("config.json")
+	config.MessageExportSettings.EnableExport = model.NewBool(isMessageExportEnabled)
+	configPath := filepath.Join(dir, "foo.json")
+	require.NoError(t, ioutil.WriteFile(configPath, []byte(config.ToJson()), 0600))
+
+	return configPath
+}