(core) support setting python version of new docs with PYTHON_VERSION_ON_CREATION

Summary:
If PYTHON_VERSION_ON_CREATION is set in the environment, new documents will be created with a specific desired python version (2 or 3).

This diff commits to offering a choice of engine, so the engine for a document no longer starts to initialize until the document has been fetched and read. Staging (and dev, and testing) has been like this for a while.

Test Plan: added test; manual testing of forks/copies etc

Reviewers: dsagal, alexmojaki

Reviewed By: dsagal, alexmojaki

Differential Revision: https://phab.getgrist.com/D3119

app/server/lib/ActiveDoc.ts

@@ -84,7 +84,7 @@ import {DocStorage} from './DocStorage';
 import {expandQuery} from './ExpandedQuery';
 import {GranularAccess, GranularAccessForBundle} from './GranularAccess';
 import {OnDemandActions} from './OnDemandActions';
-import {getLogMetaFromDocSession, supportsEngineChoices, timeoutReached} from './serverUtils';
+import {getLogMetaFromDocSession, timeoutReached} from './serverUtils';
 import {findOrAddAllEnvelope, Sharing} from './Sharing';
 import cloneDeep = require('lodash/cloneDeep');
 import flatten = require('lodash/flatten');
@@ -184,20 +184,17 @@ export class ActiveDoc extends EventEmitter {
       loadTable: this._rawPyCall.bind(this, 'load_table'),
     });
 
-    // Our DataEngine is a separate sandboxed process (one per open document). The data engine runs
+    // Our DataEngine is a separate sandboxed process (one sandbox per open document,
-    // user-defined python code including formula calculations. It maintains all document data and
+    // corresponding to one process for pynbox, more for gvisor).
-    // metadata, and applies translates higher-level UserActions into lower-level DocActions.
+    // The data engine runs user-defined python code including formula calculations.
+    // It maintains all document data and metadata, and applies translates higher-level UserActions
+    // into lower-level DocActions.
 
-    // Creation of the data engine currently needs to be deferred if we support a choice of
+    // Creation of the data engine needs to be deferred since we need to look at the document to
-    // engines, since we need to look at the document to see what kind of engine it needs.
+    // see what kind of engine it needs. This doesn't delay loading the document, but could delay
-    // This doesn't delay loading the document, but does delay first calculation and modification.
+    // first calculation and modification.
-    // So if we don't offer a choice, go ahead and start creating the data engine now, so it
+    // TODO: consider caching engine requirement for doc in home db - or running python2
-    // is created in parallel to fetching the document from external storage (if needed).
+    // in gvisor (but would still need to look at doc to know what process to start in sandbox)
-    // TODO: cache engine requirement for doc in home db so we can retain this parallelism
-    // when offering a choice of data engines.
-    if (!supportsEngineChoices()) {
-      this._getEngine().catch(e => this._log.error({client: null}, `engine for ${docName} failed to launch: ${e}`));
-    }
 
     this._activeDocImport = new ActiveDocImport(this);
 
@@ -366,6 +363,11 @@ export class ActiveDoc extends EventEmitter {
   /**
    * Create a new blank document (no "Table1") using the data engine. This is used only
    * to generate the SQL saved to initialDocSql.ts
+   *
+   * It does not set documentSettings.engine.  When a document is created during normal
+   * operation, documentSettings.engine gets set after the SQL is used to seed it, in
+   * _createDocFile()
+   *
    */
   @ActiveDoc.keepDocOpen
   public async createEmptyDocWithDataEngine(docSession: OptDocSession): Promise<ActiveDoc> {
@@ -1418,8 +1420,16 @@ export class ActiveDoc extends EventEmitter {
     await this.docStorage.exec(sql);
     const timezone = docSession.browserSettings?.timezone ?? DEFAULT_TIMEZONE;
     const locale = docSession.browserSettings?.locale ?? DEFAULT_LOCALE;
+    const documentSettings: DocumentSettings = { locale };
+    const pythonVersion = process.env.PYTHON_VERSION_ON_CREATION;
+    if (pythonVersion) {
+      if (pythonVersion !== '2' && pythonVersion !== '3') {
+        throw new Error(`PYTHON_VERSION_ON_CREATION must be 2 or 3, not: ${pythonVersion}`);
+      }
+      documentSettings.engine = (pythonVersion === '2') ? 'python2' : 'python3';
+    }
     await this.docStorage.run('UPDATE _grist_DocInfo SET timezone = ?, documentSettings = ?',
-                              [timezone, JSON.stringify({locale})]);
+                              [timezone, JSON.stringify(documentSettings)]);
   }
 
   private _makeInfo(docSession: OptDocSession, options: ApplyUAOptions = {}) {
@@ -1688,8 +1698,6 @@ export class ActiveDoc extends EventEmitter {
     // Figure out what kind of engine we need for this document.
     let preferredPythonVersion: '2' | '3' = process.env.PYTHON_VERSION === '3' ? '3' : '2';
 
-    // Currently only respect engine preference on experimental deployments (staging/dev).
-    if (process.env.GRIST_EXPERIMENTAL_PLUGINS === '1') {
     // Careful, migrations may not have run on this document and it may not have a
     // documentSettings column.  Failures are treated as lack of an engine preference.
     const docInfo = await this.docStorage.get('SELECT documentSettings FROM _grist_DocInfo').catch(e => undefined);
@@ -1707,7 +1715,6 @@ export class ActiveDoc extends EventEmitter {
         }
       }
     }
-    }
     return this._docManager.gristServer.create.NSandbox({
       comment: this._docName,
       logCalls: false,

app/server/lib/serverUtils.ts

@@ -161,10 +161,3 @@ export function getSupportedEngineChoices(): EngineCode[]|undefined {
   }
   return undefined;
 }
-
-/**
- * Check whether a choice of engine is supported.
- */
-export function supportsEngineChoices(): boolean {
-  return getSupportedEngineChoices() !== undefined;
-}