added sync mutex for consistency checks and backup

services/backup.js

@@ -6,6 +6,7 @@ const fs = require('fs-extra');
 const dataDir = require('./data_dir');
 const log = require('./log');
 const sql = require('./sql');
+const sync_mutex = require('./sync_mutex');
 
 async function regularBackup() {
     const now = new Date();
@@ -21,17 +22,25 @@ async function regularBackup() {
 }
 
 async function backupNow() {
-    const now = utils.nowDate();
+    // we don't want to backup DB in the middle of sync with potentially inconsistent DB state
+    const releaseMutex = await sync_mutex.acquire();
 
-    const backupFile = dataDir.BACKUP_DIR + "/" + "backup-" + utils.getDateTimeForFile() + ".db";
+    try {
+        const now = utils.nowDate();
 
-    fs.copySync(dataDir.DOCUMENT_PATH, backupFile);
+        const backupFile = dataDir.BACKUP_DIR + "/" + "backup-" + utils.getDateTimeForFile() + ".db";
 
-    log.info("Created backup at " + backupFile);
+        fs.copySync(dataDir.DOCUMENT_PATH, backupFile);
 
-    await sql.doInTransaction(async () => {
-        await options.setOption('last_backup_date', now);
-    });
+        log.info("Created backup at " + backupFile);
+
+        await sql.doInTransaction(async () => {
+            await options.setOption('last_backup_date', now);
+        });
+    }
+    finally {
+        releaseMutex();
+    }
 }
 
 async function cleanupOldBackups() {

services/consistency_checks.js

@@ -3,6 +3,7 @@
 const sql = require('./sql');
 const log = require('./log');
 const messaging = require('./messaging');
+const sync_mutex = require('./sync_mutex');
 
 async function runCheck(query, errorText, errorList) {
     const result = await sql.getFirstColumn(query);
@@ -80,11 +81,9 @@ async function runSyncRowChecks(table, key, errorList) {
         `Missing ${table} records for existing sync rows`, errorList);
 }
 
-async function runChecks() {
+async function runAllChecks() {
     const errorList = [];
 
-    const startTime = new Date();
-
     await runCheck(`
           SELECT 
             note_id 
@@ -139,7 +138,7 @@ async function runChecks() {
           WHERE
             (SELECT COUNT(*) FROM notes_tree WHERE notes.note_id = notes_tree.note_id AND notes_tree.is_deleted = 0) = 0
             AND notes.is_deleted = 0
-    `, );
+    `,);
 
     await runCheck(`
           SELECT 
@@ -186,7 +185,24 @@ async function runChecks() {
         await checkTreeCycles(errorList);
     }
 
-    const elapsedTimeMs = new Date().getTime() - startTime.getTime();
+    return errorList;
+}
+
+async function runChecks() {
+    let errorList;
+    let elapsedTimeMs;
+    const releaseMutex = await sync_mutex.acquire();
+
+    try {
+        const startTime = new Date();
+
+        errorList = await runAllChecks();
+
+        elapsedTimeMs = new Date().getTime() - startTime.getTime();
+    }
+    finally {
+        releaseMutex();
+    }
 
     if (errorList.length > 0) {
         log.info(`Consistency checks failed (took ${elapsedTimeMs}ms) with these errors: ` + JSON.stringify(errorList));

services/sync.js

@@ -14,22 +14,13 @@ const fs = require('fs');
 const app_info = require('./app_info');
 const messaging = require('./messaging');
 const sync_setup = require('./sync_setup');
+const sync_mutex = require('./sync_mutex');
 
-let syncInProgress = false;
 let proxyToggle = true;
 let syncServerCertificate = null;
 
 async function sync() {
-    if (syncInProgress) {
-        log.info("Sync already in progress");
-
-        return {
-            success: false,
-            message: "Sync already in progress"
-        };
-    }
-
-    syncInProgress = true;
+    const releaseMutex = await sync_mutex.acquire();
 
     try {
         if (!await sql.isDbUpToDate()) {
@@ -74,7 +65,7 @@ async function sync() {
         }
     }
     finally {
-        syncInProgress = false;
+        releaseMutex();
     }
 }
 

services/sync_mutex.js

@@ -0,0 +1,8 @@
+/**
+ * Sync makes process can make data intermittently inconsistent. Processes which require strong data consistency
+ * (like consistency checks) can use this mutex to make sure sync isn't currently running.
+ */
+
+const Mutex = require('async-mutex').Mutex;
+
+module.exports = new Mutex();