1 files changed, 211 insertions, 0 deletions
diff --git a/services/settings/IDBHelpers.jsm b/services/settings/IDBHelpers.jsm
new file mode 100644
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+++ b/services/settings/IDBHelpers.jsm
@@ -0,0 +1,211 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+var EXPORTED_SYMBOLS = ["IDBHelpers"];
+
+const DB_NAME = "remote-settings";
+const DB_VERSION = 3;
+
+// `indexedDB` is accessible in the worker global, but not the JSM global,
+// where we have to import it - and the worker global doesn't have Cu.
+if (typeof indexedDB == "undefined") {
+  Cu.importGlobalProperties(["indexedDB"]);
+}
+
+/**
+ * Wrap IndexedDB errors to catch them more easily.
+ */
+class IndexedDBError extends Error {
+  constructor(error, method = "", identifier = "") {
+    if (typeof error == "string") {
+      error = new Error(error);
+    }
+    super(`IndexedDB: ${identifier} ${method} ${error && error.message}`);
+    this.name = error.name;
+    this.stack = error.stack;
+  }
+}
+
+class ShutdownError extends IndexedDBError {
+  constructor(error, method = "", identifier = "") {
+    super(error, method, identifier);
+  }
+}
+
+// We batch operations in order to reduce round-trip latency to the IndexedDB
+// database thread. The trade-offs are that the more records in the batch, the
+// more time we spend on this thread in structured serialization, and the
+// greater the chance to jank PBackground and this thread when the responses
+// come back. The initial choice of 250 was made targeting 2-3ms on a fast
+// machine and 10-15ms on a slow machine.
+// Every chunk waits for success before starting the next, and
+// the final chunk's completion will fire transaction.oncomplete .
+function bulkOperationHelper(
+  store,
+  { reject, completion },
+  operation,
+  list,
+  listIndex = 0
+) {
+  try {
+    const CHUNK_LENGTH = 250;
+    const max = Math.min(listIndex + CHUNK_LENGTH, list.length);
+    let request;
+    for (; listIndex < max; listIndex++) {
+      request = store[operation](list[listIndex]);
+    }
+    if (listIndex < list.length) {
+      // On error, `transaction.onerror` is called.
+      request.onsuccess = bulkOperationHelper.bind(
+        null,
+        store,
+        { reject, completion },
+        operation,
+        list,
+        listIndex
+      );
+    } else if (completion) {
+      completion();
+    }
+    // otherwise, we're done, and the transaction will complete on its own.
+  } catch (e) {
+    // The executeIDB callsite has a try... catch, but it will not catch
+    // errors in subsequent bulkOperationHelper calls chained through
+    // request.onsuccess above. We do want to catch those, so we have to
+    // feed them through manually. We cannot use an async function with
+    // promises, because if we wait a microtask after onsuccess fires to
+    // put more requests on the transaction, the transaction will auto-commit
+    // before we can add more requests.
+    reject(e);
+  }
+}
+
+/**
+ * Helper to wrap some IDBObjectStore operations into a promise.
+ *
+ * @param {IDBDatabase} db
+ * @param {String|String[]} storeNames - either a string or an array of strings.
+ * @param {String} mode
+ * @param {function} callback
+ * @param {String} description of the operation for error handling purposes.
+ */
+function executeIDB(db, storeNames, mode, callback, desc) {
+  if (!Array.isArray(storeNames)) {
+    storeNames = [storeNames];
+  }
+  const transaction = db.transaction(storeNames, mode);
+  let promise = new Promise((resolve, reject) => {
+    let stores = storeNames.map(name => transaction.objectStore(name));
+    let result;
+    let rejectWrapper = e => {
+      reject(new IndexedDBError(e, desc || "execute()", storeNames.join(", ")));
+      try {
+        transaction.abort();
+      } catch (ex) {
+        Cu.reportError(ex);
+      }
+    };
+    // Add all the handlers before using the stores.
+    transaction.onerror = event =>
+      reject(new IndexedDBError(event.target.error, desc || "execute()"));
+    transaction.onabort = event =>
+      reject(
+        new IndexedDBError(
+          event.target.error || transaction.error || "IDBTransaction aborted",
+          desc || "execute()"
+        )
+      );
+    transaction.oncomplete = event => resolve(result);
+    // Simplify access to a single datastore:
+    if (stores.length == 1) {
+      stores = stores[0];
+    }
+    try {
+      // Although this looks sync, once the callback places requests
+      // on the datastore, it can independently keep the transaction alive and
+      // keep adding requests. Even once we exit this try.. catch, we may
+      // therefore experience errors which should abort the transaction.
+      // This is why we pass the rejection handler - then the consumer can
+      // continue to ensure that errors are handled appropriately.
+      // In theory, exceptions thrown from onsuccess handlers should also
+      // cause IndexedDB to abort the transaction, so this is a belt-and-braces
+      // approach.
+      result = callback(stores, rejectWrapper);
+    } catch (e) {
+      rejectWrapper(e);
+    }
+  });
+  return { promise, transaction };
+}
+
+/**
+ * Helper to wrap indexedDB.open() into a promise.
+ */
+async function openIDB(allowUpgrades = true) {
+  return new Promise((resolve, reject) => {
+    const request = indexedDB.open(DB_NAME, DB_VERSION);
+    request.onupgradeneeded = event => {
+      if (!allowUpgrades) {
+        reject(
+          new Error(
+            `IndexedDB: Error accessing ${DB_NAME} IDB at version ${DB_VERSION}`
+          )
+        );
+        return;
+      }
+      // When an upgrade is needed, a transaction is started.
+      const transaction = event.target.transaction;
+      transaction.onabort = event => {
+        const error =
+          event.target.error ||
+          transaction.error ||
+          new DOMException("The operation has been aborted", "AbortError");
+        reject(new IndexedDBError(error, "open()"));
+      };
+
+      const db = event.target.result;
+      db.onerror = event => reject(new IndexedDBError(event.target.error));
+
+      if (event.oldVersion < 1) {
+        // Records store
+        const recordsStore = db.createObjectStore("records", {
+          keyPath: ["_cid", "id"],
+        });
+        // An index to obtain all the records in a collection.
+        recordsStore.createIndex("cid", "_cid");
+        // Last modified field
+        recordsStore.createIndex("last_modified", ["_cid", "last_modified"]);
+        // Timestamps store
+        db.createObjectStore("timestamps", {
+          keyPath: "cid",
+        });
+      }
+      if (event.oldVersion < 2) {
+        // Collections store
+        db.createObjectStore("collections", {
+          keyPath: "cid",
+        });
+      }
+      if (event.oldVersion < 3) {
+        // Attachment store
+        db.createObjectStore("attachments", {
+          keyPath: ["cid", "attachmentId"],
+        });
+      }
+    };
+    request.onerror = event => reject(new IndexedDBError(event.target.error));
+    request.onsuccess = event => {
+      const db = event.target.result;
+      resolve(db);
+    };
+  });
+}
+
+var IDBHelpers = {
+  bulkOperationHelper,
+  executeIDB,
+  openIDB,
+  IndexedDBError,
+  ShutdownError,
+};