script/test/delayed_commits.js

// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

couchTests.delayed_commits = function(debug) {
  var db = new CouchDB("test_suite_db", {"X-Couch-Full-Commit":"false"});
  db.deleteDb();
  db.createDb();
  if (debug) debugger;

  run_on_modified_server(
    [{section: "couchdb",
      key: "delayed_commits",
      value: "true"}],

    function () {
      // By default, couchdb doesn't fully commit documents to disk right away,
      // it waits about a second to batch the full commit flush along with any
      // other updates. If it crashes or is restarted you may lose the most
      // recent commits.

      T(db.save({_id:"1",a:2,b:4}).ok);
      T(db.open("1") != null);

      restartServer();

      T(db.open("1") == null); // lost the update.
      // note if we waited > 1 sec before the restart, the doc would likely
      // commit.


      // Retry the same thing but with full commits on.

      var db2 = new CouchDB("test_suite_db", {"X-Couch-Full-Commit":"true"});

      T(db2.save({_id:"1",a:2,b:4}).ok);
      T(db2.open("1") != null);

      restartServer();

      T(db2.open("1") != null);

      // You can update but without committing immediately, and then ensure
      // everything is commited in the last step.

      T(db.save({_id:"2",a:2,b:4}).ok);
      T(db.open("2") != null);
      T(db.ensureFullCommit().ok);
      restartServer();

      T(db.open("2") != null);

      // However, it's possible even when flushed, that the server crashed between
      // the update and the commit, and you don't want to check to make sure
      // every doc you updated actually made it to disk. So record the instance
      // start time of the database before the updates and then check it again
      // after the flush (the instance start time is returned by the flush
      // operation). if they are the same, we know everything was updated
      // safely.

      // First try it with a crash.

      var instanceStartTime = db.info().instance_start_time;

      T(db.save({_id:"3",a:2,b:4}).ok);
      T(db.open("3") != null);

      restartServer();

      var commitResult = db.ensureFullCommit();
      T(commitResult.ok && commitResult.instance_start_time != instanceStartTime);
      // start times don't match, meaning the server lost our change

      T(db.open("3") == null); // yup lost it

      // retry with no server restart

      var instanceStartTime = db.info().instance_start_time;

      T(db.save({_id:"4",a:2,b:4}).ok);
      T(db.open("4") != null);

      var commitResult = db.ensureFullCommit();
      T(commitResult.ok && commitResult.instance_start_time == instanceStartTime);
      // Successful commit, start times match!

      restartServer();

      T(db.open("4") != null);
    });

  // Now test that when we exceed the max_dbs_open, pending commits are safely
  // written.
  T(db.save({_id:"5",foo:"bar"}).ok);
  var max = 2;
  run_on_modified_server(
    [{section: "couchdb",
      key: "delayed_commits",
      value: "true"},
     {section: "couchdb",
      key: "max_dbs_open",
      value: max.toString()}],

    function () {
      for(var i=0; i<max; i++) {
        var dbi = new CouchDB("test_suite_db" + i);
        dbi.deleteDb();
        dbi.createDb();
      }
      T(db.open("5").foo=="bar");
      for(var i=0; i<max+1; i++) {
        var dbi = new CouchDB("test_suite_db" + i);
        dbi.deleteDb();
      }
    });


  // Test that a conflict can't cause delayed commits to fail
  run_on_modified_server(
    [{section: "couchdb",
      key: "delayed_commits",
      value: "true"}],

    function() {
      //First save a document and commit it
      T(db.save({_id:"6",a:2,b:4}).ok);
      T(db.ensureFullCommit().ok);
      //Generate a conflict
      try {
        db.save({_id:"6",a:2,b:4});
      } catch( e) {
        T(e.error == "conflict");
      }
      //Wait for the delayed commit interval to pass
      var time = new Date();
      while(new Date() - time < 2000);
      //Save a new doc
      T(db.save({_id:"7",a:2,b:4}).ok);
      //Wait for the delayed commit interval to pass
      var time = new Date();
      while(new Date() - time < 2000);
      //Crash the server and make sure the last doc was written
      restartServer();
      T(db.open("7") != null);
    });
};