/**
 * Tests that an aggregation cursor is killed when it is timed out by the ClientCursorMonitor.
 *
 * This test was designed to reproduce SERVER-25585.
 */
(function() {
'use strict';

// Cursor timeout on mongod is handled by a single thread/timer that will sleep for
// "clientCursorMonitorFrequencySecs" and add the sleep value to each operation's duration when
// it wakes up, timing out those whose "now() - last accessed since" time exceeds. A cursor
// timeout of 2 seconds with a monitor frequency of 1 second means an effective timeout period
// of 1 to 2 seconds.
const cursorTimeoutMs = 2000;
const cursorMonitorFrequencySecs = 1;

const options = {
    setParameter: {
        internalDocumentSourceCursorBatchSizeBytes: 1,
        // We use the "cursorTimeoutMillis" server parameter to decrease how long it takes for a
        // non-exhausted cursor to time out. We use the "clientCursorMonitorFrequencySecs"
        // server parameter to make the ClientCursorMonitor that cleans up the timed out cursors
        // run more often. The combination of these server parameters reduces the amount of time
        // we need to wait within this test.
        cursorTimeoutMillis: cursorTimeoutMs,
        clientCursorMonitorFrequencySecs: cursorMonitorFrequencySecs,
    }
};
const conn = MongoRunner.runMongod(options);
assert.neq(null, conn, 'mongod was unable to start up with options: ' + tojson(options));

const testDB = conn.getDB('test');

// We use a batch size of 2 to ensure that the mongo shell does not exhaust the cursor on its
// first batch.
const batchSize = 2;
const numMatches = 5;

function assertCursorTimesOut(collName, pipeline) {
    // Cursor timeout only occurs outside of sessions. Otherwise we rely on the session timeout
    // mechanism to kill cursors.
    TestData.disableImplicitSessions = true;

    const res = assert.commandWorked(testDB.runCommand({
        aggregate: collName,
        pipeline: pipeline,
        cursor: {
            batchSize: batchSize,
        },
    }));

    let serverStatus = assert.commandWorked(testDB.serverStatus());
    const expectedNumTimedOutCursors = serverStatus.metrics.cursor.timedOut + 1;

    const cursor = new DBCommandCursor(testDB, res, batchSize);

    // Wait until the idle cursor background job has killed the aggregation cursor.
    assert.soon(
        function() {
            serverStatus = assert.commandWorked(testDB.serverStatus());
            return +serverStatus.metrics.cursor.timedOut === expectedNumTimedOutCursors;
        },
        function() {
            return "aggregation cursor failed to time out: " + tojson(serverStatus.metrics.cursor);
        });

    assert.eq(0, serverStatus.metrics.cursor.open.total, tojson(serverStatus));

    // We attempt to exhaust the aggregation cursor to verify that sending a getMore returns an
    // error due to the cursor being killed.
    let err = assert.throws(function() {
        cursor.itcount();
    });
    assert.eq(ErrorCodes.CursorNotFound, err.code, tojson(err));

    TestData.disableImplicitSessions = false;
}

assert.commandWorked(testDB.source.insert({local: 1}));
for (let i = 0; i < numMatches; ++i) {
    assert.commandWorked(testDB.dest.insert({foreign: 1}));
}

// Test that a regular aggregation cursor is killed when the timeout is reached.
assertCursorTimesOut('dest', []);

// Test that an aggregation cursor with a $lookup stage is killed when the timeout is reached.
assertCursorTimesOut('source', [
        {
          $lookup: {
              from: 'dest',
              localField: 'local',
              foreignField: 'foreign',
              as: 'matches',
          }
        },
        {
          $unwind: "$matches",
        },
    ]);

// Test that an aggregation cursor with nested $lookup stages is killed when the timeout is
// reached.
assertCursorTimesOut('source', [
        {
          $lookup: {
              from: 'dest',
              let : {local1: "$local"},
              pipeline: [
                  {$match: {$expr: {$eq: ["$foreign", "$$local1"]}}},
                  {
                    $lookup: {
                        from: 'source',
                        let : {foreign1: "$foreign"},
                        pipeline: [{$match: {$expr: {$eq: ["$local", "$$foreign1"]}}}],
                        as: 'matches2'
                    }
                  },
                  {
                    $unwind: "$matches2",
                  },
              ],
              as: 'matches1',
          }
        },
        {
          $unwind: "$matches1",
        },
    ]);

MongoRunner.stopMongod(conn);
})();