jstests/replsets/priority_takeover_one_node_higher_priority.js


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// Priority (1 member with non-default priority).
// 3-node replica set - one arbiter and two electable nodes with different priorities.
// Wait for replica set to stabilize with higher priority node as primary.
// Step down high priority node. Wait for the lower priority electable node to become primary.
// Eventually high priority node will run a priority takeover election to become primary.
(function() {
'use strict';
load('jstests/replsets/rslib.js');
load('jstests/replsets/libs/election_metrics.js');

var name = 'priority_takeover_one_node_higher_priority';
var replSet = new ReplSetTest({
    name: name,
    nodes: [
        {rsConfig: {priority: 3}},
        {},
        {rsConfig: {arbiterOnly: true}},
    ]
});
replSet.startSet();
replSet.initiate();

replSet.waitForState(replSet.nodes[0], ReplSetTest.State.PRIMARY);
var primary = replSet.getPrimary();

const initialPrimaryStatus = assert.commandWorked(primary.adminCommand({serverStatus: 1}));

replSet.awaitSecondaryNodes();
replSet.awaitReplication();

// Primary should step down long enough for election to occur on secondary.
var config = assert.commandWorked(primary.adminCommand({replSetGetConfig: 1})).config;
assert.commandWorked(primary.adminCommand({replSetStepDown: replSet.kDefaultTimeoutMS / 1000}));

// Step down primary and wait for node 1 to be promoted to primary.
replSet.waitForState(replSet.nodes[1], ReplSetTest.State.PRIMARY);

// Unfreeze node 0 so it can seek election.
assert.commandWorked(primary.adminCommand({replSetFreeze: 0}));

// Eventually node 0 will stand for election again because it has a higher priority.
replSet.waitForState(replSet.nodes[0], ReplSetTest.State.PRIMARY);

// Check that both the 'called' and 'successful' fields of the 'priorityTakeover' election
// reason counter have been incremented in serverStatus. We allow an increase of more than 1
// in case a slow election causes a priority takeover to fail.
const newPrimaryStatus = assert.commandWorked(primary.adminCommand({serverStatus: 1}));
verifyServerStatusElectionReasonCounterChange(initialPrimaryStatus.electionMetrics,
                                              newPrimaryStatus.electionMetrics,
                                              "priorityTakeover",
                                              1,
                                              undefined, /* expectedNumSuccessful */
                                              true /* allowGreater */);

replSet.stopSet();
})();