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/*
* Tests a possible lock-free read scenario wherein the collection on a namespace goes from
* unsharded (sent in the request to the shard) to sharded (which the lock-free state finds) to
* dropped and recreated (which the subsequent shardVersion check finds) while the lock-free state
* is being set up for a read. The lock-free state must ensure consistency with the sharding state.
* In such a case, the lock-free read state setup should be retried internally until consistent.
*
* @tags: [
* requires_sharding,
* ]
*/
(function() {
"use strict";
load("jstests/libs/fail_point_util.js"); // configureFailPoint
load("jstests/libs/parallel_shell_helpers.js"); // startParallelShell
const st = new ShardingTest({mongos: 1, config: 1, shards: 1, rs: {nodes: 1}});
// This logical session ID is used to identify the particular find command for the failpoints.
const lsid = ({id: UUID()});
const hangBeforeAutoGetCollectionLockFreeShardedStateAccessFp =
configureFailPoint(st.shard0.rs.nodes[0],
"hangBeforeAutoGetCollectionLockFreeShardedStateAccess",
{lsid: lsid.id});
const reachedAutoGetLockFreeShardConsistencyRetryFp = configureFailPoint(
st.shard0.rs.nodes[0], "reachedAutoGetLockFreeShardConsistencyRetry", {lsid: lsid.id});
const hangBeforeAutoGetShardVersionCheckFp = configureFailPoint(
st.shard0.rs.nodes[0], "hangBeforeAutoGetShardVersionCheck", {lsid: lsid.id});
const dbName = "test";
const collName = "lock_free_read_unsharded_sharded_unsharded";
const collection = st.s.getCollection(`${dbName}.${collName}`);
assert.commandWorked(st.s.adminCommand({enableSharding: dbName}));
assert.commandWorked(collection.runCommand("create"));
// Establish state on the mongos for the new collection as unsharded.
collection.find().toArray();
// Start a new read routed through the mongos that will send an UNSHARDED version with the request
// to the mongod.
const awaitFind = startParallelShell(
funWithArgs(function(lsid, ns) {
const mongos = db.getMongo();
assert.commandWorked(mongos.getCollection(ns).runCommand("find", {lsid}));
}, lsid, collection.getFullName()), st.s.port);
// Pause the operation right before lock-free read setup checks whether or not the collection is
// sharded.
hangBeforeAutoGetCollectionLockFreeShardedStateAccessFp.wait();
// Shard the collection so the lock-free read setup will find the collection sharded.
assert.commandWorked(st.s.adminCommand({shardCollection: collection.getFullName(), key: {_id: 1}}));
// Unpause the lock-free state to find a sharded collection, then wait for it to pause before the SV
// check.
hangBeforeAutoGetCollectionLockFreeShardedStateAccessFp.off();
hangBeforeAutoGetShardVersionCheckFp.wait();
// Drop the sharded collection and recreate a collection on the same namespace that's unsharded.
assert.commandWorked(collection.runCommand("drop"));
assert.commandWorked(collection.runCommand("create"));
// Release the lock-free read.
hangBeforeAutoGetShardVersionCheckFp.off();
// Make sure we reach the point in the code where the inconsistency is detected, before proceeding
reachedAutoGetLockFreeShardConsistencyRetryFp.wait();
reachedAutoGetLockFreeShardConsistencyRetryFp.off();
awaitFind();
st.stop();
})();
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