[Tarantool-patches] [PATCH 1/1] replication: check rs uuid on subscribe process

[Serge Petrenko]

28.05.2021 23:35, Vladislav Shpilevoy пишет:
> Remote node doing the subscribe might be from a different
> replicaset.
>
> Before this patch the subscribe would be retried infinitely
> because the node couldn't be found in _cluster, and the master
> assumed it must have joined to another node, and its ID should
> arrive shortly (ER_TOO_EARLY_SUBSCRIBE).
>
> The ID would never arrive, because the node belongs to another
> replicaset.
>
> The patch makes so the master checks if the peer lives in the same
> replicaset. Since it is doing a subscribe, it must have joined
> already and should have a valid replicaser UUID, regardless of
> whether it is anonymous or not.
>
> Correct behaviour is to hard cut this peer off immediately,
> without retries.
>
> Closes #6094
> Part of #5613
> ---
> Branch: http://github.com/tarantool/tarantool/tree/gerold103/gh-6094-replication-bad-error
> Issue: https://github.com/tarantool/tarantool/issues/6094
>
> The UUID ignorance on subscribe decode was introduced here:
> https://github.com/tarantool/tarantool/commit/7f8cbde3555084ad6c41f137aec4faba4648c705#diff-fc276b44b551b4eac3431c9433d4bc881790ddd7df76226d7579f80da7798f6e
>
> And I don't understand why. Maybe I miss something? The tests have
> passed. Sergey, do you remember why was it needed really?
>
> Replicaset UUID mismatch definitely means the node can't connect.
> It is not related to whether it is anonymous or not. Because it
> has nothing to do with _cluster.

Hi! Thanks for the patch!

That change was meant to help anonymous replicas fetch data from
multiple clusters. There was such an idea back then.
It never got implemented though, and I doubt it will.

So the idea was that replica should check the replicaset UUID itself.
It doesn't work now obviously. And looks like it hadn't worked before
you introduced the ER_TOO_EARLY_SUBSCRIBE error.
The test for checking uuid on replica side didn't catch this problem
because the replica was already registered on master in it.

Long story short, I'm ok with this change, but now you should remove
unnecessary replicaset uuid checks from replica side (in applier_subscribe).

And looks like replication/gh-3704-misc-replica-checks-cluster-id test is
obsolete now.


>
>   .../unreleased/gh-6094-rs-uuid-mismatch.md    |  6 ++
>   src/box/box.cc                                | 17 ++++-
>   .../gh-6094-rs-uuid-mismatch.result           | 67 +++++++++++++++++++
>   .../gh-6094-rs-uuid-mismatch.test.lua         | 25 +++++++
>   test/replication/suite.cfg                    |  1 +
>   5 files changed, 114 insertions(+), 2 deletions(-)
>   create mode 100644 changelogs/unreleased/gh-6094-rs-uuid-mismatch.md
>   create mode 100644 test/replication/gh-6094-rs-uuid-mismatch.result
>   create mode 100644 test/replication/gh-6094-rs-uuid-mismatch.test.lua
>
> diff --git a/changelogs/unreleased/gh-6094-rs-uuid-mismatch.md b/changelogs/unreleased/gh-6094-rs-uuid-mismatch.md
> new file mode 100644
> index 000000000..f4e47da3d
> --- /dev/null
> +++ b/changelogs/unreleased/gh-6094-rs-uuid-mismatch.md
> @@ -0,0 +1,6 @@
> +## bugfix/replication
> +
> +* Fixed an error when a replica, at attempt to subscribe to a foreign cluster
> +  (with different replicaset UUID), didn't notice it is not possible, and
> +  instead was stuck in an infinite retry loop printing an error about "too
> +  early subscribe" (gh-6094).
> diff --git a/src/box/box.cc b/src/box/box.cc
> index c10e0d8bf..5672073d6 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -2686,17 +2686,30 @@ box_process_subscribe(struct ev_io *io, struct xrow_header *header)
>   		tnt_raise(ClientError, ER_LOADING);
>   
>   	struct tt_uuid replica_uuid = uuid_nil;
> +	struct tt_uuid peer_replicaset_uuid = uuid_nil;
>   	struct vclock replica_clock;
>   	uint32_t replica_version_id;
>   	vclock_create(&replica_clock);
>   	bool anon;
>   	uint32_t id_filter;
> -	xrow_decode_subscribe_xc(header, NULL, &replica_uuid, &replica_clock,
> -				 &replica_version_id, &anon, &id_filter);
> +	xrow_decode_subscribe_xc(header, &peer_replicaset_uuid, &replica_uuid,
> +				 &replica_clock, &replica_version_id, &anon,
> +				 &id_filter);
>   
>   	/* Forbid connection to itself */
>   	if (tt_uuid_is_equal(&replica_uuid, &INSTANCE_UUID))
>   		tnt_raise(ClientError, ER_CONNECTION_TO_SELF);
> +	/*
> +	 * The peer should have bootstrapped from somebody since it tries to
> +	 * subscribe already. If it belongs to a different replicaset, it won't
> +	 * be ever found here, and would try to reconnect thinking its replica
> +	 * ID wasn't replicated here yet. Prevent it right away.
> +	 */
> +	if (!tt_uuid_is_equal(&peer_replicaset_uuid, &REPLICASET_UUID)) {
> +		tnt_raise(ClientError, ER_REPLICASET_UUID_MISMATCH,
> +			  tt_uuid_str(&REPLICASET_UUID),
> +			  tt_uuid_str(&peer_replicaset_uuid));
> +	}
>   
>   	/*
>   	 * Do not allow non-anonymous followers for anonymous
> diff --git a/test/replication/gh-6094-rs-uuid-mismatch.result b/test/replication/gh-6094-rs-uuid-mismatch.result
> new file mode 100644
> index 000000000..1ba189a37
> --- /dev/null
> +++ b/test/replication/gh-6094-rs-uuid-mismatch.result
> @@ -0,0 +1,67 @@
> +-- test-run result file version 2
> +test_run = require('test_run').new()
> + | ---
> + | ...
> +
> +--
> +-- gh-6094: master instance didn't check if the subscribed instance has the same
> +-- replicaset UUID as its own. As a result, if the peer is from a different
> +-- replicaset, the master couldn't find its record in _cluster, and assumed it
> +-- simply needs to wait a bit more. This led to an infinite re-subscribe.
> +--
> +box.schema.user.grant('guest', 'super')
> + | ---
> + | ...
> +
> +test_run:cmd('create server master2 with script="replication/master1.lua"')
> + | ---
> + | - true
> + | ...
> +test_run:cmd('start server master2')
> + | ---
> + | - true
> + | ...
> +test_run:switch('master2')
> + | ---
> + | - true
> + | ...
> +replication = test_run:eval('default', 'return box.cfg.listen')[1]
> + | ---
> + | ...
> +box.cfg{replication = {replication}}
> + | ---
> + | ...
> +assert(test_run:grep_log('master2', 'ER_REPLICASET_UUID_MISMATCH'))
> + | ---
> + | - ER_REPLICASET_UUID_MISMATCH
> + | ...
> +info = box.info
> + | ---
> + | ...
> +repl_info = info.replication[1]
> + | ---
> + | ...
> +assert(not repl_info.downstream and not repl_info.upstream)
> + | ---
> + | - true
> + | ...
> +assert(info.status == 'orphan')
> + | ---
> + | - true
> + | ...
> +
> +test_run:switch('default')
> + | ---
> + | - true
> + | ...
> +test_run:cmd('stop server master2')
> + | ---
> + | - true
> + | ...
> +test_run:cmd('delete server master2')
> + | ---
> + | - true
> + | ...
> +box.schema.user.revoke('guest', 'super')
> + | ---
> + | ...
> diff --git a/test/replication/gh-6094-rs-uuid-mismatch.test.lua b/test/replication/gh-6094-rs-uuid-mismatch.test.lua
> new file mode 100644
> index 000000000..d3928f52b
> --- /dev/null
> +++ b/test/replication/gh-6094-rs-uuid-mismatch.test.lua
> @@ -0,0 +1,25 @@
> +test_run = require('test_run').new()
> +
> +--
> +-- gh-6094: master instance didn't check if the subscribed instance has the same
> +-- replicaset UUID as its own. As a result, if the peer is from a different
> +-- replicaset, the master couldn't find its record in _cluster, and assumed it
> +-- simply needs to wait a bit more. This led to an infinite re-subscribe.
> +--
> +box.schema.user.grant('guest', 'super')
> +
> +test_run:cmd('create server master2 with script="replication/master1.lua"')
> +test_run:cmd('start server master2')
> +test_run:switch('master2')
> +replication = test_run:eval('default', 'return box.cfg.listen')[1]
> +box.cfg{replication = {replication}}
> +assert(test_run:grep_log('master2', 'ER_REPLICASET_UUID_MISMATCH'))
> +info = box.info
> +repl_info = info.replication[1]
> +assert(not repl_info.downstream and not repl_info.upstream)
> +assert(info.status == 'orphan')
> +
> +test_run:switch('default')
> +test_run:cmd('stop server master2')
> +test_run:cmd('delete server master2')
> +box.schema.user.revoke('guest', 'super')
> diff --git a/test/replication/suite.cfg b/test/replication/suite.cfg
> index dc39e2f74..5acb28fd4 100644
> --- a/test/replication/suite.cfg
> +++ b/test/replication/suite.cfg
> @@ -45,6 +45,7 @@
>       "gh-5435-qsync-clear-synchro-queue-commit-all.test.lua": {},
>       "gh-5536-wal-limit.test.lua": {},
>       "gh-5566-final-join-synchro.test.lua": {},
> +    "gh-6094-rs-uuid-mismatch.test.lua": {},
>       "*": {
>           "memtx": {"engine": "memtx"},
>           "vinyl": {"engine": "vinyl"}

-- 
Serge Petrenko