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From: sergos via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Serge Petrenko <sergepetrenko@tarantool.org>
Cc: tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH v2 2/2] replication: fix replica disconnect upon reconfiguration
Date: Wed, 13 Oct 2021 19:00:29 +0300
Message-ID: <31EB9C74-5BAD-4D52-A5BB-EE347C4104A5@tarantool.org> (raw)
In-Reply-To: <8e453790-534e-be84-b4b2-fd30c9740eb7@tarantool.org>

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LGTM.
Sergos


> On 12 Oct 2021, at 17:14, Serge Petrenko <sergepetrenko@tarantool.org> wrote:
> 
> 
> 
> 12.10.2021 13:14, sergos пишет:
>> Hi!
>> 
>> Thanks for the patch!
>> 
>> Just request for some addition to the test, otherwise LGTM.
>> 
>> Sergos
>> 
>> 
>>> On 5 Oct 2021, at 16:18, Serge Petrenko <sergepetrenko@tarantool.org> wrote:
>>> 
>>> Replication reconfiguration used to work as follows: upon receiving a
>>> new config disconnect from all the existing masters and try to connect
>>> to all the masters from the new config.
>>> 
>>> This lead to instances doing extra work when old config and new config
>>> had the same nodes in them: instead of doing nothing, tarantool
>>> reinitialized the connection.
>>> 
>>> There was another problem: when an existing connection is broken, master
>>> takes some time to notice that. So, when replica resets the connection,
>>> it may try to reconnect faster than the master is able to notice its
>>> absence. In this case replica wouldn't be able to reconnect due to
>>> `duplicate connection with the same replica UUID`. So replication would
>>> stop for a replication_timeout, which may be quite large (seconds or
>>> tens of seconds).
>>> 
>>> Let's prevent tarantool from reconnecting to the same instance, if there
>>> already is a working connection.
>>> 
>>> Closes #4669
>>> ---
>>> .../gh-4669-applier-reconfig-reconnect.md     |  5 ++
>>> src/box/box.cc                                | 31 ++++++---
>>> src/box/replication.cc                        | 41 ++++++++----
>>> src/box/replication.h                         |  4 +-
>>> test/instance_files/base_instance.lua         |  3 +-
>>> test/instance_files/replica.lua               | 17 +++++
>>> test/luatest_helpers/server.lua               | 65 +++++++++++++++++++
>>> .../gh_4669_applier_reconnect_test.lua        | 40 ++++++++++++
>>> 8 files changed, 184 insertions(+), 22 deletions(-)
>>> create mode 100644 changelogs/unreleased/gh-4669-applier-reconfig-reconnect.md
>>> create mode 100755 test/instance_files/replica.lua
>>> create mode 100644 test/replication-luatest/gh_4669_applier_reconnect_test.lua
>>> 
>>> diff --git a/changelogs/unreleased/gh-4669-applier-reconfig-reconnect.md b/changelogs/unreleased/gh-4669-applier-reconfig-reconnect.md
>>> new file mode 100644
>>> index 000000000..2a776872b
>>> --- /dev/null
>>> +++ b/changelogs/unreleased/gh-4669-applier-reconfig-reconnect.md
>>> @@ -0,0 +1,5 @@
>>> +## bugfix/replication
>>> +
>>> +* Fixed replica reconnecting to a living master on any `box.cfg{replication=...}`
>>> +  change. Such reconnects could lead to replica failing to restore connection
>>> +  for `replication_timeout` seconds (gh-4669).
>>> diff --git a/src/box/box.cc b/src/box/box.cc
>>> index 219ffa38d..cc4ada47e 100644
>>> --- a/src/box/box.cc
>>> +++ b/src/box/box.cc
>>> @@ -1249,7 +1249,7 @@ cfg_get_replication(int *p_count)
>>>  * don't start appliers.
>>>  */
>>> static void
>>> -box_sync_replication(bool connect_quorum)
>>> +box_sync_replication(bool do_quorum, bool do_reuse)
>>> {
>>> 	int count = 0;
>>> 	struct applier **appliers = cfg_get_replication(&count);
>>> @@ -1260,12 +1260,27 @@ box_sync_replication(bool connect_quorum)
>>> 		for (int i = 0; i < count; i++)
>>> 			applier_delete(appliers[i]); /* doesn't affect diag */
>>> 	});
>>> -
>>> -	replicaset_connect(appliers, count, connect_quorum);
>>> +	replicaset_connect(appliers, count, do_quorum, do_reuse);
>>> 
>>> 	guard.is_active = false;
>>> }
>>> 
>>> +static inline void
>>> +box_restart_replication(void)
>>> +{
>>> +	const bool do_quorum = true;
>>> +	const bool do_reuse = false;
>>> +	box_sync_replication(do_quorum, do_reuse);
>>> +}
>>> +
>>> +static inline void
>>> +box_update_replication(void)
>>> +{
>>> +	const bool do_quorum = false;
>>> +	const bool do_reuse = true;
>>> +	box_sync_replication(do_quorum, do_reuse);
>>> +}
>>> +
>>> void
>>> box_set_replication(void)
>>> {
>>> @@ -1284,7 +1299,7 @@ box_set_replication(void)
>>> 	 * Stay in orphan mode in case we fail to connect to at least
>>> 	 * 'replication_connect_quorum' remote instances.
>>> 	 */
>>> -	box_sync_replication(false);
>>> +	box_update_replication();
>>> 	/* Follow replica */
>>> 	replicaset_follow();
>>> 	/* Wait until appliers are in sync */
>>> @@ -1404,7 +1419,7 @@ box_set_replication_anon(void)
>>> 		 * them can register and others resend a
>>> 		 * non-anonymous subscribe.
>>> 		 */
>>> -		box_sync_replication(true);
>>> +		box_restart_replication();
>>> 		/*
>>> 		 * Wait until the master has registered this
>>> 		 * instance.
>>> @@ -3258,7 +3273,7 @@ bootstrap(const struct tt_uuid *instance_uuid,
>>> 	 * with connecting to 'replication_connect_quorum' masters.
>>> 	 * If this also fails, throw an error.
>>> 	 */
>>> -	box_sync_replication(true);
>>> +	box_restart_replication();
>>> 
>>> 	struct replica *master = replicaset_find_join_master();
>>> 	assert(master == NULL || master->applier != NULL);
>>> @@ -3335,7 +3350,7 @@ local_recovery(const struct tt_uuid *instance_uuid,
>>> 	if (wal_dir_lock >= 0) {
>>> 		if (box_listen() != 0)
>>> 			diag_raise();
>>> -		box_sync_replication(false);
>>> +		box_update_replication();
>>> 
>>> 		struct replica *master;
>>> 		if (replicaset_needs_rejoin(&master)) {
>>> @@ -3414,7 +3429,7 @@ local_recovery(const struct tt_uuid *instance_uuid,
>>> 		vclock_copy(&replicaset.vclock, &recovery->vclock);
>>> 		if (box_listen() != 0)
>>> 			diag_raise();
>>> -		box_sync_replication(false);
>>> +		box_update_replication();
>>> 	}
>>> 	stream_guard.is_active = false;
>>> 	recovery_finalize(recovery);
>>> diff --git a/src/box/replication.cc b/src/box/replication.cc
>>> index 1288bc9b1..10b4ac915 100644
>>> --- a/src/box/replication.cc
>>> +++ b/src/box/replication.cc
>>> @@ -507,7 +507,7 @@ replica_on_applier_state_f(struct trigger *trigger, void *event)
>>>  * upon reconfiguration of box.cfg.replication.
>>>  */
>>> static void
>>> -replicaset_update(struct applier **appliers, int count)
>>> +replicaset_update(struct applier **appliers, int count, bool keep_connect)
>>> {
>>> 	replica_hash_t uniq;
>>> 	memset(&uniq, 0, sizeof(uniq));
>>> @@ -572,22 +572,39 @@ replicaset_update(struct applier **appliers, int count)
>>> 		applier_stop(applier);
>>> 		applier_delete(applier);
>>> 	}
>>> +
>>> +	replicaset.applier.total = count;
>>> +	replicaset.applier.connected = 0;
>>> +	replicaset.applier.loading = 0;
>>> +	replicaset.applier.synced = 0;
>>> 	replicaset_foreach(replica) {
>>> 		if (replica->applier == NULL)
>>> 			continue;
>>> -		applier = replica->applier;
>>> -		replica_clear_applier(replica);
>>> -		replica->applier_sync_state = APPLIER_DISCONNECTED;
>>> +		struct replica *other = replica_hash_search(&uniq, replica);
>>> +		if (keep_connect && other != NULL &&
>>> +		    (replica->applier->state == APPLIER_FOLLOW ||
>>> +		     replica->applier->state == APPLIER_SYNC)) {
>>> +			/*
>>> +			 * Try not to interrupt working appliers upon
>>> +			 * reconfiguration.
>>> +			 */
>>> +			replicaset.applier.connected++;
>>> +			replicaset.applier.synced++;
>>> +			replica_hash_remove(&uniq, other);
>>> +			applier = other->applier;
>>> +			replica_clear_applier(other);
>>> +			replica_delete(other);
>>> +		} else {
>>> +			applier = replica->applier;
>>> +			replica_clear_applier(replica);
>>> +			replica->applier_sync_state = APPLIER_DISCONNECTED;
>>> +		}
>>> 		applier_stop(applier);
>>> 		applier_delete(applier);
>>> 	}
>>> 
>>> -	/* Save new appliers */
>>> -	replicaset.applier.total = count;
>>> -	replicaset.applier.connected = 0;
>>> -	replicaset.applier.loading = 0;
>>> -	replicaset.applier.synced = 0;
>>> 
>>> +	/* Save new appliers */
>>> 	replica_hash_foreach_safe(&uniq, replica, next) {
>>> 		replica_hash_remove(&uniq, replica);
>>> 
>>> @@ -664,11 +681,11 @@ applier_on_connect_f(struct trigger *trigger, void *event)
>>> 
>>> void
>>> replicaset_connect(struct applier **appliers, int count,
>>> -		   bool connect_quorum)
>>> +		   bool connect_quorum, bool keep_connect)
>>> {
>>> 	if (count == 0) {
>>> 		/* Cleanup the replica set. */
>>> -		replicaset_update(appliers, count);
>>> +		replicaset_update(appliers, 0, false);
>>> 		return;
>>> 	}
>>> 
>>> @@ -772,7 +789,7 @@ replicaset_connect(struct applier **appliers, int count,
>>> 
>>> 	/* Now all the appliers are connected, update the replica set. */
>>> 	try {
>>> -		replicaset_update(appliers, count);
>>> +		replicaset_update(appliers, count, keep_connect);
>>> 	} catch (Exception *e) {
>>> 		goto error;
>>> 	}
>>> diff --git a/src/box/replication.h b/src/box/replication.h
>>> index 4c82cd839..a8fed45e8 100644
>>> --- a/src/box/replication.h
>>> +++ b/src/box/replication.h
>>> @@ -439,10 +439,12 @@ replicaset_add_anon(const struct tt_uuid *replica_uuid);
>>>  * \param connect_quorum if this flag is set, fail unless at
>>>  *                       least replication_connect_quorum
>>>  *                       appliers have successfully connected.
>>> + * \param keep_connect   if this flag is set do not force a reconnect if the
>>> + *                       old connection to the replica is fine.
>>>  */
>>> void
>>> replicaset_connect(struct applier **appliers, int count,
>>> -		   bool connect_quorum);
>>> +		   bool connect_quorum, bool keep_connect);
>>> 
>>> /**
>>>  * Check if the current instance fell too much behind its
>>> diff --git a/test/instance_files/base_instance.lua b/test/instance_files/base_instance.lua
>>> index 45bdbc7e8..e579c3843 100755
>>> --- a/test/instance_files/base_instance.lua
>>> +++ b/test/instance_files/base_instance.lua
>>> @@ -5,7 +5,8 @@ local listen = os.getenv('TARANTOOL_LISTEN')
>>> box.cfg({
>>>     work_dir = workdir,
>>> --     listen = 'localhost:3310'
>>> -    listen = listen
>>> +    listen = listen,
>>> +    log = workdir..'/tarantool.log',
>>> })
>>> 
>>> box.schema.user.grant('guest', 'read,write,execute,create', 'universe')
>>> diff --git a/test/instance_files/replica.lua b/test/instance_files/replica.lua
>>> new file mode 100755
>>> index 000000000..587345f24
>>> --- /dev/null
>>> +++ b/test/instance_files/replica.lua
>>> @@ -0,0 +1,17 @@
>>> +#!/usr/bin/env tarantool
>>> +local workdir = os.getenv('TARANTOOL_WORKDIR')
>>> +local listen = os.getenv('TARANTOOL_LISTEN')
>>> +local SOCKET_DIR = os.getenv('VARDIR')
>>> +local MASTER = arg[1] or "master"
>>> +
>>> +local function master_uri()
>>> +    return SOCKET_DIR..'/'..MASTER..'.sock'
>>> +end
>>> +
>>> +box.cfg({
>>> +    work_dir = workdir,
>>> +    listen = listen,
>>> +    replication = master_uri(),
>>> +})
>>> +
>>> +_G.ready = true
>>> diff --git a/test/luatest_helpers/server.lua b/test/luatest_helpers/server.lua
>>> index 018ea4f7d..0306a24ef 100644
>>> --- a/test/luatest_helpers/server.lua
>>> +++ b/test/luatest_helpers/server.lua
>>> @@ -5,6 +5,7 @@ local fiber = require('fiber')
>>> local fio = require('fio')
>>> local fun = require('fun')
>>> local json = require('json')
>>> +local errno = require('errno')
>>> 
>>> local checks = require('checks')
>>> local luatest = require('luatest')
>>> @@ -59,6 +60,70 @@ function Server:initialize()
>>>     getmetatable(getmetatable(self)).initialize(self)
>>> end
>>> 
>>> +-- A copy of test_run:grep_log.
>>> +function Server:grep_log(what, bytes, opts)
>>> +    local opts = opts or {}
>>> +    local noreset = opts.noreset or false
>>> +    -- if instance has crashed provide filename to use grep_log
>>> +    local filename = opts.filename or self:eval('return box.cfg.log')
>>> +    local file = fio.open(filename, {'O_RDONLY', 'O_NONBLOCK'})
>>> +
>>> +    local function fail(msg)
>>> +        local err = errno.strerror()
>>> +        if file ~= nil then
>>> +            file:close()
>>> +        end
>>> +        error(string.format("%s: %s: %s", msg, filename, err))
>>> +    end
>>> +
>>> +    if file == nil then
>>> +        fail("Failed to open log file")
>>> +    end
>>> +    io.flush() -- attempt to flush stdout == log fd
>>> +    local filesize = file:seek(0, 'SEEK_END')
>>> +    if filesize == nil then
>>> +        fail("Failed to get log file size")
>>> +    end
>>> +    local bytes = bytes or 65536 -- don't read whole log - it can be huge
>>> +    bytes = bytes > filesize and filesize or bytes
>>> +    if file:seek(-bytes, 'SEEK_END') == nil then
>>> +        fail("Failed to seek log file")
>>> +    end
>>> +    local found, buf
>>> +    repeat -- read file in chunks
>>> +        local s = file:read(2048)
>>> +        if s == nil then
>>> +            fail("Failed to read log file")
>>> +        end
>>> +        local pos = 1
>>> +        repeat -- split read string in lines
>>> +            local endpos = string.find(s, '\n', pos)
>>> +            endpos = endpos and endpos - 1 -- strip terminating \n
>>> +            local line = string.sub(s, pos, endpos)
>>> +            if endpos == nil and s ~= '' then
>>> +                -- line doesn't end with \n or eof, append it to buffer
>>> +                -- to be checked on next iteration
>>> +                buf = buf or {}
>>> +                table.insert(buf, line)
>>> +            else
>>> +                if buf ~= nil then -- prepend line with buffered data
>>> +                    table.insert(buf, line)
>>> +                    line = table.concat(buf)
>>> +                    buf = nil
>>> +                end
>>> +                if string.match(line, "Starting instance") and not noreset then
>>> +                    found = nil -- server was restarted, reset search
>>> +                else
>>> +                    found = string.match(line, what) or found
>>> +                end
>>> +            end
>>> +            pos = endpos and endpos + 2 -- jump to char after \n
>>> +        until pos == nil
>>> +    until s == ''
>>> +    file:close()
>>> +    return found
>>> +end
>>> +
>>> --- Generates environment to run process with.
>>> -- The result is merged into os.environ().
>>> -- @return map
>>> diff --git a/test/replication-luatest/gh_4669_applier_reconnect_test.lua b/test/replication-luatest/gh_4669_applier_reconnect_test.lua
>>> new file mode 100644
>>> index 000000000..19e10b136
>>> --- /dev/null
>>> +++ b/test/replication-luatest/gh_4669_applier_reconnect_test.lua
>>> @@ -0,0 +1,40 @@
>>> +local t = require('luatest')
>>> +local cluster = require('test.luatest_helpers.cluster')
>>> +
>>> +local g = t.group('gh-4669-applier-reconnect')
>>> +
>>> +local function check_follow_master(server)
>>> +    return t.assert_equals(
>>> +        server:eval('return box.info.replication[1].upstream.status'), 'follow')
>>> +end
>>> +
>>> +g.before_each(function()
>>> +    g.cluster = cluster:new({})
>>> +    g.master = g.cluster:build_server(
>>> +        {}, {alias = 'master'}, 'base_instance.lua')
>>> +    g.replica = g.cluster:build_server(
>>> +        {args={'master'}}, {alias = 'replica'}, 'replica.lua')
>>> +
>>> +    g.cluster:join_server(g.master)
>>> +    g.cluster:join_server(g.replica)
>>> +    g.cluster:start()
>>> +    check_follow_master(g.replica)
>>> +end)
>>> +
>>> +g.after_each(function()
>>> +    g.cluster:stop()
>>> +end)
>>> +
>>> +-- Test that appliers aren't recreated upon replication reconfiguration.
>>> +g.test_applier_connection_on_reconfig = function(g)
>>> +    g.replica:eval([[
>>> +        box.cfg{
>>> +            replication = {
>>> +                os.getenv("TARANTOOL_LISTEN"),
>>> +                box.cfg.replication[1],
>>> +            }
>>> +        }
>>> +    ]])
>> Should we test this with dynamic add/remove of a 2nd replica?
> 
> No problem. Here's the diff:
> 
> ============================
> 
> diff --git a/test/replication-luatest/gh_4669_applier_reconnect_test.lua b/test/replication-luatest/gh_4669_applier_reconnect_test.lua
> index 19e10b136..e082515fd 100644
> --- a/test/replication-luatest/gh_4669_applier_reconnect_test.lua
> +++ b/test/replication-luatest/gh_4669_applier_reconnect_test.lua
> @@ -14,9 +14,12 @@ g.before_each(function()
>          {}, {alias = 'master'}, 'base_instance.lua')
>      g.replica = g.cluster:build_server(
>          {args={'master'}}, {alias = 'replica'}, 'replica.lua')
> +    g.replica2 = g.cluster:build_server(
> +        {args={'master'}}, {alias = 'replica2'}, 'replica.lua')
> 
>      g.cluster:join_server(g.master)
>      g.cluster:join_server(g.replica)
> +    g.cluster:join_server(g.replica2)
>      g.cluster:start()
>      check_follow_master(g.replica)
>  end)
> @@ -26,12 +29,20 @@ g.after_each(function()
>  end)
> 
>  -- Test that appliers aren't recreated upon replication reconfiguration.
> +-- Add and then remove two extra replicas to the configuration. The master
> +-- connection should stay intact.
>  g.test_applier_connection_on_reconfig = function(g)
>      g.replica:eval([[
>          box.cfg{
>              replication = {
>                  os.getenv("TARANTOOL_LISTEN"),
>                  box.cfg.replication[1],
> +                os.getenv('VARDIR')..'/replica2.sock'
> +            }
> +        }
> +        box.cfg{
> +            replication = {
> +                box.cfg.replication[2]
>              }
>          }
>      ]])
> 
> ============================
> 
>> 
>>> +    check_follow_master(g.replica)
>>> +    t.assert_equals(g.master:grep_log("exiting the relay loop"), nil)
>>> +end
>>> -- 
>>> 2.30.1 (Apple Git-130)
>>> 
> 
> -- 
> Serge Petrenko


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      reply	other threads:[~2021-10-13 16:00 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-05 13:18 [Tarantool-patches] [PATCH v2 0/2] replication: fix reconnect on box.cfg.replication change Serge Petrenko via Tarantool-patches
2021-10-05 13:18 ` [Tarantool-patches] [PATCH v2 1/2] replicaiton: make anon replica connect to quorum upon reconfiguration Serge Petrenko via Tarantool-patches
2021-10-12  9:56   ` sergos via Tarantool-patches
2021-10-12 13:38     ` Serge Petrenko via Tarantool-patches
2021-10-13 16:00       ` sergos via Tarantool-patches
2021-10-05 13:18 ` [Tarantool-patches] [PATCH v2 2/2] replication: fix replica disconnect " Serge Petrenko via Tarantool-patches
2021-10-12 10:14   ` sergos via Tarantool-patches
2021-10-12 14:14     ` Serge Petrenko via Tarantool-patches
2021-10-13 16:00       ` sergos via Tarantool-patches [this message]

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