database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-13 07:41:39 +03:00
Code Activity

Add support for prepared transactions to built-in logical replication.

Browse Source 
To add support for streaming transactions at prepare time into the
built-in logical replication, we need to do the following things:

* Modify the output plugin (pgoutput) to implement the new two-phase API
callbacks, by leveraging the extended replication protocol.

* Modify the replication apply worker, to properly handle two-phase
transactions by replaying them on prepare.

* Add a new SUBSCRIPTION option "two_phase" to allow users to enable
two-phase transactions. We enable the two_phase once the initial data sync
is over.

We however must explicitly disable replication of two-phase transactions
during replication slot creation, even if the plugin supports it. We
don't need to replicate the changes accumulated during this phase,
and moreover, we don't have a replication connection open so we don't know
where to send the data anyway.

The streaming option is not allowed with this new two_phase option. This
can be done as a separate patch.

We don't allow to toggle two_phase option of a subscription because it can
lead to an inconsistent replica. For the same reason, we don't allow to
refresh the publication once the two_phase is enabled for a subscription
unless copy_data option is false.

Author: Peter Smith, Ajin Cherian and Amit Kapila based on previous work by Nikhil Sontakke and Stas Kelvich
Reviewed-by: Amit Kapila, Sawada Masahiko, Vignesh C, Dilip Kumar, Takamichi Osumi, Greg Nancarrow
Tested-By: Haiying Tang
Discussion: https://postgr.es/m/02DA5F5E-CECE-4D9C-8B4B-418077E2C010@postgrespro.ru
Discussion: https://postgr.es/m/CAA4eK1+opiV4aFTmWWUF9h_32=HfPOW9vZASHarT0UA5oBrtGw@mail.gmail.com
This commit is contained in:
Amit Kapila
2021-07-14 07:33:50 +05:30
parent 6c9c283166
commit a8fd13cab0
43 changed files with 2382 additions and 191 deletions
Download Patch File Download Diff File Expand all files Collapse all files

131
src/backend/commands/subscriptioncmds.c
View File

@ -59,6 +59,7 @@
#define SUBOPT_REFRESH 0x00000040
#define SUBOPT_BINARY 0x00000080
#define SUBOPT_STREAMING 0x00000100
#define SUBOPT_TWOPHASE_COMMIT 0x00000200
/* check if the 'val' has 'bits' set */
#define IsSet(val, bits) (((val) & (bits)) == (bits))
@ -79,6 +80,7 @@ typedef struct SubOpts
bool refresh;
bool binary;
bool streaming;
bool twophase;
} SubOpts;
static List *fetch_table_list(WalReceiverConn *wrconn, List *publications);
@ -123,6 +125,8 @@ parse_subscription_options(List *stmt_options, bits32 supported_opts, SubOpts *o
opts->binary = false;
if (IsSet(supported_opts, SUBOPT_STREAMING))
opts->streaming = false;
if (IsSet(supported_opts, SUBOPT_TWOPHASE_COMMIT))
opts->twophase = false;
/* Parse options */
foreach(lc, stmt_options)
@ -237,6 +241,29 @@ parse_subscription_options(List *stmt_options, bits32 supported_opts, SubOpts *o
opts->specified_opts |= SUBOPT_STREAMING;
opts->streaming = defGetBoolean(defel);
}
else if (strcmp(defel->defname, "two_phase") == 0)
{
/*
* Do not allow toggling of two_phase option. Doing so could cause
* missing of transactions and lead to an inconsistent replica.
* See comments atop worker.c
*
* Note: Unsupported twophase indicates that this call originated
* from AlterSubscription.
*/
if (!IsSet(supported_opts, SUBOPT_TWOPHASE_COMMIT))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("unrecognized subscription parameter: \"%s\"", defel->defname)));
if (IsSet(opts->specified_opts, SUBOPT_TWOPHASE_COMMIT))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options")));
opts->specified_opts |= SUBOPT_TWOPHASE_COMMIT;
opts->twophase = defGetBoolean(defel);
}
else
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
@ -325,6 +352,25 @@ parse_subscription_options(List *stmt_options, bits32 supported_opts, SubOpts *o
errmsg("subscription with %s must also set %s",
"slot_name = NONE", "create_slot = false")));
}
/*
* Do additional checking for the disallowed combination of two_phase and
* streaming. While streaming and two_phase can theoretically be
* supported, it needs more analysis to allow them together.
*/
if (opts->twophase &&
IsSet(supported_opts, SUBOPT_TWOPHASE_COMMIT) &&
IsSet(opts->specified_opts, SUBOPT_TWOPHASE_COMMIT))
{
if (opts->streaming &&
IsSet(supported_opts, SUBOPT_STREAMING) &&
IsSet(opts->specified_opts, SUBOPT_STREAMING))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
/*- translator: both %s are strings of the form "option = value" */
errmsg("%s and %s are mutually exclusive options",
"two_phase = true", "streaming = true")));
}
}
/*
@ -385,7 +431,7 @@ CreateSubscription(CreateSubscriptionStmt *stmt, bool isTopLevel)
supported_opts = (SUBOPT_CONNECT | SUBOPT_ENABLED | SUBOPT_CREATE_SLOT |
SUBOPT_SLOT_NAME | SUBOPT_COPY_DATA |
SUBOPT_SYNCHRONOUS_COMMIT | SUBOPT_BINARY |
SUBOPT_STREAMING);
SUBOPT_STREAMING | SUBOPT_TWOPHASE_COMMIT);
parse_subscription_options(stmt->options, supported_opts, &opts);
/*
@ -455,6 +501,10 @@ CreateSubscription(CreateSubscriptionStmt *stmt, bool isTopLevel)
values[Anum_pg_subscription_subenabled - 1] = BoolGetDatum(opts.enabled);
values[Anum_pg_subscription_subbinary - 1] = BoolGetDatum(opts.binary);
values[Anum_pg_subscription_substream - 1] = BoolGetDatum(opts.streaming);
values[Anum_pg_subscription_subtwophasestate - 1] =
CharGetDatum(opts.twophase ?
LOGICALREP_TWOPHASE_STATE_PENDING :
LOGICALREP_TWOPHASE_STATE_DISABLED);
values[Anum_pg_subscription_subconninfo - 1] =
CStringGetTextDatum(conninfo);
if (opts.slot_name)
@ -532,10 +582,35 @@ CreateSubscription(CreateSubscriptionStmt *stmt, bool isTopLevel)
*/
if (opts.create_slot)
{
bool twophase_enabled = false;
Assert(opts.slot_name);
walrcv_create_slot(wrconn, opts.slot_name, false,
/*
* Even if two_phase is set, don't create the slot with
* two-phase enabled. Will enable it once all the tables are
* synced and ready. This avoids race-conditions like prepared
* transactions being skipped due to changes not being applied
* due to checks in should_apply_changes_for_rel() when
* tablesync for the corresponding tables are in progress. See
* comments atop worker.c.
*
* Note that if tables were specified but copy_data is false
* then it is safe to enable two_phase up-front because those
* tables are already initially in READY state. When the
* subscription has no tables, we leave the twophase state as
* PENDING, to allow ALTER SUBSCRIPTION ... REFRESH
* PUBLICATION to work.
*/
if (opts.twophase && !opts.copy_data && tables != NIL)
twophase_enabled = true;
walrcv_create_slot(wrconn, opts.slot_name, false, twophase_enabled,
CRS_NOEXPORT_SNAPSHOT, NULL);
if (twophase_enabled)
UpdateTwoPhaseState(subid, LOGICALREP_TWOPHASE_STATE_ENABLED);
ereport(NOTICE,
(errmsg("created replication slot \"%s\" on publisher",
opts.slot_name)));
@ -865,6 +940,12 @@ AlterSubscription(AlterSubscriptionStmt *stmt, bool isTopLevel)
if (IsSet(opts.specified_opts, SUBOPT_STREAMING))
{
if ((sub->twophasestate != LOGICALREP_TWOPHASE_STATE_DISABLED) && opts.streaming)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("cannot set %s for two-phase enabled subscription",
"streaming = true")));
values[Anum_pg_subscription_substream - 1] =
BoolGetDatum(opts.streaming);
replaces[Anum_pg_subscription_substream - 1] = true;
@ -927,6 +1008,17 @@ AlterSubscription(AlterSubscriptionStmt *stmt, bool isTopLevel)
errmsg("ALTER SUBSCRIPTION with refresh is not allowed for disabled subscriptions"),
errhint("Use ALTER SUBSCRIPTION ... SET PUBLICATION ... WITH (refresh = false).")));
/*
* See ALTER_SUBSCRIPTION_REFRESH for details why this is
* not allowed.
*/
if (sub->twophasestate == LOGICALREP_TWOPHASE_STATE_ENABLED && opts.copy_data)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("ALTER SUBSCRIPTION with refresh and copy_data is not allowed when two_phase is enabled"),
errhint("Use ALTER SUBSCRIPTION ...SET PUBLICATION with refresh = false, or with copy_data = false"
", or use DROP/CREATE SUBSCRIPTION.")));
PreventInTransactionBlock(isTopLevel, "ALTER SUBSCRIPTION with refresh");
/* Make sure refresh sees the new list of publications. */
@ -966,6 +1058,17 @@ AlterSubscription(AlterSubscriptionStmt *stmt, bool isTopLevel)
errmsg("ALTER SUBSCRIPTION with refresh is not allowed for disabled subscriptions"),
errhint("Use ALTER SUBSCRIPTION ... SET PUBLICATION ... WITH (refresh = false).")));
/*
* See ALTER_SUBSCRIPTION_REFRESH for details why this is
* not allowed.
*/
if (sub->twophasestate == LOGICALREP_TWOPHASE_STATE_ENABLED && opts.copy_data)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("ALTER SUBSCRIPTION with refresh and copy_data is not allowed when two_phase is enabled"),
errhint("Use ALTER SUBSCRIPTION ...SET PUBLICATION with refresh = false, or with copy_data = false"
", or use DROP/CREATE SUBSCRIPTION.")));
PreventInTransactionBlock(isTopLevel, "ALTER SUBSCRIPTION with refresh");
/* Only refresh the added/dropped list of publications. */
@ -986,6 +1089,30 @@ AlterSubscription(AlterSubscriptionStmt *stmt, bool isTopLevel)
parse_subscription_options(stmt->options, SUBOPT_COPY_DATA, &opts);
/*
* The subscription option "two_phase" requires that
* replication has passed the initial table synchronization
* phase before the two_phase becomes properly enabled.
*
* But, having reached this two-phase commit "enabled" state
* we must not allow any subsequent table initialization to
* occur. So the ALTER SUBSCRIPTION ... REFRESH is disallowed
* when the user had requested two_phase = on mode.
*
* The exception to this restriction is when copy_data =
* false, because when copy_data is false the tablesync will
* start already in READY state and will exit directly without
* doing anything.
*
* For more details see comments atop worker.c.
*/
if (sub->twophasestate == LOGICALREP_TWOPHASE_STATE_ENABLED && opts.copy_data)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("ALTER SUBSCRIPTION ... REFRESH with copy_data is not allowed when two_phase is enabled"),
errhint("Use ALTER SUBSCRIPTION ... REFRESH with copy_data = false"
", or use DROP/CREATE SUBSCRIPTION.")));
PreventInTransactionBlock(isTopLevel, "ALTER SUBSCRIPTION ... REFRESH");
AlterSubscription_refresh(sub, opts.copy_data);