[Tarantool-patches] [PATCH] replication: add support of qsync to the snapshot machinery
Serge Petrenko
sergepetrenko at tarantool.org
Thu Jun 11 12:02:54 MSK 2020
10.06.2020 17:34, Leonid Vasiliev пишет:
> To support qsync replication, the waiting for confirmation of
> current "sync" transactions during a timeout has been added to
> the snapshot machinery. In the case of rollback or the timeout
> expiration, the snapshot will be cancelled.
>
> Closes #4850
> ---
> Dirty version without tests.
>
> https://github.com/tarantool/tarantool/issues/4850
> a part of https://github.com/tarantool/tarantool/tree/gh-4842-sync-replication
>
> src/box/gc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> src/box/txn_limbo.h | 19 +++++++++++
> 2 files changed, 111 insertions(+)
>
> diff --git a/src/box/gc.c b/src/box/gc.c
> index 8e8ffea..fb7b37a 100644
> --- a/src/box/gc.c
> +++ b/src/box/gc.c
> @@ -57,6 +57,9 @@
> #include "engine.h" /* engine_collect_garbage() */
> #include "wal.h" /* wal_collect_garbage() */
> #include "checkpoint_schedule.h"
> +#include "trigger.h"
> +#include "txn.h"
> +#include "txn_limbo.h"
>
> struct gc_state gc;
>
> @@ -65,6 +68,26 @@ gc_cleanup_fiber_f(va_list);
> static int
> gc_checkpoint_fiber_f(va_list);
>
> +//TODO: quorum timeout should be used instead
> +double snap_confirm_timeout = 5.0; /* seconds */
> +
> +/**
> + * Waitpoint stores information about the progress of confirmation.
> + * In the case of multimaster support, it will store a bitset
> + * or array instead of the boolean.
> + */
> +struct confirm_waitpoint {
> + /**
> + * Variable for wake up the fiber that is waiting for
> + * the end of confirmation.
> + */
> + struct fiber_cond confirm_cond;
> + /**
> + * Result flag.
> + */
> + bool is_confirm;
> +};
> +
> /**
> * Comparator used for ordering gc_consumer objects
> * lexicographically by their vclock in a binary tree.
> @@ -377,6 +400,64 @@ gc_add_checkpoint(const struct vclock *vclock)
> }
>
> static int
> +gc_txn_commit_cb(struct trigger *trigger, void *event)
> +{
> + (void)event;
> + struct confirm_waitpoint *cwp =
> + (struct confirm_waitpoint *)trigger->data;
> + cwp->is_confirm = true;
> + fiber_cond_signal(&cwp->confirm_cond);
> + return 0;
> +}
> +
> +static int
> +gc_txn_rollback_cb(struct trigger *trigger, void *event)
> +{
> + (void)event;
> + struct confirm_waitpoint *cwp =
> + (struct confirm_waitpoint *)trigger->data;
> + fiber_cond_signal(&cwp->confirm_cond);
> + return 0;
> +}
> +
> +/**
> + * Waiting for confirmation of all "sync" transactions
> + * during snap_confirm_timeout or fail.
> + */
> +static int
> +gc_wait_confirm(void)
> +{
> + /* initialization of a waitpoint. */
> + struct confirm_waitpoint cwp;
> + fiber_cond_create(&cwp.confirm_cond);
> + cwp.is_confirm = false;
> +
> + /* Set triggers for the last limbo transaction. */
> + struct trigger on_complete;
> + trigger_create(&on_complete, gc_txn_commit_cb, &cwp, NULL);
> + struct trigger on_rollback;
> + trigger_create(&on_rollback, gc_txn_rollback_cb, &cwp, NULL);
> + struct txn_limbo_entry *tle = txn_limbo_last_entry(&txn_limbo);
> + txn_on_commit(tle->txn, &on_complete);
> + txn_on_rollback(tle->txn, &on_rollback);
> +
> + int rc = fiber_cond_wait_timeout(&cwp.confirm_cond,
> + snap_confirm_timeout);
> + fiber_cond_destroy(&cwp.confirm_cond);
> + if (rc != 0) {
> + /* Clear the triggers if the timeout has been reached. */
> + trigger_clear(&on_complete);
> + trigger_clear(&on_rollback);
> + return -1;
> + }
> + if (!cwp.is_confirm) {
> + /* The transaction has been rollbacked. */
> + return -1;
> + }
> + return 0;
> +}
> +
> +static int
> gc_do_checkpoint(bool is_scheduled)
> {
> int rc;
> @@ -395,6 +476,17 @@ gc_do_checkpoint(bool is_scheduled)
> rc = wal_begin_checkpoint(&checkpoint);
> if (rc != 0)
> goto out;
> +
> + /*
> + * Wait the confirms on all "sync" transactions before
> + * create a snapshot.
> + */
> + if (!txn_limbo_is_empty(&txn_limbo)) {
> + rc = gc_wait_confirm();
> + if (rc != 0)
> + goto out;
> + }
> +
> rc = engine_commit_checkpoint(&checkpoint.vclock);
> if (rc != 0)
> goto out;
> diff --git a/src/box/txn_limbo.h b/src/box/txn_limbo.h
> index de415cd..c0b821a 100644
> --- a/src/box/txn_limbo.h
> +++ b/src/box/txn_limbo.h
> @@ -166,6 +166,25 @@ txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry);
> void
> txn_limbo_read_confirm(struct txn_limbo *limbo, int64_t lsn);
>
> +/**
> + * Return TRUE if limbo is empty.
> + */
> +static inline bool
> +txn_limbo_is_empty(struct txn_limbo *limbo)
> +{
> + return rlist_empty(&limbo->queue);
> +}
> +
> +/**
> + * Return a pointer to the last txn_limbo_entry of limbo.
> + */
> +static inline struct txn_limbo_entry *
> +txn_limbo_last_entry(struct txn_limbo *limbo)
> +{
> + return rlist_last_entry(&limbo->queue, struct txn_limbo_entry,
> + in_queue);
> +}
> +
> void
> txn_limbo_init();
>
Thanks for the patch! LGTM.
--
Serge Petrenko
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