[PATCH 2/5] txn: run on_rollback triggers on txn_abort
Vladimir Davydov
vdavydov.dev at gmail.com
Mon Jul 8 19:37:55 MSK 2019
On Mon, Jul 08, 2019 at 03:14:08PM +0300, Konstantin Osipov wrote:
> * Vladimir Davydov <vdavydov.dev at gmail.com> [19/07/08 13:02]:
> > > This manipulation should be in txn_abort(), not in
> > > txn_run_triggers(). It's txn_abort().
> >
> > But this function is also called from completion callback, where it has
> > to set the txn as well. That's why I put it there, otherwise we would
> > have to set/restore txn context in txn_complete as well. I'm not really
> > against it - just pointint it out. I'll prepare a patch that does that,
> > see how it looks.
>
> Yes, so, basically, txn_begin(), txn_abort(), txn_complete()
> should manage the fiber key.
Okay, please take a look at the patch below.
>
> >
> > > > fiber_set_txn(fiber(), txn);
> > > > /* Rollback triggers must not throw. */
> > > > if (trigger_run(trigger, txn) != 0) {
> > > > @@ -357,7 +358,7 @@ txn_run_triggers(struct txn *txn, struct rlist *trigger)
> > > > unreachable();
> > > > panic("commit/rollback trigger failed");
> > > > }
> > > > - fiber_set_txn(fiber(), NULL);
> > > > + fiber_set_txn(fiber(), old_txn);
> > >
> > > Ideally we should never need to restore old_txn. All transaction
> > > statements, like txn_begin() or txn_abort() should set the txn,
> > > and whenever the transaction yields, the txn should be cleared.
> >
> > But we do want the transaction to remain attached to the fiber once
> > it resumes its execution so that we can raise an error on 'commit'.
> > Actually, we used to clear txn on yield, but then it was reworked
> > to make 'commit' more user-friendly.
>
> I don't get it. When a transaction is resumed after a yield, it
> has to set its key again anyway.
It's not a transaction that is resumed, it's fiber. So we do need to
know which transaction is assigned to a fiber.
> Basically, transaction == fiber
> is no longer true, and each time a transaction starts running it
> should update its key. Better yet, let's kill the transaction key
> in the fiber altogether and pass the txn around by value.
We can't kill the transaction key, because when transactions are used
from Lua it's the only way to get txn.
---
>From 21f26c3437b3733ebd3acfb643886fce755db263 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov.dev at gmail.com>
Date: Fri, 5 Jul 2019 17:08:45 +0300
Subject: [PATCH] txn: run on_rollback triggers on txn_abort
When a memtx transaction is aborted on yield, it isn't enough to
rollback individual statements - we must also run on_rollback triggers,
otherwise changes done to the schema by an aborted DDL transaction will
be visible to other fibers until an attempt to commit it is made.
diff --git a/src/box/txn.c b/src/box/txn.c
index 818f405b..c605345d 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -342,11 +342,6 @@ fail:
static inline void
txn_run_triggers(struct txn *txn, struct rlist *trigger)
{
- /*
- * Some triggers require for in_txn variable to be set so
- * restore it for the time triggers are in progress.
- */
- fiber_set_txn(fiber(), txn);
/* Rollback triggers must not throw. */
if (trigger_run(trigger, txn) != 0) {
/*
@@ -357,7 +352,6 @@ txn_run_triggers(struct txn *txn, struct rlist *trigger)
unreachable();
panic("commit/rollback trigger failed");
}
- fiber_set_txn(fiber(), NULL);
}
/**
@@ -412,7 +406,15 @@ txn_entry_done_cb(struct journal_entry *entry, void *data)
{
struct txn *txn = data;
txn->signature = entry->res;
+ /*
+ * Some commit/rollback triggers require for in_txn fiber
+ * variable to be set so restore it for the time triggers
+ * are in progress.
+ */
+ assert(in_txn() == NULL);
+ fiber_set_txn(fiber(), txn);
txn_complete(txn);
+ fiber_set_txn(fiber(), NULL);
}
static int64_t
@@ -497,14 +499,15 @@ txn_write(struct txn *txn)
* After this point the transaction must not be used
* so reset the corresponding key in the fiber storage.
*/
- fiber_set_txn(fiber(), NULL);
txn->start_tm = ev_monotonic_now(loop());
if (txn->n_new_rows + txn->n_applier_rows == 0) {
/* Nothing to do. */
txn->signature = 0;
txn_complete(txn);
+ fiber_set_txn(fiber(), NULL);
return 0;
}
+ fiber_set_txn(fiber(), NULL);
return txn_write_to_wal(txn);
}
@@ -555,7 +558,12 @@ txn_rollback(struct txn *txn)
void
txn_abort(struct txn *txn)
{
+ assert(in_txn() == txn);
txn_rollback_to_svp(txn, NULL);
+ if (txn->has_triggers) {
+ txn_run_triggers(txn, &txn->on_rollback);
+ txn->has_triggers = false;
+ }
txn->is_aborted = true;
}
diff --git a/test/box/transaction.result b/test/box/transaction.result
index 9da53e5b..857314b7 100644
--- a/test/box/transaction.result
+++ b/test/box/transaction.result
@@ -698,3 +698,27 @@ box.space.memtx:drop()
box.space.vinyl:drop()
---
...
+--
+-- Check that changes done to the schema by a DDL statement are
+-- rolled back when the transaction is aborted on fiber yield.
+--
+s = box.schema.space.create('test')
+---
+...
+box.begin() s:create_index('pk') s:insert{1}
+---
+...
+fiber.sleep(0)
+---
+...
+s.index.pk == nil
+---
+- true
+...
+box.commit() -- error
+---
+- error: Transaction has been aborted by a fiber yield
+...
+s:drop()
+---
+...
diff --git a/test/box/transaction.test.lua b/test/box/transaction.test.lua
index a6789316..8ffae2fe 100644
--- a/test/box/transaction.test.lua
+++ b/test/box/transaction.test.lua
@@ -363,3 +363,13 @@ if box.space.test then box.space.test:drop() end
box.space.memtx:drop()
box.space.vinyl:drop()
+--
+-- Check that changes done to the schema by a DDL statement are
+-- rolled back when the transaction is aborted on fiber yield.
+--
+s = box.schema.space.create('test')
+box.begin() s:create_index('pk') s:insert{1}
+fiber.sleep(0)
+s.index.pk == nil
+box.commit() -- error
+s:drop()
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