...
ConsistentCut splits WAL on 2 global areas - Before
and After
. It guarantees that every transaction committed Before
also will be committed Before
on every other node participated in the transaction. It means that an Ignite node nodes can safely recover itself themself to the consistent Before
state without any coordination with each other nodes.
The border between Before
and After
areas consists of two WAL records - ConsistentCutStartRecord
and ConsistentCutFinishRecord
. It guarantees that the Before
consists of:
...
Code Block | ||||
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/** */ public class ConsistentCutStartRecord extends WALRecord { /** Consistent Cut ID. */ private final UUID idcutId; } /** */ public class ConsistentCutFinishRecord extends WALRecord { /** Consistent Cut ID. */ private final UUID idcutId; /** * Collections of transactions committed BEFORE. */ private final Set<GridCacheVersion> before; /** * Collections of transactions committed AFTER. */ private final Set<GridCacheVersion> after; } |
lastFinishedCutId
holds previous ConsistentCutId
, or null.DistributedProcess
with special message holds new ConsistentCutId
(goal is to notify every node in a cluster about running incremental snapshot). ConsistentCutId
by discovery.ConsistentCutId
by transaction message (Prepare, Finish)ConsistentCutId
, every node: ConsistentCut<Boolean>
future. Complete with true
if consistent, otherwise false
. ConsistentCut
future.committingTx
(goal is to track COMMITTING transactions, that aren't part of IgniteTxManager#activeTx
)ConsistentCutId
.IgniteTxManager#activeTx.
Set listeners on those tx#finishFuture.
ConsistentCutStartRecord
to WAL with the received ConsistentCutId
.committingTxs.
Set listeners on those tx#finishFuture.
committingTxs
to null.
DistributedProcess
is alive running every node signs is signing output transaction messages:ConsistentCutId
(to trigger ConsistentCut
on remote node, if not yet).ConsistentCutId
(to trigger...) and transaction ConsistentCutId
(to notify nodes which side of cut this transaction belongs to).Finish messages is signed with transaction ConsistentCutId
on txCutId
on the node that commits first (see below in Signing messages):committingTxs
, and marks the transaction with extracted from the message txCutId.
check If transaction state is UNKNOWN or status is RECOVERY_FINISH, then complete ConsistentCut
as inconsistentwith exception.
txCutId
equals to local, then transaction put into after
, otherwise it's put into before
.ConsistentCutFinishRecord
into WAL with the collections ( before
, after
). ConsistentCut
future as consistent.ConsistentCut
,
on every node:lastFinishedCutId
with the current.
ConsistentCut
future becomes null....
tx.finalizationStatus
== RECOVERY_FINISH)....
id
is just a unique ConsistentCut
ID (is assigned on the node initiator).
On the picture below on left side is a diagram of sending transaction messages. Before sending message it checks whether cut is running with cutMarker()
. If it is then wrap wraps the message, otherwise send ordinary message (PrepareRequest
in example).
Ignite transaction protocol includes multiple messages. But only some of them affects meaningful (relating to the algorithm) that change state of transactions (PREPARED, COMMITTED):
...
Those messages are wrapped in MarkerMessage
ConsistentCutAwareMessage
that is prepared right before sending message on other node. They used the current ConsistentCutMarker
for setting the markerConsistentCutId
.
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class MarkerMessageConsistentCutAwareMessage { Message msg; ConsistentCutMarkerUUID markercutId; } |
Also some messages require to be signed with additional ConsistentCutMarker
ConsistentCutId
to check it them on primary/backup node.
...
Those messages are wrapped in TransactionFinishMarkerMessage
ConsistentCutAwareTxFinishMessage
that is prepared right before transaction starts committing on first committing node. They used the current ConsistentCutMarker
for setting the txMarker
. txMarker
can ConsistentCutId
for this setting. txCutId
can be null, if transaction starts committing before ConsistentCut starts.
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class TransactionFinishMarkerMessageConsistentCutAwareTransactionFinishMessage extends MarkerMessageConsistentCutAwareMessage { @Nullable ConsistentCutMarkerUUID txMarkertxCutId; } |