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https://issues.apache.org/jira/browse/IGNITE-4337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15732726#comment-15732726
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Alexey Goncharuk commented on IGNITE-4337:
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I would rather name it {{IgniteWriteAheadLog}} then.
> Introduce persistence interface to allow build reliable persistence plugins
> ---------------------------------------------------------------------------
>
> Key: IGNITE-4337
> URL: https://issues.apache.org/jira/browse/IGNITE-4337
> Project: Ignite
> Issue Type: Sub-task
> Components: general
> Reporter: Alexey Goncharuk
> Fix For: 2.0
>
>
> With page memory interface introduced, it may be possible to build a
> persistence layer around this architecture. I think we should move the
> PageMemory interface itself to {{org.apache.ignite.plugin.storage}} package
> and introduce the following interface to allow other components to log it's
> activity in crash-resistant way:
> {code}
> /**
> *
> */
> public interface IgniteWriteAheadLogManager extends GridCacheSharedManager {
> /**
> * @return {@code true} If we have to always write full pages.
> */
> public boolean isAlwaysWriteFullPages();
> /**
> * @return {@code true} if WAL will perform fair syncs on fsync call.
> */
> public boolean isFullSync();
> /**
> * Resumes logging after start. When WAL manager is started, it will skip
> logging any updates until this
> * method is called to avoid logging changes induced by the state restore
> procedure.
> */
> public void resumeLogging(WALPointer lastWrittenPtr) throws
> IgniteCheckedException;
> /**
> * Appends the given log entry to the write-ahead log.
> *
> * @param entry entry to log.
> * @return WALPointer that may be passed to {@link #fsync(WALPointer)}
> method to make sure the record is
> * written to the log.
> * @throws IgniteCheckedException If failed to construct log entry.
> * @throws StorageException If IO error occurred while writing log entry.
> */
> public WALPointer log(WALRecord entry) throws IgniteCheckedException,
> StorageException;
> /**
> * Makes sure that all log entries written to the log up until the
> specified pointer are actually persisted to
> * the underlying storage.
> *
> * @param ptr Optional pointer to sync. If {@code null}, will sync up to
> the latest record.
> * @throws IgniteCheckedException If
> * @throws StorageException
> */
> public void fsync(WALPointer ptr) throws IgniteCheckedException,
> StorageException;
> /**
> * Invoke this method to iterate over the written log entries.
> *
> * @param start Optional WAL pointer from which to start iteration.
> * @return Records iterator.
> * @throws IgniteException If failed to start iteration.
> * @throws StorageException If IO error occurred while reading WAL
> entries.
> */
> public WALIterator replay(WALPointer start) throws
> IgniteCheckedException, StorageException;
> /**
> * Gives a hint to WAL manager to clear entries logged before the given
> pointer. Some entries before the
> * the given pointer will be kept because there is a configurable WAL
> history size. Those entries may be used
> * for partial partition rebalancing.
> *
> * @param ptr Pointer for which it is safe to clear the log.
> * @return Number of deleted WAL segments.
> */
> public int truncate(WALPointer ptr);
> }
> {code}
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