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Date: Thu, 8 Dec 2016 16:57:58 +0000 (UTC)
From: "Alexey Goncharuk (JIRA)" <jira@apache.org>
To: issues@ignite.apache.org
Message-ID: <JIRA.13024355.1480494487000.474041.1481216278334@Atlassian.JIRA>
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Subject: [jira] [Commented] (IGNITE-4337) Introduce persistence interface to
 allow build reliable persistence plugins
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archived-at: Thu, 08 Dec 2016 16:58:00 -0000


    [ https://issues.apache.org/jira/browse/IGNITE-4337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15732726#comment-15732726 ] 

Alexey Goncharuk commented on IGNITE-4337:
------------------------------------------

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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