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java.lang.Objectorg.apache.zookeeper.server.persistence.FileTxnLog
public class FileTxnLog
This class implements the TxnLog interface. It provides api's to access the txnlogs and add entries to it.
The format of a Transactional log is as follows:
LogFile: FileHeader TxnList ZeroPad FileHeader: { magic 4bytes (ZKLG) version 4bytes dbid 8bytes } TxnList: Txn || Txn TxnList Txn: checksum Txnlen TxnHeader Record 0x42 checksum: 8bytes Adler32 is currently used calculated across payload -- Txnlen, TxnHeader, Record and 0x42 Txnlen: len 4bytes TxnHeader: { sessionid 8bytes cxid 4bytes zxid 8bytes time 8bytes type 4bytes } Record: See Jute definition file for details on the various record types ZeroPad: 0 padded to EOF (filled during preallocation stage)
Nested Class Summary | |
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static class |
FileTxnLog.FileTxnIterator
this class implements the txnlog iterator interface which is used for reading the transaction logs |
Nested classes/interfaces inherited from interface org.apache.zookeeper.server.persistence.TxnLog |
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TxnLog.TxnIterator |
Field Summary | |
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static int |
TXNLOG_MAGIC
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static int |
VERSION
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Constructor Summary | |
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FileTxnLog(java.io.File logDir)
constructor for FileTxnLog. |
Method Summary | |
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boolean |
append(TxnHeader hdr,
org.apache.jute.Record txn)
append an entry to the transaction log |
void |
close()
close all the open file handles |
void |
commit()
commit the logs. |
long |
getDbId()
the dbid of this transaction database |
long |
getLastLoggedZxid()
get the last zxid that was logged in the transaction logs |
static java.io.File[] |
getLogFiles(java.io.File[] logDirList,
long snapshotZxid)
Find the log file that starts at, or just before, the snapshot. |
protected java.util.zip.Checksum |
makeChecksumAlgorithm()
creates a checksum alogrithm to be used |
TxnLog.TxnIterator |
read(long zxid)
start reading all the transactions from the given zxid |
void |
rollLog()
rollover the current log file to a new one. |
static void |
setPreallocSize(long size)
method to allow setting preallocate size of log file to pad the file. |
boolean |
truncate(long zxid)
truncate the current transaction logs |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static final int TXNLOG_MAGIC
public static final int VERSION
Constructor Detail |
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public FileTxnLog(java.io.File logDir)
logDir
- the directory where the txnlogs are storedMethod Detail |
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public static void setPreallocSize(long size)
size
- the size to set to in bytesprotected java.util.zip.Checksum makeChecksumAlgorithm()
public void rollLog() throws java.io.IOException
rollLog
in interface TxnLog
java.io.IOException
public void close() throws java.io.IOException
close
in interface TxnLog
java.io.IOException
public boolean append(TxnHeader hdr, org.apache.jute.Record txn) throws java.io.IOException
append
in interface TxnLog
hdr
- the header of the transactiontxn
- the transaction part of the entry
returns true iff something appended, otw false
java.io.IOException
public static java.io.File[] getLogFiles(java.io.File[] logDirList, long snapshotZxid)
logDirList
- array of filessnapshotZxid
- return files at, or before this zxid
public long getLastLoggedZxid()
getLastLoggedZxid
in interface TxnLog
public void commit() throws java.io.IOException
commit
in interface TxnLog
java.io.IOException
public TxnLog.TxnIterator read(long zxid) throws java.io.IOException
read
in interface TxnLog
zxid
- the zxid to start reading transactions from
java.io.IOException
public boolean truncate(long zxid) throws java.io.IOException
truncate
in interface TxnLog
zxid
- the zxid to truncate the logs to
java.io.IOException
public long getDbId() throws java.io.IOException
getDbId
in interface TxnLog
java.io.IOException
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