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Whirled's Passport system is using player stats to award "badges," and a few changes to stats are necessary to allow mutliple clients to safely modify stats simultaneously:

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- add a modCount field to Stat to assist detecting if a stat has been updated in the repository since being loaded into memory
- StatRepository.updateStat() is rewritten to support optionally failing if modCount has been updated (existing Stat code should not be affected by this change)
- added StatRepository.loadStat() and StatRepository.updateStatIfCurrent() to support loadingand updating of single stats.


git-svn-id: svn+ssh://src.earth.threerings.net/vilya/trunk@661 c613c5cb-e716-0410-b11b-feb51c14d237
This commit is contained in:
Tom Conkling
2008-07-17 20:40:36 +00:00
parent cf1779e8b8
commit 0e74ed2842
3 changed files with 114 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/java/com/threerings/stats/data/Stat.java
+20
View File
@@ -122,6 +122,23 @@ public abstract class Stat
_modified = modified;
}
/**
* Returns the modification count of this Stat when it was loaded from the repository.
*/
public byte getModCount ()
{
return _modCount;
}
/**
* Sets the modification count for this Stat. StatRepository calls this when converting
* a StatRecord into a Stat; it shouldn't be called otherwise.
*/
public void setModCount (byte modCount)
{
_modCount = modCount;
}
/** Writes our custom streamable fields. */
public void writeObject (ObjectOutputStream out)
throws IOException
@@ -192,6 +209,9 @@ public abstract class Stat
* was loaded from the database. */
protected transient boolean _modified;
/** The last known modification count for this stat, if it was read from the database. */
protected transient byte _modCount;
/** Used for computing our stat codes. */
protected static CRC32 _crc = new CRC32();
src/java/com/threerings/stats/server/persist/StatRecord.java
+21 -1
View File
@@ -52,9 +52,16 @@ public class StatRecord extends PersistentRecord
/** The qualified column identifier for the {@link #statData} field. */
public static final ColumnExp STAT_DATA_C =
new ColumnExp(StatRecord.class, STAT_DATA);
/** The column identifier for the {@link #modCount} field. */
public static final String MOD_COUNT = "modCount";
/** The qualified column identifier for the {@link #modCount} field. */
public static final ColumnExp MOD_COUNT_C =
new ColumnExp(StatRecord.class, MOD_COUNT);
// AUTO-GENERATED: FIELDS END
public static final int SCHEMA_VERSION = 2;
public static final int SCHEMA_VERSION = 4;
/** The identifier of the player this is a stat for. */
@Id
@@ -70,6 +77,13 @@ public class StatRecord extends PersistentRecord
@Column(name="STAT_DATA", length=65535)
public byte[] statData;
/**
* The number of times this stat has been updated, so that simultaneous attempts to update
* the same stat in the repository can be caught and handled. Stored as a byte because
* we don't expect to ever have more than a couple simultaneous attempts to update a stat.
*/
public byte modCount;
/**
* An empty constructor for unmarshalling.
*/
@@ -82,11 +96,17 @@ public class StatRecord extends PersistentRecord
* A constructor that populates all our fields.
*/
public StatRecord (int playerId, int statCode, byte[] data)
{
this(playerId, statCode, data, (byte)0);
}
public StatRecord (int playerId, int statCode, byte[] data, byte modCount)
{
super();
this.playerId = playerId;
this.statCode = statCode;
this.statData = data;
this.modCount = modCount;
}
// AUTO-GENERATED: METHODS START
src/java/com/threerings/stats/server/persist/StatRepository.java
+73 -9
View File
@@ -10,8 +10,6 @@ import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Set;
import java.util.logging.Level;
import com.google.inject.Singleton;
import com.google.inject.Inject;
@@ -57,6 +55,32 @@ public class StatRepository extends DepotRepository
loadStringCodes(null);
}
/**
* Loads a single stat for the specified player.
*/
public Stat loadStat (int playerId, int statCode)
throws PersistenceException
{
Where where = new Where(StatRecord.PLAYER_ID_C, playerId, StatRecord.STAT_CODE_C, statCode);
StatRecord record = load(StatRecord.class, where);
return (null != record ? decodeStat(record.statCode, record.statData, record.modCount)
: null);
}
/**
* Saves a single stat for the specified player, if the stat hasn't been modified in the
* repository since being loaded (that is, if its modCount field in the repository hasn't
* changed).
*
* @return true if the stat was written to the repository, false if its modCount prevented
* it from being written.
*/
public boolean updateStatIfCurrent (int playerId, Stat stat)
throws PersistenceException
{
return this.updateStat(playerId, stat, true);
}
/**
* Loads the stats associated with the specified player.
*
@@ -67,7 +91,7 @@ public class StatRepository extends DepotRepository
ArrayList<Stat> stats = new ArrayList<Stat>();
Where where = new Where(StatRecord.PLAYER_ID_C, playerId);
for (StatRecord record : findAll(StatRecord.class, where)) {
Stat stat = decodeStat(record.statCode, record.statData);
Stat stat = decodeStat(record.statCode, record.statData, record.modCount);
if (stat != null) {
stats.add(stat);
}
@@ -97,6 +121,8 @@ public class StatRepository extends DepotRepository
/**
* Writes out any of the stats in the supplied array that have been modified since they were
* first loaded. Exceptions that occur while writing the stats will be caught and logged.
*
*
*/
public void writeModified (int playerId, Stat[] stats)
{
@@ -104,7 +130,7 @@ public class StatRepository extends DepotRepository
try {
if (stats[ii].getType().isPersistent() &&
stats[ii].isModified()) {
updateStat(playerId, stats[ii]);
updateStat(playerId, stats[ii], false);
}
} catch (Exception e) {
log.warning("Error flushing modified stat [stat=" + stats[ii] + "].", e);
@@ -171,20 +197,20 @@ public class StatRepository extends DepotRepository
/**
* Instantiates the appropriate stat class and decodes the stat from the data.
*/
protected Stat decodeStat (int statCode, byte[] data)
protected Stat decodeStat (int statCode, byte[] data, byte modCount)
{
Stat.Type type = Stat.getType(statCode);
if (type == null) {
log.warning("Unable to decode stat, unknown type [code=" + statCode + "].");
return null;
}
return decodeStat(type.newStat(), data);
return decodeStat(type.newStat(), data, modCount);
}
/**
* Instantiates the appropriate stat class and decodes the stat from the data.
*/
protected Stat decodeStat (Stat stat, byte[] data)
protected Stat decodeStat (Stat stat, byte[] data, byte modCount)
{
String errmsg = null;
Exception error = null;
@@ -193,6 +219,7 @@ public class StatRepository extends DepotRepository
// decode its contents from the serialized data
ByteArrayInputStream bin = new ByteArrayInputStream(data);
stat.unpersistFrom(new ObjectInputStream(bin), this);
stat.setModCount(modCount);
return stat;
} catch (ClassNotFoundException cnfe) {
@@ -210,8 +237,10 @@ public class StatRepository extends DepotRepository
/**
* Updates the specified stat in the database, inserting it if necessary.
*
* @return true if the update was successful, false if it failed.
*/
protected void updateStat (int playerId, final Stat stat)
protected boolean updateStat (int playerId, final Stat stat, boolean failIfUncurrent)
throws PersistenceException
{
ByteArrayOutInputStream out = new ByteArrayOutInputStream();
@@ -222,7 +251,42 @@ public class StatRepository extends DepotRepository
throw new PersistenceException(errmsg, ioe);
}
store(new StatRecord(playerId, stat.getCode(), out.toByteArray()));
byte nextModCount = (byte)((stat.getModCount() + 1) % Byte.MAX_VALUE);
// update the row in the database only if it has the expected modCount
int numRows = updatePartial(
StatRecord.class,
new Where(StatRecord.PLAYER_ID_C, playerId,
StatRecord.STAT_CODE_C, stat.getCode(),
StatRecord.MOD_COUNT_C, stat.getModCount()),
StatRecord.getKey(playerId, stat.getCode()),
StatRecord.STAT_DATA_C, out.toByteArray(), StatRecord.MOD_COUNT_C, nextModCount);
if (numRows == 0) {
// If we failed to update any rows, it could be because we saw an unexpected modCount,
// or because the stat did not already exist in the repo. If it didn't exist, let's
// try to create it.
if (loadStat(playerId, stat.getCode()) == null) {
try {
insert(new StatRecord(playerId, stat.getCode(), out.toByteArray(),
nextModCount));
numRows = 1;
} catch (DuplicateKeyException e) {
// somebody else inserted the StatRecord before we were able to.
numRows = 0;
}
}
if (numRows == 0 && !failIfUncurrent) {
// give up and store the stat anyway
log.warning("Possible collision while storing StatRecord (playerId: " +
playerId + " stat: " + stat.getType().name() + ")");
store(new StatRecord(playerId, stat.getCode(), out.toByteArray(), nextModCount));
numRows = 1;
}
}
return (numRows > 0);
}
/** Helper function for {@link #getStringCode}. */