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Hibernate: avoid potential deadlock on c3p0 

If StartGameHandler takes the last connection available in the c3p0
pool, then Game.start() will block inside sessionProvider.get().  But
since this is nested within, StartGameHandler never gets to the
`finally` block where it releases its connection.
This commit is contained in:
Matt Mullins 2020-04-09 22:23:42 -07:00
parent 296a692db9
commit d421fcb254
2 changed files with 33 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
src/main/java/net/socialgamer/cah/data/Game.java
View File

@ -703,47 +703,39 @@ public class Game {
* game is already started, or doesn't have enough cards, but hopefully callers and
* clients would prevent that from happening!
*/
public boolean start() {
Session session = null;
try {
session = sessionProvider.get();
if (state != GameState.LOBBY || !hasEnoughCards(session)) {
return false;
}
boolean started;
final int numPlayers = players.size();
if (numPlayers >= 3) {
// Pick a random start judge, though the "next" judge will actually go first.
judgeIndex = (int) (Math.random() * numPlayers);
started = true;
} else {
started = false;
}
if (started) {
currentUniqueId = uniqueIdProvider.get();
logger.info(String.format("Starting game %d with card sets %s, Cardcast %s, %d blanks, %d "
+ "max players, %d max spectators, %d score limit, players %s, unique %s.",
id, options.cardSetIds, cardcastDeckIds, options.blanksInDeck, options.playerLimit,
options.spectatorLimit, options.scoreGoal, players, currentUniqueId));
// do this stuff outside the players lock; they will lock players again later for much less
// time, and not at the same time as trying to lock users, which has caused deadlocks
final List<CardSet> cardSets;
synchronized (options.cardSetIds) {
cardSets = loadCardSets(session);
blackDeck = loadBlackDeck(cardSets);
whiteDeck = loadWhiteDeck(cardSets);
}
metrics.gameStart(currentUniqueId, cardSets, options.blanksInDeck, options.playerLimit,
options.scoreGoal, !StringUtils.isBlank(options.password));
startNextRound();
gameManager.broadcastGameListRefresh();
}
return started;
} finally {
if (null != session) {
session.close();
}
public boolean start(Session session) {
if (state != GameState.LOBBY || !hasEnoughCards(session)) {
return false;
}
boolean started;
final int numPlayers = players.size();
if (numPlayers >= 3) {
// Pick a random start judge, though the "next" judge will actually go first.
judgeIndex = (int) (Math.random() * numPlayers);
started = true;
} else {
started = false;
}
if (started) {
currentUniqueId = uniqueIdProvider.get();
logger.info(String.format("Starting game %d with card sets %s, Cardcast %s, %d blanks, %d "
+ "max players, %d max spectators, %d score limit, players %s, unique %s.",
id, options.cardSetIds, cardcastDeckIds, options.blanksInDeck, options.playerLimit,
options.spectatorLimit, options.scoreGoal, players, currentUniqueId));
// do this stuff outside the players lock; they will lock players again later for much less
// time, and not at the same time as trying to lock users, which has caused deadlocks
final List<CardSet> cardSets;
synchronized (options.cardSetIds) {
cardSets = loadCardSets(session);
blackDeck = loadBlackDeck(cardSets);
whiteDeck = loadWhiteDeck(cardSets);
}
metrics.gameStart(currentUniqueId, cardSets, options.blanksInDeck, options.playerLimit,
options.scoreGoal, !StringUtils.isBlank(options.password));
startNextRound();
gameManager.broadcastGameListRefresh();
}
return started;
}
public List<CardSet> loadCardSets(final Session session) {

2
src/main/java/net/socialgamer/cah/handlers/StartGameHandler.java
View File

@ -80,7 +80,7 @@ public class StartGameHandler extends GameWithPlayerHandler {
data.put(ErrorInformation.WHITE_CARDS_PRESENT, game.loadWhiteDeck(cardSets).totalCount());
data.put(ErrorInformation.WHITE_CARDS_REQUIRED, game.getRequiredWhiteCardCount());
return error(ErrorCode.NOT_ENOUGH_CARDS, data);
} else if (!game.start()) {
} else if (!game.start(hibernateSession)) {
return error(ErrorCode.NOT_ENOUGH_PLAYERS);
} else {
return data;