[GitHub] [hadoop] steveloughran commented on a diff in pull request #5675: HADOOP-18740. S3A prefetch cache blocks should be accessed by RW locks

[via GitHub]

steveloughran commented on code in PR #5675:
URL: https://github.com/apache/hadoop/pull/5675#discussion_r1213038983


##
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##
@@ -310,7 +333,12 @@ public void close() throws IOException {
 int numFilesDeleted = 0;
 
 for (Entry entry : blocks.values()) {
-  entry.takeLock(Entry.LockType.WRITE);
+  boolean lockAcquired = entry.takeLock(Entry.LockType.WRITE, 5, 
TimeUnit.SECONDS);

Review Comment:
   pull the number into a constant. Know that I automatically -1 all inline 
constants in production code and save time all round.



##
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##
@@ -127,11 +128,33 @@ void takeLock(LockType lockType) {
  */
 void releaseLock(LockType lockType) {
   if (LockType.READ == lockType) {
-this.lock.readLock().unlock();
+lock.readLock().unlock();
   } else if (LockType.WRITE == lockType) {
-this.lock.writeLock().unlock();
+lock.writeLock().unlock();
   }
 }
+
+/**
+ * Try to take the read or write lock within the given timeout.
+ *
+ * @param lockType type of the lock.
+ * @param timeout the time to wait for the given lock.
+ * @param unit the time unit of the timeout argument.
+ * @return true if the lock of the given lock type was acquired.
+ */
+boolean takeLock(LockType lockType, long timeout, TimeUnit unit) {

Review Comment:
   should this and the others be private? you don't want other classes playing 
with your lock code...



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[GitHub] [hadoop] steveloughran commented on a diff in pull request #5675: HADOOP-18740. S3A prefetch cache blocks should be accessed by RW locks

[via GitHub]

steveloughran commented on code in PR #5675:
URL: https://github.com/apache/hadoop/pull/5675#discussion_r1211811893


##
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##
@@ -99,6 +106,32 @@ public String toString() {
   "([%03d] %s: size = %d, checksum = %d)",
   blockNumber, path, size, checksum);
 }
+
+/**
+ * Take the read or write lock.
+ *
+ * @param lockType type of the lock.
+ */
+void takeLock(LockType lockType) {
+  if (LockType.READ == lockType) {
+this.lock.readLock().lock();

Review Comment:
   remove the `this.`



##
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##
@@ -99,6 +106,32 @@ public String toString() {
   "([%03d] %s: size = %d, checksum = %d)",
   blockNumber, path, size, checksum);
 }
+
+/**
+ * Take the read or write lock.
+ *
+ * @param lockType type of the lock.
+ */
+void takeLock(LockType lockType) {
+  if (LockType.READ == lockType) {
+this.lock.readLock().lock();
+  } else if (LockType.WRITE == lockType) {
+this.lock.writeLock().lock();
+  }
+}
+
+/**
+ * Release the read or write lock.
+ *
+ * @param lockType type of the lock.
+ */
+void releaseLock(LockType lockType) {
+  if (LockType.READ == lockType) {
+this.lock.readLock().unlock();

Review Comment:
   remove the `this.`



##
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##
@@ -268,12 +310,15 @@ public void close() throws IOException {
 int numFilesDeleted = 0;
 
 for (Entry entry : blocks.values()) {
+  entry.takeLock(Entry.LockType.WRITE);

Review Comment:
   should we be acquiring locks in close()?
   good: no race condition in close
   bad) the usual
   
   also, L303: should closed be atomic?



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