DefaultUpdateHandler heap space exception when file to download is 0b

[yildiz-online]

Due to a bug in my app, the update4j xml generated ended up with a 0b file size instead of correct size(65mo), leading to this exception in the client using that xml:

Part of the XML file:

file uri="http://files.yildiz-games.be/play50hz/player/retro-player.jar" path="${user.dir}/lib/retro-player.jar" size="0" checksum="1"

Exception:

Downloading 0 B 0% [> ] Exception in thread "Progress Printer" java.lang.OutOfMemoryError: Java heap space
at java.base/java.util.Arrays.copyOf(Unknown Source)
at java.base/java.util.StringJoiner.add(Unknown Source)
at java.base/java.lang.String.join(Unknown Source)
at org.update4j.util.StringUtils.repeat(StringUtils.java:123)
at org.update4j.service.DefaultUpdateHandler.renderProgress(DefaultUpdateHandler.java:189)
at org.update4j.service.DefaultUpdateHandler$1.run(DefaultUpdateHandler.java:127)
at java.base/java.util.TimerThread.mainLoop(Unknown Source)
at java.base/java.util.TimerThread.run(Unknown Source)

Same file with expected size(65mo) is handled correctly.

[mordechaim]

Thanks, I'll look into this.

Does this happen on JDK 11+ too?

[yildiz-online]

Sorry forgot to mention env,
java 11, win64

[mordechaim]

Sorry forgot to mention env,
java 11, win64

The env usually doesn't matter but in the case of String::repeat I created a polyfill to work on earlier versions. It seems to be a bug in the core JDK.

I'll look into it when I have a chance.

[mordechaim]

I have a hunch is an int overflow bug.

[mordechaim]

The problem is here:

update4j/src/main/java/org/update4j/ConfigImpl.java

Line 354 in 2c4c04c

handler.updateDownloadFileProgress(file, (float) (currentCompleted / file.getSize()));

Which is a divide by zero. While for integers is fails with an ArithmeticException it will silently pass for real numbers with value Float.POSITIVE_INFINITY.

Then in this line:

update4j/src/main/java/org/update4j/service/DefaultUpdateHandler.java

Lines 188 to 189 in 2c4c04c

	int pieces = (int) ((progressWidth - 2) * currentFrac);
	String line = repeat(pieces, "=");

we multiple an int by Infinity which results in Integer.MAX_VALUE.

Attempting to repeat a string by max value will cause an OutOfMemoryError

[mordechaim]

I think this a very special case that should probably not be handled by update4j. It will fail regardless in the file validation phase.

[yildiz-online]

Totally agree that it should fail (input is wrong anyway) but would be nice to have a better suited exception thrown early to avoid filling the heap space .

Or maybe ignore files with size 0 and checksum 1 ?

[mordechaim]

The safest and least intrusive would be to simply clamp the progress between 0 and 1 and never allow leaking out of those bounds.