[KARAF-4802] Auto Deploy does not release resource

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0.5, 4.0.7
• Fix Version/s: 4.1.0, 4.0.9
• Component/s: karaf
• Labels: leak

Environment

JDK 1.8.0_102 / Win10 (x64)

• Flags: Patch, Important
• Assignee: Freeman Yue Fang
• Reporter: Frederic ARNOUD
• Created: 21/Oct/16 14:32
• Updated: 14/Sep/18 08:35
• Resolved: 12/Jan/17 06:00

Description

Calling getLastModified() opens the input stream.

In org.apache.karaf.deployer.blueprint-4.0.7-sources.jar:

org/apache/karaf/deployer/blueprint/BlueprintTransformer.java:94:
url.openConnection().getLastModified()
=> calls sun.net.www.protocol.file.FileURLConnection#getLastModified()
=> calls sun.net.www.protocol.file.FileURLConnection#initializeHeaders()
=> calls sun.net.www.protocol.file.FileURLConnection#connect()
in this function at line 57: this.connected is false
and line 61: this.isDirectory is false
Here they open the input stream:
error source is at line 69: open input stream and keep it in this.is

Note:
There's a mistake at line (since they try to open the stream):
sun/net/www/protocol/file/FileURLConnection.java:90 with a nice empty try/catch!

AFAIK, there's no way to know if stream was open or not.
I checked HttpURLConnection, it does the same (and HttpsURLConnection also).

IMHO you should add a function like this one (in BlueprintTransformer.java):

    protected static long getLastModified(URL url) throws IOException {
        URLConnection urlConnection = url.openConnection();
        try(InputStream is = urlConnection.getInputStream()) {
            return urlConnection.getLastModified();
        }
    }

To limit number of stream access, I did this in my code (in function similar to transform(URL, OutputStream)):

        final URLConnection urlConnection = url.openConnection();
        // keep original last modification date
        final long lastModified = urlConnection.getLastModified();
        try (InputStream in = urlConnection.getInputStream()) {
            source = readAllBytes(in);
        }

Note:
When no object reference the InputStream, InputStream class will automatically close the stream while processing finalizations.
Before this process, we cannot delete file in deploy directory.

(sorry I did not find component for this class)

Same issue should appear in other deployers (not checked).