race condition in XRLog/JDKXRLogger

[syjer]

We're having what seems to be a race condition in our tests, which run in parallel in different threads :

Caused by: java.lang.NullPointerException
	at com.openhtmltopdf.util.JDKXRLogger.getLogger(JDKXRLogger.java:103)
	at com.openhtmltopdf.util.JDKXRLogger.isLogLevelEnabled(JDKXRLogger.java:75)
	at com.openhtmltopdf.util.XRLog.log(XRLog.java:122)
	at com.openhtmltopdf.util.XRLog.log(XRLog.java:85)
	at com.openhtmltopdf.context.StyleReference.getStylesheets(StyleReference.java:253)
	at com.openhtmltopdf.context.StyleReference.setDocumentContext(StyleReference.java:102)
	at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.setDocumentP(PdfBoxRenderer.java:319)
	at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.setDocumentP(PdfBoxRenderer.java:292)
	at com.openhtmltopdf.pdfboxout.PdfBoxRenderer.<init>(PdfBoxRenderer.java:247)
	at com.openhtmltopdf.pdfboxout.PdfRendererBuilder.buildPdfRenderer(PdfRendererBuilder.java:67)
	at com.openhtmltopdf.pdfboxout.PdfRendererBuilder.run(PdfRendererBuilder.java:42)

I will put up a test case which reproduces the problem

Originally posted by @testinfected in #552 (comment)

[syjer]

Thanks to @testinfected 👍 .

Code for reproducing the error:

public static void main(String[] args) throws Exception {

        int p = 20;
        CountDownLatch latch = new CountDownLatch(p);
        for (int i = 0; i < p;i++) {
            new Thread(() -> {
                latch.countDown();
                try {
                    latch.await();
                    XRLog.log(Level.SEVERE, LogMessageId.LogMessageId0Param.CASCADE_IS_ABSOLUTE_CSS_UNKNOWN_GIVEN);
                } catch (InterruptedException e) {
                }
            }).start();
        }
    }

[syjer]

seems that moving

openhtmltopdf/openhtmltopdf-core/src/main/java/com/openhtmltopdf/util/JDKXRLogger.java

Line 111 in 801780b

initPending = false;

after the call initializeJDKLogManager() is enough to fix it. And it may make sense :).

We could even wrap the initializeJDKLogManager in a try {} block and setting the variable in a finally block.