Docker容器阻止中的Apache Batik转码器 [英] Apache Batik Transcoder inside Docker Container Blocking

问题描述

我们正在docker容器中运行Spring应用程序.我们的应用程序可以提取SVG文件并将其转换为PDF格式，以嵌入到PDF中.

We're running a Spring application within a docker container. Our application can take SVG files and transform them into PDF format to be embedded within a PDF.

该应用程序可以在osx上正常工作，并且可以按预期进行转码.但是，当从具有不同文件系统的Docker容器中运行时，转码器会卡住并在某些奇异的递归文件搜索循环中使cpu失灵.

The application works correctly on osx and transcodes as expected. However when run from inside a docker container, which has a different file system, the transcoder gets stuck and thrashes the cpu in some bizarre recursive file searching loop.

java.lang.Thread.State: RUNNABLE
    at java.io.UnixFileSystem.getBooleanAttributes0(Native Method)
    at java.io.UnixFileSystem.getBooleanAttributes(UnixFileSystem.java:242)
    at java.io.File.isFile(File.java:882)
    at org.apache.commons.io.filefilter.FileFileFilter.accept(FileFileFilter.java:59)
    at org.apache.commons.io.filefilter.AndFileFilter.accept(AndFileFilter.java:122)
    at org.apache.commons.io.filefilter.AndFileFilter.accept(AndFileFilter.java:122)
    at org.apache.commons.io.filefilter.OrFileFilter.accept(OrFileFilter.java:118)
    at java.io.File.listFiles(File.java:1291)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:357)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364)
    at org.apache.commons.io.DirectoryWalker.walk(DirectoryWalker.java:364

下面是运行PDFTranscoder的线程的堆栈跟踪.递归调用Walk一段时间，然后最终调用getBooleanAttributes0，一切都将阻塞.

Here's a look at the stack trace of a thread that ran the PDFTranscoder. Walk is called recursively for a while and then eventually getBooleanAttributes0 is called and everything blocks.

经过进一步研究，我们发现可以仔细查看strace命令的情况，并发现该系统实质上是在无休止的循环中发送垃圾邮件.

After some further research, we found out we could take a closer look at what is happening with the strace command and saw that the system is essentially spamming the following in an endless loop.

stat("/./sys/devices/pci0000:00/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/PNP0103:00/subsystem/devices/pcspkr/input/input1/subsystem/input0/subsystem/input0/uniq", {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0 <0.000224>

我们似乎被禁止或挂在stat通话中.但是我们现在已经对系统调用进行了深入的研究，以至于很难调试.有人有什么想法吗?

We seem to be getting blocked or hanging in the stat call. But we've delved so deep into system calls now that it's proving hard to debug. Does anyone have any ideas?

推荐答案

我遇到了同样的错误.在尝试了许多修复后，我得出的结论是，这是您在Mac OS X上拥有可用字体的问题，而您的(无头)Docker容器OS没有字体.在各处搜索字体时，代码转换器不会出现故障.我通过强制代码转换器使用默认字体来解决此问题(并且不会自动寻找其他字体)，如下所示:

I was getting the same error. After trying many things to fix it, I came to the conclusion that it's an issue with your having fonts available to you on Mac OS X, while your (headless) Docker container OS has no fonts. The transcoder is not failing gracefully while searching for fonts all over the place. I solved it by forcing the transcoder to use the default fonts (and to not automatically look for other fonts) like this:

...
PDFTranscoder transcoder = new PDFTranscoder();
transcoder.addTranscodingHint(PDFTranscoder.KEY_AUTO_FONTS, false);
...
transcoder.transcode(transcoderInput, transcoderOutput);
...

请注意，这当然有一个缺点，当它遇到14种字体之外的一种时，会回退到其已知的字体.我尝试过解决问题的方法，但到目前为止还算不上运气.

Note this has the downside, of course, of falling back to its known fonts when it encounters one outside of the 14 fonts. I tried things to fix that but so far no luck.

我希望这对某人有帮助.

I hope this helps someone.

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