Sebastian Nagel created NUTCH-2578:
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Summary: Avoid lock by MimeUtil in constructor of protocol.Content
Key: NUTCH-2578
URL: https://issues.apache.org/jira/browse/NUTCH-2578
Project: Nutch
Issue Type: Improvement
Components: protocol
Affects Versions: 1.14
Reporter: Sebastian Nagel
Fix For: 1.15
The constructor of the class o.a.n.protocol.Content instantiates a new MimeUtil
object. That's not cheap as it always creates a new tika.MimeTypes object and
there is a lock on the job/jar file when config files are read:
{noformat}
"FetcherThread" #146 daemon prio=5 os_prio=0 tid=0x00007f70523c3800 nid=0x1de2
waiting for monitor entry [0x00007f70193a8000]
java.lang.Thread.State: BLOCKED (on object monitor)
at java.util.zip.ZipFile.getEntry(ZipFile.java:314)
- waiting to lock <0x00000005e0285758> (a java.util.jar.JarFile)
at java.util.jar.JarFile.getEntry(JarFile.java:240)
at java.util.jar.JarFile.getJarEntry(JarFile.java:223)
at sun.misc.URLClassPath$JarLoader.getResource(URLClassPath.java:1042)
at sun.misc.URLClassPath$JarLoader.findResource(URLClassPath.java:1020)
at sun.misc.URLClassPath$1.next(URLClassPath.java:267)
at sun.misc.URLClassPath$1.hasMoreElements(URLClassPath.java:277)
at java.net.URLClassLoader$3$1.run(URLClassLoader.java:601)
at java.net.URLClassLoader$3$1.run(URLClassLoader.java:599)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader$3.next(URLClassLoader.java:598)
at java.net.URLClassLoader$3.hasMoreElements(URLClassLoader.java:623)
at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
at
sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
at java.util.Collections.list(Collections.java:5239)
at
org.apache.tika.config.ServiceLoader.identifyStaticServiceProviders(ServiceLoader.java:325)
at
org.apache.tika.config.ServiceLoader.loadStaticServiceProviders(ServiceLoader.java:352)
at
org.apache.tika.config.ServiceLoader.loadServiceProviders(ServiceLoader.java:274)
at
org.apache.tika.detect.DefaultEncodingDetector.<init>(DefaultEncodingDetector.java:45)
at
org.apache.tika.config.TikaConfig.getDefaultEncodingDetector(TikaConfig.java:92)
at org.apache.tika.config.TikaConfig.<init>(TikaConfig.java:248)
at
org.apache.tika.config.TikaConfig.getDefaultConfig(TikaConfig.java:386)
at org.apache.tika.Tika.<init>(Tika.java:116)
at org.apache.nutch.util.MimeUtil.<init>(MimeUtil.java:69)
at org.apache.nutch.protocol.Content.<init>(Content.java:83)
at
org.apache.nutch.protocol.http.api.HttpBase.getProtocolOutput(HttpBase.java:316)
at org.apache.nutch.fetcher.FetcherThread.run(FetcherThread.java:341)
{noformat}
If there are many Fetcher threads this may cause a significant bottleneck,
running a Fetcher with 120 threads I've found up to 50 threads waiting for this
lock:
{noformat}
# pid 7195 is a Fetcher map task
% sudo -u yarn jstack 7195 \
| grep -A25 'waiting to lock' \
| grep -F 'org.apache.tika.Tika.<init>' \
| wc -l
49
{noformat}
As MimeUtil is thread-safe [including the called Tika
detector|https://www.mail-archive.com/[email protected]/msg00296.html], the
best solution seems to cache the MimeUtil object in the actual protocol
implementation as it is done in Nutch 2.x ([lib-http HttpBase, line
#151|https://github.com/apache/nutch/blob/2.x/src/plugin/lib-http/src/java/org/apache/nutch/protocol/http/api/HttpBase.java#L151]).
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