问题
My specs:
-Ubuntu 64bit
-Neo4j 2.0
-32 GB of Ram
-AMD FX-8350 Eight COre Processor
The problem:
I'm making a request to my Neo4j server with the following query:
MATCH (being:my_label_2) RETURN being
And gives me this error:
OutOfMemoryError
Requested array size exceeds VM limit
StackTrace:
java.lang.StringCoding$StringEncoder.encode(StringCoding.java:300)
java.lang.StringCoding.encode(StringCoding.java:344)
java.lang.String.getBytes(String.java:916)
org.neo4j.server.rest.repr.OutputFormat.toBytes(OutputFormat.java:194)
org.neo4j.server.rest.repr.OutputFormat.formatRepresentation(OutputFormat.java:147)
org.neo4j.server.rest.repr.OutputFormat.response(OutputFormat.java:130)
org.neo4j.server.rest.repr.OutputFormat.ok(OutputFormat.java:67)
org.neo4j.server.rest.web.CypherService.cypher(CypherService.java:101)
java.lang.reflect.Method.invoke(Method.java:606)
org.neo4j.server.rest.transactional.TransactionalRequestDispatcher.dispatch(TransactionalRequestDispatcher.java:139)
org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)
This works fine with "my_label_1" which returns around 30k results
What I believe is the problem:
I don't have enough memory allocated to my JVM
Attempts made to fix/things I've found online:
I read what the manual says to do
And what the Ubuntu Forums say to do
So I've tried going to my neo4 folder (with cd as usual) and running it with the arguments this way:
sudo bin/neo4j start -Xmx4096M
However that didn't work. When Neo4j starts it does warn me that I might not have enough space with:
WARNING: Max 1024 open files allowed, minimum of 40 000 recommended. See the Neo4j manual.
Using additional JVM arguments: -server -XX:+DisableExplicitGC -Dorg.neo4j.server.properties=conf/neo4j-server.properties -Djava.util.logging.config.file=conf/logging.properties -Dlog4j.configuration=file:conf/log4j.properties -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled
Question
I know I'm definitely using the arguments wrong, I honestly don't have much experience with JVM configurations. How should I approach this, am I missing something?
回答1:
You should put JVM setting into the conf/neo4j-wrapper.conf file. It should look like this:
user@pc:> head -n 7 neo4j-enterprise-2.0.0/conf/neo4j-wrapper.conf
wrapper.java.additional=-Dorg.neo4j.server.properties=conf/neo4j-server.properties
wrapper.java.additional=-Djava.util.logging.config.file=conf/logging.properties
wrapper.java.additional=-Dlog4j.configuration=file:conf/log4j.properties
# Java Additional Parameters
wrapper.java.additional=-XX:+UseConcMarkSweepGC
wrapper.java.additional=-XX:+CMSClassUnloadingEnabled
Note that you can configure different aspects of neo4j via different files, so it's better to read description to every file in that conf/ directory in order to get familiar with what can be done and how exactly.
来源：https://stackoverflow.com/questions/22717508/increase-heap-space-available-for-jvm-outofmemoryerror-requested-array-size-ex