I've been thinking about this and I think the situation we are in is
okay. The variable is an int and so should be read in one memory access
(i would think?). So at worst, the result might be stale? Since this
read is just for informational type purposes, (eg its ok if this
particular method returns a stale value, by the time you read it its
likely to have changed anyway), I think its okay.
I think. Everything I read about the Java memory model, I quickly forget.
robert engels wrote:
FYI, any time one thread reads a value while another thread updates it
it needs to be synchronized, or with current JVMs a volatile variable.
The Java Memory Model requires this.
Otherwise you can get a partial value (when the underlying value
requires more than one memory access to retrieve).
On Nov 29, 2007, at 6:43 AM, Mark Miller (JIRA) wrote:
[
https://issues.apache.org/jira/browse/LUCENE-1026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12546702
]
Mark Miller commented on LUCENE-1026:
-------------------------------------
Hey Mark, few more questions:
1. Why is StopWatch needed?
StopWatch could certainly be taken out. I simply used it for
timing...to show someone else that it doesn't take that long to get
an accessor. I have no problem with removing it.
2. No need to synchronize on this since you're only returning the
value, not performing any modifications to it.
Its possible this could be taken out. I doubt there would be any
noticeable trouble if you tried to read that value while another
thread was updating it.
3. open() - is there a real need to throw an exception if someone
called the accessor.open() twice?
No real need I suppose. I believe this came in from the original
code. I have no objections to taking it out.
SimpleSearchServer is an attempt to give an example that shows how
this code can be used to create a very simple class that allows
multi-threaded access to a Lucene index. I whipped it out extremely
quickly, but its something I would like to build on. It can be nice
to hide the IndexAccessor code behind a simple to use class that
hides Lucene and a lot of complexity.
Thanks for your work on this!
- Mark
Provide a simple way to concurrently access a Lucene index from
multiple threads
--------------------------------------------------------------------------------
Key: LUCENE-1026
URL: https://issues.apache.org/jira/browse/LUCENE-1026
Project: Lucene - Java
Issue Type: New Feature
Components: Index, Search
Reporter: Mark Miller
Priority: Minor
Attachments: DefaultIndexAccessor.java,
DefaultMultiIndexAccessor.java, IndexAccessor.java,
IndexAccessorFactory.java, MultiIndexAccessor.java,
shai-IndexAccessor-2.zip, shai-IndexAccessor.zip,
shai-IndexAccessor3.zip, SimpleSearchServer.java, StopWatch.java,
TestIndexAccessor.java
For building interactive indexes accessed through a network/internet
(multiple threads).
This builds upon the LuceneIndexAccessor patch. That patch was not
very newbie friendly and did not properly handle MultiSearchers (or
at the least made it easy to get into trouble).
This patch simplifies things and provides out of the box support for
sharing the IndexAccessors across threads. There is also a simple
test class and example SearchServer to get you started.
Future revisions will be zipped.
Works pretty solid as is, but could use the ability to warm new
Searchers.
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