NoClassDefFoundError: org/apache/hadoop/hbase/rest/Main

Hi All,

This is my first mail in the apache mailing list... please bear with me as
I
am absolutely new to Hadoop and its family.

This is my question... I have some data on my hdfs in the following form.

(number:int,word:chararray, word2:chararray,somethingelse:int)

I want to get this data into a neatly formed HBase Table. I chose the
simpler way instead of writing my own udf. I wanted to do this....

register ../hbase/hbase-0.20.4.jar;
register ../hbase/hbase-0.20.4-test.jar;
A = Load '/some_data';
B = STORE A into 'hbase://something' USING
org.apache.pig.backend.hadoop.hbase.HBaseStorage;
dump B;

but this is the error I get when I do that

2010-07-22 16:38:35,041 [main] INFO
org.apache.pig.backend.hadoop.executionengine.HExecutionEngine -
Connecting
to hadoop file system at: hdfs://MyMachine01:9000
2010-07-22 16:38:35,550 [main] INFO
org.apache.pig.backend.hadoop.executionengine.HExecutionEngine -
Connecting
to map-reduce job tracker at: MyMachine01:9001
2010-07-22 16:38:35,868 [main] ERROR org.apache.pig.tools.grunt.Grunt -
ERROR 2998: Unhandled internal error.
org/apache/hadoop/hbase/mapreduce/TableInputFormat

I have checked my hbase-0.20.4.jar file and it does have a
TableInputFormat
class. I added the right path to hadoop-env.sh in the CLASSPATH field. I
added the conf folder to the classpath and also the test jar.

I don't know why it wouldn't work. My HBase installation went really
smooth.
I am able to check the status of the HBase in the hbase shell and still I
get this error. I am totally lost at this point. I would really appreciate
any help in this regard.

Thanks a bunch.
V.

Hi,

I've checked the Release Notes of HDFS 0.21 and saw two fixes from hadoop-
append included, other two not, but still some more that have to do with
sync 
stuff.
Is Hadoop-append for HBase made obsolete with HDFS 0.21?

Thank you,

Thomas Koch, http://www.koch.ro

Hello folks,

I created a branch for doing the append/sync support for Hadoop 0.20. You
can fetch the branch via

http://svn.apache.org/repos/asf/hadoo...anch-0.20-append/

If you feel that there are some JIRAS that need to go into this branch,
please update the fix-version of those JIRAS with the tag
"0.20-append</jira/secure/IssueNavigator.jspa?reset=true&mode=hide&sorter/order=DESC&sorter/field=priority&resolution=-1&pid=12310942&fixfor=12315103>
".

thanks,
dhruba

On Mon, May 10, 2010 at 11:35 PM, Dhruba Borthakur
<dhru### @gmail.com> wrote:


 @Allen: we are definitely behind 0.21 release. Tom White is guiding
that
 release and most developers are committed to removing blockers for
that
 release. Todd rightly mentions that the work being done for 0.20
benefits
 0.21 as well.

 @Jay: Thanks for summing it up so well. I completely agree with your
 viewpoint.

 thanks
 dhruba


 On Mon, May 10, 2010 at 2:06 PM, Jay Booth <jayb### @gmail.com>
wrote:

> Given that the 0.20-append branch pretty much already exists
> unofficially, via IRC, IM and email forwarded patchsets, it seems
like
> giving it an official home is just recognizing the status quo.
> Especially since 0.21 probably won't be getting rolled out into
> production everywhere the first day it's officially released.  If
the
> work's going on anyways, I don't see how giving people a shared
home
> hurts matters, if anything it gives them a better shared
touchpoint
> for forward-porting bugfixes to 0.21.
>
> A case could be made that by making it more painful to run
> 0.20-append, more momentum is created towards 0.21 but since Tom
is
> already on top of 21 and seemingly doing an excellent job, and
since
> the HBase community will probably be some of the first people to
move
> to 0.21 anyways, I don't see why having 0.20-append will damage
0.21's
> momentum at this point.
>
>
>
> On Mon, May 10, 2010 at 4:21 PM, Michael Segel
> <michae### @hotmail.com> wrote:
> >
> >
> >
> >> From: to### @cloudera.com
> >> Date: Mon, 10 May 2010 10:45:13 -0700
> >> Subject: Re: Hadoop support for hbase
> >> To: gene### @hadoop.apache.org
> >>
> >
> >> > The above is a fallacious setup.  How does a branch
in 0.20 detract
> >> > from the 0.21 momentum (The append feature that
we'd work on in 0.20
> >> > branch has little relation to how append works in
0.21).
> >>
> >> For what it's worth, though, the majority of the size of
the 0.20
> >> append patch is made up of additional unit tests. I have
started
> >> forward-porting these new tests to the trunk append and
it's already
> >> exposed a number of bugs. So while it's tempting to say
that the 0.20
> >> append is "wasted effort", it really is benefiting the
entire
> >> community and the 0.21 release as well.
> >>
> >> -Todd
> >>
> >
> > Sometimes you have to slow down to go faster.
> >
> >
> >
> > 

I've found examples using the older mapred interface but not the newer
mapreduce interface. I want to write a mapper that is configured to only
pull out specific rows(which are the mapper's keys) and a specific column's
value(which is the mapper's value).


Is there any examples of something like this available?

James Kilbride

Hey,

We're using stock CHD2 without any patches so I'm not sure if we have
hdfs630 or not. For HBase we're currently on 0.20.3 and will be testing
and
moving to 0.20.5 soon

What I did with this rollout of just config changes was take one region
server down at a time and restart the datanode on the same server. So what
I
gather I should have done was shutdown all the region servers before
restarting any of the data nodes?

I guess if I split it into different parts it would be :-

- HBase Rolling update for point/config releases is supported
  - Update masters first
  - Then update region servers in turn

- HDFS Data nodes don't support rolling updates? (Maybe better in the hdfs
list I guess)
  - Take down HBase
  - Take down datanodes
  - Update all the datanodes code/configs
  - Start datanodes
  - Start HBase

Would you be able to let me know which of these I've got right/wrong?

Thanks,

On 29 June 2010 15:50, Michael Segel <michae### @hotmail.com>
wrote:


 Dan,

 I don't think you can do that because your 'new/updated' node will
clash
 with the rest of the cloud.
 (We're talking code and not just cloud tuning parameters.) [Read
different
 jars...]

 If you're going to push an update out, then it has to be an 'all or
 nothing' push.

 Since we're using Cloudera's release, moving from CDH2 to CDH3
represents a
 full backup, down the cloud, remove the software completely, and then
then
 install new CDH3. Outside of that major switch, if we were going from
one
 sub release to another, it would be just a $> yum update
hadoop-0.20 call on
 each node.
 Again, you have to take the cloud down to do that.

 So the bottom line... if you're going to do upgrades, you'll need to
plan
 for some down time.

 HTH

 -Mike

 > From: dan.ha### @mendeley.com
 > Date: Tue, 29 Jun 2010 14:43:26 +0100
 > Subject: Rolling out Hadoop/HBase updates
 > To: us### @hbase.apache.org
 >
 > Hey,
 >
 > I've been thinking about how we do out configuration and code
updates for
 > Hadoop and HBase and was wondering what others do and what is
the best
 > practice to avoid errors with HBase.
 >
 > Currently we do a rolling update where we restart the services
on one
 node
 > at a time, so shutting down the region server then restarting
the
 datanode
 > and task trackers depending on what we are updating and what has
change.
 But
 > with this I have occasional found errors with the HBase cluster
 afterwards
 > due to corrupt META table which I think could have been caused
by
 restarting
 > the datanode, or maybe not waiting long enough for the cluster
to sort
 out
 > loosing a region server before moving on to the next.
 >
 > The most resent error upon restarting a node was :-
 >
 > 2010-06-29 10:46:44,970 ERROR
 > org.apache.hadoop.hbase.regionserver.HRegionServer: Error
closing
 > files,3822b1ea8ae015f3ec932cafaa282dd211d768ad,1275145898366
 > java.io.IOException: Filesystem closed
 >         at
org.apache.hadoop.hdfs.DFSClient.checkOpen(DFSClient.java:230)
 >
 > 2010-06-29 10:46:44,970 FATAL
 > org.apache.hadoop.hbase.regionserver.HRegionServer: Shutting
down
 > HRegionServer: file system not available
 > java.io.IOException: File system is not available
 >         at
 >

org.apache.hadoop.hbase.util.FSUtils.checkFileSystemAvailable(FSUtils.java:129)
 >
 >
 > Followed by this for every region being served :-
 >
 > 2010-06-29 10:46:44,996 ERROR
 > org.apache.hadoop.hbase.regionserver.HRegionServer: Error
closing
 > documents,082595c0-6d01-11df-936c-0026b95e484c,1275676410202
 > java.io.IOException: Filesystem closed
 >         at
org.apache.hadoop.hdfs.DFSClient.checkOpen(DFSClient.java:230)
 >
 >
 > After updating all the nodes all the region server shut down
after a
 > few minutes reporting the following :-
 >
 > 2010-06-29 11:21:59,508 WARN org.apache.hadoop.hdfs.DFSClient:
Error
 > Recovery for block blk_-1437671530216085093_2565663 bad
datanode[0]
 > 10.0.11.4:50010
 >
 > 2010-06-29 11:22:09,481 FATAL
org.apache.hadoop.hbase.regionserver.HLog:
 > Could not append. Requesting close of hlog
 > java.io.IOException: All datanodes 10.0.11.4:50010 are bad.
Aborting...
 >         at
 >

org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.processDatanodeError(DFSClient.java:2542)
 >
 >
 > 2010-06-29 11:22:09,482 FATAL
 > org.apache.hadoop.hbase.regionserver.LogRoller: Log rolling
failed with
 > ioe:
 > java.io.IOException: All datanodes 10.0.11.4:50010 are bad.
Aborting...
 >         at
 >

org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.processDatanodeError(DFSClient.java:2542)
 >
 > 2010-06-29 11:22:10,344 ERROR
 > org.apache.hadoop.hbase.regionserver.HRegionServer: Unable to
close log
 in
 > abort
 > java.io.IOException: All datanodes 10.0.11.4:50010 are bad.
Aborting...
 >         at
 >

org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.processDatanodeError(DFSClient.java:2542)
 >
 >
 > This was fixed by restarting the master and starting the region
servers
 > again, but it would be nice to know how to roll out changes
cleaner.
 >
 > How do other people here roll out updates to HBase / Hadoop?
What order
 do
 > you restart services in and how long do you wait before moving
to the
 next
 > node?
 >
 > Just so you know we currently have 5 nodes and are getting
another 10 to
 add
 > soon.
 >
 > Thanks,
 >
 > --
 > Dan Harvey | Datamining Engineer
 > www.mendeley.com/profiles/dan-harvey
 >
 > Mendeley Limited | London, UK | www.mendeley.com
 > Registered in England and Wales | Company Number 6419015

 

Hello,

In my current application environment, I need to have two HBase
clusters running in two different racks, to form a fault-tolerant
group to tolerate power failure. Then I have an HBase client, which is
sitting outside of these two clusters,  to make invocation to the
these two HBase clusters.

In my previous work, I just need to simply use the class of “HTable”,
and passed in an instance of HBaseConfiguration. And To construct the
HBaseConfiguration instance, I just need to pass in the path
information of the “hbase-site.xml”. And in the hbase-site.xml, there
is only one parameter called “hbase.rootdir” that need to configure.

Before HBase0.20.0, there used to be a parameter called “hbase.master”
that I can specify. But in HBase0.20.0, I found that it does not work
any more, likely because that the HBase master is managed by the
Zookeeper, and the master node now becomes dynamic.

Could you show me what are the APIs that I need to use, in order for
me to specify the end-point address of the HBase cluster, for the
HBase client invocation?

Regards,

Jun

Hi,

I have just started my career with Hadoop. I tried to execute the example
given in
http://hadoop.apache.org/common/docs/...d_tutorial.htmlas
explained in the tutorial. I was not able to execute the program as
described in the tutorial. I am getting the error as shown below. I tried
executing with some other examples. They are also showing the same
“ClassNotFoundException”. I tried to find the solution in various
websites
but i could not find it. Please help me to find the problem.

Exception in thread "main"
java.lang.ClassNotFoundException: org.myorg.WordCount
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)

Le 28/07/2010 14:03, er### @apache.org a écrit :
 Author: erans
 Date: Wed Jul 28 12:03:41 2010
 New Revision: 980032
 
 URL: http://svn.apache.org/viewvc?rev=980032&view=rev
 Log:
 MATH-395: Another bug uncovered; all things being equal, the code now
behaves
 like the Puthon implementation.
 MATH-397: Modified "BrentOptimizer" following the changes in
 "AbstractUnivariateRealOptimizer".
 
 Modified:
    
commons/proper/math/trunk/src/main/java/org/apache/commons/math/ConvergingAlgorithmImpl.java
    
commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/AbstractUnivariateRealOptimizer.java
    
commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/BrentOptimizer.java
    
commons/proper/math/trunk/src/test/java/org/apache/commons/math/optimization/MultiStartUnivariateRealOptimizerTest.java
    
commons/proper/math/trunk/src/test/java/org/apache/commons/math/optimization/univariate/BrentOptimizerTest.java

[snip]

       */
 -    private double localMin(UnivariateRealFunction f,
 -                            GoalType goalType,
 +    private double localMin(boolean isMinim,
                              double lo, double mid, double hi,
                              double eps, double t)

Perhaps we should change this method name to localExtremum ? It seems we
forgot to do that earlier despite the method was able to either minimize
or maximize a function.

[snip]

 Modified:
commons/proper/math/trunk/src/test/java/org/apache/commons/math/optimization/MultiStartUnivariateRealOptimizerTest.java
 URL:
http://svn.apache.org/viewvc/commons/...032&view=diff
 

Hi,

Is org.apache.hadoop.mapred.lib.MultipleOutputFormat deprecated? I did not
find @deprecated comments in source file in 0.20.2

But I cannot use following:

job.setOutputFormatClass( 
org.apache.hadoop.mapred.lib.MultipleOutputFormat
)


The type does not match.

All,
  I have followed the instructions on
http://wiki.apache.org/hadoop/EclipseEnvironment to download the latest
trunk source code and build .jar for common, hdfs and mapred. but how
should
I proceed to configure and start a hadoop cluster(psudo distributed)  with
these latest .jar? I knew how to configured/start the hadoop cluster with
formal hadoop package(hadoop-*.tar.gz with all stuff of common, hdfs and
mapred there). I  googled but didn't find the related information, most
information I got after compile is to run unit test.

  Can anyone help?  Thanks for the help.

Best Regards,
Fred

    [
https://issues.apache.org/jira/browse...3#action_12893793
] 

Hadoop QA commented on PIG-1452:

     [
https://issues.apache.org/jira/browse...nels:all-tabpanel
]

Giridharan Kesavan updated PIG-1452:

     [
https://issues.apache.org/jira/browse...nels:all-tabpanel
]

Giridharan Kesavan updated PIG-1452:

There will be an Apache Asia Roadshow event on August 14 - 15 in Shanghai,
China. As Hadoop is a very hot topic in China, we would like to invite a
keynote talk on Hadoop in the event. The event could cover $2-3K travel
cost
for the speaker. Visit here [1] for more information on the event.

If someone is interested in delivering the keynote, please drop me a note.
Thanks!

-Jack

[1] http://www.apachecon.com/2010/Asia/cfp

Hi Tomasz

On Wed, Jul 28, 2010 at 7:42 PM, <tome### @apache.org> wrote:

 Author: tomekopo
 Date: Wed Jul 28 18:41:59 2010
 New Revision: 980151

 URL: http://svn.apache.org/viewvc?rev=980151&view=rev
 Log:
 - Fixed broken layout of 'settings' tab;
 - Fixed broken layout of 'authentication' tab;
 - Fixed moved 'last' link;
 - Fixed title of the page;
 - Add cutting long message in log entries list;


If this last bit applies to a top-right pane where a list of entries is
displayed then it may not be necessary. When displaying a list, you should
use entry/title which is supposed to be very short but use entry/content
for
displaying the actual log entry content, without cutting it

thanks, Sergey

Hi Sergey,

On Wed, Jul 28, 2010 at 10:12 PM, Sergey Beryozkin
<sberyo### @gmail.com> wrote:
 Hi Tomasz

 On Wed, Jul 28, 2010 at 7:42 PM, <tome### @apache.org> wrote:

> Author: tomekopo
> Date: Wed Jul 28 18:41:59 2010
> New Revision: 980151
>
> URL: http://svn.apache.org/viewvc?rev=980151&view=rev
> Log:
> - Fixed broken layout of 'settings' tab;
> - Fixed broken layout of 'authentication' tab;
> - Fixed moved 'last' link;
> - Fixed title of the page;
> - Add cutting long message in log entries list;
>
>
 If this last bit applies to a top-right pane where a list of entries
is
 displayed then it may not be necessary. When displaying a list, you
should
 use entry/title which is supposed to be very short but use
entry/content for
 displaying the actual log entry content, without cutting it

 thanks, Sergey

Thanks for you advice. I think it's better to use predefined value. I'll
fix it.

     [
https://issues.apache.org/jira/browse...nels:all-tabpanel
]

Carl Steinbach updated HIVE-597:

Hi, this is my first post here,
I have a bug I can solve :(
The context:
The platform: I'm using iPOJO 1.6.2, Felix 2.0.5, Jetty 1.0.1, XMLRPC or
JsonRPC
The application :
I have two iPOJO components (service-exporter and real-service)
service-exporter requires the real-service and expose it as a Json RPC
service.

Its a simple application the real-service is like a "hello world"example.
And I use a frontend using jscript to call the json service, and
everything
is OK, but only 15 calls!!  I need to update the bundle to have it running
again (another 15 calls)
Later, I changed the JSON RPC exporter for an XMLRPC exporter to see if it
was an Jabsorb problem. but it throws the exception after 15 services
calls
 too.

Someone has an idea about what its happening here?

the trace exception is here:

java.lang.NoClassDefFoundError: sun/reflect/MethodAccessorImpl
at sun.misc.Unsafe.defineClass(Native Method)
at sun.reflect.ClassDefiner.defineClass(ClassDefiner.java:45)
 at
sun.reflect.MethodAccessorGenerator$1.run(MethodAccessorGenerator.java:381)
at java.security.AccessController.doPrivileged(Native Method)
 at
sun.reflect.MethodAccessorGenerator.generate(MethodAccessorGenerator.java:377)
at
sun.reflect.MethodAccessorGenerator.generateMethod(MethodAccessorGenerator.java:59)
 at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:28)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
at
org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:115)
 at
org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.execute(ReflectiveXmlRpcHandler.java:106)
at
org.apache.xmlrpc.server.XmlRpcServerWorker.execute(XmlRpcServerWorker.java:46)
 at org.apache.xmlrpc.server.XmlRpcServer.execute(XmlRpcServer.java:86)
at
org.apache.xmlrpc.server.XmlRpcStreamServer.execute(XmlRpcStreamServer.java:200)
 at
org.apache.xmlrpc.webserver.XmlRpcServletServer.execute(XmlRpcServletServer.java:112)
at
org.apache.xmlrpc.webserver.XmlRpcServlet.doPost(XmlRpcServlet.java:196)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
 at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:502)
at
org.mortbay.jetty.servlet.OsgiServletHolder.handle(OsgiServletHolder.java:101)
 at
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:363)
at
org.mortbay.jetty.servlet.OsgiServletHandler.handle(OsgiServletHandler.java:117)
 at
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
at
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
 at
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:324)
 at
org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:534)
at
org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:879)
 at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:741)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:213)
 at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:403)
at
org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
 at
org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:522)
Caused by: java.lang.ClassNotFoundException:
sun.reflect.MethodAccessorImpl
 at
org.apache.felix.framework.ModuleImpl.findClassOrResourceByDelegation(ModuleImpl.java:814)
at org.apache.felix.framework.ModuleImpl.access$100(ModuleImpl.java:61)
 at
org.apache.felix.framework.ModuleImpl$ModuleClassLoader.loadClass(ModuleImpl.java:1733)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
 at
org.apache.felix.ipojo.handlers.dependency.Dependency$SmartProxyFactory.loadClass(Dependency.java:900)
... 33 more

This looks pretty cool. I like the idea of using the Servlet interface
instead of Callable/Runnable.

I have two comments:

1) The request/response pair passed to the servlet should be entirely
synthetic. This is true in general AFAIK[1]; in Sling it is especially
true because request.getResourceResolver() will return a closed resource
resolver.

2) Even with synthetic request/response objects, I suspect that not all
servlets are going to work in the background (or s/going to/should/).
Thus, what about using a marker interface on the servlet to declare that
it should be run in the background. Or... to declare that it can be run
in the background.

Justin

[1] that is, the ServletRequest and ServletResponse objects are not
meant to be used outside of the request thread owned by the servlet
container.

On 7/13/10 7:58 AM, bdelac### @apache.org wrote:
 Author: bdelacretaz
 Date: Tue Jul 13 11:58:51 2010
 New Revision: 963686
 
 URL: http://svn.apache.org/viewvc?rev=963686&view=rev
 Log:
 SLING-550 - first shot at background servlets engine, works for some
simple cases, no job control yet
 
 Added:
     sling/trunk/contrib/extensions/bgservlets/   (with props)
     sling/trunk/contrib/extensions/bgservlets/pom.xml   (with props)
     sling/trunk/contrib/extensions/bgservlets/src/
     sling/trunk/contrib/extensions/bgservlets/src/main/
     sling/trunk/contrib/extensions/bgservlets/src/main/java/
     sling/trunk/contrib/extensions/bgservlets/src/main/java/org/
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/ExecutionEngine.java
  (with props)
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/impl/
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/impl/BackgroundServletStarterFilter.java
  (with props)
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/impl/BackgroundTestServlet.java
  (with props)
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/impl/ExecutionEngineImpl.java
  (with props)
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/impl/FilterChainExecutionJob.java
  (with props)
    
sling/trunk/contrib/extensions/bgservlets/src/main/java/org/apache/sling/bgservlets/impl/ServletResponseWrapper.java
  (with props)
 
 Propchange: sling/trunk/contrib/extensions/bgservlets/
 

Hi Justin,

On Tue, Jul 13, 2010 at 3:11 PM, Justin Edelson
<justin### @gmail.com> wrote:
 ...This looks pretty cool. I like the idea of using the Servlet
interface
 instead of Callable/Runnable....

Yes...it came out of a brainstorm session with my colleagues, I cannot
claim ownership of the idea ;-)

The main thing is allowing Joe Sling Programmer to create background
tasks easily.


 I have two comments:

 1) The request/response pair passed to the servlet should be entirely
 synthetic. This is true in general AFAIK[1]; in Sling it is
especially
 true because request.getResourceResolver() will return a closed
resource
 resolver....

Yes, I already have some TODOs to look at that. It's probably not a
good idea to use request/response objects outside of the current
request's cycle. Right now I'm just hacking with minimal code, leaving
quite a few TODOs for such things.


 2) Even with synthetic request/response objects, I suspect that not
all
 servlets are going to work in the background (or s/going to/should/).
 Thus, what about using a marker interface on the servlet to declare
that
 it should be run in the background. Or... to declare that it can be
run
 in the background...

At present the class that decides to run the servlet in the background
is a Filter early in the chain, so it's not aware of which servlet is
used. Filtering servlets like you suggest might complicate things
quite a bit, and scripts cannot easily be marked like a servlet. What
would be simpler is to filter by path or path regexp, configurable in
that filter...or we can just assume for now that servlets will fail
loudly if unable to run in the background.

Thanks for the feedback!

-Bertrand