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https://issues.apache.org/jira/browse/HBASE-6656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13833983#comment-13833983
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Mauricio Morales commented on HBASE-6656:
-----------------------------------------
I can understand and agree to that (this is an anti-pattern and should be
avoided). I'm trying to recall the details of the application back when we had
this issue. To shed some more light into this, we were trying to achieve an
auto-indexing table. That is, basically, when you insert into TABLE1, the put
coprocessors would check and index the entries in TABLE1_index.
This can certainly be replaced by an offline indexer so we free the
inline-coprocessor calls altogether. We ended up discarding this solution due
to performance issues (all the more reasons to avoid coprocessors if possible).
> Cannot call a Coprocessor Endpoint from a RegionObserver
> --------------------------------------------------------
>
> Key: HBASE-6656
> URL: https://issues.apache.org/jira/browse/HBASE-6656
> Project: HBase
> Issue Type: Bug
> Components: Coprocessors
> Affects Versions: 0.92.1
> Environment: CentOS5
> Reporter: Mauricio Morales
>
> I'm trying to call a Coprocessor Endpoint from within the preGet handler of a
> RegionObserver, and it's throwing Class Loader issues.
> The exact same Coprocessor Endpoint works perfectly from remote Java client,
> however, fails from within the same Region Server.
> For our particular test environment, only 1 Region Server is available, so I
> guess it's a "local" call that fails, and perhaps a remote RegionServer
> wouldn't fail, but that doesn't justify the issue :).
> The Code within the RegionObserver is roughly (way reduced) as follows:
> ---
> @Override
> public void preGet(ObserverContext<RegionCoprocessorEnvironment> e, Get
> get, List<KeyValue> results)
> throws IOException {
> Map<byte[], Set<byte[]>> results;
> // scan: for all regions
> try {
>
> Batch.Call<PlatformStatsIndexEndpointProtocol,Set<byte[]>> batchCall = new
> Batch.Call<PlatformStatsIndexEndpointProtocol,Set<byte[]>>() {
> public Set<byte[]>
> call(PlatformStatsIndexEndpointProtocol instance) throws IOException{
> return instance.getKeyTokenByPrefix(index,
> match, additionalMatches);
> }
> };
> results =
> indexTable.coprocessorExec(PlatformStatsIndexEndpointProtocol.class, null,
> null, batchCall);
> } catch (Throwable e1) {
> e1.printStackTrace();
> throw new IOException(e1);
> }
>
> Set<byte[]> finalResultSet = new HashSet<byte[]>();
> for (Map.Entry<byte[], Set<byte[]>> e : results.entrySet()) {
> finalResultSet.addAll(e.getValue());
> }
> }
> ---
> The Code for the Coprocessor Endpoint is irrelevant, as it never gets
> executed.
> This is the Exception I get on the Client side (Server side logged exception
> below).
> ---
> Thu Aug 23 17:37:45 CST 2012,
> org.apache.hadoop.hbase.client.HTable$5@26659db7,java.io.IOException:
> java.io.IOException: java.io.IOException: java.lang.IllegalArgumentException:
> interface com.company.hbase.platformstats.PlatformStatsIndexEndpointProtocol
> is not visible from class loader
> at
> com.company.hbase.platformstats.IndexQueryRegionObserver.preGet(IndexQueryRegionObserver.java:100)
> at
> org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost.preGet(RegionCoprocessorHost.java:553)
> at org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:3737)
> at org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:3639)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.get(HRegionServer.java:1785)
> at sun.reflect.GeneratedMethodAccessor53.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:364)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1336)
> Caused by: java.io.IOException: java.lang.IllegalArgumentException: interface
> com.company.hbase.platformstats.PlatformStatsIndexEndpointProtocol is not
> visible from class loader
> at
> com.company.hbase.platformstats.PlatformStatsIndexer.getKeyTokens(PlatformStatsIndexer.java:390)
> at
> com.company.hbase.platformstats.PlatformStatsIndexer.getKeyTokensBySubstring(PlatformStatsIndexer.java:348)
> at
> com.company.hbase.platformstats.IndexQueryRegionObserver.searchTokens(IndexQueryRegionObserver.java:148)
> at
> com.company.hbase.platformstats.IndexQueryRegionObserver.preGet(IndexQueryRegionObserver.java:97)
> ... 9 more
> Caused by: java.lang.IllegalArgumentException: interface
> com.company.hbase.platformstats.PlatformStatsIndexEndpointProtocol is not
> visible from class loader
> at java.lang.reflect.Proxy.getProxyClass(Proxy.java:353)
> at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:581)
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation$4.call(HConnectionManager.java:1451)
> at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionServerWithRetries(HConnectionManager.java:1345)
> at org.apache.hadoop.hbase.client.HTable.get(HTable.java:657)
> at Test.queryIndex(Test.java:109)
> at Test.main(Test.java:42)
> ---
> This is the Server Side exception logged:
> ---
> 2012-08-23 19:37:44,705 ERROR
> org.apache.hadoop.hbase.regionserver.HRegionServer:
> java.io.IOException: java.io.IOException: java.lang.IllegalArgumentException:
> interface com.company.hbase.platformstats.PlatformStatsIndexEndpointProtocol
> is not
> visible from class loader
> at
> com.company.hbase.platformstats.IndexQueryRegionObserver.preGet(IndexQueryRegionObserver.java:100)
> at
> org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost.preGet(RegionCoprocessorHost.java:553)
> at org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:3737)
> at org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:3639)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.get(HRegionServer.java:1785)
> at sun.reflect.GeneratedMethodAccessor53.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:364)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1336)
> Caused by: java.io.IOException: java.lang.IllegalArgumentException: interface
> com.company.hbase.platformstats.PlatformStatsIndexEndpointProtocol is not
> visible from class loader
> at
> com.company.hbase.platformstats.PlatformStatsIndexer.getKeyTokens(PlatformStatsIndexer.java:390)
> at
> com.company.hbase.platformstats.PlatformStatsIndexer.getKeyTokensBySubstring(PlatformStatsIndexer.java:348)
> at
> com.company.hbase.platformstats.IndexQueryRegionObserver.searchTokens(IndexQueryRegionObserver.java:148)
> at
> com.company.hbase.platformstats.IndexQueryRegionObserver.preGet(IndexQueryRegionObserver.java:97)
> ... 9 more
> Caused by: java.lang.IllegalArgumentException: interface
> com.company.hbase.platformstats.PlatformStatsIndexEndpointProtocol is not
> visible from class loader
> at java.lang.reflect.Proxy.getProxyClass(Proxy.java:353)
> at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:581)
> at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation$4.call(HConnectionManager.java:1451)
> at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
> ---
> I'm not senior java developer, so this Class Loader visibility issue goes
> beyond my reach. I have the theory that because it's a local call, the
> ClassLoaders for the very same Protocol interface may be different (1 reads
> from the .jar, another from the remote HTable client call); but I have not
> been able to prove nor fix this behavior.
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