Thank you for the reply. But I got it to write on Kudu.
Still, I don't know why, but I get this error:
"java.lang.AssertionError: Tried to resume the execution of
Deferred@2021942318(state=DONE, result=true, callback=<none>, errback=<none>))
although it's not in state=PAUSED. This occurred after the completion of
Deferred@1753159143(state=RUNNING, result=Written with success.,
callback=<none>, errback=<none>) which was originally returned by
callback=com.foo.kudu.KuduDAOImpl$1@3e69008f@1047068815"
The only way I discover to reach kudu was like this:
public void asyncWrite(String tableName, Foo foo) {
Deferred<Deferred<Boolean>> res = new Deferred<>();
res.addCallback(new Callback<Deferred<Deferred<String>>,
Deferred<Boolean>>() {
@Override
public Deferred<Deferred<String>> call(Deferred<Boolean>
booleanDeferred){
return booleanDeferred.addCallbacks(new
Callback<Deferred<String>, Boolean>() {
@Override
public Deferred<String> call(Boolean aBoolean) throws
Exception {
if (aBoolean) {
Deferred<String> stringDeferred =
kuduClient.openTable(tableName)
.addCallbacks(new Callback<String,
KuduTable>() {
@Override
public String call(KuduTable kuduTable)
throws KuduException {
AsyncKuduSession session =
kuduClient.newSession();
session.setFlushMode(SessionConfiguration.FlushMode.AUTO_FLUSH_SYNC);
Upsert upst = kuduTable.newUpsert();
PartialRow row = upst.getRow();
row.addString("house_id",
foo.getId());
session.apply(upst);
session.close();
LOGGER.info("Written with
success.");
return "Written with success.";
}
}, (Callback<Object, KuduException>) e -> {
LOGGER.error(e.getMessage());
return e;
});
return stringDeferred;
} else {
throw new Exception("Table doesn't exists");
}
}
}, (Callback<Object, Exception>) e -> {
System.out.println(e.getMessage());
return e;
});
}
});
//executing the callback
res.callback(kuduClient.tableExists(tableName));
}
A little of the background of my project. The clients read and write on other
Database, and when they write something, the same information is sent to Kudu.
I don't want to block the client with the Kudu part, because the client only
needs the other DataBase to work.
José Ribeiro
________________________________
De: Dan Burkert <danburk...@apache.org>
Enviado: 9 de abril de 2018 17:21
Para: user@kudu.apache.org
Assunto: Re: AsyncKudu
Hi José,
The Deferred class is indeed pretty difficult to come to grips with, which is
why we don't really recommend the async API for most use cases. I've
personally found the
Deferred<https://github.com/OpenTSDB/async/blob/master/src/Deferred.java> class
docs to be pretty useful when getting up to speed with it. Using the
AsyncKuduSession is particularly tricky because it doesn't expose backpressure
in an intuitive way, and it becomes very easy to accidentally have a huge
number of writes buffered in the client heap (the sync client solves this by
simply blocking so more rows can't be produced).
kudu-ts<https://github.com/danburkert/kudu-ts/blob/master/core/src/main/java/org/kududb/ts/core/KuduTS.java>
has a little bit of code that uses the async client to open and scan tables,
so it may be helpful to look over that. It doesn't use the async session, I
think because it was easier just to use the sync client for writing.
- Dan
On Mon, Apr 9, 2018 at 3:10 AM, José Ribeiro
<jose.enes.ribe...@hotmail.com<mailto:jose.enes.ribe...@hotmail.com>> wrote:
Hello, I'm having difficulties in the AsyncKudu API. Since there isn't any
valuable examples with asynchronous kudu client, can you please help me in this
example?
I want to use AsyncKudu to write in the kudu database. The steps i want to use
are:
1. verify that the table exists;
2. if exists, open table;
3. write on the table;
Can someone explain me how to do this with AsyncKudu? I'm having trouble in
understanding the Deferred class that is always returned in every asyncKudu
method. Thank you.
