I have tried this  with the latest 7.3.1 and also tried to simplify my client (node.js) code  I am still getting errors, not every but most runs. However now  I am getting a stack trace back in the server protocol info message. This is coming on the event port

I have an event "messenger" defined and then run code

var session1 = new basex.Session("localhost", 1984, "admin", "admin");
var session2 = new basex.Session("localhost", 1984, "admin", "admin");

 session2.watch("messenger", watchCallback, this)
// below forced to run after above
 session1.execute("XQUERY db:event('messenger', 99)", this);
----------
// called on receipt of event
function watchCallback(name, msg) {
        session1.close(this);
        session2.close(this);
};
---------  the info message on the event port ---
 
Improper use? Potential bug? Your feedback is welcome:
Contact: basex-talk@mailman.uni-konstanz.de
Version: BaseX 7.3.1 beta
Java: Sun Microsystems Inc., 1.6.0_26
OS: Linux, i386
Stack Trace:
java.lang.NullPointerException
  org.basex.server.ClientListener.notify(ClientListener.java:296)
  org.basex.core.Events.notify(Events.java:114)
  org.basex.query.func.FNDb.event(FNDb.java:689)
  org.basex.query.func.FNDb.item(FNDb.java:100)
  org.basex.query.expr.ParseExpr.iter(ParseExpr.java:45)
  org.basex.query.func.FNDb.iter(FNDb.java:85)
  org.basex.query.QueryContext.iter(QueryContext.java:292)
  org.basex.query.QueryContext.iter(QueryContext.java:244)
  org.basex.query.QueryProcessor.iter(QueryProcessor.java:76)
  org.basex.core.cmd.AQuery.query(AQuery.java:94)
  org.basex.core.cmd.XQuery.run(XQuery.java:22)
  org.basex.core.Command.run(Command.java:363)
  org.basex.core.Command.exec(Command.java:342)
  org.basex.core.Command.execute(Command.java:78)
  org.basex.server.ClientListener.run(ClientListener.java:150)

-----------------------------------------------------------
Any ideas?
/Andy

On Sun, Jun 3, 2012 at 10:28 PM, Andy Bunce <bunce.andy@gmail.com> wrote:
I have made some progress on this...
I think the  protocol response to the watch is in fact {port}{id}\0
Where {port} is a  basex server port to connect in order to receive events and {id} some identifier.
The client should connect to the port and send {id}\0. The response is \0. After this the connection will receive events in the form {name}{msg}

I have implemented this in node.js. One difficulty is the very asynchronous nature of node
I have tried to recreate something based on the c# example in node allowing for this. It runs fine the first time after the server is started, in subsequent runs the event is never received.

The log from the 1st run is
21:19:01.858 [127.0.0.1:38155] LOGIN admin OK
21:19:01.861 [127.0.0.1:38156] LOGIN test1 OK
21:19:02.003 [127.0.0.1:38155] CREATE EVENT messenger
21:19:02.005 [127.0.0.1:38155] OK 143.0 ms
21:19:02.027 [127.0.0.1:38156] OK 13.41 ms
21:19:02.247 [127.0.0.1:38156] QUERY(0) for $i in 1 to 1000000 where $i=3 return $i OK 219.51 ms
21:19:02.248 [127.0.0.1:38156] QUERY(0) OK 0.5 ms
21:19:02.252 [127.0.0.1:38155] QUERY(0) db:event('messenger', 'Hello World!') OK 230.45 ms
21:19:02.254 [127.0.0.1:38155] QUERY(0) OK 0.76 ms
21:19:02.584 [127.0.0.1:38155] EXEC(0) OK 329.22 ms
21:19:02.943 [127.0.0.1:38156] EXEC(0) OK 694.17 ms
21:19:02.945 [127.0.0.1:38156] OK 0.34 ms
21:19:03.004 [127.0.0.1:38155] DROP EVENT messenger
21:19:03.005 [127.0.0.1:38155] OK 2.18 ms
21:19:03.006 [127.0.0.1:38155] EXIT
21:19:03.011 [127.0.0.1:38155] OK 6.03 ms
21:19:03.012 [127.0.0.1:38155] LOGOUT admin OK
21:19:03.014 [127.0.0.1:38156] EXIT
21:19:03.019 [127.0.0.1:38156] OK 6.57 ms
21:19:03.020 [127.0.0.1:38156] LOGOUT test1 OK

The next run gives

19:16.106 [127.0.0.1:38158] LOGIN admin OK
21:19:16.112 [127.0.0.1:38158] CREATE EVENT messenger
21:19:16.115 [127.0.0.1:38158] OK 27.79 ms
21:19:16.151 [127.0.0.1:38159] LOGIN test1 OK
21:19:16.192 [127.0.0.1:38158] QUERY(0) db:event('messenger', 'Hello World!') OK 0.98 ms
21:19:16.200 [127.0.0.1:38158] QUERY(0) OK 7.4 ms
21:19:16.207 [127.0.0.1:38159] OK 0.65 ms
21:19:16.220 [127.0.0.1:38159] QUERY(0) for $i in 1 to 1000000 where $i=3 return $i OK 7.77 ms
21:19:16.231 [127.0.0.1:38159] QUERY(0) OK 4.3 ms
21:19:16.253 [127.0.0.1:38158] EXEC(0) Error: null
21:19:16.732 [127.0.0.1:38159] EXEC(0) OK 459.42 ms
21:19:20.036 [127.0.0.1:38158] LOGOUT admin OK
21:19:20.042 [127.0.0.1:38159] LOGOUT test1 OK
The problem seems to EXEC(0) Error: null
Any ideas what the cause might be or how I can debug this further.
/Andy


On Thu, May 17, 2012 at 12:04 PM, Andreas Weiler <andreas.weiler@uni-konstanz.de> wrote:
Hi Andy,

1) The documentation at http://docs.basex.org/wiki/Server_Protocol shows nothing in the Server Response column. This seems not to be the case. It looks like a standard BaseX protocol type response is to be expected?

yes you are right, the server response is a standard basex info message.

2) The example at https://github.com/BaseXdb/basex-examples/blob/master/src/main/java/org/basex/examples/api/EventExample.java shows session2 watching and then executing. Does the server protocol identify "event pushes" in some way. That is when I receive a message how can I tell if is a event or a command response?

the event reponse is send over a separate socket connection.

-- Andreas

Am 17.05.2012 um 12:22 schrieb Andy Bunce:

Hi,
I am looking at adding  WATCH and UNWATCH to my Node.js BaseX interface and I have a couple of questions before I start.

1) The documentation at http://docs.basex.org/wiki/Server_Protocol shows nothing in the Server Response column. This seems not to be the case. It looks like a standard BaseX protocol type response is to be expected?

2) The example at https://github.com/BaseXdb/basex-examples/blob/master/src/main/java/org/basex/examples/api/EventExample.java shows session2 watching and then executing. Does the server protocol identify "event pushes" in some way. That is when I receive a message how can I tell if is a event or a command response?

/Andy
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