[Apache Httpclient] Connection refused

[Iris Hoekstra]

We have built a small application based on Apache Httpclient to test the speed of our database connection. The problem is that we get 'Connection refused' errors at completely unpredictable moments.

We're creating 50 threads that each wait for a random number of miliseconds and then do this:

private boolean execute(String argInsurancePolicyNumber) {
 
boolean result = true;
 
Connection conn = null;
PreparedStatement stat = null;
ResultSet resultSet = null;
String sql = null;
 
sql = "select * from sysusr.table1 T1_HINT_K0101 where DEPT_NR = ? and POL_NR = ? and ING_DTM_OCC <= ? and EIND_DTM_OCC > ?";
 
try {
conn = this.dataSource.getConnection();
stat = conn.prepareStatement(sql);
 
stat.setString(1, argInsurancePolicyNumber.substring(0,2));
stat.setString(2, argInsurancePolicyNumber.substring(2,8));
stat.setString(3, "20060505");
stat.setString(4, "20060505");
 
resultSet = stat.executeQuery();  // see below for this method
}
catch (Throwable t) {
result = false;
t.printStackTrace();
}
finally {
try {
resultSet.close();
}
catch (Throwable t) {
t.printStackTrace();
      }
try {
stat.close();
}
catch (Throwable t) {
t.printStackTrace();
}
try {
conn.close();
}
catch (Throwable t) {
t.printStackTrace();
}
}
 
return result;
}

The 'executeQuery' method eventually does this:

String tijden = "";
 
byte[] responseBody = null;
int statusCode = 0;
 
FireXmlParser parser = null;
Object[] result = new Object[2];
 
this.post = this.createPostMethod("/QW01/W01", 3);  // see below for this method
 
tijden = Long.toString(System.currentTimeMillis()) + ";";
 
this.post.addParameter("qedsql", argQuery);
 
parser = new FireXmlParser();
 
try {
tijden = tijden + Long.toString(System.currentTimeMillis()) + ";";
 
statusCode = FireXmlHttpURLConnectionApache.client.executeMethod(post);
 
tijden = tijden + Long.toString(System.currentTimeMillis()) + ";";
 
if (statusCode != HttpStatus.SC_OK) {
System.err.println("Method failed: " + post.getStatusLine());
}
 
// Read the response body.
responseBody = post.getResponseBody();
 
tijden = tijden + Long.toString(System.currentTimeMillis()) + ";";
 
parser.parse(responseBody);
 
tijden = tijden + Long.toString(System.currentTimeMillis()) + ";";
 
result[0] = parser.getResultSet();
 
tijden = tijden + Long.toString(System.currentTimeMillis()) + ";";
 
}
catch (ConnectException e) {
e.printStackTrace();
System.err.println("Fatal protocol violation: " + e.getMessage());
result[0] = new SQLException(e.getMessage());
}
catch (HttpException e) {
System.err.println("Fatal protocol violation: " + e.getMessage());
}
catch (IOException e) {
System.err.println("Fatal transport error: " + e.getMessage());
}
finally {
post.abort();
post.releaseConnection();
    }
 
result[1] = tijden;
 
this.post.removeParameter("qedsql");
fireXmlHttpConnectionPoolApache.connectionReady(this);
 
return result;

The PostMethod is created like this:

private PostMethod createPostMethod(String argPath, int argNumberOfRecoveries) {
 
PostMethod post = null;
 
post = new PostMethod();
post.setPath(argPath);
post.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(argNumberOfRecoveries, false));
post.addRequestHeader("Connection", "close");
 
return post;
}

Please let me know if this doesn't make sense. I find it hard to decide what to post and what to leave out.

Sometimes it starts throwing exceptions that look like this:

29-sep-2006 9:53:19 org.apache.commons.httpclient.HttpMethodDirector executeWithRetry
INFO: I/O exception (java.net.ConnectException) caught when processing request: Connection refused: connect

If this happens we make it go through three more retries (of necessary). Sometimes that isn't enough and we get:
java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:364)
at java.net.Socket.connect(Socket.java:507)
at java.net.Socket.connect(Socket.java:457)
at java.net.Socket.<init>(Socket.java:365)
at java.net.Socket.<init>(Socket.java:238)
at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:79)
at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:121)
at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:709)
at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$HttpConnectionAdapter.open(MultiThreadedHttpConnectionManager.java:1321)
at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:393)
at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:396)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:324)
etc.

I have been trying to figure this one out for more than a week but I still don't understand
what *really* causes a 'connection refused'. I guess that is because there may be many different causes.

Any clues pointing me in the right direction will be much appreciated.
[ September 29, 2006: Message edited by: Iris Hoekstra ]

[Ben Souther]

Moving to the Other Open Source Projects forum.