Saturday, February 28, 2009

Complex investigation, easy solution

Yesterday I was facing one production issue where somehow at some time the connection to a database which is located at another server will be reset. I was getting java.lang.SqlException(io exception: connection resrt). I have reused a method that will reconnect to the database. I hope it works in the next deployment and i believe it should work. Code snippet as below:



public Connection getDBConnection(String dbName) throws OracleConnException, Exception {
if (logger.isInfoEnabled()) {
logger.info("getDBConnection(String) - String dbName=" + dbName); //$NON-NLS-1$
}

Connection cachedConnection = null;
if (ocDataSource == null) {
ocDataSource = new HashMap();
this.printSQL("new HashMap");
}

OracleDataSource ds = (OracleDataSource) ocDataSource.get(dbName);

if(ds == null){
this.printSQL("creatingNewOracleDS");
ds = createNewOracleDS(dbName);
this.printSQL("createdNewOracleDS");
ocDataSource.put(dbName.trim(), ds);
}

int i = 0;
int retry = KenanAdaptorProperties.getORACLE_RETRY_NUM();

for(i = 0; i < retry; i++){
try {
this.printSQL("ds.getConnection() " + ds.getPortNumber());

cachedConnection = ds.getConnection();
this.printSQL("error in connection? ");

if(!isConnectionAlive(cachedConnection)){
this.printSQL("connection is not alive???");
try { ds.close(); } catch(Exception e){
//log.debug("Can't close DataSource object!");
}
ds = null;

ocDataSource.remove(dbName);

ds = createNewOracleDS(dbName);
ocDataSource.put(dbName, ds);
} else {
break;
}

} catch (SQLException se){
logger.error("getDBConnection(String)", se); //$NON-NLS-1$
} catch (Exception e){
this.printSQL("Exception:\r\n" + Util.getStackTraceForLog(e));
}

// sleep for a specific amount of time!
//make it configurable
try {
Thread.sleep(KenanAdaptorProperties.getORACLE_RETRY_SLEEP_TIME());
} catch (InterruptedException e) {
// log.debug("Interrupted Exception:\r\n" + Util.getStackTraceForLog(e));
}

}

if(i == retry){
throw new OracleConnException("Connection is not established. Failed after " + retry + " retries.");
}

return cachedConnection;
}

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