CreateStatement() doesn't detect conn reset by peer

Question

Hi to all. Well... it's almost explained in the subject. I am trying to recycle bad connections in a connection pool, so I use createStaement() in order to detect if the connection is valid (I previously tried with isClosed(), but it catches even less bad connections). The problem is that eventually the createStatement() doesn't fail while testing, although the connection is closed, so wen I try to use it... boom. This occurs (sometimes, not always) after the database is shut down and restarted by night for maintainance purposes. But notice that when the db is shutting down, or restarting, then I receive the corresponding SQLException, but it seems that when it is working again, createStatement() is ok (I check it every 60 seconds), but some condition may have occur that makes the connection JUST OPENED by the pool to be bad. The error I receive when using the conn is Connection reset by peer. I guess that the error is related to communications, but can't identify it, because it seems to be random.
Anybody can help me?
Thanks in advance
PS: I know there are other topics in the forum related to Connection reset by peer error, but I have not found my problem.

Answer 1

A blast-from-the-past thread...
I have my own connection pool implementation; I don't know how easy this is to add on to an existing pool. (Which is a big reason why I have my own pool code.) You'll need some way to get each connection from the pool in turn; a basic pool may not support that. You'll need to be suitably careful to synchronize so that you don't ping the connection while another thread is using the same connection.
I have a background thread ("PoolManager") which does in pseudocode:
    while (true) {
        sleep 10 minutes;
        foreach pool {
            log pool statistics, e.g. pool size, number of open connections, number of fetched connections;
            foreach connection in the pool {
                synchronize (connection) {
                    log connection's last use time, how many times used, etc;
                    if (connection not currently in use) {
                        if (auto-close old connections configured &&
                            now > last use time + 20 minutes) {
                             close connection;
                             continue;
                        if (now > last use time + 10 minutes)
                            // To make auto-close work, this  execute doesn't update the last use time.
                            // Exceptions during this close the connection.
                            execute "select 42 from dual" on the connection;
   }"long last_use_time" is stored for each connection, and set to currentTimeMillis() when the connection is fetched from the pool. The "10 minutes" etc times are configurable, and the dummy ping statement is per-pool configurable.