# uwsgi --async 1000 --ugreen
import uwsgi
import psycopg2


def async_wait(conn):
    # conn can be a connection or a cursor
    if not hasattr(conn, 'poll'):
        conn = conn.connection

    # interesting part: suspend until ready
    while True:
        state = conn.poll()
        if state == psycopg2.extensions.POLL_OK:
            break
        elif state == psycopg2.extensions.POLL_READ:
            uwsgi.wait_fd_read(conn.fileno())
            uwsgi.suspend()
        elif state == psycopg2.extensions.POLL_WRITE:
            uwsgi.wait_fd_write(conn.fileno())
            uwsgi.suspend()
        else:
            raise Exception("Unexpected result from poll: %r", state)


def application(env, start_response):

    start_response('200 Ok', [('Content-type', 'text/html')])

    conn = psycopg2.connect("dbname=template1 user=postgres", async=True)

    # suspend until connection
    async_wait(conn)

    curs = conn.cursor()

    yield "<table>"

    curs.execute("SELECT * FROM tests")

    # suspend until result
    async_wait(curs)

    while True:
        row = curs.fetchone()
        if not row:
            break
        yield "<tr><td>%s</td></tr>" % str(row)

    yield "</table>"

    conn.close()