/** Resets the members to which to connect. */
private ClientSession resetMembers() {
if (connectMembers.isEmpty() || connectMembers.size() < members.size() - 1) {
connectMembers = new ArrayList<>(members);
}
return this;
}
/**
* Sends a session request.
*
* @param request The request to send.
* @param future The future to complete once the response is received.
* @param checkOpen Whether to check if the session is open.
* @param <T> The request type.
* @param <U> The response type.
* @return The provided future to be completed once the response is received.
*/
private <T extends Request<T>, U extends Response<U>> CompletableFuture<U> request(
T request, CompletableFuture<U> future, boolean checkOpen, boolean recordFailures) {
context.checkThread();
// If the session already expired, immediately fail the future.
if (checkOpen && !isOpen()) {
future.completeExceptionally(new IllegalStateException("session expired"));
return future;
}
// If we're already connected to a server, use the existing connection. The connection will be
// reset in the event
// of an error on any connection, or callers can reset connections as well.
if (connection != null) {
return request(request, connection, future, checkOpen, true);
}
// If we've run out of servers to which to attempt to connect, determine whether we should
// expire the
// session based on the responses from servers with which we did successfully communicate and
// the
// time we were last able to successfully communicate with a correct server process. The
// failureTime
// indicates the first time we received a NO_LEADER_ERROR from a server.
if (connectMembers.isEmpty()) {
// If open checks are not being performed, don't retry connecting to the servers. Simply fail.
if (!checkOpen) {
LOGGER.warn("Failed to connect to cluster");
future.completeExceptionally(new IllegalStateException("session not open"));
}
// If retries have already been scheduled, queue a callback to be called to retry the request.
else if (retryFuture != null) {
retries.add(
() -> {
LOGGER.debug("Retrying: {}", request);
request(request, future, true, true);
});
}
// If all servers indicated that no leader could be found and a session timeout has elapsed,
// time out the session.
else if (failureTime > 0 && failureTime + timeout < System.currentTimeMillis()) {
LOGGER.warn("Lost session");
resetConnection().onExpire();
future.completeExceptionally(new IllegalStateException("session expired"));
}
// If not all servers responded with a NO_LEADER_EXCEPTION or less than a session timeout has
// expired,
// schedule a retry to attempt to connect to servers again.
else {
LOGGER.warn("Failed to communicate with cluster. Retrying");
retryFuture = context.schedule(Duration.ofMillis(200), this::retryRequests);
retries.add(() -> resetMembers().request(request, future, true, true));
}
return future;
}
// Remove the next random member from the members list.
Address member = connectMembers.remove(random.nextInt(connectMembers.size()));
// Connect to the server. If the connection fails, recursively attempt to connect to the next
// server,
// otherwise setup the connection and send the request.
if (connectFuture == null) {
// If there's no existing connect future, create a new one.
LOGGER.info("Connecting: {}", member.socketAddress());
connectFuture =
client
.connect(member)
.thenCompose(this::setupConnection)
.whenComplete(
(connection, error) -> {
connectFuture = null;
if (!checkOpen || isOpen()) {
if (error == null) {
request(request, connection, future, checkOpen, recordFailures);
} else {
LOGGER.info("Failed to connect: {}", member.socketAddress());
resetConnection().request(request, future, checkOpen, recordFailures);
}
} else {
future.completeExceptionally(new IllegalStateException("session not open"));
}
});
} else {
// We don't want concurrent requests to attempt to connect to the same server at the same
// time, so
// if the connection is already being attempted, piggyback on the existing connect future.
connectFuture.whenComplete(
(connection, error) -> {
if (!checkOpen || isOpen()) {
if (error == null) {
request(request, connection, future, checkOpen, recordFailures);
} else {
request(request, future, checkOpen, recordFailures);
}
} else {
future.completeExceptionally(new IllegalStateException("session not open"));
}
});
}
return future;
}