private Map<String, String> queryExhibitors(Exhibitors localExhibitors) {
Map<String, String> values = newValues();
long start = System.currentTimeMillis();
int retries = 0;
boolean done = false;
while (!done) {
List<String> hostnames = Lists.newArrayList(localExhibitors.getHostnames());
if (hostnames.size() == 0) {
done = true;
} else {
String hostname = hostnames.get(random.nextInt(hostnames.size()));
try {
String encoded =
restClient.getRaw(hostname, localExhibitors.getRestPort(), restUriPath, MIME_TYPE);
values.putAll(decodeExhibitorList(encoded));
done = true;
} catch (Throwable e) {
if (retryPolicy.allowRetry(
retries++, System.currentTimeMillis() - start, RetryLoop.getDefaultRetrySleeper())) {
log.warn("Couldn't get servers from Exhibitor. Retrying.", e);
} else {
log.error("Couldn't get servers from Exhibitor. Giving up.", e);
done = true;
}
}
}
}
return values;
}
@VisibleForTesting
protected void poll() {
Exhibitors localExhibitors = exhibitors.get();
Map<String, String> values = queryExhibitors(localExhibitors);
int count = getCountFromValues(values);
if (count == 0) {
log.warn("0 count returned from Exhibitors. Using backup connection values.");
values = useBackup(localExhibitors);
count = getCountFromValues(values);
}
if (count > 0) {
int port = Integer.parseInt(values.get(VALUE_PORT));
StringBuilder newConnectionString = new StringBuilder();
List<String> newHostnames = Lists.newArrayList();
for (int i = 0; i < count; ++i) {
if (newConnectionString.length() > 0) {
newConnectionString.append(",");
}
String server = values.get(VALUE_SERVER_PREFIX + i);
newConnectionString.append(server).append(":").append(port);
newHostnames.add(server);
}
String newConnectionStringValue = newConnectionString.toString();
if (!newConnectionStringValue.equals(connectionString.get())) {
log.info(
"Connection string has changed. Old value (%s), new value (%s)",
connectionString.get(), newConnectionStringValue);
}
Exhibitors newExhibitors =
new Exhibitors(
newHostnames,
localExhibitors.getRestPort(),
new Exhibitors.BackupConnectionStringProvider() {
@Override
public String getBackupConnectionString() throws Exception {
return masterExhibitors
.get()
.getBackupConnectionString(); // this may be overloaded by clients. Make sure
// there is always a method call to get the
// value.
}
});
connectionString.set(newConnectionStringValue);
exhibitors.set(newExhibitors);
}
}
private Map<String, String> useBackup(Exhibitors localExhibitors) {
Map<String, String> values = newValues();
try {
String backupConnectionString = localExhibitors.getBackupConnectionString();
int thePort = -1;
int count = 0;
for (String spec : backupConnectionString.split(",")) {
spec = spec.trim();
String[] parts = spec.split(":");
if (parts.length == 2) {
String hostname = parts[0];
int port = Integer.parseInt(parts[1]);
if (thePort < 0) {
thePort = port;
} else if (port != thePort) {
log.warn("Inconsistent port in connection component: " + spec);
}
values.put(VALUE_SERVER_PREFIX + count, hostname);
++count;
} else {
log.warn("Bad backup connection component: " + spec);
}
}
values.put(VALUE_COUNT, Integer.toString(count));
values.put(VALUE_PORT, Integer.toString(thePort));
} catch (Exception e) {
log.error("Couldn't get backup connection string", e);
}
return values;
}
