/**
* Retrieves a list of pages from Scalaris.
*
* @param <T>
* @param connection the connection to Scalaris
* @param opType operation type indicating what is being read
* @param scalaris_keys the keys under which the page list is stored in Scalaris
* @param failNotFound whether the operation should fail if the key is not found or not (the value
* contains null if not failed!)
* @param timeAtStart the start time of the method using this method
* @param statName name for the time measurement statistics
* @return a result object with the page list on success
*/
protected static final <T> ValueResult<List<T>> getPageList3(
Connection connection,
ScalarisOpType opType,
Collection<String> scalaris_keys,
boolean failNotFound,
final long timeAtStart,
String statName,
ErlangConverter<List<T>> conv) {
List<InvolvedKey> involvedKeys = new ArrayList<InvolvedKey>();
if (connection == null) {
return new ValueResult<List<T>>(
false,
involvedKeys,
"no connection to Scalaris",
true,
statName,
System.currentTimeMillis() - timeAtStart);
}
final MyScalarisSingleOpExecutor executor =
new MyScalarisSingleOpExecutor(new TransactionSingleOp(connection), involvedKeys);
final ScalarisReadListOp1<T> readOp =
new ScalarisReadListOp1<T>(
scalaris_keys, Options.getInstance().OPTIMISATIONS.get(opType), conv, failNotFound);
executor.addOp(readOp);
try {
executor.run();
} catch (Exception e) {
return new ValueResult<List<T>>(
false,
involvedKeys,
e.getClass().getCanonicalName()
+ " reading page list at \""
+ involvedKeys.toString()
+ "\" from Scalaris: "
+ e.getMessage(),
e instanceof ConnectionException,
statName,
System.currentTimeMillis() - timeAtStart);
}
return new ValueResult<List<T>>(
involvedKeys, readOp.getValue(), statName, System.currentTimeMillis() - timeAtStart);
}
/**
* Retrieves a random page title from Scalaris.
*
* @param connection the connection to Scalaris
* @param random the random number generator to use
* @return a result object with the page list on success
*/
public static final ValueResult<NormalisedTitle> getRandomArticle(
Connection connection, Random random) {
final long timeAtStart = System.currentTimeMillis();
final String statName = "random article";
final Optimisation optimisation =
Options.getInstance().OPTIMISATIONS.get(ScalarisOpType.PAGE_LIST);
final ErlangConverter<List<ErlangValue>> conv =
new ErlangConverter<List<ErlangValue>>() {
@Override
public List<ErlangValue> convert(ErlangValue v) throws ClassCastException {
return v.listValue();
}
};
final List<String> scalarisKeys = Arrays.asList(getPageListKey(0));
if (optimisation instanceof APPEND_INCREMENT_BUCKETS) {
List<InvolvedKey> involvedKeys = new ArrayList<InvolvedKey>();
if (connection == null) {
return new ValueResult<NormalisedTitle>(
false,
involvedKeys,
"no connection to Scalaris",
true,
statName,
System.currentTimeMillis() - timeAtStart);
}
final MyScalarisSingleOpExecutor executor =
new MyScalarisSingleOpExecutor(new TransactionSingleOp(connection), involvedKeys);
final ScalarisReadRandomListEntryOp1<ErlangValue> readOp =
new ScalarisReadRandomListEntryOp1<ErlangValue>(
scalarisKeys, optimisation, conv, true, random);
executor.addOp(readOp);
try {
executor.run();
} catch (Exception e) {
return new ValueResult<NormalisedTitle>(
false,
involvedKeys,
e.getClass().getCanonicalName()
+ " reading page list at \""
+ involvedKeys.toString()
+ "\" from Scalaris: "
+ e.getMessage(),
e instanceof ConnectionException,
statName,
System.currentTimeMillis() - timeAtStart);
}
// return if successful, otherwise fall back and read the whole list
// as with no optimisation
if (readOp.getValue() != null) {
return new ValueResult<NormalisedTitle>(
involvedKeys,
NormalisedTitle.fromNormalised(readOp.getValue().stringValue()),
statName,
System.currentTimeMillis() - timeAtStart);
}
}
ValueResult<List<ErlangValue>> result =
getPageList3(
connection, ScalarisOpType.PAGE_LIST, scalarisKeys, true, timeAtStart, statName, conv);
ValueResult<NormalisedTitle> vResult;
if (result.success) {
String randomTitle = result.value.get(random.nextInt(result.value.size())).stringValue();
vResult =
new ValueResult<NormalisedTitle>(
result.involvedKeys, NormalisedTitle.fromNormalised(randomTitle));
} else {
vResult =
new ValueResult<NormalisedTitle>(
false, result.involvedKeys, result.message, result.connect_failed);
}
vResult.stats = result.stats;
return vResult;
}