Examples with ConditionalWriter org.apache.accumulo.core.client.ConditionalWriter used on opensource projects

Example 11 with ConditionalWriter

use of org.apache.accumulo.core.client.ConditionalWriter in project accumulo by apache.

the class ConditionalWriterIT method testOffline.

@Test
public void testOffline() throws Exception {
    String table = getUniqueNames(1)[0];
    Connector conn = getConnector();
    conn.tableOperations().create(table);
    try (ConditionalWriter cw = conn.createConditionalWriter(table, new ConditionalWriterConfig())) {
        conn.tableOperations().offline(table, true);
        ConditionalMutation cm1 = new ConditionalMutation("r1", new Condition("tx", "seq"));
        cm1.put("tx", "seq", "1");
        cm1.put("data", "x", "a");
        Result result = cw.write(cm1);
        try {
            Status status = result.getStatus();
            Assert.fail("Expected exception writing conditional mutation to offline table. Got status: " + status);
        } catch (AccumuloException ae) {
            Assert.assertEquals(TableOfflineException.class, ae.getCause().getClass());
        }
        try {
            conn.createConditionalWriter(table, new ConditionalWriterConfig());
            Assert.fail("Expected exception creating conditional writer to offline table");
        } catch (TableOfflineException e) {
        }
    }
}

Example 12 with ConditionalWriter

use of org.apache.accumulo.core.client.ConditionalWriter in project incubator-rya by apache.

the class PcjTables method updateCardinality.

/**
 * Update the cardinality of a PCJ by a {@code delta}.
 *
 * @param accumuloConn - A connection to the Accumulo that hosts the PCJ table. (not null)
 * @param pcjTableName - The name of the PCJ table that will have its cardinality updated. (not null)
 * @param delta - How much the cardinality will change.
 * @throws PCJStorageException The cardinality could not be updated.
 */
private void updateCardinality(final Connector accumuloConn, final String pcjTableName, final long delta) throws PCJStorageException {
    checkNotNull(accumuloConn);
    checkNotNull(pcjTableName);
    ConditionalWriter conditionalWriter = null;
    try {
        conditionalWriter = accumuloConn.createConditionalWriter(pcjTableName, new ConditionalWriterConfig());
        boolean updated = false;
        while (!updated) {
            // Write the conditional update request to Accumulo.
            final long cardinality = getPcjMetadata(accumuloConn, pcjTableName).getCardinality();
            final ConditionalMutation mutation = makeUpdateCardinalityMutation(cardinality, delta);
            final ConditionalWriter.Result result = conditionalWriter.write(mutation);
            // Interpret the result.
            switch(result.getStatus()) {
                case ACCEPTED:
                    updated = true;
                    break;
                case REJECTED:
                    break;
                case UNKNOWN:
                    // We do not know if the mutation succeeded. At best, we
                    // can hope the metadata hasn't been updated
                    // since we originally fetched it and try again.
                    // Otherwise, continue forwards as if it worked. It's
                    // okay if this number is slightly off.
                    final long newCardinality = getPcjMetadata(accumuloConn, pcjTableName).getCardinality();
                    if (newCardinality != cardinality) {
                        updated = true;
                    }
                    break;
                case VIOLATED:
                    throw new PCJStorageException("The cardinality could not be updated because the commit violated a table constraint.");
                case INVISIBLE_VISIBILITY:
                    throw new PCJStorageException("The condition contains a visibility the updater can not satisfy.");
            }
        }
    } catch (AccumuloException | AccumuloSecurityException | TableNotFoundException e) {
        throw new PCJStorageException("Could not update the cardinality value of the PCJ Table named: " + pcjTableName, e);
    } finally {
        if (conditionalWriter != null) {
            conditionalWriter.close();
        }
    }
}

Example 13 with ConditionalWriter

use of org.apache.accumulo.core.client.ConditionalWriter in project accumulo-examples by apache.

the class ARS method cancel.

public void cancel(String what, String when, String who) throws Exception {
    String row = what + ":" + when;
    // its important to use an isolated scanner so that only whole mutations are seen
    try (ConditionalWriter cwriter = conn.createConditionalWriter(rTable, new ConditionalWriterConfig());
        Scanner scanner = new IsolatedScanner(conn.createScanner(rTable, Authorizations.EMPTY))) {
        while (true) {
            scanner.setRange(new Range(row));
            int seq = -1;
            String reservation = null;
            for (Entry<Key, Value> entry : scanner) {
                String cf = entry.getKey().getColumnFamilyData().toString();
                String cq = entry.getKey().getColumnQualifierData().toString();
                String val = entry.getValue().toString();
                if (cf.equals("tx") && cq.equals("seq")) {
                    seq = Integer.parseInt(val);
                } else if (cf.equals("res") && val.equals(who)) {
                    reservation = cq;
                }
            }
            if (reservation != null) {
                ConditionalMutation update = new ConditionalMutation(row, new Condition("tx", "seq").setValue(seq + ""));
                update.putDelete("res", reservation);
                update.put("tx", "seq", (seq + 1) + "");
                Status status = cwriter.write(update).getStatus();
                switch(status) {
                    case ACCEPTED:
                        // successfully canceled reservation
                        return;
                    case REJECTED:
                    case UNKNOWN:
                        // EXCERCISE exponential back-off could be used here
                        break;
                    default:
                        throw new RuntimeException("Unexpected status " + status);
                }
            } else {
                // not reserved, nothing to do
                break;
            }
        }
    }
}

Example 14 with ConditionalWriter

use of org.apache.accumulo.core.client.ConditionalWriter in project accumulo-examples by apache.

the class ARS method reserve.

public ReservationResult reserve(String what, String when, String who) throws Exception {
    String row = what + ":" + when;
    // EXCERCISE This code assumes there is no reservation and tries to create one. If a reservation exist then the update will fail. This is a good strategy
    // when it is expected there are usually no reservations. Could modify the code to scan first.
    // The following mutation requires that the column tx:seq does not exist and will fail if it does.
    ConditionalMutation update = new ConditionalMutation(row, new Condition("tx", "seq"));
    update.put("tx", "seq", "0");
    update.put("res", String.format("%04d", 0), who);
    ReservationResult result = ReservationResult.RESERVED;
    // it is important to use an isolated scanner so that only whole mutations are seen
    try (ConditionalWriter cwriter = conn.createConditionalWriter(rTable, new ConditionalWriterConfig());
        Scanner scanner = new IsolatedScanner(conn.createScanner(rTable, Authorizations.EMPTY))) {
        while (true) {
            Status status = cwriter.write(update).getStatus();
            switch(status) {
                case ACCEPTED:
                    return result;
                case REJECTED:
                case UNKNOWN:
                    // read the row and decide what to do
                    break;
                default:
                    throw new RuntimeException("Unexpected status " + status);
            }
            // EXCERCISE in the case of many threads trying to reserve a slot, this approach of immediately retrying is inefficient. Exponential back-off is good
            // general solution to solve contention problems like this. However in this particular case, exponential back-off could penalize the earliest threads
            // that attempted to make a reservation by putting them later in the list. A more complex solution could involve having independent sub-queues within
            // the row that approximately maintain arrival order and use exponential back off to fairly merge the sub-queues into the main queue.
            scanner.setRange(new Range(row));
            int seq = -1;
            int maxReservation = -1;
            for (Entry<Key, Value> entry : scanner) {
                String cf = entry.getKey().getColumnFamilyData().toString();
                String cq = entry.getKey().getColumnQualifierData().toString();
                String val = entry.getValue().toString();
                if (cf.equals("tx") && cq.equals("seq")) {
                    seq = Integer.parseInt(val);
                } else if (cf.equals("res")) {
                    // data differently in Accumulo so that finding the reserver could be done quickly.
                    if (val.equals(who))
                        if (maxReservation == -1)
                            // already have the first reservation
                            return ReservationResult.RESERVED;
                        else
                            // already on wait list
                            return ReservationResult.WAIT_LISTED;
                    // EXCERCISE the way this code finds the max reservation is very inefficient.... it would be better if it did not have to scan the entire row.
                    // One possibility is to just use the sequence number. Could also consider sorting the data in another way and/or using an iterator.
                    maxReservation = Integer.parseInt(cq);
                }
            }
            Condition condition = new Condition("tx", "seq");
            if (seq >= 0)
                // only expect a seq # if one was seen
                condition.setValue(seq + "");
            update = new ConditionalMutation(row, condition);
            update.put("tx", "seq", (seq + 1) + "");
            update.put("res", String.format("%04d", maxReservation + 1), who);
            // EXCERCISE if set capacity is implemented, then result should take capacity into account
            if (maxReservation == -1)
                // if successful, will be first reservation
                result = ReservationResult.RESERVED;
            else
                result = ReservationResult.WAIT_LISTED;
        }
    }
}

Example 15 with ConditionalWriter

use of org.apache.accumulo.core.client.ConditionalWriter in project incubator-rya by apache.

the class AccumuloRyaInstanceDetailsRepository method update.

@Override
public void update(final RyaDetails oldDetails, final RyaDetails newDetails) throws NotInitializedException, ConcurrentUpdateException, RyaDetailsRepositoryException {
    // Preconditions.
    requireNonNull(oldDetails);
    requireNonNull(newDetails);
    if (!newDetails.getRyaInstanceName().equals(instanceName)) {
        throw new RyaDetailsRepositoryException("The instance name that was in the provided 'newDetails' does not match " + "the instance name that this repository is connected to. Make sure you're connected to the" + "correct Rya instance.");
    }
    if (!isInitialized()) {
        throw new NotInitializedException("Could not update the details for the Rya instanced named '" + instanceName + "' because it has not been initialized yet.");
    }
    // Use a conditional writer so that we can detect when the old details
    // are no longer the currently stored ones.
    ConditionalWriter writer = null;
    try {
        // Setup the condition that ensures the details have not changed since the edits were made.
        final byte[] oldDetailsBytes = serializer.serialize(oldDetails);
        final Condition condition = new Condition(COL_FAMILY, COL_QUALIFIER);
        condition.setValue(oldDetailsBytes);
        // Create the mutation that only performs the update if the details haven't changed.
        final ConditionalMutation mutation = new ConditionalMutation(ROW_ID);
        mutation.addCondition(condition);
        final byte[] newDetailsBytes = serializer.serialize(newDetails);
        mutation.put(COL_FAMILY, COL_QUALIFIER, new Value(newDetailsBytes));
        // Do the write.
        writer = connector.createConditionalWriter(detailsTableName, new ConditionalWriterConfig());
        final Result result = writer.write(mutation);
        switch(result.getStatus()) {
            case REJECTED:
            case VIOLATED:
                throw new ConcurrentUpdateException("Could not update the details for the Rya instance named '" + instanceName + "' because the old value is out of date.");
            case UNKNOWN:
            case INVISIBLE_VISIBILITY:
                throw new RyaDetailsRepositoryException("Could not update the details for the Rya instance named '" + instanceName + "'.");
        }
    } catch (final TableNotFoundException | AccumuloException | AccumuloSecurityException e) {
        throw new RyaDetailsRepositoryException("Could not update the details for the Rya instance named '" + instanceName + "'.");
    } finally {
        if (writer != null) {
            writer.close();
        }
    }
}