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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package com.jcabi.dynamo;
import com.amazonaws.AmazonClientException;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.Condition;
import com.amazonaws.services.dynamodbv2.model.ReturnConsumedCapacity;
import com.amazonaws.services.dynamodbv2.model.ScanRequest;
import com.amazonaws.services.dynamodbv2.model.ScanResult;
import com.amazonaws.services.dynamodbv2.model.Select;
import com.google.common.collect.Iterables;
import com.jcabi.aspects.Immutable;
import com.jcabi.aspects.Loggable;
import com.jcabi.aspects.Tv;
import com.jcabi.log.Logger;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import lombok.EqualsAndHashCode;
import lombok.ToString;
/**
* Scan-based valve.
*
* @since 0.1
*/
@Immutable
@ToString
@Loggable(Loggable.DEBUG)
@EqualsAndHashCode(of = { "limit", "attributes" })
@SuppressWarnings("PMD.GuardLogStatement")
public final class ScanValve implements Valve {
/**
* Limit to use for every query.
*/
private final transient int limit;
/**
* Attributes to fetch.
*/
@Immutable.Array
private final transient String[] attributes;
/**
* Public ctor.
*/
public ScanValve() {
this(Tv.HUNDRED, new ArrayList<>(0));
}
/**
* Public ctor.
* @param lmt Limit
* @param attrs Attributes to pre-load
*/
private ScanValve(final int lmt, final Iterable attrs) {
this.limit = lmt;
this.attributes = Iterables.toArray(attrs, String.class);
}
// @checkstyle ParameterNumber (5 lines)
@Override
public Dosage fetch(final Credentials credentials,
final String table, final Map conditions,
final Collection keys) throws IOException {
final AmazonDynamoDB aws = credentials.aws();
try {
final Collection attrs = new HashSet<>(
Arrays.asList(this.attributes)
);
attrs.addAll(keys);
final ScanRequest request = new ScanRequest()
.withTableName(table)
.withAttributesToGet(attrs)
.withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL)
.withScanFilter(conditions)
.withLimit(this.limit);
final long start = System.currentTimeMillis();
final ScanResult result = aws.scan(request);
Logger.info(
this,
// @checkstyle LineLength (1 line)
"#items(): loaded %d item(s) from '%s' and stooped at %s, using %s, %s, in %[ms]s",
result.getCount(), table,
result.getLastEvaluatedKey(),
conditions,
new PrintableConsumedCapacity(
result.getConsumedCapacity()
).print(),
System.currentTimeMillis() - start
);
return new ScanValve.NextDosage(credentials, request, result);
} catch (final AmazonClientException ex) {
throw new IOException(
String.format(
"Failed to fetch from \"%s\" by %s and %s",
table, conditions, keys
),
ex
);
} finally {
aws.shutdown();
}
}
@Override
public int count(final Credentials credentials, final String table,
final Map conditions) {
final AmazonDynamoDB aws = credentials.aws();
try {
final ScanRequest request = new ScanRequest()
.withTableName(table)
.withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL)
.withScanFilter(conditions)
.withSelect(Select.COUNT)
.withLimit(Integer.MAX_VALUE);
final long start = System.currentTimeMillis();
final ScanResult result = aws.scan(request);
final int count = result.getCount();
Logger.info(
this,
// @checkstyle LineLength (1 line)
"#total(): COUNT=%d in '%s' using %s, %s, in %[ms]s",
count, request.getTableName(), request.getFilterExpression(),
new PrintableConsumedCapacity(
result.getConsumedCapacity()
).print(),
System.currentTimeMillis() - start
);
return count;
} finally {
aws.shutdown();
}
}
/**
* With given limit.
* @param lmt Limit to use
* @return New query valve
*/
public ScanValve withLimit(final int lmt) {
return new ScanValve(lmt, Arrays.asList(this.attributes));
}
/**
* With this extra attribute to pre-fetch.
* @param name Name of attribute to pre-load
* @return New query valve
*/
public ScanValve withAttributeToGet(final String name) {
return new ScanValve(
this.limit,
Iterables.concat(
Arrays.asList(this.attributes),
Collections.singletonList(name)
)
);
}
/**
* With these extra attributes to pre-fetch.
* @param names Name of attributes to pre-load
* @return New query valve
*/
public ScanValve withAttributeToGet(final String... names) {
return new ScanValve(
this.limit,
Iterables.concat(
Arrays.asList(this.attributes),
Arrays.asList(names)
)
);
}
/**
* Next dosage.
*
* @since 0.1
*/
@ToString
@Loggable(Loggable.DEBUG)
@EqualsAndHashCode(of = { "credentials", "request", "result" })
private final class NextDosage implements Dosage {
/**
* AWS client.
*/
private final transient Credentials credentials;
/**
* Query request.
*/
private final transient ScanRequest request;
/**
* Query request.
*/
private final transient ScanResult result;
/**
* Public ctor.
* @param creds Credentials
* @param rqst Query request
* @param rslt Query result
*/
NextDosage(final Credentials creds, final ScanRequest rqst,
final ScanResult rslt) {
this.credentials = creds;
this.request = rqst;
this.result = rslt;
}
@Override
public List> items() {
return this.result.getItems();
}
@Override
public boolean hasNext() {
return this.result.getLastEvaluatedKey() != null;
}
@Override
public Dosage next() {
if (!this.hasNext()) {
throw new IllegalStateException(
"Nothing left in the iterator"
);
}
final AmazonDynamoDB aws = this.credentials.aws();
try {
final ScanRequest rqst = this.request.withExclusiveStartKey(
this.result.getLastEvaluatedKey()
);
final long start = System.currentTimeMillis();
final ScanResult rslt = aws.scan(rqst);
Logger.info(
this,
// @checkstyle LineLength (1 line)
"#next(): loaded %d item(s) from '%s' and stopped at %s, using %s, %s, in %[ms]s",
rslt.getCount(), rqst.getTableName(), rqst.getScanFilter(),
rslt.getLastEvaluatedKey(),
new PrintableConsumedCapacity(
rslt.getConsumedCapacity()
).print(),
System.currentTimeMillis() - start
);
return new ScanValve.NextDosage(this.credentials, rqst, rslt);
} finally {
aws.shutdown();
}
}
}
}
