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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.fs.s3a.impl;
import java.util.Locale;
import com.amazonaws.services.s3.model.CopyObjectRequest;
import com.amazonaws.services.s3.model.GetObjectMetadataRequest;
import com.amazonaws.services.s3.model.GetObjectRequest;
import com.amazonaws.services.s3.model.ObjectMetadata;
import com.amazonaws.services.s3.transfer.model.CopyResult;
import com.google.common.annotations.VisibleForTesting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.commons.lang3.tuple.ImmutablePair;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.s3a.S3ObjectAttributes;
import org.apache.hadoop.fs.s3a.RemoteFileChangedException;
import static org.apache.hadoop.fs.s3a.Constants.*;
/**
* Object change detection policy.
* Determines which attribute is used to detect change and what to do when
* change is detected.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public abstract class ChangeDetectionPolicy {
private static final Logger LOG =
LoggerFactory.getLogger(ChangeDetectionPolicy.class);
@VisibleForTesting
public static final String CHANGE_DETECTED = "change detected on client";
private final Mode mode;
private final boolean requireVersion;
/**
* Version support is only warned about once per S3A instance.
* This still means that on a long-lived application which destroys
* filesystems it'll appear once-per-query in the logs, but at least
* it will not appear once per file read.
*/
private final LogExactlyOnce logNoVersionSupport = new LogExactlyOnce(LOG);
/**
* The S3 object attribute used to detect change.
*/
public enum Source {
ETag(CHANGE_DETECT_SOURCE_ETAG),
VersionId(CHANGE_DETECT_SOURCE_VERSION_ID),
/** you can't ask for this explicitly outside of tests. */
None("none");
private final String source;
Source(String source) {
this.source = source;
}
private static Source fromString(String trimmed) {
for (Source value : values()) {
if (value.source.equals(trimmed)) {
return value;
}
}
LOG.warn("Unrecognized " + CHANGE_DETECT_SOURCE + " value: \"{}\"",
trimmed);
return fromString(CHANGE_DETECT_SOURCE_DEFAULT);
}
static Source fromConfiguration(Configuration configuration) {
String trimmed = configuration.get(CHANGE_DETECT_SOURCE,
CHANGE_DETECT_SOURCE_DEFAULT).trim()
.toLowerCase(Locale.ENGLISH);
return fromString(trimmed);
}
}
/**
* What to do when change is detected.
*/
public enum Mode {
/** Client side validation. */
Client(CHANGE_DETECT_MODE_CLIENT),
/** Server side validation. */
Server(CHANGE_DETECT_MODE_SERVER),
/** Warn but continue. */
Warn(CHANGE_DETECT_MODE_WARN),
/** No checks. */
None(CHANGE_DETECT_MODE_NONE);
private final String mode;
Mode(String mode) {
this.mode = mode;
}
private static Mode fromString(String trimmed) {
for (Mode value : values()) {
if (value.mode.equals(trimmed)) {
return value;
}
}
LOG.warn("Unrecognized " + CHANGE_DETECT_MODE + " value: \"{}\"",
trimmed);
return fromString(CHANGE_DETECT_MODE_DEFAULT);
}
static Mode fromConfiguration(Configuration configuration) {
String trimmed = configuration.get(CHANGE_DETECT_MODE,
CHANGE_DETECT_MODE_DEFAULT)
.trim()
.toLowerCase(Locale.ENGLISH);
return fromString(trimmed);
}
}
protected ChangeDetectionPolicy(Mode mode, boolean requireVersion) {
this.mode = mode;
this.requireVersion = requireVersion;
}
public Mode getMode() {
return mode;
}
public abstract Source getSource();
public boolean isRequireVersion() {
return requireVersion;
}
public LogExactlyOnce getLogNoVersionSupport() {
return logNoVersionSupport;
}
/**
* Reads the change detection policy from Configuration.
*
* @param configuration the configuration
* @return the policy
*/
public static ChangeDetectionPolicy getPolicy(Configuration configuration) {
Mode mode = Mode.fromConfiguration(configuration);
Source source = Source.fromConfiguration(configuration);
boolean requireVersion = configuration.getBoolean(
CHANGE_DETECT_REQUIRE_VERSION, CHANGE_DETECT_REQUIRE_VERSION_DEFAULT);
return createPolicy(mode, source, requireVersion);
}
/**
* Create a policy.
* @param mode mode pf checks
* @param source source of change
* @param requireVersion throw exception when no version available?
* @return the policy
*/
@VisibleForTesting
public static ChangeDetectionPolicy createPolicy(final Mode mode,
final Source source, final boolean requireVersion) {
switch (source) {
case ETag:
return new ETagChangeDetectionPolicy(mode, requireVersion);
case VersionId:
return new VersionIdChangeDetectionPolicy(mode, requireVersion);
default:
return new NoChangeDetection();
}
}
/**
* String value for logging.
* @return source and mode.
*/
@Override
public String toString() {
return "Policy " + getSource() + "/" + getMode();
}
/**
* Pulls the attribute this policy uses to detect change out of the S3 object
* metadata. The policy generically refers to this attribute as
* {@code revisionId}.
*
* @param objectMetadata the s3 object metadata
* @param uri the URI of the object
* @return the revisionId string as interpreted by this policy, or potentially
* null if the attribute is unavailable (such as when the policy says to use
* versionId but object versioning is not enabled for the bucket).
*/
public abstract String getRevisionId(ObjectMetadata objectMetadata,
String uri);
/**
* Like {{@link #getRevisionId(ObjectMetadata, String)}}, but retrieves the
* revision identifier from {@link S3ObjectAttributes}.
*
* @param s3Attributes the object attributes
* @return the revisionId string as interpreted by this policy, or potentially
* null if the attribute is unavailable (such as when the policy says to use
* versionId but object versioning is not enabled for the bucket).
*/
public abstract String getRevisionId(S3ObjectAttributes s3Attributes);
/**
* Like {{@link #getRevisionId(ObjectMetadata, String)}}, but retrieves the
* revision identifier from {@link CopyResult}.
*
* @param copyResult the copy result
* @return the revisionId string as interpreted by this policy, or potentially
* null if the attribute is unavailable (such as when the policy says to use
* versionId but object versioning is not enabled for the bucket).
*/
public abstract String getRevisionId(CopyResult copyResult);
/**
* Applies the given {@link #getRevisionId(ObjectMetadata, String) revisionId}
* as a server-side qualification on the {@code GetObjectRequest}.
*
* @param request the request
* @param revisionId the revision id
*/
public abstract void applyRevisionConstraint(GetObjectRequest request,
String revisionId);
/**
* Applies the given {@link #getRevisionId(ObjectMetadata, String) revisionId}
* as a server-side qualification on the {@code CopyObjectRequest}.
*
* @param request the request
* @param revisionId the revision id
*/
public abstract void applyRevisionConstraint(CopyObjectRequest request,
String revisionId);
/**
* Applies the given {@link #getRevisionId(ObjectMetadata, String) revisionId}
* as a server-side qualification on the {@code GetObjectMetadataRequest}.
*
* @param request the request
* @param revisionId the revision id
*/
public abstract void applyRevisionConstraint(GetObjectMetadataRequest request,
String revisionId);
/**
* Takes appropriate action based on {@link #getMode() mode} when a change has
* been detected.
*
* @param revisionId the expected revision id
* @param newRevisionId the detected revision id
* @param uri the URI of the object being accessed
* @param position the position being read in the object
* @param operation the operation being performed on the object (e.g. open or
* re-open) that triggered the change detection
* @param timesAlreadyDetected number of times a change has already been
* detected on the current stream
* @return a pair of: was a change detected, and any exception to throw.
* If the change was detected, this updates a counter in the stream
* statistics; If an exception was returned it is thrown after the counter
* update.
*/
public ImmutablePair onChangeDetected(
String revisionId,
String newRevisionId,
String uri,
long position,
String operation,
long timesAlreadyDetected) {
String positionText = position >= 0 ? (" at " + position) : "";
switch (mode) {
case None:
// something changed; we don't care.
return new ImmutablePair<>(false, null);
case Warn:
if (timesAlreadyDetected == 0) {
// only warn on the first detection to avoid a noisy log
LOG.warn(
String.format(
"%s change detected on %s %s%s. Expected %s got %s",
getSource(), operation, uri, positionText, revisionId,
newRevisionId));
return new ImmutablePair<>(true, null);
}
return new ImmutablePair<>(false, null);
case Client:
case Server:
default:
// mode == Client or Server; will trigger on version failures
// of getObjectMetadata even on server.
return new ImmutablePair<>(true,
new RemoteFileChangedException(uri,
operation,
String.format("%s "
+ CHANGE_DETECTED
+ " during %s%s."
+ " Expected %s got %s",
getSource(), operation, positionText, revisionId, newRevisionId)));
}
}
/**
* Change detection policy based on {@link ObjectMetadata#getETag() eTag}.
*/
static class ETagChangeDetectionPolicy extends ChangeDetectionPolicy {
ETagChangeDetectionPolicy(Mode mode, boolean requireVersion) {
super(mode, requireVersion);
}
@Override
public String getRevisionId(ObjectMetadata objectMetadata, String uri) {
return objectMetadata.getETag();
}
@Override
public String getRevisionId(S3ObjectAttributes s3Attributes) {
return s3Attributes.getETag();
}
@Override
public String getRevisionId(CopyResult copyResult) {
return copyResult.getETag();
}
@Override
public void applyRevisionConstraint(GetObjectRequest request,
String revisionId) {
if (revisionId != null) {
LOG.debug("Restricting get request to etag {}", revisionId);
request.withMatchingETagConstraint(revisionId);
} else {
LOG.debug("No etag revision ID to use as a constraint");
}
}
@Override
public void applyRevisionConstraint(CopyObjectRequest request,
String revisionId) {
if (revisionId != null) {
LOG.debug("Restricting copy request to etag {}", revisionId);
request.withMatchingETagConstraint(revisionId);
} else {
LOG.debug("No etag revision ID to use as a constraint");
}
}
@Override
public void applyRevisionConstraint(GetObjectMetadataRequest request,
String revisionId) {
LOG.debug("Unable to restrict HEAD request to etag; will check later");
}
@Override
public Source getSource() {
return Source.ETag;
}
@Override
public String toString() {
return "ETagChangeDetectionPolicy mode=" + getMode();
}
}
/**
* Change detection policy based on
* {@link ObjectMetadata#getVersionId() versionId}.
*/
static class VersionIdChangeDetectionPolicy extends
ChangeDetectionPolicy {
VersionIdChangeDetectionPolicy(Mode mode, boolean requireVersion) {
super(mode, requireVersion);
}
@Override
public String getRevisionId(ObjectMetadata objectMetadata, String uri) {
String versionId = objectMetadata.getVersionId();
if (versionId == null) {
// this policy doesn't work if the bucket doesn't have object versioning
// enabled (which isn't by default)
getLogNoVersionSupport().warn(
CHANGE_DETECT_MODE + " set to " + Source.VersionId
+ " but no versionId available while reading {}. "
+ "Ensure your bucket has object versioning enabled. "
+ "You may see inconsistent reads.",
uri);
}
return versionId;
}
@Override
public String getRevisionId(S3ObjectAttributes s3Attributes) {
return s3Attributes.getVersionId();
}
@Override
public String getRevisionId(CopyResult copyResult) {
return copyResult.getVersionId();
}
@Override
public void applyRevisionConstraint(GetObjectRequest request,
String revisionId) {
if (revisionId != null) {
LOG.debug("Restricting get request to version {}", revisionId);
request.withVersionId(revisionId);
} else {
LOG.debug("No version ID to use as a constraint");
}
}
@Override
public void applyRevisionConstraint(CopyObjectRequest request,
String revisionId) {
if (revisionId != null) {
LOG.debug("Restricting copy request to version {}", revisionId);
request.withSourceVersionId(revisionId);
} else {
LOG.debug("No version ID to use as a constraint");
}
}
@Override
public void applyRevisionConstraint(GetObjectMetadataRequest request,
String revisionId) {
if (revisionId != null) {
LOG.debug("Restricting metadata request to version {}", revisionId);
request.withVersionId(revisionId);
} else {
LOG.debug("No version ID to use as a constraint");
}
}
@Override
public Source getSource() {
return Source.VersionId;
}
@Override
public String toString() {
return "VersionIdChangeDetectionPolicy mode=" + getMode();
}
}
/**
* Don't check for changes.
*/
static class NoChangeDetection extends ChangeDetectionPolicy {
NoChangeDetection() {
super(Mode.None, false);
}
@Override
public Source getSource() {
return Source.None;
}
@Override
public String getRevisionId(final ObjectMetadata objectMetadata,
final String uri) {
return null;
}
@Override
public String getRevisionId(final S3ObjectAttributes s3ObjectAttributes) {
return null;
}
@Override
public String getRevisionId(CopyResult copyResult) {
return null;
}
@Override
public void applyRevisionConstraint(final GetObjectRequest request,
final String revisionId) {
}
@Override
public void applyRevisionConstraint(CopyObjectRequest request,
String revisionId) {
}
@Override
public void applyRevisionConstraint(GetObjectMetadataRequest request,
String revisionId) {
}
@Override
public String toString() {
return "NoChangeDetection";
}
}
}
