/*
* 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.cassandra.db;
import java.util.Objects;
import java.security.MessageDigest;
import org.apache.cassandra.serializers.MarshalException;
import org.apache.cassandra.utils.FBUtilities;
/**
* Stores the information relating to the liveness of the primary key columns of a row.
* <p>
* A {@code LivenessInfo} can first be empty. If it isn't, it contains at least a timestamp,
* which is the timestamp for the row primary key columns. On top of that, the info can be
* ttl'ed, in which case the {@code LivenessInfo} also has both a ttl and a local expiration time.
* <p>
* Please note that if a liveness info is ttl'ed, that expiration is <b>only</b> an expiration
* of the liveness info itself (so, of the timestamp), and once the info expires it becomes
* {@code EMPTY}. But if a row has a liveness info which expires, the rest of the row data is
* unaffected (of course, the rest of said row data might be ttl'ed on its own but this is
* separate).
*/
public class LivenessInfo
{
public static final long NO_TIMESTAMP = Long.MIN_VALUE;
public static final int NO_TTL = 0;
public static final int NO_EXPIRATION_TIME = Integer.MAX_VALUE;
public static final LivenessInfo EMPTY = new LivenessInfo(NO_TIMESTAMP);
protected final long timestamp;
protected LivenessInfo(long timestamp)
{
this.timestamp = timestamp;
}
public static LivenessInfo create(long timestamp, int nowInSec)
{
return new LivenessInfo(timestamp);
}
public static LivenessInfo expiring(long timestamp, int ttl, int nowInSec)
{
return new ExpiringLivenessInfo(timestamp, ttl, nowInSec + ttl);
}
public static LivenessInfo create(long timestamp, int ttl, int nowInSec)
{
return ttl == NO_TTL
? create(timestamp, nowInSec)
: expiring(timestamp, ttl, nowInSec);
}
// Note that this ctor takes the expiration time, not the current time.
// Use when you know that's what you want.
public static LivenessInfo withExpirationTime(long timestamp, int ttl, int localExpirationTime)
{
return ttl == NO_TTL ? new LivenessInfo(timestamp) : new ExpiringLivenessInfo(timestamp, ttl, localExpirationTime);
}
/**
* Whether this liveness info is empty (has no timestamp).
*
* @return whether this liveness info is empty or not.
*/
public boolean isEmpty()
{
return timestamp == NO_TIMESTAMP;
}
/**
* The timestamp for this liveness info.
*
* @return the liveness info timestamp (or {@link #NO_TIMESTAMP} if the info is empty).
*/
public long timestamp()
{
return timestamp;
}
/**
* Whether the info has a ttl.
*/
public boolean isExpiring()
{
return false;
}
/**
* The ttl (if any) on the row primary key columns or {@link #NO_TTL} if it is not
* expiring.
*
* Please note that this value is the TTL that was set originally and is thus not
* changing.
*/
public int ttl()
{
return NO_TTL;
}
/**
* The expiration time (in seconds) if the info is expiring ({@link #NO_EXPIRATION_TIME} otherwise).
*
*/
public int localExpirationTime()
{
return NO_EXPIRATION_TIME;
}
/**
* Whether that info is still live.
*
* A {@code LivenessInfo} is live if it is either not expiring, or if its expiration time if after
* {@code nowInSec}.
*
* @param nowInSec the current time in seconds.
* @return whether this liveness info is live or not.
*/
public boolean isLive(int nowInSec)
{
return !isEmpty();
}
/**
* Adds this liveness information to the provided digest.
*
* @param digest the digest to add this liveness information to.
*/
public void digest(MessageDigest digest)
{
FBUtilities.updateWithLong(digest, timestamp());
}
/**
* Validate the data contained by this liveness information.
*
* @throws MarshalException if some of the data is corrupted.
*/
public void validate()
{
}
/**
* The size of the (useful) data this liveness information contains.
*
* @return the size of the data this liveness information contains.
*/
public int dataSize()
{
return TypeSizes.sizeof(timestamp());
}
/**
* Whether this liveness information supersedes another one (that is
* whether is has a greater timestamp than the other or not).
*
* @param other the {@code LivenessInfo} to compare this info to.
*
* @return whether this {@code LivenessInfo} supersedes {@code other}.
*/
public boolean supersedes(LivenessInfo other)
{
return timestamp > other.timestamp;
}
/**
* Returns a copy of this liveness info updated with the provided timestamp.
*
* @param newTimestamp the timestamp for the returned info.
* @return if this liveness info has a timestamp, a copy of it with {@code newTimestamp}
* as timestamp. If it has no timestamp however, this liveness info is returned
* unchanged.
*/
public LivenessInfo withUpdatedTimestamp(long newTimestamp)
{
return new LivenessInfo(newTimestamp);
}
@Override
public String toString()
{
return String.format("[ts=%d]", timestamp);
}
@Override
public boolean equals(Object other)
{
if(!(other instanceof LivenessInfo))
return false;
LivenessInfo that = (LivenessInfo)other;
return this.timestamp() == that.timestamp()
&& this.ttl() == that.ttl()
&& this.localExpirationTime() == that.localExpirationTime();
}
@Override
public int hashCode()
{
return Objects.hash(timestamp(), ttl(), localExpirationTime());
}
private static class ExpiringLivenessInfo extends LivenessInfo
{
private final int ttl;
private final int localExpirationTime;
private ExpiringLivenessInfo(long timestamp, int ttl, int localExpirationTime)
{
super(timestamp);
assert ttl != NO_TTL && localExpirationTime != NO_EXPIRATION_TIME;
this.ttl = ttl;
this.localExpirationTime = localExpirationTime;
}
@Override
public int ttl()
{
return ttl;
}
@Override
public int localExpirationTime()
{
return localExpirationTime;
}
@Override
public boolean isExpiring()
{
return true;
}
@Override
public boolean isLive(int nowInSec)
{
return nowInSec < localExpirationTime;
}
@Override
public void digest(MessageDigest digest)
{
super.digest(digest);
FBUtilities.updateWithInt(digest, localExpirationTime);
FBUtilities.updateWithInt(digest, ttl);
}
@Override
public void validate()
{
if (ttl < 0)
throw new MarshalException("A TTL should not be negative");
if (localExpirationTime < 0)
throw new MarshalException("A local expiration time should not be negative");
}
@Override
public int dataSize()
{
return super.dataSize()
+ TypeSizes.sizeof(ttl)
+ TypeSizes.sizeof(localExpirationTime);
}
@Override
public LivenessInfo withUpdatedTimestamp(long newTimestamp)
{
return new ExpiringLivenessInfo(newTimestamp, ttl, localExpirationTime);
}
@Override
public String toString()
{
return String.format("[ts=%d ttl=%d, let=%d]", timestamp, ttl, localExpirationTime);
}
}
}