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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,
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 * See the License for the specific language governing permissions and
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package org.apache.cassandra.db;

import java.util.Objects;
import java.security.MessageDigest;

import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.db.rows.Cell;
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.
 * 

* 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. *

* Please note that if a liveness info is ttl'ed, that expiration is only 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 = Cell.NO_TTL; /** * Used as flag for representing an expired liveness. * * TTL per request is at most 20 yrs, so this shouldn't conflict * (See {@link org.apache.cassandra.cql3.Attributes#MAX_TTL}) */ public static final int EXPIRED_LIVENESS_TTL = Integer.MAX_VALUE; public static final int NO_EXPIRATION_TIME = Cell.NO_DELETION_TIME; 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) { assert ttl != EXPIRED_LIVENESS_TTL; return new ExpiringLivenessInfo(timestamp, ttl, ExpirationDateOverflowHandling.computeLocalExpirationTime(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) { if (ttl == EXPIRED_LIVENESS_TTL) return new ExpiredLivenessInfo(timestamp, ttl, 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). * *
* * If timestamps are the same and none of them are expired livenessInfo, * livenessInfo with greater TTL supersedes another. It also means, if timestamps are the same, * ttl superseders no-ttl. This is the same rule as {@link Conflicts#resolveRegular} * * If timestamps are the same and one of them is expired livenessInfo. Expired livenessInfo * supersedes, ie. tombstone supersedes. * * If timestamps are the same and both of them are expired livenessInfo(Ideally it shouldn't happen), * greater localDeletionTime wins. * * @param other * the {@code LivenessInfo} to compare this info to. * * @return whether this {@code LivenessInfo} supersedes {@code other}. */ public boolean supersedes(LivenessInfo other) { if (timestamp != other.timestamp) return timestamp > other.timestamp; if (isExpired() ^ other.isExpired()) return isExpired(); if (isExpiring() == other.isExpiring()) return localExpirationTime() > other.localExpirationTime(); return isExpiring(); } protected boolean isExpired() { return false; } /** * 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); } public LivenessInfo withUpdatedTimestampAndLocalDeletionTime(long newTimestamp, int newLocalDeletionTime) { return LivenessInfo.create(newTimestamp, ttl(), newLocalDeletionTime); } @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()); } /** * Effectively acts as a PK tombstone. This is used for Materialized Views to shadow * updated entries while co-existing with row tombstones. * * See {@link org.apache.cassandra.db.view.ViewUpdateGenerator#deleteOldEntryInternal}. */ private static class ExpiredLivenessInfo extends ExpiringLivenessInfo { private ExpiredLivenessInfo(long timestamp, int ttl, int localExpirationTime) { super(timestamp, ttl, localExpirationTime); assert ttl == EXPIRED_LIVENESS_TTL; assert timestamp != NO_TIMESTAMP; } @Override public boolean isExpired() { return true; } @Override public boolean isLive(int nowInSec) { // used as tombstone to shadow entire PK return false; } @Override public LivenessInfo withUpdatedTimestamp(long newTimestamp) { return new ExpiredLivenessInfo(newTimestamp, 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); } } }





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