net.logstash.logback.composite.FastISOTimestampFormatter Maven / Gradle / Ivy
Show all versions of logstash-logback-encoder Show documentation
/*
* Copyright 2013-2022 the original author or authors.
*
* Licensed 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 net.logstash.logback.composite;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;
import java.time.zone.ZoneOffsetTransition;
/**
* A fast alternative to DateTimeFormatter when formatting millis using an ISO format.
*
* This class is thread safe.
*
*
Note: This class is for internal use only and subject to backward incompatible change
* at any time.
*
* @author brenuart
*/
class FastISOTimestampFormatter {
private static final long MILLISECONDS_PER_MINUTE = 60_000;
/**
* ThreadLocal with reusable {@link StringBuilder} instances.
* Initialized with a size large enough to hold formats that do not include the Zone.
* Will need to grow on first use otherwise.
*/
private static ThreadLocal STRING_BUILDERS = ThreadLocal.withInitial(() -> new StringBuilder(30));
/**
* The actual DateTimeFormatter used to format the timestamp when the cached
* value cannot be used
*/
private final DateTimeFormatter formatter;
/**
* Holds the cached formatted value. Can be reused only when the timestamp to format
* is in the same ZoneOffset as the cached value.
*
* This class is immutable and a new instance is created when needed. Two concurrent threads may create two
* identical instances but only one will eventually remain. This strategy is cheaper than a lock or a volatile
* field.
*/
private ZoneOffsetState zoneOffsetState;
/**
* Whether trailing zero should be trimmed from the millis part
*/
private final boolean trimMillis;
/* Visible for testing */
FastISOTimestampFormatter(DateTimeFormatter formatter, boolean trimMillis) {
this.formatter = formatter;
this.trimMillis = trimMillis;
this.zoneOffsetState = new ZoneOffsetState(System.currentTimeMillis());
}
/**
* Format the {@code timestampInMillis} millis.
*
* @param timestampInMillis the millis to format
* @return the formatted result
*/
public String format(long timestampInMillis) {
ZoneOffsetState current = this.zoneOffsetState;
if (!current.canFormat(timestampInMillis)) {
current = new ZoneOffsetState(timestampInMillis);
this.zoneOffsetState = current;
}
return current.format(timestampInMillis);
}
/**
* Create a fast formatter using the same format as {@link DateTimeFormatter#ISO_OFFSET_DATE_TIME}.
*
* @param zoneId the zone override
* @return a fast formatter
*/
public static FastISOTimestampFormatter isoOffsetDateTime(ZoneId zoneId) {
return new FastISOTimestampFormatter(DateTimeFormatter.ISO_OFFSET_DATE_TIME.withZone(zoneId), true);
}
/**
* Create a fast formatter using the same format as {@link DateTimeFormatter#ISO_ZONED_DATE_TIME}.
*
* @param zoneId the zone override
* @return a fast formatter
*/
public static FastISOTimestampFormatter isoZonedDateTime(ZoneId zoneId) {
return new FastISOTimestampFormatter(DateTimeFormatter.ISO_ZONED_DATE_TIME.withZone(zoneId), true);
}
/**
* Create a fast formatter using the same format as {@link DateTimeFormatter#ISO_LOCAL_DATE_TIME}.
*
* @param zoneId the zone override
* @return a fast formatter
*/
public static FastISOTimestampFormatter isoLocalDateTime(ZoneId zoneId) {
return new FastISOTimestampFormatter(DateTimeFormatter.ISO_LOCAL_DATE_TIME.withZone(zoneId), true);
}
/**
* Create a fast formatter using the same format as {@link DateTimeFormatter#ISO_DATE_TIME}.
*
* @param zoneId the zone override
* @return a fast formatter
*/
public static FastISOTimestampFormatter isoDateTime(ZoneId zoneId) {
return new FastISOTimestampFormatter(DateTimeFormatter.ISO_DATE_TIME.withZone(zoneId), true);
}
/**
* Create a fast formatter using the same format as {@link DateTimeFormatter#ISO_INSTANT}.
*
* @param zoneId the zone override
* @return a fast formatter
*/
public static FastISOTimestampFormatter isoInstant(ZoneId zoneId) {
return new FastISOTimestampFormatter(DateTimeFormatter.ISO_INSTANT.withZone(zoneId), false);
}
/**
* State valid during a zone transition.
* Does not change frequently, typically before/after day-light transition.
*/
private class ZoneOffsetState {
private final long zoneTransitionStart;
private final long zoneTransitionStop;
private final boolean cachingEnabled;
private TimestampPeriod cachedTimestampPeriod;
ZoneOffsetState(long timestampInMillis) {
// Determine how long we can cache the previous result.
// ZoneOffsets are usually expressed in hour:minutes but the Java time API accepts ZoneOffset with
// a resolution up to the second:
// - If the minutes/seconds parts of the ZoneOffset are zero, then we can cache for as long as one hour.
// - If the ZoneOffset is expressed in "minutes", then we can cache the date/hour/minute part for as long as a minute.
// - If the ZoneOffset is expressed in seconds, then we can cache only for one second.
//
// Also, take care of ZoneOffset transition (e.g. day light saving time).
ZoneId zoneId = formatter.getZone();
if (zoneId == null) {
throw new IllegalArgumentException("formatter must be configured with a Zone override to format millis");
}
Instant now = Instant.ofEpochMilli(timestampInMillis);
ZoneOffset zoneOffset;
/*
* The Zone has a fixed offset that will never change.
*/
if (zoneId.getRules().isFixedOffset()) {
zoneOffset = zoneId.getRules().getOffset(now);
this.zoneTransitionStart = 0;
this.zoneTransitionStop = Long.MAX_VALUE;
}
/*
* The Zone has multiple offsets. Determine the one applicable at the given timestamp
* and how long it is valid.
*/
else {
ZoneOffsetTransition zoneOffsetTransition = zoneId.getRules().nextTransition(now);
this.zoneTransitionStart = timestampInMillis;
this.zoneTransitionStop = zoneOffsetTransition.toEpochSecond() * 1_000;
zoneOffset = zoneOffsetTransition.getOffsetBefore();
}
/*
* Determine the precision of the zone offset.
*
* If the offset is expressed with HH:mm without seconds, then the date/time part remains constant during
* one minute and is not affected by the zone offset. This means we can safely deduce the second and millis
* from a long timestamp.
*
* The same applies for the minutes part if the offset contains hours only. In this case, the date/time part
* remains constant for a complete hour increasing the time we can reuse that part. However, tests have shown
* that the extra computation required to extract the minutes from the timestamp during rendering negatively
* impact the overall performance.
*
* Caching is therefore limited to one minute which is good enough for our usage.
*/
int offsetSeconds = zoneOffset.getTotalSeconds();
this.cachingEnabled = (offsetSeconds % 60 == 0);
}
/**
* Check whether the given timestamp is within the ZoneOffset represented by this state.
*
* @param timestampInMillis the timestamp millis
* @return {@code true} if the timestamp is within the ZoneOffset represented by this state
*/
public boolean canFormat(long timestampInMillis) {
return timestampInMillis >= this.zoneTransitionStart && timestampInMillis < this.zoneTransitionStop;
}
/**
* Format a timestamp expressed in millis.
* Note: you must first invoke {@link #canFormat(long)} to check that the state can be used to format the timestamp.
*
* @param timestampInMillis the timestamp milis to format
* @return the formatted timestamp
*/
public String format(long timestampInMillis) {
// If caching is disabled...
//
if (!this.cachingEnabled) {
return buildFromFormatter(timestampInMillis);
}
// If tstamp is within the caching period...
//
TimestampPeriod currentTimestampPeriod = this.cachedTimestampPeriod;
if (currentTimestampPeriod != null && currentTimestampPeriod.canFormat(timestampInMillis)) {
return buildFromCache(currentTimestampPeriod, timestampInMillis);
}
// ... otherwise, use the formatter and cache the formatted value
//
String formatted = buildFromFormatter(timestampInMillis);
cachedTimestampPeriod = createNewCache(timestampInMillis, formatted);
return formatted;
}
private TimestampPeriod createNewCache(long timestampInMillis, String formatted) {
// Examples of the supported formats:
//
// ISO_OFFSET_DATE_TIME 2020-01-01T10:20:30.123+01:00
// ISO_ZONED_DATE_TIME 2020-01-01T10:20:30.123+01:00[Europe/Brussels]
// ISO_LOCAL_DATE_TIME 2020-01-01T10:20:30.123
// ISO_DATE_TIME 2020-01-01T10:20:30.123+01:00[Europe/Brussels]
// ISO_INSTANT 2020-01-01T09:20:30.123Z
// +---------------+ +---------------------+
// prefix suffix
//
// Seconds start at position 17 and are two digits long.
// Millis are optional.
// The part up to the minutes (included)
String prefix = formatted.substring(0, 17);
// The part of after the millis (i.e. the timezone)
int pos = formatted.indexOf('+', 17);
if (pos == -1) {
pos = formatted.indexOf('-', 17);
}
if (pos == -1 && formatted.charAt(formatted.length() - 1) == 'Z') {
pos = formatted.length() - 1;
}
String suffix = pos == -1 ? "" : formatted.substring(pos);
// Determine how long we can use this cache
long timstampInMinutes = timestampInMillis / MILLISECONDS_PER_MINUTE;
long minuteStartInMillis = timstampInMinutes * MILLISECONDS_PER_MINUTE;
long minuteStopInMillis = (timstampInMinutes + 1) * MILLISECONDS_PER_MINUTE;
// Store in cache
return new TimestampPeriod(minuteStartInMillis, minuteStopInMillis, prefix, suffix);
}
private String buildFromCache(TimestampPeriod cache, long timestampInMillis) {
return cache.format(timestampInMillis);
}
}
/* visible for testing */
String buildFromFormatter(long timestampInMillis) {
return FastISOTimestampFormatter.this.formatter.format(Instant.ofEpochMilli(timestampInMillis));
}
private class TimestampPeriod {
private final long periodStartInMillis;
private final long periodStopInMillis;
private final String suffix;
private final String prefix;
TimestampPeriod(long periodStartInMillis, long periodStopInMillis, String prefix, String suffix) {
this.periodStartInMillis = periodStartInMillis;
this.periodStopInMillis = periodStopInMillis;
this.prefix = prefix;
this.suffix = suffix;
}
public boolean canFormat(long timestampInMillis) {
return timestampInMillis >= this.periodStartInMillis && timestampInMillis < this.periodStopInMillis;
}
public String format(long timestampInMillis) {
StringBuilder sb = STRING_BUILDERS.get();
sb.setLength(0);
sb.append(prefix);
int millisSincePeriodStart = (int) (timestampInMillis - this.periodStartInMillis); // seconds & millis
int seconds = millisSincePeriodStart / 1_000;
int millis = millisSincePeriodStart % 1000;
// seconds are always TWO digits...
//
if (seconds < 10) {
sb.append('0');
}
sb.append(seconds);
// millis are optional, max 3 significant digits (trailing 0 removed)
//
if (millis > 0) {
int dotPos = sb.length();
sb.append('.');
// add leading 0...
if (millis < 100) {
sb.append('0');
}
if (millis < 10) {
sb.append('0');
}
// add millis value...
sb.append(millis);
// remove trailing 0...
if (FastISOTimestampFormatter.this.trimMillis) {
while (sb.length() > dotPos) {
if (sb.charAt(sb.length() - 1) == '0') {
sb.setLength(sb.length() - 1);
}
else {
break;
}
}
}
}
// suffix...
//
sb.append(this.suffix);
return sb.toString();
}
}
}