net.openhft.chronicle.queue

Interface RollCycle

All Known Implementing Classes:

LargeRollCycles, LegacyRollCycles, RollCycles, SparseRollCycles, TestRollCycles

public interface RollCycle

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_INDEX_COUNT

Method Summary

Modifier and Type	Method and Description
default int	current(@NotNull net.openhft.chronicle.core.time.TimeProvider time, long epoch) Returns the current cycle.
int	defaultIndexCount()
int	defaultIndexSpacing() Returns the space between excerpts that are explicitly indexed.
@NotNull String	format() Returns the format that is to be applied when file names are calculated for a new roll cycle.
int	lengthInMillis() Returns the length in milliseconds (i.e.
long	maxMessagesPerCycle()
int	toCycle(long index) Returns the cycle for the given index.
long	toIndex(int cycle, long sequenceNumber) Returns the index for the provided cycle and sequenceNumber.
long	toSequenceNumber(long index) Returns the sequence number for the provided index.

Field Detail

MAX_INDEX_COUNT

static final int MAX_INDEX_COUNT

See Also:

Constant Field Values

Method Detail

format

@NotNull
@NotNull String format()

Returns the format that is to be applied when file names are calculated for a new roll cycle.

For example, the following formats can be returned:

• "yyyyMMdd-HHmm" (MINUTELY)
• "yyyyMMdd" (DAILY)

Lexicographical order of formatted cycles must preserve chronological order, i.e. if cycle1 < cycle2, the same relation must be kept for their string representations.

Returns:

the format that is to be applied when file names are calculated for a new roll cycle

lengthInMillis

int lengthInMillis()

Returns the length in milliseconds (i.e. the maximum duration) for a roll cycle.

For example, the following lengths can be returned:

• 60 * 1,000 = 60,000 (MINUTELY)
• 24 * 60 * 60 * 1,000 = 86,400,000 (DAILY)

Returns:

the length in milliseconds (i.e. the maximum duration) for a roll cycle

defaultIndexCount

int defaultIndexCount()

Returns:

the size of each index array, note: indexCount^2 is the maximum number of index queue entries.

defaultIndexSpacing

int defaultIndexSpacing()

Returns the space between excerpts that are explicitly indexed.

A higher number means higher sequential write performance but slower random access read. The sequential read performance is not affected by this property.

For example, the following default index spacing can be returned:

• 16 (MINUTELY)
• 64 (DAILY)

Returns:

the space between excerpts that are explicitly indexed

current

default int current(@NotNull
                    @NotNull net.openhft.chronicle.core.time.TimeProvider time,
                    long epoch)

Returns the current cycle. Default epoch is 0 so for a DAILY cycle this will return the number of days since 1970-01-01T00:00:00Z.

Parameters:

epoch - an EPOCH offset, to all the user to define their own epoch

Returns:

the current cycle

toIndex

long toIndex(int cycle,
             long sequenceNumber)

Returns the index for the provided cycle and sequenceNumber.

An index is made up of cycle shifted left + sequenceNumber. sequenceNumber starts at 0 for each new cycle. DAILY cycle has cycleShift=32 and sequenceMask=0xFFFFFFFF so the top 32 bits are for cycle and bottom 32 bits are for sequence. This means you can only store 2^32 entries per day. HUGE_DAILY has shift=48 and mask=0xFFFFFFFFFFFF thus allowing 2^48 entries per day.

Parameters:

cycle - to be composed into an index

sequenceNumber - to be composed into an index

Returns:

the index for the given cycle and sequenceNumber

toSequenceNumber

long toSequenceNumber(long index)

Returns the sequence number for the provided index.

An index comprises both a cycle and a sequence number but the way the index is composed of said properties may vary. This method decomposes the provided index and extracts the sequence number.

Parameters:

index - to use to extract the sequence number

Returns:

the sequence number for the provided index

toCycle

int toCycle(long index)

Returns the cycle for the given index.

An index comprises both a cycle and a sequence number but the way the index is composed of said properties may vary. This method decomposes the provided index and extracts the cycle.

Parameters:

index - to use when extracting the cycle

Returns:

the sequence number for the given index

maxMessagesPerCycle

long maxMessagesPerCycle()

Returns:

the maximum number of messages per cycle