HLClock

v1.0.0

HLClock v1.0.0 HLClock.Timestamp View Source

HLC Timestamp

Implements the necessary components of the HLC tuple (i.e. logical time and logical counter) with extension to support node ids to provide unique timestamps even in cases where time and counter are the same

Binary representations assume big endianness for interop simplicity with other languages/representations.

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Types

t()

Functions

before?(t1, t2)

Determines if the clock's timestamp "happened before" a different timestamp

compare(_, _)

Exhaustive comparison of two timestamps: precedence is in order of time component, logical counter, and finally node identifier

decode(arg)

Construct a Timestamp from the binary representation

encode(map)

Pack the rich Timestamp struct as a 128 bit byte array

from_string(tstr)

Recover a Timestamp from the string representation.

new(time, counter, node_id \\ 0)

Construct a timestamp from its principal components: logical time (initially node's physical time), logical counter (initally zero), and the node id

recv(local, remote, physical_time, max_drift)

Given the current timestamp for this node and a provided remote timestamp, perform the merge of both logical time and logical counters. Returns the new current timestamp for the local node

send(map, pt, max_drift)

Generate a single HLC Timestamp for sending to other nodes or local causality tracking

to_datetime(timestamp)

Create a millisecond granularity DateTime struct representing the logical time portion of the Timestamp.

to_os_time(timestamp)

Return the logical, monotonic time portion. Unlike System.monotonic_time, if timestamps are regularly exchanged with other nodes and/or clients, this monotonic timestamp will represent a cluster wide monotonic value.

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t()

View Source 
t() :: %HLClock.Timestamp{
  counter: integer(),
  node_id: integer(),
  time: integer()
}

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before?(t1, t2)

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Determines if the clock's timestamp "happened before" a different timestamp

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compare(_, _)

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Exhaustive comparison of two timestamps: precedence is in order of time component, logical counter, and finally node identifier

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decode(arg)

View Source

Construct a Timestamp from the binary representation

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encode(map)

View Source

Pack the rich Timestamp struct as a 128 bit byte array

48 bits - Physical time 16 bits - Logical time 64 bits - Node ID

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from_string(tstr)

View Source

Recover a Timestamp from the string representation.

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new(time, counter, node_id \\ 0)

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Construct a timestamp from its principal components: logical time (initially node's physical time), logical counter (initally zero), and the node id

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recv(local, remote, physical_time, max_drift)

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Given the current timestamp for this node and a provided remote timestamp, perform the merge of both logical time and logical counters. Returns the new current timestamp for the local node

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send(map, pt, max_drift)

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Generate a single HLC Timestamp for sending to other nodes or local causality tracking

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to_datetime(timestamp)

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Create a millisecond granularity DateTime struct representing the logical time portion of the Timestamp.

Given that this representation looses the logical counter and node information, it should be used as a reference only. Including the counter in the DateTime struct would create absurd but still ordered timestamps.

Example 

iex> _t0 = HLClock.Timestamp.new(1410652800000, 0, 0)
%HLClock.Timestamp{counter: 0, node_id: 0, time: 1410652800000}

...> << time_and_counter :: size(64), _ :: size(64) >> = encoded
<<1, 72, 113, 117, 132, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0>>

...> DateTime.from_unix(time_and_counter, :microsecond)
{:ok, #DateTime<4899-07-30 06:31:40.800000Z>}
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to_os_time(timestamp)

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Return the logical, monotonic time portion. Unlike System.monotonic_time, if timestamps are regularly exchanged with other nodes and/or clients, this monotonic timestamp will represent a cluster wide monotonic value.