Aphora

v0.3.5

Aphora v0.3.5 Aphora.Worker View Source

This module implements a GenServer, which can generate guaranteed unique aphora_id/0 on demand.

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Types

aphora_id()

A aphora_id/0 is a 72 Bits long unique & sortable identifier, which doesn't require any centralised coordination.

counter()

A counter/0 is a 12 Bits long identifier, which by default has a value of 0. It only increments, if two aphora_id/0 are to be generated within the same timestamp/0.

timestamp()

A timestamp/0 is a positive integer, which is equals to the time in which it was generated within timestamp/1. It consists of System.os_time/1 minus the Aphora.Config.epoch/0.

Functions

build_id(state)

Returns the unique aphora_id/0.

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

init(state)

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

start_link(state)
timestamp(epoch)

Returns the timestamp/0.

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aphora_id() View Source (since 0.1.0) 
aphora_id() :: String.t()

A aphora_id/0 is a 72 Bits long unique & sortable identifier, which doesn't require any centralised coordination.

It consists out of:

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counter() View Source (since 0.2.0) 
counter() :: non_neg_integer()

A counter/0 is a 12 Bits long identifier, which by default has a value of 0. It only increments, if two aphora_id/0 are to be generated within the same timestamp/0.

This allows for a total of 4_096 aphora_id/0 to be generated within the same timestamp/0 on the same unique Aphora.Config.worker/0 & Aphora.Config.datacenter/0 combination.

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timestamp() View Source (since 0.1.0) 
timestamp() :: non_neg_integer()

A timestamp/0 is a positive integer, which is equals to the time in which it was generated within timestamp/1. It consists of System.os_time/1 minus the Aphora.Config.epoch/0.

It has a total size of 45 Bits within the aphora_id/0 and a millisecond precision.
This allows for 35_184_372_088_832 millisecond or around 1115 years of millisecond precision timestamps.

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build_id(state) View Source (since 0.1.0) 
build_id(%{
  datacenter: Aphora.Config.datacenter(),
  worker: Aphora.Config.worker(),
  timestamp: timestamp(),
  counter: counter()
}) :: aphora_id()

Returns the unique aphora_id/0.

It first combines the binary representation of the information within the state into a 72 Bits binary.
Afterwards it gets encoded using Base.url_encode64/2 without a padding, so it can be easily used for any URI.

Examples 

iex> Aphora.Worker.build_id(%{datacenter: 2, worker: 981_207, timestamp: 912_988_800_000_000, counter: 423})
"AAM-W8UboAAAAg741wABpw"
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child_spec(init_arg) View Source

Returns a specification to start this module under a supervisor.

See Supervisor.

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init(state) View Source

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

init_arg is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning {:ok, state, {:continue, continue}} is similar to {:ok, state} except that immediately after entering the loop the c:handle_continue/2 callback will be invoked with the value continue as first argument.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

  • The GenServer is disabled by configuration but might be enabled later.
  • An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

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start_link(state) View Source

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timestamp(epoch) View Source (since 0.1.0) 
timestamp(Aphora.Config.epoch()) :: timestamp()

Returns the timestamp/0.

It gets calculated by taking the current time System.os_time/1 and substracting the Aphora.Config.epoch/0 of it.

Examples 

iex> Aphora.Worker.timestamp(0) == System.os_time(:millisecond)
true