Aphora v0.3.5 Aphora.Worker View Source
This module implements a GenServer
, which can generate guaranteed unique aphora_id/0
on demand.
Link to this section Summary
Types
A aphora_id/0
is a 72 Bits
long unique & sortable identifier, which doesn't require any centralised coordination.
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
.
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
Returns the unique aphora_id/0
.
Returns a specification to start this module under a supervisor.
Invoked when the server is started. start_link/3
or start/3
will
block until it returns.
Returns the timestamp/0
.
Link to this section Types
aphora_id()
View Source
(since 0.1.0)
aphora_id() :: String.t()
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:
45 Bits
timestamp/0
.5 Bits
Aphora.Config.datacenter/0
.10 Bits
Aphora.Config.worker/0
.12 Bits
counter/0
.
counter()
View Source
(since 0.2.0)
counter() :: non_neg_integer()
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.
timestamp()
View Source
(since 0.1.0)
timestamp() :: non_neg_integer()
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.
Link to this section Functions
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()
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"
child_spec(init_arg) View Source
Returns a specification to start this module under a supervisor.
See Supervisor
.
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 callingSupervisor.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
.
start_link(state) View Source
timestamp(epoch)
View Source
(since 0.1.0)
timestamp(Aphora.Config.epoch()) :: timestamp()
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