View Source ProcessHub (ProcessHub v0.1.3-alpha)
This is the main public API module for the ProcessHub
library.
Table of Contents
- Description
- Features
- Installation
- Example usage
- Configurable strategies
- Distribution strategy
- Cluster discovery and formation
- Resilience and reliability
- Locking mechanism
- Hooks
- Contributing
- Types
- Public API functions
Description
Library for building distributed systems that are scalable. It handles the distribution of processes within a cluster of nodes while providing a globally synchronized process registry.
ProcessHub takes care of starting, stopping and monitoring processes in the cluster. It scales automatically when cluster is updated and handles network partitions.
Building distributed systems is hard and designing one is all about trade-offs. There are many things to consider and each system has its own requirements. This library aims to be flexible and configurable to suit different use cases.
ProcessHub is designed to be decentralized in its architecture. It does not rely on a single node to manage the cluster. Each node in the cluster is considered equal. Consensus is achieved by using a hash ring implementation.
ProcessHub is built with scalability and availability in mind. Most of the operations are asynchronous and non-blocking. It can guarantee eventual consistency.
ProcessHub provides a set of configurable strategies for building distributed applications in Elixir.
ProcessHub requires a distributed node
ProcessHub is distributed in its nature, and for that reason, it needs to operate in a distributed environment. This means that the Elixir instance has to be started as a distributed node. For example:
iex --sname mynode --cookie mycookie -S mix
.If the node is not started as a distributed node, starting the
ProcessHub
will fail with the following error:{:error, :local_node_not_alive}
Features
Main features include:
- Distribute processes within a cluster of nodes.
- Provides globally synchronized process registry.
- Automatic hub cluster forming and healing when nodes join or leave the cluster.
- Process state handover.
- Strategies for redundancy handling and process replication.
- Strategies for handling network failures and partitions automatically.
- Strategies for handling process migration and synchronization when nodes join/leave the cluster automatically.
- Hooks for triggering events on specific actions.
Installation
Add
process_hub
to your list of dependencies inmix.exs
:def deps do [ {:process_hub, "~> 0.1.3-alpha"} ] end
Start the
ProcessHub
supervisor under your application supervision tree:defmodule MyApp.Application do use Application def start(_type, _args) do children = [ ProcessHub.child_spec(%ProcessHub{hub_id: :my_hub}) ] opts = [strategy: :one_for_one, name: MyApp.Supervisor] Supervisor.start_link(children, opts) end end
It is possible to start multiple hubs under the same supervision tree.
Each hub must have a unique hub_id/0
.
Example usage
The following example shows how to start 2 elixir nodes, connect them and start processes
under the ProcessHub
cluster. This demonstrates how the processes are distributed within
the cluster.
Note: The examples below assume that the ProcessHub
is already started under the
supervision tree. If not please refer to the Installation section.
Note: Make sure you have a GenServer module called MyProcess
defined in your project.
defmodule MyProcess do
use GenServer
def start_link() do
GenServer.start_link(__MODULE__, nil)
end
def init(_) do
{:ok, nil}
end
end
Node 1
Start the first node with the following command:
iex --name node1@127.0.0.1 --cookie mycookie -S mix
# Run the following in the iex console to start 5 processes under the hub.
iex> ProcessHub.start_children(:my_hub, [
...> %{id: :some_id1, start: {MyProcess, :start_link, []}},
...> %{id: :another_id2, start: {MyProcess, :start_link, []}},
...> %{id: :child_3, start: {MyProcess, :start_link, []}},
...> %{id: :child_4, start: {MyProcess, :start_link, []}},
...> %{id: "the_last_child", start: {MyProcess, :start_link, []}}
...> ])
{:ok, :start_initiated}
# Check the started processes by running the command below.
iex> ProcessHub.which_children(:my_hub, [:global])
[
node1@127.0.0.1: [
{"the_last_child", #PID<0.250.0>, :worker, [MyProcess]},
{:child_4, #PID<0.249.0>, :worker, [MyProcess]},
{:child_3, #PID<0.248.0>, :worker, [MyProcess]},
{:another_id2, #PID<0.247.0>, :worker, [MyProcess]},
{:some_id1, #PID<0.246.0>, :worker, [MyProcess]}
]
]
Node 2
We will use this node to connect to the first node and see how the processes are automatically distributed.
Start the second node.
iex --name node2@127.0.0.1 --cookie mycookie -S mix
# Connect the second node to the first node.
iex> Node.connect(:"node1@127.0.0.1")
true
# Check the started procsses by running the command below and
# see how some of the processes are distributed to the second node.
iex> ProcessHub.which_children(:my_hub, [:global])
[
"node2@127.0.0.1": [
{:child_3, #PID<0.261.0>, :worker, [MyProcess]},
{:some_id1, #PID<21674.247.0>, :worker, [MyProcess]}
],
"node1@127.0.0.1": [
{"the_last_child", #PID<21674.251.0>, :worker, [MyProcess]},
{:child_4, #PID<21674.250.0>, :worker, [MyProcess]},
{:another_id2, #PID<21674.248.0>, :worker, [MyProcess]}
]
]
Configurable strategies
ProcessHub comes with 9 different strategies that can be used to configure the hub. All strategies are Elixir structs that implement their own base protocol.
In fact, you can define your own strategies by implementing the base protocols.
When configuring the hub, you can pass the strategies as part of the t/0
struct.
Look at the documentation for each strategy for more information on how to configure them.
An example can be seen below.
defmodule MyApp.Application do
use Application
def start(_type, _args) do
children = [process_hub()]
opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)
end
defp process_hub() do
{ProcessHub, %ProcessHub{
hub_id: :my_hub,
# Configure the redundancy strategy.
redundancy_strategy: %ProcessHub.Strategy.Redundancy.Replication{
replication_factor: 2,
replication_model: :active_passive,
redundancy_signal: :all
},
# Configure the migration strategy.
migration_strategy: %ProcessHub.Strategy.Migration.HotSwap{
retention: 2000,
handover: true
},
# Configure the synchronization strategy.
synchronization_strategy: %ProcessHub.Strategy.Synchronization.PubSub{
sync_interval: 10000
},
# Configure the partition tolerance strategy.
partition_tolerance_strategy: %ProcessHub.Strategy.PartitionTolerance.StaticQuorum{
quorum_size: 2
}
}}
end
end
Redundancy Strategy
ProcessHub.Strategy.Redundancy.Base
- defines the base protocol for redundancy strategies.
This strategy is used to define how many replicas of a process should be started
across the cluster. Starting multiple instances of a process across the cluster is useful
for redundancy and fault tolerance.
Available strategies are:
ProcessHub.Strategy.Redundancy.Singularity
- only 1 process perchild_id/0
without any replicas. This is also the default strategy and contains no special configuration options.ProcessHub.Strategy.Redundancy.Replication
- starts multiple replicas of a process across the cluster. The number of replicas is defined by the:replication_factor
option. This strategy also supports:active_active
and:active_passive
modes. Meaning we may have one active process and the rest are passive. The mode is defined by the:replication_model
option. This information will be passed to the started process. The default mode is:active_active
, meaning all processes are equal and considered active.
Migration Strategy
ProcessHub.Strategy.Migration.Base
- defines the base protocol for migration strategies.
This strategy is used to define how the processes are migrated when a node joins or leaves the cluster.
Migration is the process of moving processes from one node to another. One of the reasons why migration happens is when a node leaves the cluster. When a node leaves the cluster, it is possible that some processes are still running on that node, so these need to be migrated to another node. Also, when a new node joins the cluster, other nodes may migrate some processes over to the new node.
At the moment, there are 2 migration strategies available:
ProcessHub.Strategy.Migration.ColdSwap
- migrate processes by stopping the process on the old node before starting it on the new node. This is the default strategy and defines no special configuration options.ProcessHub.Strategy.Migration.HotSwap
- this strategy is used to migrate processes by starting the process on the new node before stopping it on the old node. This strategy is useful when we want to avoid any downtime. This strategy is also useful when the process is stateful, and we want to avoid any data loss by handing over the state from the old process to the new process. See the module for handover examples.
Synchronization Strategy
ProcessHub.Strategy.Synchronization.Base
- defines the base protocol for synchronization
strategies which define the method that is used to synchronize the process registry.
Available strategies are:
ProcessHub.Strategy.Synchronization.PubSub
- uses a publish/subscribe model to synchronize the process registry. Each node in the cluster will subscribe to a topic and publish any changes to the topic. These changes could be events such as adding or removing a process from the registry. This is the default and recommended synchronization strategy for most users.ProcessHub.Strategy.Synchronization.Gossip
- uses a gossip protocol to synchronize the process registry. Using this strategy is recommended when the number of nodes in the cluster is large. The Gossip strategy selects a predefined number of nodes to gossip with and exchange information about the process registry. These selected nodes will choose other nodes to gossip with and so on until all nodes in the cluster are synchronized. It has higher latency than the PubSub strategy specially when the cluster is rather small.
Partition Tolerance Strategy
ProcessHub.Strategy.PartitionTolerance.Base
- defines the base protocol for partition tolerance
strategies which define the method that is used to handle network partitions.
Available strategies are:
ProcessHub.Strategy.PartitionTolerance.Divergence
- this strategy is used to handle network partitions by diverging the cluster into multiple subclusters. Each subcluster will have its own hub and will be considered as a separate cluster. This strategy is the default strategy. When the network partition is healed, the subclusters will merge back into a single cluster.ProcessHub.Strategy.PartitionTolerance.StaticQuorum
- this strategy is used to handle network partitions by using a static quorum. The quorum size is defined by the:quorum_size
option. When a partition happens, theProcessHub.DistributedSupervisor
process will terminate along with its children. This strategy is useful when the number of nodes in the cluster is known and rather fixed.ProcessHub.Strategy.PartitionTolerance.DynamicQuorum
- this strategy is used to handle network partitions by using a dynamic quorum. The quorum size is defined by the:quorum_size
option and:threshold_time
option. The system automatically over time adapts to the number of nodes in the cluster. When a partition happens, theProcessHub.DistributedSupervisor
process will terminate along with its children.Using DynamicQuorum Strategy
When scaling down too many nodes at once, the system may consider itself to be in a network partition. Read the documentation for the
ProcessHub.Strategy.PartitionTolerance.DynamicQuorum
strategy for more information.
Distribution Strategy
ProcessHub uses consistent hashing to distribute processes. When the cluster is updated, the hash ring is recalculated. The recalculation is done in a way that each node is assigned a unique hash value, and they form a hash ring. Each node in the cluster keeps track of the ProcessHub cluster and updates its local hash ring accordingly.
To find the node that the process belongs to, the system will use the hash ring to calculate
the hash value of the process ID (child_id/0
) and assign it to the node with the closest hash value.
When the cluster is updated and the hash ring is recalculated, it does not mean that all processes will be shuffled. Only the processes that are affected by the change will be redistributed. This is done to avoid unnecessary process migrations.
For example, when a node leaves the cluster, only the processes that were running on that node will be redistributed. The rest of the processes will stay on the same node. When a new node joins the cluster, only some of the processes will be redistributed to the new node, and the rest will stay on the same node.
The hash ring implementation does not guarantee that all processes will always be evenly distributed, but it does its best to distribute them as evenly as possible.
This strategy is used by default and is not configurable at the moment.
Cluster Discovery and Formation
ProcessHub monitors connecting and disconnecting nodes and forms a cluster automatically
from the connected nodes that share the same hub_id/0
. It's not required to start
the ProcessHub
on all nodes in the cluster.
Resilience and Reliability
ProcessHub uses the Supervisor
behavior and leverages the features that come with it.
Each hub starts its own ProcessHub.DistributedSupervisor
process, which is responsible for
starting, stopping, and monitoring the processes in its local cluster.
When a process dies unexpectedly, the ProcessHub.DistributedSupervisor
will restart it
automatically.
ProcessHub also takes care of validating the child_spec/0
before starting it and makes sure
it's started on the right node that the process belongs to.
If the process is being started on the wrong node, the initialization request will be forwarded
to the correct node.
Locking Mechanism
ProcessHub utilizes the :blockade
library to provide event-driven communication
and a locking mechanism.
It locks the local event queue by increasing its priority for some operations.
This allows the system to queue events and process them in order to preserve data integrity.
Other events can be processed once the priority level is set back to default.
To avoid deadlocks, the system places a timeout on the event queue priority and restores it to its original value if the timeout is reached.
Hooks
Hooks are used to trigger events on specific actions. Hooks can be registered by passing the
handlers to the :hooks
option of the t/0
configuration struct or by inserting them
dynamically using the ProcessHub.Service.HookManager
module.
ProcessHub heavily uses hooks internally in the integration tests.
Hooks have to be in the format of an mfa
tuple. Basically, they are functions that will be called
when the hook is triggered.
It is possible to register a hook handler with a wildcard argument :_
, which will be replaced
with the hook data when the hook is dispatched.
Example hook registration using the t/0
configuration struct:
# Register a hook handler for the `:cluster_join` event with a wildcard argument.
defmodule MyApp.Application do
use Application
def start(_type, _args) do
children = [
ProcessHub.child_spec(%ProcessHub{
hub_id: :my_hub,
hooks: [
ProcessHub.Constant.Hook.cluster_join(), {MyModule, :my_function, [:some_data, :_]}
]
})
]
opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)
end
end
Example hook registration using the ProcessHub.Service.HookManager
module:
# Register a hook handler for the `:cluster_join` event with a wildcard argument.
ProcessHub.Service.HookManager.register_hook(:my_hub, ProcessHub.Constant.Hook.cluster_join(), {MyModule, :my_function, [:some_data, :_]})
Example hook handler:
# The hook handler should be in the following format:
defmodule MyModule do
def my_function(:some_data, dynamic_hook_data) do
# Do something with the data.
end
end
Available hooks
Event Key | Trigger | Data |
---|---|---|
cluster_join | Node joins the cluster | node() |
cluster_leave | Node leaves the cluster | node() |
registry_pid_inserted | Process registered | {child_id(), [{node(), pid()}]} |
registry_pid_removed | Process unregistered | child_id() |
child_migrated | Process migrated | {child_id(), node()} |
priority_state_updated | Priority state updated | {priority_level(), list()} |
pre_nodes_redistribution | Nodes redistribution start | `{:nodeup | :nodedown, node()}` |
post_nodes_redistribution | Nodes redistribution end | `{:nodeup | :nodedown, node()}` |
See ProcessHub.Constant.Hook
module for more information.
Contributing
Contributions are welcome and appreciated. If you have any ideas, suggestions, or bugs to report, please open an issue or a pull request on GitHub.
Summary
Types
The child_id
defines the name of the child. It is used to identify the child.
Each child must have a unique child_id()
in the cluster. A single child may have
multiple pid()
s across the cluster.
The child_spec
defines the specification of a child process.
The hub_id
defines the name of the hub. It is used to identify the hub.
The init_opts()
defines the options that can be passed to the start_children/3
, start_child/3
,
stop_children/3
, and stop_child/3
functions.
The reply_to
defines the pid()
s that will receive the response from the hub
when a child is started or stopped.
The stop_opts()
defines the options that can be passed to the stop_children/3
and stop_child/3
functions.
This is the base configuration structure for the hub and has to be passed to the start_link/1
function.
Functions
This function can be used to wait for the ProcessHub
child start or stop
functions to complete.
Returns information about processes that are registered with the given child_id/0
.
Returns the child specification for the ProcessHub.Initializer
supervisor.
Checks if the ProcessHub
with the given hub_id/0
is alive.
Checks if the ProcessHub
with the given hub_id/0
is locked.
Checks if the ProcessHub
with the given hub_id/0
is in a network-partitioned state.
Returns a list of nodes where the ProcessHub
with the given hub_id/0
is running.
Returns all information registered regarding the child processes.
Starts a child process that will be distributed across the cluster.
The t:child_spec()
:id
must be unique.
Starts multiple child processes that will be distributed across the cluster.
Starts the ProcessHub
with the given hub_id/0
and settings.
Stops the ProcessHub
with the given hub_id/0
.
Stops a child process in the cluster.
Stops multiple child processes in the cluster.
Works similarly to Supervisor.which_children/1
, but wraps the result in a tuple
containing the node name and the children.
Types
The child_id
defines the name of the child. It is used to identify the child.
Each child must have a unique child_id()
in the cluster. A single child may have
multiple pid()
s across the cluster.
The child_spec
defines the specification of a child process.
@type hub_id() :: atom()
The hub_id
defines the name of the hub. It is used to identify the hub.
@type init_opts() :: [ async_wait: boolean(), timeout: non_neg_integer(), check_mailbox: boolean(), check_existing: boolean() ]
The init_opts()
defines the options that can be passed to the start_children/3
, start_child/3
,
stop_children/3
, and stop_child/3
functions.
:async_wait
- is optional and is used to define whether the function should return another function that can be used to wait for the children to start or stop. The default isfalse
.:timeout
is optional and is used to define the timeout for the function. The timeout option should be used withasync_wait: true
. The default is5000
(5 seconds).:check_mailbox
- is optional and is used to define whether the function should clear the mailbox of any existing messages that may overlap. It is recommended to keep this optiontrue
to avoid any unexpected behavior wherestart_child/3
orstart_children/3
call timeout but eventually the calling process receives the start responses later. These messages will stay in that process's mailbox, and when the same process calls start child functions again with the samechild_id()
s, it will receive the old responses.This option should be used withasync_wait: true
. The default istrue
.:check_existing
- is optional and is used to define whether the function should check if the children are already started. The default istrue
.
@type reply_to() :: [pid()]
The reply_to
defines the pid()
s that will receive the response from the hub
when a child is started or stopped.
@type stop_opts() :: [async_wait: boolean(), timeout: non_neg_integer()]
The stop_opts()
defines the options that can be passed to the stop_children/3
and stop_child/3
functions.
:async_wait
- is optional and is used to define whether the function should return another function that can be used to wait for the children to stop. The default isfalse
.:timeout
is optional and is used to define the timeout for the function. The timeout option should be used withasync_wait: true
. The default is5000
(5 seconds).
@type t() :: %ProcessHub{ hooks: ProcessHub.Service.HookManager.hooks(), hub_id: hub_id(), migration_strategy: ProcessHub.Strategy.Migration.ColdSwap.t() | ProcessHub.Strategy.Migration.HotSwap.t(), partition_tolerance_strategy: ProcessHub.Strategy.PartitionTolerance.Divergence.t() | ProcessHub.Strategy.PartitionTolerance.StaticQuorum.t() | ProcessHub.Strategy.PartitionTolerance.DynamicQuorum.t(), redundancy_strategy: ProcessHub.Strategy.Redundancy.Singularity.t() | ProcessHub.Strategy.Redundancy.Replication.t(), synchronization_strategy: ProcessHub.Strategy.Synchronization.PubSub.t() | ProcessHub.Strategy.Synchronization.Gossip.t() }
This is the base configuration structure for the hub and has to be passed to the start_link/1
function.
:hub_id
is the name of the hub and is required.:hooks
are optional and are used to define the hooks that can be triggered on specific events.:redundancy_strategy
is optional and is used to define the strategy for redundancy. The default isProcessHub.Strategy.Redundancy.Singularity
.:migration_strategy
is optional and is used to define the strategy for migration. The default isProcessHub.Strategy.Migration.ColdSwap
.:synchronization_strategy
is optional and is used to define the strategy for synchronization. The default isProcessHub.Strategy.Synchronization.PubSub
.:partition_tolerance_strategy
is optional and is used to define the strategy for partition tolerance. The default isProcessHub.Strategy.PartitionTolerance.Divergence
.
Functions
This function can be used to wait for the ProcessHub
child start or stop
functions to complete.
The await/1
function should be used with the async_wait: true
option.
Keep in mind that the await/1
function will block the calling process until
the response is received. If the response is not received within the timeout
period, the function will return {:error, term()}
.
Example
iex> ref = ProcessHub.start_child(:my_hub, child_spec, [async_wait: true])
iex> ProcessHub.await(ref)
{:ok, {:my_child, [{:mynode, #PID<0.123.0>}]}}
@spec child_lookup(hub_id(), child_id()) :: {child_spec(), [{node(), pid()}]} | nil
Returns information about processes that are registered with the given child_id/0
.
This function queries results from the local ets
table and does not make any network calls.
The return results contain the child_spec/0
and a list of tuples where the first element is the node
where the child is started, and the second element is the pid()
of the started child.
Example
iex> {} = {_child_spec, _node_pid_tuples} = ProcessHub.child_lookup(:my_hub, :my_child)
{%{id: :my_child, start: {MyProcess, :start_link, []}}, [{:mynode, #PID<0.123.0>}]}
@spec child_spec(t()) :: %{ id: ProcessHub, start: {ProcessHub.Initializer, :start_link, [...]}, type: :supervisor }
Returns the child specification for the ProcessHub.Initializer
supervisor.
Checks if the ProcessHub
with the given hub_id/0
is alive.
A hub is considered alive if the ProcessHub.Initializer
supervisor process
is running along with the required child processes for the hub to function.
Example
iex> ProcessHub.is_alive?(:not_existing)
false
Checks if the ProcessHub
with the given hub_id/0
is locked.
A hub is considered locked if the ProcessHub
local event queue has a priority level
greater than or equal to 10. This is used to throttle the hub from processing
any new events and conserve data integrity.
Example
iex> ProcessHub.is_locked?(:my_hub)
false
Checks if the ProcessHub
with the given hub_id/0
is in a network-partitioned state.
A hub is considered partitioned if the ProcessHub.Strategy.PartitionTolerance
strategy
has detected a network partition. When a network partition is detected, the hub will
terminate the ProcessHub.DistributedSupervisor
process along with its children.
Example
iex> ProcessHub.is_partitioned?(:my_hub)
false
Returns a list of nodes where the ProcessHub
with the given hub_id/0
is running.
Nodes where the ProcessHub
is running with the same hub_id/0
are considered
to be part of the same cluster.
Example
iex> ProcessHub.nodes(:my_hub, [:include_local])
[:remote_node]
@spec process_registry(hub_id()) :: ProcessHub.Service.ProcessRegistry.registry()
Returns all information registered regarding the child processes.
This function queries results from the local ets
table and does not make any network calls.
@spec start_child(hub_id(), child_spec(), init_opts()) :: (-> {:ok, list()}) | {:error, :no_children | {:already_started, [atom() | binary(), ...]}} | {:ok, :start_initiated}
Starts a child process that will be distributed across the cluster.
The t:child_spec()
:id
must be unique.
Example
iex> child_spec = %{id: :my_child, start: {MyProcess, :start_link, []}}
iex> ProcessHub.start_child(:my_hub, child_spec)
{:ok, :start_initiated}
By default, the start_child/3
function is asynchronous and returns immediately.
To wait for the child to start, you can pass async_wait: true
to the opts
argument.
When async_wait: true
, you must await the response from the function.
See init_opts/0
for more options.
Example with synchronous wait
The synchronous response includes the status code :ok
or :error
, a tuple containing the child_id/0
and
a list of tuples where the first key is the node where the child is started, and the second key is the
pid()
of the started child. By default, the list should contain only one tuple, but if the
redundancy strategy is configured for replicas, it may contain more than one tuple.
iex> child_spec = %{id: :my_child, start: {MyProcess, :start_link, []}}
iex> ProcessHub.start_child(:my_hub, child_spec, [async_wait: true]) |> ProcessHub.await()
{:ok, {:my_child, [{:mynode, #PID<0.123.0>}]}}
@spec start_children(hub_id(), [child_spec()], init_opts()) :: (-> {:ok, list()}) | {:ok, :start_initiated} | {:error, :no_children | {:error, :children_not_list} | {:already_started, [atom() | binary(), ...]}}
Starts multiple child processes that will be distributed across the cluster.
Same as start_child/3
, except it starts multiple children at once and is more
efficient than calling start_child/3
multiple times.
Warning
Using
start_children/3
withasync_wait: true
can lead to timeout errors, especially when the number of children is large.
Starts the ProcessHub
with the given hub_id/0
and settings.
It is recommended to start the ProcessHub
under a supervision tree.
@spec stop(atom()) :: :ok | {:error, :not_alive}
Stops the ProcessHub
with the given hub_id/0
.
Stops a child process in the cluster.
By default, this function is asynchronous and returns immediately.
You can wait for the child to stop by passing async_wait: true
in the opts
argument.
When async_wait: true
, you must await the response from the function.
Example
iex> ProcessHub.stop_child(:my_hub, :my_child)
{:ok, :stop_initiated}
See stop_opts/0
for more options.
Example with synchronous wait
iex> ProcessHub.stop_child(:my_hub, :my_child, [async_wait: true]) |> ProcessHub.await()
{:ok, {:my_child, [:mynode]}}
@spec stop_children(hub_id(), [child_id()], stop_opts()) :: (-> {:ok, list()}) | {:ok, :stop_initiated} | {:error, list()}
Stops multiple child processes in the cluster.
This function is similar to stop_child/3
, but it stops multiple children at once, making it more
efficient than calling stop_child/3
multiple times.
Warning
Using
stop_children/3
withasync_wait: true
can lead to timeout errors, especially when stopping a large number of child processes.
@spec which_children(hub_id(), [:global | :local] | nil) :: list() | {node(), [ {any(), :restarting | :undefined | pid(), :supervisor | :worker, :dynamic | list()} ]}
Works similarly to Supervisor.which_children/1
, but wraps the result in a tuple
containing the node name and the children.
It's recommended to use ProcessHub.process_registry/1
instead when fast lookups
are required, as it makes no network calls.
Available options:
:global
- returns a list of all child processes started by all nodes in the cluster. The return result will be in the format of[{:node, children}]
.:local
- returns a list of all child processes started by the local node. The return result will be in the format of{:node, children}
.