add :subscribe_after option to InOrder subscription

CHANGELOG.md

@@ -6,6 +6,13 @@ The format is based on [Keep a
 Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## 0.4.0 - 2021-06-10
+
+### Added
+
+- Added `:subscribe_after` option which determines how long the producer will
+  wait before checking whether it should subscribe or not
+
 ## 0.3.0 - 2021-06-04
 
 ### Changed

lib/kelvin/in_order_subscription.ex

@@ -21,6 +21,10 @@ defmodule Kelvin.InOrderSubscription do
     `false` if the author intends on manually subscribing the producer. This
     producer can be manually subscribed by `send/2`ing a message of
     `:subscribe` to the process.
+  * `:subscribe_after` - (default: `Enum.random(3_000..5_000)`) the amount of
+    time to wait after initializing to query the `:subscribe_on_init?` option.
+    This can be useful to prevent all producers from trying to subscribe at
+    the same time and to await an active connection to the EventStoreDB.
   * `:catch_up_chunk_size` - (default: `256`) the number of events to query
     for each read chunk while catching up. This option presents a trade-off
     between network queries and query duration over the network.
@@ -42,7 +46,11 @@ defmodule Kelvin.InOrderSubscription do
       self: Keyword.get(opts, :name, self())
     }
 
-    Process.send_after(self(), :check_auto_subscribe, Enum.random(3_000..5_000))
+    Process.send_after(
+      self(),
+      :check_auto_subscribe,
+      opts[:subscribe_after] || Enum.random(3_000..5_000)
+    )
 
     {:producer, state}
   end