fork_worker does not work with preload_app! (#2468)

Related to #2466 Close #2467 [ci skip]
puma · Oct 29, 2020 · f0dffd4 · f0dffd4
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diff --git a/5.0-Upgrade.md b/5.0-Upgrade.md
@@ -1,6 +1,6 @@
 # Welcome to Puma 5: Spoony Bard.
 
-![https://i1.kym-cdn.com/entries/icons/original/000/006/385/Spoony_Bard.jpg](https://i1.kym-cdn.com/entries/icons/original/000/006/385/Spoony_Bard.jpg) 
+![https://i1.kym-cdn.com/entries/icons/original/000/006/385/Spoony_Bard.jpg](https://i1.kym-cdn.com/entries/icons/original/000/006/385/Spoony_Bard.jpg)
 
 >Note: Puma 5 now automatically uses `WEB_CONCURRENCY` env var if set see [this post for an explanation](https://github.com/puma/puma/issues/2393#issuecomment-702352208). If your memory use goes up after upgrading to Puma 5 it indicates you're now running with multiple workers (processes). You can decrease memory use by tuning this number to be lower.
 
@@ -34,9 +34,9 @@ Users of this option should see reduced request queue latency and possibly less
 
 Add the following to your `puma.rb` to try it:
 
-```ruby 
+```ruby
 wait_for_less_busy_worker
-# or 
+# or
 wait_for_less_busy_worker 0.001
 ```
 
@@ -52,7 +52,7 @@ Production testing at GitLab suggests values between `0.001` and `0.010` are bes
 
 To use it, you can add this to your `puma.rb`:
 
-```ruby 
+```ruby
 nakayoshi_fork
 ```
 
@@ -68,7 +68,7 @@ Puma 5 introduces an experimental new cluster-mode configuration option, `fork_w
 10004           \_ puma: cluster worker 3: 10000 [puma]
 ```
 
-This allows the usage of `preload` with `phased_restart`. It also may improve memory usage because the worker process loads additional code after processing requests.
+It is compatible with phased restarts. It also may improve memory usage because the worker process loads additional code after processing requests.
 
 To learn more about using `refork` and `fork_worker`, see [the documentation](https://github.com/puma/puma/blob/master/docs/fork_worker.md).
 

diff --git a/docs/fork_worker.md b/docs/fork_worker.md
@@ -24,6 +24,8 @@ Similar to the `preload_app!` option, the `fork_worker` option allows your appli
 
 ### Limitations
 
+- Not compatible with the `preload_app!` option
+
 - This mode is still very experimental so there may be bugs or edge-cases, particularly around expected behavior of existing hooks. Please open a [bug report](https://github.com/puma/puma/issues/new?template=bug_report.md) if you encounter any issues.
 
 - In order to fork new workers cleanly, worker 0 shuts down its server and stops serving requests so there are no open file descriptors or other kinds of shared global state between processes, and to maximize copy-on-write efficiency across the newly-forked workers. This may temporarily reduce total capacity of the cluster during a phased restart / refork.