doc: recommend worker_processes if the app uses SIGCHLD

If worker_processes are not enabled, our SIGCHLD handler may
conflict with one installed by the application.  Fortunately it is
uncommon in Ruby web apps to rely on SIGCHLD, but it happens and
that is bad.

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/yahns_config.txt b/Documentation/yahns_config.txt
index 2505907..45bcfd9 100644
--- a/Documentation/yahns_config.txt
+++ b/Documentation/yahns_config.txt
@@ -495,6 +495,12 @@ Ruby it is running under.
     pthread_atfork(3)-style hooks.  See WORKER_PROCESSES-LEVEL DIRECTIVES
     for details.
 
+    Using worker_processes is strongly recommended if your application
+    relies on using a SIGCHLD handler for reaping forked processes.
+    Without worker_processes, yahns must reserve SIGCHLD for rolling
+    back SIGUSR2 upgrades, leading to conflicts if the appplication
+    expects to handle SIGCHLD.
+
     Default: nil (single process, no master/worker separation)
 
 ## WORKER_PROCESSES-LEVEL DIRECTIVES