From af898378b9f7d2622dbe916e0f376955b91c14f8 Mon Sep 17 00:00:00 2001
From: Florian Klink <flokli@flokli.de>
Date: Thu, 6 Oct 2022 10:04:07 +0200
Subject: [PATCH 1/2] use sd-notify to signal readyness

Provide a way to signal nsncd has successfully started up, and is ready
to accept connections.

A more reliable way would be to only signal this once at least one
worker has started up, but this is good enough (tm) for now.

This can be used in a systemd.service file with Type=notify.
---
 Cargo.lock    | 7 +++++++
 Cargo.toml    | 1 +
 nsncd.service | 1 +
 src/main.rs   | 4 +++-
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index f299e96..c2a1bf4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -446,6 +446,7 @@ dependencies = [
  "num-derive",
  "num-traits",
  "once_cell",
+ "sd-notify",
  "slog",
  "slog-async",
  "slog-term",
@@ -647,6 +648,12 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c8132065adcfd6e02db789d9285a0deb2f3fcb04002865ab67d5fb103533898"
 
+[[package]]
+name = "sd-notify"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "621e3680f3e07db4c9c2c3fb07c6223ab2fab2e54bd3c04c3ae037990f428c32"
+
 [[package]]
 name = "serde"
 version = "1.0.145"
diff --git a/Cargo.toml b/Cargo.toml
index 9756298..554ba20 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,6 +24,7 @@ crossbeam-channel = "^0.5"
 nix = "^0.21.2"
 num-derive = "^0.3"
 num-traits = "^0.2"
+sd-notify = "0.4.1"
 # Indirect dependency, constrained for MSRV
 once_cell = "~1.14"
 
diff --git a/nsncd.service b/nsncd.service
index 7f6c3d0..99af01d 100644
--- a/nsncd.service
+++ b/nsncd.service
@@ -18,6 +18,7 @@ Description=name-service non-caching daemon
 [Service]
 ExecStart=/usr/lib/nsncd
 Restart=always
+Type=notify
 
 [Install]
 WantedBy=multi-user.target
diff --git a/src/main.rs b/src/main.rs
index a1d7c3a..76e4a8e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -54,6 +54,7 @@ use std::time::Duration;
 
 use anyhow::{Context, Result};
 use crossbeam_channel as channel;
+use sd_notify::NotifyState;
 use slog::{debug, error, o, Drain};
 
 mod ffi;
@@ -83,7 +84,6 @@ fn main() -> Result<()> {
         "worker_count" => worker_count,
         "handoff_timeout" => ?handoff_timeout,
     );
-
     let mut wg = WorkGroup::new();
     let tx = spawn_workers(&mut wg, &logger, worker_count);
 
@@ -93,6 +93,8 @@ fn main() -> Result<()> {
     std::fs::set_permissions(path, std::fs::Permissions::from_mode(0o777))?;
     spawn_acceptor(&mut wg, &logger, listener, tx, handoff_timeout);
 
+    let _ = sd_notify::notify(true, &[NotifyState::Ready]);
+
     let (result, handles) = wg.run();
     if let Err(e) = result {
         // if a thread unwound with a panic, just start panicing here. the nss

From 9fa26c5298b7e5e255a0109efcb39d90368e3ae6 Mon Sep 17 00:00:00 2001
From: Geoffrey Thomas <geofft@twosigma.com>
Date: Tue, 18 Oct 2022 11:29:51 -0400
Subject: [PATCH 2/2] Downgrade sd_notify to 0.3 for MSRV

---
 Cargo.lock | 4 ++--
 Cargo.toml | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index c2a1bf4..6de3729 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -650,9 +650,9 @@ checksum = "9c8132065adcfd6e02db789d9285a0deb2f3fcb04002865ab67d5fb103533898"
 
 [[package]]
 name = "sd-notify"
-version = "0.4.1"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "621e3680f3e07db4c9c2c3fb07c6223ab2fab2e54bd3c04c3ae037990f428c32"
+checksum = "0cd08a21f852bd2fe42e3b2a6c76a0db6a95a5b5bd29c0521dd0b30fa1712ec8"
 
 [[package]]
 name = "serde"
diff --git a/Cargo.toml b/Cargo.toml
index 554ba20..3a5407a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,7 +24,8 @@ crossbeam-channel = "^0.5"
 nix = "^0.21.2"
 num-derive = "^0.3"
 num-traits = "^0.2"
-sd-notify = "0.4.1"
+# Hold at 0.3: 0.4 MSRV is too new
+sd-notify = "~0.3"
 # Indirect dependency, constrained for MSRV
 once_cell = "~1.14"