Add example launchctl-file for MacOS (#856)

* Add example LaunchCtl-file for MacOS

Signed-off-by: Morten Siebuhr <sbhr@sbhr.dk>

* Rewrite program location in launctctl file

This seem to be the way most plist files does it.

Signed-off-by: Morten Siebuhr <sbhr@sbhr.dk>

* Make launct-agent run as nobody/nobody

Signed-off-by: Morten Siebuhr <sbhr@sbhr.dk>

* Rename plist per general naming scheme

Signed-off-by: Morten Siebuhr <sbhr@sbhr.dk>

* Pass arguments-file when launched through launchctl

Signed-off-by: Morten Siebuhr <sbhr@sbhr.dk>

examples/launchctl/README.md

@@ -0,0 +1,26 @@
+# MacOS LaunchAgent
+
+If you're installing through a package manager, you probably don't need to deal
+with this file.
+
+The `plist` file should be put in `~/Library/LaunchAgents/` (user-install) or
+`/Library/LaunchAgents/` (global install), and the binary installed at
+`/usr/local/bin/node_exporter`.
+
+Ex. install globally by
+
+    sudo cp -n node_exporter /usr/local/bin/
+    sudo cp -n examples/launchctl/io.prometheus.node_exporter.plist /Library/LaunchAgents/
+    sudo launchctl bootstrap system/ /Library/LaunchAgents/io.prometheus.node_exporter.plist
+
+    # Optionally configure by dropping CLI arguments in a file
+    echo -- '--web.listen-address=:9101' | sudo tee /usr/local/etc/node_exporter.args
+
+    # Check it's running
+    sudo launchctl list | grep node_exporter
+
+    # See full process state
+    sudo launchctl print system/io.prometheus.node_exporter
+
+    # View logs
+    sudo tail /tmp/node_exporter.log

examples/launchctl/io.prometheus.node_exporter.plist

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <key>Label</key>
+  <string>io.prometheus.node_exporter</string>
+  <key>ProgramArguments</key>
+  <array>
+    <string>sh</string>
+    <string>-c</string>
+    <string>/usr/local/bin/node_exporter $(&lt; /usr/local/etc/node_exporter.args)</string>
+  </array>
+  <key>UserName</key>
+  <string>nobody</string>
+  <key>GroupName</key>
+  <string>nobody</string>
+  <key>RunAtLoad</key>
+  <true/>
+  <key>KeepAlive</key>
+  <false/>
+  <key>WorkingDirectory</key>
+  <string>/usr/local</string>
+  <key>StandardErrorPath</key>
+  <string>/tmp/node_exporter.log</string>
+  <key>StandardOutPath</key>
+  <string>/tmp/node_exporter.log</string>
+  <key>HardResourceLimits</key>
+  <dict>
+    <key>NumberOfFiles</key>
+    <integer>4096</integer>
+  </dict>
+  <key>SoftResourceLimits</key>
+  <dict>
+    <key>NumberOfFiles</key>
+    <integer>4096</integer>
+  </dict>
+</dict>
+</plist>