From a84eecc88893d81fa208c16007178610a914492a Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Fri, 11 Mar 2022 16:28:12 +0000
Subject: [PATCH] Platform sanity checks

---
 setup/base/base.go         |  1 +
 setup/base/sanity_other.go |  8 ++++++++
 setup/base/sanity_unix.go  | 27 +++++++++++++++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 setup/base/sanity_other.go
 create mode 100644 setup/base/sanity_unix.go

diff --git a/setup/base/base.go b/setup/base/base.go
index ef3b2be29..692a77d5c 100644
--- a/setup/base/base.go
+++ b/setup/base/base.go
@@ -100,6 +100,7 @@ const (
 // The componentName is used for logging purposes, and should be a friendly name
 // of the compontent running, e.g. "SyncAPI"
 func NewBaseDendrite(cfg *config.Dendrite, componentName string, options ...BaseDendriteOptions) *BaseDendrite {
+	platformSanityChecks()
 	useHTTPAPIs := false
 	cacheMetrics := true
 	for _, opt := range options {
diff --git a/setup/base/sanity_other.go b/setup/base/sanity_other.go
new file mode 100644
index 000000000..48fe6e1f8
--- /dev/null
+++ b/setup/base/sanity_other.go
@@ -0,0 +1,8 @@
+//go:build !linux && !darwin && !netbsd && !freebsd && !openbsd && !solaris && !dragonfly && !aix
+// +build !linux,!darwin,!netbsd,!freebsd,!openbsd,!solaris,!dragonfly,!aix
+
+package base
+
+func platformSanityChecks() {
+	// Nothing to do yet.
+}
diff --git a/setup/base/sanity_unix.go b/setup/base/sanity_unix.go
new file mode 100644
index 000000000..de29a6b86
--- /dev/null
+++ b/setup/base/sanity_unix.go
@@ -0,0 +1,27 @@
+//go:build linux || darwin || netbsd || freebsd || openbsd || solaris || dragonfly || aix
+// +build linux darwin netbsd freebsd openbsd solaris dragonfly aix
+
+package base
+
+import (
+	"syscall"
+
+	"github.com/sirupsen/logrus"
+)
+
+func platformSanityChecks() {
+	// If Dendrite is running as root, that's probably bad.
+	if syscall.Geteuid() == 0 {
+		logrus.Warnf("IMPORTANT: Dendrite is currently running as root, this is potentially dangerous!")
+	}
+
+	// Dendrite needs a relatively high number of file descriptors in order
+	// to function properly, particularly when federating with lots of servers.
+	// If we run out of file descriptors, we might run into problems accessing
+	// PostgreSQL amongst other things. Complain at startup if we think the
+	// number of file descriptors is too low.
+	var rLimit syscall.Rlimit
+	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit); err == nil && rLimit.Cur < 65535 {
+		logrus.Warnf("IMPORTANT: Process file descriptor limit is currently %d, it is recommended to raise the limit for Dendrite to at least 65535 to avoid issues", rLimit.Cur)
+	}
+}