From 0b086a9625cd2e8219711e04579466a43d4a4e99 Mon Sep 17 00:00:00 2001
From: Jason Tedor <jason@tedor.me>
Date: Wed, 3 Aug 2016 13:43:51 -0400
Subject: [PATCH] Do not log on explicit no unsafe

Motivation:

When Netty components are initialized, Netty attempts to determine if it
has access to unsafe. If Netty is not able to access unsafe (because of
security permissions, or because the JVM was started with an explicit
flag to tell Netty to not look for unsafe), Netty logs an info-level
message that looks like a warning:

Your platform does not provide complete low-level API for accessing
direct buffers reliably. Unless explicitly requested, heap buffer will
always be preferred to avoid potential system unstability.

This log message can appear in applications that depend on Netty for
networking, and this log message can be scary to end-users of such
platforms. This log message should not be emitted if the application was
started with an explicit flag telling Netty to not look for unsafe.

Modifications:

This commit refactors the unsafe detection logic to expose whether or
not the JVM was started with a flag telling Netty to not look for
unsafe. With this exposed information, the log message on unsafe being
unavailable can be modified to not be emitted when Netty is explicitly
told to not look for unsafe.

Result:

No log message is produced when unsafe is unavailable because Netty was
told to not look for it.
---
 .../util/internal/PlatformDependent.java      | 27 ++++++++++++-------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/common/src/main/java/io/netty/util/internal/PlatformDependent.java b/common/src/main/java/io/netty/util/internal/PlatformDependent.java
index e8c823ea67..686a2cf314 100644
--- a/common/src/main/java/io/netty/util/internal/PlatformDependent.java
+++ b/common/src/main/java/io/netty/util/internal/PlatformDependent.java
@@ -85,6 +85,7 @@ public final class PlatformDependent {
 
     private static final boolean CAN_ENABLE_TCP_NODELAY_BY_DEFAULT = !isAndroid();
 
+    private static final boolean IS_EXPLICIT_NO_UNSAFE = explicitNoUnsafe0();
     private static final boolean HAS_UNSAFE = hasUnsafe0();
     private static final boolean CAN_USE_CHM_V8 = HAS_UNSAFE && JAVA_VERSION < 8;
     private static final boolean DIRECT_BUFFER_PREFERRED =
@@ -116,7 +117,7 @@ public final class PlatformDependent {
             logger.debug("-Dio.netty.noPreferDirect: {}", !DIRECT_BUFFER_PREFERRED);
         }
 
-        if (!hasUnsafe() && !isAndroid()) {
+        if (!hasUnsafe() && !isAndroid() && !IS_EXPLICIT_NO_UNSAFE) {
             logger.info(
                     "Your platform does not provide complete low-level API for accessing direct buffers reliably. " +
                     "Unless explicitly requested, heap buffer will always be preferred to avoid potential system " +
@@ -1063,18 +1064,13 @@ public final class PlatformDependent {
         }
     }
 
-    private static boolean hasUnsafe0() {
-        boolean noUnsafe = SystemPropertyUtil.getBoolean("io.netty.noUnsafe", false);
+    private static boolean explicitNoUnsafe0() {
+        final boolean noUnsafe = SystemPropertyUtil.getBoolean("io.netty.noUnsafe", false);
         logger.debug("-Dio.netty.noUnsafe: {}", noUnsafe);
 
-        if (isAndroid()) {
-            logger.debug("sun.misc.Unsafe: unavailable (Android)");
-            return false;
-        }
-
         if (noUnsafe) {
             logger.debug("sun.misc.Unsafe: unavailable (io.netty.noUnsafe)");
-            return false;
+            return true;
         }
 
         // Legacy properties
@@ -1087,6 +1083,19 @@ public final class PlatformDependent {
 
         if (!tryUnsafe) {
             logger.debug("sun.misc.Unsafe: unavailable (io.netty.tryUnsafe/org.jboss.netty.tryUnsafe)");
+            return true;
+        }
+
+        return false;
+    }
+
+    private static boolean hasUnsafe0() {
+        if (isAndroid()) {
+            logger.debug("sun.misc.Unsafe: unavailable (Android)");
+            return false;
+        }
+
+        if (IS_EXPLICIT_NO_UNSAFE) {
             return false;
         }