replace shell call with a file based detection + user opt in/out (facebook#9956)

java/src/main/java/org/rocksdb/util/Environment.java

@@ -1,21 +1,14 @@
 // Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 package org.rocksdb.util;
 
+import java.io.File;
 import java.io.IOException;
 
 public class Environment {
   private static String OS = System.getProperty("os.name").toLowerCase();
   private static String ARCH = System.getProperty("os.arch").toLowerCase();
-  private static boolean MUSL_LIBC;
+  private static String MUSL_ENVIRONMENT = System.getenv("ROCKSDB_ENVIRONMENT_MUSL");
-
+  private static Boolean MUSL_LIBC;
-  static {
-    try {
-      final Process p = new ProcessBuilder("/usr/bin/env", "sh", "-c", "ldd /usr/bin/env | grep -q musl").start();
-      MUSL_LIBC = p.waitFor() == 0;
-    } catch (final IOException | InterruptedException e) {
-      MUSL_LIBC = false;
-    }
-  }
 
   public static boolean isAarch64() {
     return ARCH.contains("aarch64");
@@ -50,10 +43,28 @@ public class Environment {
         OS.contains("nux");
   }
 
+  /**
+   * lazy evaluation to prevent OS calls when "is this musl?" is not necessary
+   * no need to have a windows box report suspicious behaviour that the jvm attempts IO on unix paths
+   */
   public static boolean isMuslLibc() {
+    if(MUSL_LIBC == null) MUSL_LIBC = resolveIsMuslLibc();
     return MUSL_LIBC;
   }
 
+  static boolean resolveIsMuslLibc() {
+    // explicit user input in case any below calls cause issues in their environment
+    if("true".equalsIgnoreCase(MUSL_ENVIRONMENT)) return true;
+    if("false".equalsIgnoreCase(MUSL_ENVIRONMENT)) return false;
+    if(!isUnix()) return false; // not unix therefore not musl
+    File[] allFilesInLib = new File("/lib/").listFiles();
+    if(allFilesInLib == null) return false;
+    for(File f : allFilesInLib) {
+      if(f.getPath().startsWith("/lib/libc.musl")) return true;
+    }
+    return false;
+  }
+
   public static boolean isSolaris() {
     return OS.contains("sunos");
   }

java/src/test/java/org/rocksdb/util/EnvironmentTest.java

@@ -5,27 +5,34 @@
 package org.rocksdb.util;
 
 import org.junit.AfterClass;
+import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
 import java.lang.reflect.Field;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.Matchers.is;
 
 public class EnvironmentTest {
   private final static String ARCH_FIELD_NAME = "ARCH";
   private final static String OS_FIELD_NAME = "OS";
+
+  private final static String MUSL_ENVIRONMENT_FIELD_NAME = "MUSL_ENVIRONMENT";
   private final static String MUSL_LIBC_FIELD_NAME = "MUSL_LIBC";
 
+
   private static String INITIAL_OS;
   private static String INITIAL_ARCH;
-  private static boolean INITIAL_MUSL_LIBC;
+  private static String INITIAL_MUSL_ENVIRONMENT;
+  private static Boolean INITIAL_MUSL_LIBC;
 
   @BeforeClass
   public static void saveState() {
     INITIAL_ARCH = getEnvironmentClassField(ARCH_FIELD_NAME);
     INITIAL_OS = getEnvironmentClassField(OS_FIELD_NAME);
     INITIAL_MUSL_LIBC = getEnvironmentClassField(MUSL_LIBC_FIELD_NAME);
+    INITIAL_MUSL_ENVIRONMENT = getEnvironmentClassField(MUSL_ENVIRONMENT_FIELD_NAME);
   }
 
   @Test
@@ -236,6 +243,21 @@ public class EnvironmentTest {
     setEnvironmentClassField(MUSL_LIBC_FIELD_NAME, false);
   }
 
+  @Test
+  public void resolveIsMuslLibc() {
+    setEnvironmentClassField(MUSL_LIBC_FIELD_NAME, null);
+    setEnvironmentClassFields("win", "anyarch");
+    assertThat(Environment.isUnix()).isFalse();
+
+    // with user input, will resolve to true if set as true. Even on OSs that appear absurd for musl. Users choice
+    assertThat(Environment.resolveIsMuslLibc()).isFalse();
+    setEnvironmentClassField(MUSL_ENVIRONMENT_FIELD_NAME, "true");
+    assertThat(Environment.resolveIsMuslLibc()).isTrue();
+    setEnvironmentClassField(MUSL_ENVIRONMENT_FIELD_NAME, "false");
+    assertThat(Environment.resolveIsMuslLibc()).isFalse();
+
+  }
+
   private void setEnvironmentClassFields(String osName,
       String osArch) {
     setEnvironmentClassField(OS_FIELD_NAME, osName);
@@ -246,6 +268,7 @@ public class EnvironmentTest {
   public static void restoreState() {
     setEnvironmentClassField(OS_FIELD_NAME, INITIAL_OS);
     setEnvironmentClassField(ARCH_FIELD_NAME, INITIAL_ARCH);
+    setEnvironmentClassField(MUSL_ENVIRONMENT_FIELD_NAME, INITIAL_MUSL_ENVIRONMENT);
     setEnvironmentClassField(MUSL_LIBC_FIELD_NAME, INITIAL_MUSL_LIBC);
   }