Enforce that java.io.tmpdir exists on startup

server/src/main/java/org/elasticsearch/bootstrap/Elasticsearch.java

@@ -108,6 +108,13 @@ protected void execute(Terminal terminal, OptionSet options, Environment env) th
         final Path pidFile = pidfileOption.value(options);
         final boolean quiet = options.has(quietOption);
 
+        // a misconfigured java.io.tmpdir can cause hard-to-diagnose problems later, so reject it immediately
+        try {
+            env.validateTmpFile();
+        } catch (IOException e) {
+            throw new UserException(ExitCodes.CONFIG, e.getMessage());
+        }
+
         try {
             init(daemonize, pidFile, quiet, env);
         } catch (NodeValidationException e) {

server/src/main/java/org/elasticsearch/env/Environment.java

@@ -27,6 +27,7 @@
 import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URISyntaxException;
@@ -87,9 +88,14 @@ public class Environment {
     private final Path pidFile;
 
     /** Path to the temporary file directory used by the JDK */
-    private final Path tmpFile = PathUtils.get(System.getProperty("java.io.tmpdir"));
+    private final Path tmpFile;
 
     public Environment(final Settings settings, final Path configPath) {
+        this(settings, configPath, PathUtils.get(System.getProperty("java.io.tmpdir")));
+    }
+
+    // Should only be called directly by this class's unit tests
+    Environment(final Settings settings, final Path configPath, final Path tmpPath) {
         final Path homeFile;
         if (PATH_HOME_SETTING.exists(settings)) {
             homeFile = PathUtils.get(PATH_HOME_SETTING.get(settings)).normalize();
@@ -103,6 +109,8 @@ public Environment(final Settings settings, final Path configPath) {
             configFile = homeFile.resolve("config");
         }
 
+        tmpFile = Objects.requireNonNull(tmpPath);
+
         pluginsFile = homeFile.resolve("plugins");
 
         List<String> dataPaths = PATH_DATA_SETTING.get(settings);
@@ -302,6 +310,16 @@ public Path tmpFile() {
         return tmpFile;
     }
 
+    /** Ensure the configured temp directory is a valid directory */
+    public void validateTmpFile() throws IOException {
+        if (Files.exists(tmpFile) == false) {
+            throw new FileNotFoundException("Temporary file directory [" + tmpFile + "] does not exist or is not accessible");
+        }
+        if (Files.isDirectory(tmpFile) == false) {
+            throw new IOException("Configured temporary file directory [" + tmpFile + "] is not a directory");
+        }
+    }
+
     public static FileStore getFileStore(final Path path) throws IOException {
         return new ESFileStore(Files.getFileStore(path));
     }

server/src/test/java/org/elasticsearch/env/EnvironmentTests.java

@@ -21,13 +21,15 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.test.ESTestCase;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.URL;
 import java.nio.file.Path;
 
 import static org.hamcrest.CoreMatchers.endsWith;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.CoreMatchers.startsWith;
 import static org.hamcrest.Matchers.arrayWithSize;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -37,11 +39,11 @@
  * Simple unit-tests for Environment.java
  */
 public class EnvironmentTests extends ESTestCase {
-    public Environment newEnvironment() throws IOException {
+    public Environment newEnvironment() {
         return newEnvironment(Settings.EMPTY);
     }
 
-    public Environment newEnvironment(Settings settings) throws IOException {
+    public Environment newEnvironment(Settings settings) {
         Settings build = Settings.builder()
                 .put(settings)
                 .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toAbsolutePath())
@@ -146,4 +148,23 @@ public void testNodeDoesNotRequireLocalStorageButHasPathData() {
         assertThat(e, hasToString(containsString("node does not require local storage yet path.data is set to [" + pathData + "]")));
     }
 
+    public void testNonExistentTempPathValidation() {
+        Settings build = Settings.builder()
+            .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+            .build();
+        Environment environment = new Environment(build, null, createTempDir().resolve("this_does_not_exist"));
+        FileNotFoundException e = expectThrows(FileNotFoundException.class, environment::validateTmpFile);
+        assertThat(e.getMessage(), startsWith("Temporary file directory ["));
+        assertThat(e.getMessage(), endsWith("this_does_not_exist] does not exist or is not accessible"));
+    }
+
+    public void testTempPathValidationWhenRegularFile() throws IOException {
+        Settings build = Settings.builder()
+            .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+            .build();
+        Environment environment = new Environment(build, null, createTempFile("something", ".test"));
+        IOException e = expectThrows(IOException.class, environment::validateTmpFile);
+        assertThat(e.getMessage(), startsWith("Configured temporary file directory ["));
+        assertThat(e.getMessage(), endsWith(".test] is not a directory"));
+    }
 }