WHIRR-163. Support environment variable interpolation in configuratio…

…n properties.

git-svn-id: https://svn.apache.org/repos/asf/incubator/whirr/trunk@1050191 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -23,6 +23,9 @@ Trunk (unreleased changes)
 
     WHIRR-150. Allow retrieval of instance roles. (tomwhite)
 
+    WHIRR-163. Support environment variable interpolation in configuration
+    properties. (tomwhite)
+
   BUG FIXES
 
     WHIRR-128. Fix DNS resolution for clients running within EC2.

core/src/main/java/org/apache/whirr/service/ClusterSpec.java

@@ -43,7 +43,9 @@
 import org.apache.commons.configuration.Configuration;
 import org.apache.commons.configuration.ConfigurationException;
 import org.apache.commons.configuration.PropertiesConfiguration;
+import org.apache.commons.configuration.interpol.ConfigurationInterpolator;
 import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang.text.StrLookup;
 import org.jclouds.io.Payload;
 
 /**
@@ -52,6 +54,18 @@
  */
 public class ClusterSpec {
 
+  static {
+    // Environment variable interpolation (e.g. {env:MY_VAR}) is supported
+    // natively in Commons Configuration 1.7, but until it's released we
+    // do it ourselves here
+    ConfigurationInterpolator.registerGlobalLookup("env", new StrLookup() {
+      @Override
+      public String lookup(String key) {
+        return System.getenv(key);
+      }
+    });
+  }
+
   public enum Property {
     SERVICE_NAME(String.class, false),
     INSTANCE_TEMPLATES(String.class, false),

core/src/test/java/org/apache/whirr/service/ClusterSpecTest.java

@@ -22,6 +22,7 @@
 import static org.hamcrest.Matchers.startsWith;
 import static org.junit.Assert.assertThat;
 
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Iterators;
 import com.google.common.collect.Lists;
 import com.google.common.io.Files;
@@ -32,6 +33,7 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 
 import org.apache.commons.configuration.Configuration;
 import org.apache.commons.configuration.ConfigurationException;
@@ -87,6 +89,21 @@ public void testGetConfigurationForKeysWithPrefix()
     assertThat(prefixKeys.get(0), is("a.b"));
     assertThat(prefixKeys.get(1), is("a.c"));
   }
+
+  @Test
+  public void testEnvVariableInterpolation() {
+    Map<String, String> envMap = System.getenv();
+    assertThat(envMap.isEmpty(), is(false));
+    String undefinedEnvVar = "UNDEFINED_ENV_VAR";
+    assertThat(envMap.containsKey(undefinedEnvVar), is(false));
+    Entry<String, String> firstEntry = Iterables.get(envMap.entrySet(), 0);
+    Configuration conf = new PropertiesConfiguration();
+    conf.setProperty("a", String.format("${env:%s}", firstEntry.getKey()));
+    conf.setProperty("b", String.format("${env:%s}", undefinedEnvVar));
+    assertThat(conf.getString("a"), is(firstEntry.getValue()));
+    assertThat(conf.getString("b"),
+        is(String.format("${env:%s}", undefinedEnvVar)));
+  }
 
   @Test
   public void testDefaultPublicKey()