Use uppercase letters for environment variable naming.

agent/agent-core/src/main/java/org/bithon/agent/configuration/ConfigurationManager.java

@@ -51,7 +51,7 @@
  * 1. The default agent configuration located under the agent-distribution/conf
  * 2. The external configuration specified via -Dbithon.configuration.location command line argument
  * 3. All parameters defined by -Dbithon.xxx
- * 4. All environment variables starting with bithon_
+ * 4. All environment variables starting with BITHON_
  * 5. Dynamic configuration from the remote controller
  *
  * Different configuration sources may contain the same property keys,
@@ -124,7 +124,7 @@ static ConfigurationManager create(File defaultConfigLocation) {
         return new ConfigurationManager(PropertySource.from(PropertySourceType.INTERNAL, defaultConfigLocation, true),
                                         ExternalSource.build(),
                                         CommandLineArgsSource.build("bithon."),
-                                        EnvironmentSource.build("bithon_"));
+                                        EnvironmentSource.build("BITHON_"));
     }
 
     // Sorted in priority

agent/agent-core/src/main/java/org/bithon/agent/configuration/source/EnvironmentSource.java

@@ -19,6 +19,7 @@
 import org.bithon.agent.instrumentation.expt.AgentException;
 
 import java.io.IOException;
+import java.util.Locale;
 import java.util.Map;
 
 /**
@@ -31,9 +32,10 @@ public static PropertySource build(String envPrefix) {
         StringBuilder propertyText = new StringBuilder();
 
         for (Map.Entry<String, String> entry : Helper.getEnvironmentVariables().entrySet()) {
-            String name = entry.getKey();
+            String name = entry.getKey().toLowerCase(Locale.ENGLISH);
             String value = entry.getValue();
-            if (name.startsWith(envPrefix) && !value.isEmpty()) {
+            String prefix = envPrefix.toLowerCase(Locale.ENGLISH);
+            if (name.startsWith(prefix) && !value.isEmpty()) {
                 name = name.substring(envPrefix.length())
                            // For env, the underscore is used as a replacement of '.' character,
                            // Here we need to convert these characters back

agent/agent-core/src/test/java/org/bithon/agent/configuration/TestConfigurationManager.java

@@ -191,8 +191,8 @@ public void test_Environment() {
                                                       ));
 
             configurationMock.when(Helper::getEnvironmentVariables)
-                             .thenReturn(ImmutableMap.of("bithon_t", "t1",
-                                                         "bithon_test_prop", "from_env"));
+                             .thenReturn(ImmutableMap.of("BITHON_T", "t1",
+                                                         "BITHON_TEST_PROP", "from_env"));
 
             ConfigurationManager manager = ConfigurationManager.create(defaultConfigLocation);
 
@@ -201,6 +201,33 @@ public void test_Environment() {
         }
     }
 
+    @Test
+    public void test_Environment_CaseCompatibility() {
+        try (MockedStatic<Helper> configurationMock = Mockito.mockStatic(Helper.class)) {
+            configurationMock.when(Helper::getCommandLineInputArgs)
+                    .thenReturn(Arrays.asList("-Xms512M",
+                            // A property without assignment
+                            // to verify the processing is correct with such configuration
+                            "-Dbithon.test",
+                            // Override the in file configuration
+                            "-Dbithon.test.prop=from_command_line",
+
+                            // Also set the external configuration
+                            "-Dbithon.configuration.location=" + externalConfigLocation
+                    ));
+
+            configurationMock.when(Helper::getEnvironmentVariables)
+                    .thenReturn(ImmutableMap.of("bithon_t", "t1",
+                            "bithon_test_prop", "from_env"));
+
+            ConfigurationManager manager = ConfigurationManager.create(defaultConfigLocation);
+
+            TestProp config = manager.getConfig(TestProp.class);
+            Assert.assertEquals("from_env", config.getProp());
+        }
+    }
+
+
     static class TwoProps {
         private String prop1;
         private String prop2;
@@ -238,9 +265,9 @@ public void test_PropFromDifferentSource() {
                                                       ));
 
             configurationMock.when(Helper::getEnvironmentVariables)
-                             .thenReturn(ImmutableMap.of("bithon_t", "t1",
+                             .thenReturn(ImmutableMap.of("BITHON_T", "t1",
                                                          //Overwrite the prop2
-                                                         "bithon_test_prop2", "from_env"));
+                                                         "BITHON_TEST_PROP2", "from_env"));
 
             ConfigurationManager manager = ConfigurationManager.create(defaultConfigLocation);
 

doc/configuration/agent/README.md

@@ -52,15 +52,15 @@ java -Dbithon.application.name=bithon-server -Dbithon.application.env=local -jar
 
 ## Environment variables
 
-Configurations can also be set by environment variables. This is helpful when the agent is loaded in docker environment.
+Configurations can also be set by environment variables. This is helpful when the agent is loaded in docker/container environment.
 
 ```text
-export bithon_application_name=bithon-server
-export bithon_application_env=local
+export BITHON_APPLICATION_NAME=bithon-server
+export BITHON_APPLICATION_ENV=local
 java -jar bithon-server.jar
 ```
 
-Note that all environment variables are in underscore mode.
+Note that all environment variables are in underscore mode and uppercase.
 
 ## Dynamic Configuration