Warn on potentially wrong endpoint configuration (#1928)

* Warn on potentially wrong endpoint configuration

* spotless

* address review comments

custom/src/main/java/com/splunk/opentelemetry/EndpointProtocolValidator.java

@@ -0,0 +1,150 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.splunk.opentelemetry;
+
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.Map;
+import java.util.function.Consumer;
+
+class EndpointProtocolValidator {
+
+  private static final int OTLP_GRPC_PORT = 4317;
+  private static final int OTLP_HTTP_PROTOBUF_PORT = 4318;
+
+  private final Map<String, String> customized;
+  private final ConfigProperties config;
+  private final Consumer<String> warn;
+
+  private EndpointProtocolValidator(
+      Map<String, String> customized, ConfigProperties config, Consumer<String> warn) {
+    this.customized = customized;
+    this.config = config;
+    this.warn = warn;
+  }
+
+  /** Warn when the port number in OTLP endpoint doesn't agree with configured protocol. */
+  static void validate(
+      Map<String, String> customized, ConfigProperties config, Consumer<String> warn) {
+    EndpointProtocolValidator validator = new EndpointProtocolValidator(customized, config, warn);
+    validator.verifyEndpointProtocol();
+  }
+
+  private void verifyEndpointProtocol() {
+    String protocol = getString("otel.exporter.otlp.protocol", "http/protobuf");
+    String endpoint =
+        getString("otel.exporter.otlp.endpoint", "http://localhost:" + getPort(protocol));
+    if (!verifyEndpointProtocol(
+        protocol, endpoint, "otel.exporter.otlp.protocol", "otel.exporter.otlp.endpoint")) {
+      // there already was a mismatch between endpoint port and protocol,
+      // skip looking at signal specific endpoints
+      return;
+    }
+
+    for (String signal : new String[] {"traces", "metrics", "logs"}) {
+      verifySignalEndpointProtocol(signal, protocol, endpoint);
+    }
+  }
+
+  private boolean verifyEndpointProtocol(
+      String protocol, String endpoint, String protocolKey, String endpointKey) {
+    int port = getEndpointPort(endpoint);
+    if ("http/protobuf".equals(protocol)) {
+      if (port == OTLP_GRPC_PORT) {
+        warn.accept(protocolWarning("grpc", "http/protobuf", endpoint, protocolKey, endpointKey));
+        return false;
+      }
+    } else if ("grpc".equals(protocol)) {
+      if (port == OTLP_HTTP_PROTOBUF_PORT) {
+        warn.accept(protocolWarning("http/protobuf", "grpc", endpoint, protocolKey, endpointKey));
+        return false;
+      }
+    }
+    return true;
+  }
+
+  private static String protocolWarning(
+      String endpointProtocol,
+      String configuredProtocol,
+      String endpoint,
+      String protocolKey,
+      String endpointKey) {
+    return "The value for "
+        + endpointKey
+        + " ("
+        + endpoint
+        + ") appears to be a "
+        + endpointProtocol
+        + " endpoint (port "
+        + getPort(endpointProtocol)
+        + " is the default port for OTLP with "
+        + endpointProtocol
+        + " protocol) but value for "
+        + protocolKey
+        + " is "
+        + configuredProtocol
+        + ". This is likely to be a configuration error. You may need to change the endpoint port to "
+        + getPort(configuredProtocol)
+        + " (default port for OTLP with "
+        + configuredProtocol
+        + " protocol) or change the protocol to "
+        + endpointProtocol
+        + ".";
+  }
+
+  private static int getPort(String protocol) {
+    return "http/protobuf".equals(protocol) ? OTLP_HTTP_PROTOBUF_PORT : OTLP_GRPC_PORT;
+  }
+
+  private void verifySignalEndpointProtocol(
+      String signal, String defaultProtocol, String defaultEndpoint) {
+    String protocolKey = "otel.exporter.otlp." + signal + ".protocol";
+    String endpointKey = "otel.exporter.otlp." + signal + ".endpoint";
+    String protocol = getString(protocolKey, defaultProtocol);
+    String endpoint =
+        getString(endpointKey, addSignalEndpointSuffix(defaultEndpoint, signal, protocol));
+    verifyEndpointProtocol(protocol, endpoint, protocolKey, endpointKey);
+  }
+
+  private static String addSignalEndpointSuffix(String endpoint, String signal, String protocol) {
+    if ("http/protobuf".equals(protocol)) {
+      return endpoint + "/v1/" + signal;
+    }
+    return endpoint;
+  }
+
+  private int getEndpointPort(String endpoint) {
+    if (endpoint != null) {
+      try {
+        URL endpointUrl = new URL(endpoint);
+        return endpointUrl.getPort();
+      } catch (MalformedURLException ignore) {
+        // ignore
+      }
+    }
+    return -1;
+  }
+
+  private String getString(String key, String defaultValue) {
+    String value = customized.get(key);
+    if (value == null) {
+      value = config.getString(key);
+    }
+    return value == null ? defaultValue : value;
+  }
+}

custom/src/main/java/com/splunk/opentelemetry/SplunkConfiguration.java

@@ -107,6 +107,8 @@ Map<String, String> customize(ConfigProperties config) {
       customized.put("otel.instrumentation.logback-appender.enabled", "false");
     }
 
+    EndpointProtocolValidator.validate(customized, config, logger::warning);
+
     return customized;
   }
 

custom/src/test/java/com/splunk/opentelemetry/EndpointProtocolValidatorTest.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.splunk.opentelemetry;
+
+import static com.splunk.opentelemetry.SplunkConfigurationTest.configuration;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class EndpointProtocolValidatorTest {
+
+  @Test
+  void testDefaultConfiguration() {
+    ConfigProperties config = configuration(Map::of);
+    List<String> messages = new ArrayList<>();
+    EndpointProtocolValidator.validate(Collections.emptyMap(), config, messages::add);
+    assertThat(messages).isEmpty();
+  }
+
+  @Test
+  void testGrpcEndpoint() {
+    ConfigProperties config =
+        configuration(() -> Map.of("otel.exporter.otlp.endpoint", "http://localhost:4317"));
+    List<String> messages = new ArrayList<>();
+    EndpointProtocolValidator.validate(Collections.emptyMap(), config, messages::add);
+    assertThat(messages).hasSize(1);
+  }
+
+  @Test
+  void testGrpcEndpointAndProtocol() {
+    ConfigProperties config =
+        configuration(
+            () ->
+                Map.of(
+                    "otel.exporter.otlp.endpoint",
+                    "http://localhost:4317",
+                    "otel.exporter.otlp.protocol",
+                    "grpc"));
+    List<String> messages = new ArrayList<>();
+    EndpointProtocolValidator.validate(Collections.emptyMap(), config, messages::add);
+    assertThat(messages).isEmpty();
+  }
+
+  @Test
+  void testUnknownEndpoint() {
+    ConfigProperties config =
+        configuration(() -> Map.of("otel.exporter.otlp.endpoint", "http://localhost:5000"));
+    List<String> messages = new ArrayList<>();
+    EndpointProtocolValidator.validate(Collections.emptyMap(), config, messages::add);
+    assertThat(messages).isEmpty();
+  }
+
+  @Test
+  void testSignalGrpcEndpoint() {
+    ConfigProperties config =
+        configuration(
+            () ->
+                Map.of(
+                    "otel.exporter.otlp.traces.endpoint",
+                    "http://localhost:4317",
+                    "otel.exporter.otlp.metrics.endpoint",
+                    "http://localhost:4317",
+                    "otel.exporter.otlp.logs.endpoint",
+                    "http://localhost:4317"));
+    List<String> messages = new ArrayList<>();
+    EndpointProtocolValidator.validate(Collections.emptyMap(), config, messages::add);
+    assertThat(messages).hasSize(3);
+  }
+}

custom/src/test/java/com/splunk/opentelemetry/SplunkConfigurationTest.java

@@ -101,8 +101,7 @@ private static ConfigProperties configuration() {
     return configuration(Map::of);
   }
 
-  private static ConfigProperties configuration(
-      Supplier<Map<String, String>> testPropertiesSupplier) {
+  static ConfigProperties configuration(Supplier<Map<String, String>> testPropertiesSupplier) {
     AutoConfiguredOpenTelemetrySdk sdk =
         AutoConfiguredOpenTelemetrySdk.builder()
             // don't create the SDK