Prevent the usage of OpenTelemetry in GcpDefaultsConfigSourceFactory

This is needed because GcpDefaultsConfigSourceFactory
is called very early in the application startup
and can thus mess up the OpenTelemetry configuration
performed later by Quarkus

Fixes: quarkusio/quarkus#35500

common/runtime/src/main/java/io/quarkiverse/googlecloudservices/common/GcpDefaultsConfigSourceFactory.java

@@ -16,18 +16,39 @@
 import io.smallrye.config.PropertiesConfigSource;
 
 public class GcpDefaultsConfigSourceFactory implements ConfigSourceFactory {
+
+    private static final String OPENTELEMETRY_CONTEXT_CONTEXT_STORAGE_PROVIDER_SYS_PROP = "io.opentelemetry.context.contextStorageProvider";
+
     @Override
     public Iterable<ConfigSource> getConfigSources(final ConfigSourceContext context) {
         ConfigValue enableMetadataServer = context.getValue("quarkus.google.cloud.enable-metadata-server");
         if (enableMetadataServer.getValue() != null) {
             if (Converters.getImplicitConverter(Boolean.class).convert(enableMetadataServer.getValue())) {
-                String defaultProjectId = ServiceOptions.getDefaultProjectId();
-                if (defaultProjectId != null) {
-                    return singletonList(
-                            new PropertiesConfigSource(Map.of("quarkus.google.cloud.project-id", defaultProjectId),
-                                    "GcpDefaultsConfigSource",
-                                    -Integer.MAX_VALUE));
+                String previousContextStorageSysProp = null;
+                try {
+                    // Google HTTP Client under the hood which attempts to record traces via OpenCensus which is wired
+                    // to delegate to OpenTelemetry.
+                    // This can lead to problems with the Quarkus OpenTelemetry extension which expects Vert.x to be running,
+                    // something that is not the case at build time, see https://github.com/quarkusio/quarkus/issues/35500
+                    previousContextStorageSysProp = System.setProperty(OPENTELEMETRY_CONTEXT_CONTEXT_STORAGE_PROVIDER_SYS_PROP,
+                            "default");
+
+                    String defaultProjectId = ServiceOptions.getDefaultProjectId();
+                    if (defaultProjectId != null) {
+                        return singletonList(
+                                new PropertiesConfigSource(Map.of("quarkus.google.cloud.project-id", defaultProjectId),
+                                        "GcpDefaultsConfigSource",
+                                        -Integer.MAX_VALUE));
+                    }
+                } finally {
+                    if (previousContextStorageSysProp == null) {
+                        System.clearProperty(OPENTELEMETRY_CONTEXT_CONTEXT_STORAGE_PROVIDER_SYS_PROP);
+                    } else {
+                        System.setProperty(OPENTELEMETRY_CONTEXT_CONTEXT_STORAGE_PROVIDER_SYS_PROP,
+                                previousContextStorageSysProp);
+                    }
                 }
+
             }
         }
         return emptyList();