EUDB compliance recommendations and example (#1191)

* EUDB compliance recommendations and example

* Fix spelling issue

* Addressing code review comments.

docs/EUDB-compliance.md

@@ -0,0 +1,68 @@
+# EUDB Guidance for 1DS C++ SDK
+
+In order to satisfy the Microsoft commitment to ensuring Privacy and Compliance, specifically
+EUDB compliance with respect to EU 'Schrems II' decision, it is imperative for certain
+commercial products to perform EUDB URL upload determination during application launch.
+
+1DS Collector service accepts data from all One Observability client SDKs. By default, traffic
+simply flows to whichever region can best handle the traffic. This approach works well for
+system required metadata. However some client scenarios require that data is sent to a specific
+geographic location only.
+
+1DS C++ SDK supports ability to specify / adjust the upload URL at runtime.
+
+Two approaches could be applied to implement EUDB-compliant data upload.
+
+## Option 1: Create two instances of 1DS C++ SDK - one for US collector, another for EU collector
+
+See [Multiple Log Managers Example](https://github.com/microsoft/cpp_client_telemetry/tree/main/examples/cpp/SampleCppLogManagers)
+that illustrates how to create multiple instances, each acting as a separate vertical pillar with
+their own data collection URL. Two instances `LogManagerUS` and `LogManagerEU` may be configured
+each with their own data collection URL, for example:
+
+- For US customers: `https://us-mobile.events.data.microsoft.com/OneCollector/1.0/`
+- For EU customers: `https://eu-mobile.events.data.microsoft.com/OneCollector/1.0/`
+
+Depending on data requirements and outcome of dynamic EUDB determination, i.e. organization /
+M365 Commercial Tenant is located in EU, the app decides to use `LogManagerEU` instance for
+telemetry. Default `LogManager` instance can still be used for region-agnostic "global"
+collection of required system diagnostics data. Remember to use the proper compliant instance
+depending on event type.
+
+## Option 2: Autodetect the corresponding data collection URL on app start
+
+EventSender example has been modified to illustrate the concept:
+
+- Application starts.
+
+- `LogManager::Initialize(...)` is called with `ILogConfiguration[CFG_STR_COLLECTOR_URL]` set to
+empty value `""`. This configuration instructs the SDK to run in offline mode. All data gets
+logged to offline storage and not uploaded. This setting has the same effect as running in
+paused state. Key difference is that irrespective of upload timer cadence - even for immediate
+priority events, 1DS SDK never attempts to trigger the upload. This special configuration option
+is safer than simply issuing `PauseTransmission` on app start.
+
+Then application must perform asynchronous EUDB URL detection once in its own asynchronous task /
+thread. URL detection process is asynchronous and may take significant amount of time from hundred
+milliseconds to seconds. In order to avoid affecting application launch startup performance,
+application may perform other startup and logging actions concurrently. All events get logged
+in offline cache.
+
+- As part of the configuration update process - application calls `LogManager::PauseTransmission()`
+done to ensure exclusive access to uploader configuration.
+
+- Once the EUDB URL is obtained from remote configuration provisioning service (ECS, MSGraph,
+OneSettings, etc.), or read cached value from local app configuration storage, the value is supplied
+to 1DS SDK:
+
+`ILogConfiguration[CFG_STR_COLLECTOR_URL] = eudb_url`
+
+This assignment of URL is done once during application start. Application does not need to change the
+data collection URL after that.
+
+Note that 1DS SDK itself does not provide a feature to store the cached URL value. It is up to the
+product owners to decide what caching mechanism they would like to use: registry, ECS cache, Unity
+player settings, mobile app settings provider, etc.
+
+- Finally the app code could call `LogManager::ResumeTransmission()` - to apply the new configuration
+settings and enable the data upload to compliant destination.

examples/cpp/EventSender/EventSender.cpp

@@ -3,6 +3,7 @@
 #include <iostream>
 #include <iterator>
 #include <fstream>
+#include <chrono>
 
 #include "LogManager.hpp"
 
@@ -71,6 +72,40 @@ const char* defaultConfig = static_cast<const char *> JSON_CONFIG
     }
 );
 
+// Mock function that performs random selection of destination URL. 1DS SDK does not define how the app needs to perform
+// the region determination. Products should use MSGraph API, OCPS, or other remote config provisioning sources, such as
+// ECS: https://learn.microsoft.com/en-us/deployedge/edge-configuration-and-experiments - in order to identify what 1DS
+// collector to use for specific Enterprise or Consumer end-user telemetry uploads. Note that the EUDB URL determination
+// is performed asynchronously and could take a few seconds. EUDB URL for Enterprise applications may be cached
+// in app-specific configuration storage. 1DS SDK does not provide a feature to cache the data collection URL used for
+// a previous session.
+//
+// Note that this function to determine the URL is called once, early at boot.
+std::string GetEudbCollectorUrl()
+{
+    const auto randSeed = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count();
+    srand(static_cast<unsigned>(randSeed));
+    return (rand() % 2) ? "https://us-mobile.events.data.microsoft.com/OneCollector/1.0/" : "https://eu-mobile.events.data.microsoft.com/OneCollector/1.0/";
+}
+
+void UpdateUploadUrl()
+{
+    printf("Performing collector URL detection...\n");
+    // Transmissions must be paused prior to adjusting the URL.
+    LogManager::PauseTransmission();
+
+    // Obtain a reference to current configuration.
+    auto& config = LogManager::GetLogConfiguration();
+
+    // Update configuration in-place. This is done once after the regional data collection URL is determined.
+    config[CFG_STR_COLLECTOR_URL] = GetEudbCollectorUrl();
+
+    // Resume transmission once EUDB collector URL detection is obtained. In case if EUDB collector determination fails, only required
+    // system diagnostics data containing no EUPI MAY be uploaded to global data collection endpoint. It is up to product teams to
+    // decide what strategy works best for their product.
+    LogManager::ResumeTransmission();
+}
+
 int main(int argc, char *argv[])
 {
     // 2nd (optional) parameter - path to custom SDK configuration
@@ -87,24 +122,43 @@ int main(int argc, char *argv[])
 
     // LogManager configuration
     auto& config = LogManager::GetLogConfiguration();
-    config = MAT::FromJSON(jsonConfig);
+    auto customLogConfig = MAT::FromJSON(jsonConfig);
+    config = customLogConfig; // Assignment operation COLLATES the default + custom config
 
     // LogManager initialization
     ILogger *logger = LogManager::Initialize();
-    bool utcActive = (bool)(config[CFG_STR_UTC][CFG_BOOL_UTC_ACTIVE]);
+    const bool utcActive = (bool)(config[CFG_STR_UTC][CFG_BOOL_UTC_ACTIVE]);
 
     printf("Running in %s mode...\n", (utcActive) ? "UTC" : "direct upload");
     if (utcActive)
     {
-        printf("UTC provider group Id: %s\n", (const char *)(config[CFG_STR_UTC][CFG_STR_PROVIDER_GROUP_ID]));
-        printf("UTC large payloads:    %s\n", ((bool)(config[CFG_STR_UTC][CFG_BOOL_UTC_LARGE_PAYLOADS])) ? "supported" : "not supported");
+        printf("UTC provider group Id: %s\n", static_cast<const char*>(config[CFG_STR_UTC][CFG_STR_PROVIDER_GROUP_ID]));
+        printf("UTC large payloads:    %s\n", static_cast<bool>(config[CFG_STR_UTC][CFG_BOOL_UTC_LARGE_PAYLOADS]) ? "supported" : "not supported");
     }
     else
     {
-        printf("Collector URL:         %s\n", (const char *)(config[CFG_STR_COLLECTOR_URL]));
+        // LogManager::ILogConfiguration[CFG_STR_COLLECTOR_URL] defaults to global URL.
+        //
+        // If app-provided JSON config is empty on start, means the app intended to asynchronously
+        // obtain the data collection URL for EUDB compliance. App subsequently sets an empty URL -
+        // by assigning an empty value to the log manager instance CFG_STR_COLLECTOR_URL. At this
+        // point the Uploads are not performed until EUDB-compliant endpoint URL is obtained.
+        //
+        // Note that since ILogConfiguration configuration tree does not provide a thread-safety
+        // guarantee between the main thread and SDK uploader thread(s), adjusting the upload
+        // parameters, e.g. URL or timers, requires the app to pause transmission, adjust params,
+        // then resume transmission.
+        //
+        if (!customLogConfig.HasConfig(CFG_STR_COLLECTOR_URL))
+        {
+            // If configuration provided as a parameter does not contain the URL
+            UpdateUploadUrl();
+        }
+        const std::string url = config[CFG_STR_COLLECTOR_URL];
+        printf("Collector URL:         %s\n", url.c_str());
     }
 
-    printf("Token (iKey):          %s\n", (const char *)(config[CFG_STR_PRIMARY_TOKEN]));
+    printf("Token (iKey):          %s\n", static_cast<const char*>(config[CFG_STR_PRIMARY_TOKEN]));
 
 #if 0
     // Code example that shows how to convert ILogConfiguration to JSON

lib/api/IRuntimeConfig.hpp

@@ -34,6 +34,12 @@ namespace MAT_NS_BEGIN
         /// <returns>A string that contains the collector URI.</returns>
         virtual std::string GetCollectorUrl() = 0;
 
+        /// <summary>
+        /// Check used by uploader sequence to verify if URL is defined.
+        /// </summary>
+        /// <returns>true if URL is set, false otherwise.</returns>
+        virtual bool IsCollectorUrlSet() = 0;
+
         /// <summary>
         /// Adds extension fields (created by the configuration provider) to an
         /// event.

lib/config/RuntimeConfig_Default.hpp

@@ -104,6 +104,12 @@ namespace MAT_NS_BEGIN
             return std::string(url);
         }
 
+        virtual bool IsCollectorUrlSet() override
+        {
+            const char* url = config[CFG_STR_COLLECTOR_URL];
+            return (url != nullptr) && (url[0] != '\0');
+        }
+
         virtual void DecorateEvent(std::map<std::string, std::string>& extension, std::string const& experimentationProject, std::string const& eventName) override
         {
             UNREFERENCED_PARAMETER(extension);

lib/tpm/TransmissionPolicyManager.cpp

@@ -106,6 +106,11 @@ namespace MAT_NS_BEGIN {
         if (guard.isPaused()) {
             return;
         }
+        if (!m_config.IsCollectorUrlSet())
+        {
+            LOG_TRACE("Collector URL is not set, no upload.");
+            return;
+        }
         LOCKGUARD(m_scheduledUploadMutex);
         if (delay.count() < 0 || m_timerdelay.count() < 0)
         {