Enable sidecar by default, only when telemetry is enabled

ext/configuration.h

@@ -185,11 +185,17 @@ enum ddtrace_sampling_rules_format {
     DD_INTEGRATIONS
 
 #ifndef _WIN32
-#define DD_CONFIGURATION \
-    CONFIG(BOOL, DD_TRACE_SIDECAR_TRACE_SENDER, "false", .ini_change = zai_config_system_ini_change) \
-    DD_CONFIGURATION_ALL
+#  if PHP_VERSION_ID >= 80300
+#    define DD_CONFIGURATION \
+        CONFIG(BOOL, DD_TRACE_SIDECAR_TRACE_SENDER, "true", .ini_change = zai_config_system_ini_change) \
+        DD_CONFIGURATION_ALL
+#  else
+#    define DD_CONFIGURATION \
+        CONFIG(BOOL, DD_TRACE_SIDECAR_TRACE_SENDER, "false", .ini_change = zai_config_system_ini_change) \
+        DD_CONFIGURATION_ALL
+#  endif
 #else
-#define DD_CONFIGURATION DD_CONFIGURATION_ALL
+#  define DD_CONFIGURATION DD_CONFIGURATION_ALL
 #endif
 
 #define CALIAS CONFIG

ext/ddtrace.c

@@ -398,7 +398,15 @@ static void dd_activate_once(void) {
 
     // must run before the first zai_hook_activate as ddtrace_telemetry_setup installs a global hook
     if (!ddtrace_disable) {
+
 #ifndef _WIN32
+        if (get_global_DD_TRACE_SIDECAR_TRACE_SENDER() && !get_global_DD_INSTRUMENTATION_TELEMETRY_ENABLED()){
+            // We enabled sending traces through the sidecar by default
+            // That said a few customers have explicitly disabled telemetry to disable the sidecar
+            // So if telemetry is disabled, we will disable the sidecar and send a one shot telemetry call
+            disable_sidecar_sending();
+            // TODO: report the fallback in telemetry
+        }
         if (get_global_DD_INSTRUMENTATION_TELEMETRY_ENABLED() || get_global_DD_TRACE_SIDECAR_TRACE_SENDER())
 #endif
         {
@@ -410,6 +418,15 @@ static void dd_activate_once(void) {
     }
 }
 
+#ifndef _WIN32
+void disable_sidecar_sending(void){
+    zend_string *zero = zend_string_init("0", 1, 0);
+    zend_alter_ini_entry(zai_config_memoized_entries[DDTRACE_CONFIG_DD_TRACE_SIDECAR_TRACE_SENDER].ini_entries[0]->name, zero,
+                    ZEND_INI_SYSTEM, ZEND_INI_STAGE_RUNTIME);
+    zend_string_release(zero);
+}
+#endif
+
 static pthread_once_t dd_activate_once_control = PTHREAD_ONCE_INIT;
 
 static void ddtrace_activate(void) {

ext/ddtrace.h

@@ -51,6 +51,9 @@ bool ddtrace_alter_default_propagation_style(zval *old_value, zval *new_value);
 bool ddtrace_alter_dd_env(zval *old_value, zval *new_value);
 bool ddtrace_alter_dd_version(zval *old_value, zval *new_value);
 void dd_force_shutdown_tracing(void);
+#ifndef _WIN32
+void disable_sidecar_sending(void);
+#endif
 
 typedef struct {
     int type;

ext/startup_logging.c

@@ -160,6 +160,7 @@ static void _dd_get_startup_config(HashTable *ht) {
     _dd_add_assoc_zstring(ht, ZEND_STRL("dd_version"), zend_string_copy(get_DD_VERSION()));
     // "health_metrics_enabled" N/A for PHP
     _dd_add_assoc_zstring(ht, ZEND_STRL("architecture"), php_get_uname('m'));
+    _dd_add_assoc_bool(ht, ZEND_STRL("instrumentation_telemetry_enabled"), get_global_DD_INSTRUMENTATION_TELEMETRY_ENABLED());
 
     // PHP-specific values
     _dd_add_assoc_string(ht, ZEND_STRL("sapi"), sapi_module.name);
@@ -181,6 +182,7 @@ static void _dd_get_startup_config(HashTable *ht) {
                           _dd_implode_keys(get_DD_TRACE_TRACED_INTERNAL_FUNCTIONS()));
     _dd_add_assoc_bool(ht, ZEND_STRL("enabled_from_env"), get_DD_TRACE_ENABLED());
     _dd_add_assoc_string(ht, ZEND_STRL("opcache.file_cache"), _dd_get_ini(ZEND_STRL("opcache.file_cache")));
+    _dd_add_assoc_bool(ht, ZEND_STRL("sidecar_trace_sender"), get_global_DD_TRACE_SIDECAR_TRACE_SENDER());
 }
 
 #ifndef _WIN32

tests/ext/sidecar_disabled_when_telemetry_disabled.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Sidecar should be disabled when telemetry is disabled
+--SKIPIF--
+<?php include 'startup_logging_skipif_unix.inc'; ?>
+--FILE--
+<?php
+include_once 'startup_logging.inc';
+
+$logs = dd_get_startup_logs([], [
+    'DD_TRACE_DEBUG' => '1',
+    'DD_INSTRUMENTATION_TELEMETRY_ENABLED' => '0',
+]);
+
+dd_dump_startup_logs($logs, [
+    'instrumentation_telemetry_enabled',
+    'sidecar_trace_sender',
+]);
+
+?>
+--EXPECT--
+instrumentation_telemetry_enabled: false
+sidecar_trace_sender: false

tests/ext/startup_logging.phpt

@@ -9,6 +9,8 @@ $logs = dd_get_startup_logs(['-ddatadog.trace.sources_path='], ['DD_TRACE_DEBUG'
 
 // Ignore any Agent connection errors for now
 unset($logs['agent_error']);
+// Ignore sidecar config as it depends on specific versions of PHP for now
+unset($logs['sidecar_trace_sender']);
 
 dd_dump_startup_logs($logs);
 ?>
@@ -34,6 +36,7 @@ service_mapping: []
 distributed_tracing_enabled: true
 dd_version: null
 architecture: "%s"
+instrumentation_telemetry_enabled: true
 sapi: "cgi-fcgi"
 datadog.trace.sources_path: null
 open_basedir_configured: false

tests/ext/startup_logging_json.phpt

@@ -9,6 +9,8 @@ $logs = json_decode(\DDTrace\startup_logs(), true);
 
 // Ignore any Agent connection errors for now
 unset($logs['agent_error']);
+// Ignore sidecar config as it depends on specific versions of PHP for now
+unset($logs['sidecar_trace_sender']);
 
 dd_dump_startup_logs($logs);
 ?>
@@ -33,6 +35,7 @@ service_mapping: []
 distributed_tracing_enabled: true
 dd_version: null
 architecture: "%s"
+instrumentation_telemetry_enabled: true
 sapi: "cli"
 datadog.trace.sources_path: null
 open_basedir_configured: false

tests/ext/startup_logging_skipif_unix.inc

@@ -0,0 +1,6 @@
+<?php
+
+include_once 'startup_logging.inc';
+if (!dd_get_php_cgi()) die('skip: php-cgi SAPI required');
+if (strncasecmp(PHP_OS, "WIN", 3) == 0) die('skip: There is no background sender on Windows');
+// if ( version_compare(phpversion(),'8.3.0', '<')) die('skip: this test works only on PHP 8.3');