Add back C library implementations for fdb_database_open_tenant and 3 other methods (#12593)

This allows 7.x python libraries to load these methods. It does this on startup to set up python/C API stuff, regardless
of whether the API user actually invokes this functionality (which was experimental and is now removed).

More details: rdar://166307379

Testing:
ctest -R c_api
ctest -R python

20251211-224723-gglass-17ed16f020aa18de compressed=True data_size=35311862 duration=5560013 ended=100000 fail_fast=1000 max_runs=100000 pass=100000 priority=100 remaining=0 runtime=1:01:01 sanity=False started=100000 stopped=20251211-234824 submitted=20251211-224723 timeout=5400 username=gglass

bindings/c/fdb_c.cpp

@@ -413,6 +413,33 @@ extern "C" DLLEXPORT void fdb_database_destroy(FDBDatabase* d) {
 	CATCH_AND_DIE(DB(d)->delref(););
 }
 
+// Define these symbols so that older client bindings (in particular,
+// python) can load them at startup. Nobody should be calling this
+// stuff in 8.0.0+ because it has always been experimental and is now
+// deleted.
+extern "C" DLLEXPORT fdb_error_t fdb_database_open_tenant(FDBDatabase* d,
+                                                          uint8_t const* tenant_name,
+                                                          int tenant_name_length,
+                                                          FDBTenant** out_tenant) {
+	fprintf(stderr, "Unexpected call to removed functionality [fdb_database_open_tenant]\n");
+	abort();
+}
+
+extern "C" DLLEXPORT fdb_error_t fdb_tenant_create_transaction(FDBTenant* tenant, FDBTransaction** out_transaction) {
+	fprintf(stderr, "Unexpected call to removed functionality [fdb_tenant_create_transaction]\n");
+	abort();
+}
+
+extern "C" DLLEXPORT WARN_UNUSED_RESULT FDBFuture* fdb_tenant_get_id(FDBTenant* tenant) {
+	fprintf(stderr, "Unexpected call to removed functionality [fdb_tenant_get_id]\n");
+	abort();
+}
+
+extern "C" DLLEXPORT void fdb_tenant_destroy(FDBTenant* tenant) {
+	fprintf(stderr, "Unexpected call to removed functionality [fdb_tenant_destroy]\n");
+	abort();
+}
+
 extern "C" DLLEXPORT fdb_error_t fdb_database_create_transaction(FDBDatabase* d, FDBTransaction** out_transaction) {
 	CATCH_AND_RETURN(Reference<ITransaction> tr = DB(d)->createTransaction();
 	                 if (g_api_version <= 15) tr->setOption(FDBTransactionOptions::ACCESS_SYSTEM_KEYS);

bindings/c/foundationdb/fdb_c.h

@@ -376,6 +376,25 @@ DLLEXPORT WARN_UNUSED_RESULT fdb_error_t fdb_database_set_option(FDBDatabase* d,
 DLLEXPORT WARN_UNUSED_RESULT fdb_error_t fdb_database_create_transaction(FDBDatabase* d,
                                                                          FDBTransaction** out_transaction);
 
+/*
+ * Dummy versions of tenant-related functions are needed in the FDB C library
+ * because 7.x python bindings always load these functions on startup.
+ * (In 8.0+, users should not be invoking this deleted experimental
+ * functionality directly.)
+ */
+typedef struct FDB_tenant FDBTenant;
+DLLEXPORT WARN_UNUSED_RESULT fdb_error_t fdb_database_open_tenant(FDBDatabase* d,
+                                                                  uint8_t const* tenant_name,
+                                                                  int tenant_name_length,
+                                                                  FDBTenant** out_tenant);
+
+DLLEXPORT WARN_UNUSED_RESULT fdb_error_t fdb_tenant_create_transaction(FDBTenant* tenant,
+                                                                       FDBTransaction** out_transaction);
+
+DLLEXPORT WARN_UNUSED_RESULT FDBFuture* fdb_tenant_get_id(FDBTenant* tenant);
+
+DLLEXPORT void fdb_tenant_destroy(FDBTenant* tenant);
+
 DLLEXPORT WARN_UNUSED_RESULT FDBFuture* fdb_database_reboot_worker(FDBDatabase* db,
                                                                    uint8_t const* address,
                                                                    int address_length,

bindings/python/fdb/impl.py

@@ -1302,6 +1302,25 @@ class Database(_TransactionCreator):
     def _set_option(self, option, param, length):
         self.capi.fdb_database_set_option(self.dpointer, option, param, length)
 
+    # XXX Adding this back temporarily to test C bindings changes to ensure
+    # that 7.x tenant-having python libraries can pass startup with 8.0.0
+    # libfdb_c.so. Client code that actually calls tenant related APIs will
+    # of course not obtain useful functionality. Returning `None` here seems
+    # both necessary and sufficient to ensure that clients don't think that
+    # they are able to obtain tenant-related functionality.
+    #
+    # TODO(gglass): remove once we think the C library has been fixed
+    # up.  We don't want to ship this stuff in 8.0.0 python bindings
+    # as that would perpetuate these unwanted dependencies on the C
+    # library.
+    def open_tenant(self, name):
+        tname = name  # this is a bug
+        pointer = ctypes.c_void_p()
+        self.capi.fdb_database_open_tenant(
+            self.dpointer, tname, len(tname), ctypes.byref(pointer)
+        )
+        return None
+
     def create_transaction(self):
         pointer = ctypes.c_void_p()
         self.capi.fdb_database_create_transaction(self.dpointer, ctypes.byref(pointer))
@@ -1653,6 +1672,27 @@ def init_c_api():
     _capi.fdb_database_destroy.argtypes = [ctypes.c_void_p]
     _capi.fdb_database_destroy.restype = None
 
+    # XXX Adding this back temporarily to test C bindings changes to put
+    # this stuff back in, to avoid breaking 7.x tenant-having python libraries
+    # that want to load these symbols on process startup.
+    #
+    # TODO(gglass): remove once we think the C library has been fixed
+    # up.  We don't want to ship this stuff in 8.0.0 python bindings
+    # as that would perpetuate these unwanted dependencies on the C
+    # library.  Alternatively, only initialize this stuff in a non-default
+    # mode to be used only by internal testing with the very specific
+    # goal of ensuring that the C library has symbols to satisfy
+    # 7.x python client libraries.  Like "SIMULATE_7X_PYTHON_BINDINGS"
+    # mode.
+    _capi.fdb_database_open_tenant.argtypes = [
+        ctypes.c_void_p,
+        ctypes.c_void_p,
+        ctypes.c_int,
+        ctypes.POINTER(ctypes.c_void_p),
+    ]
+    _capi.fdb_database_open_tenant.restype = ctypes.c_int
+    _capi.fdb_database_open_tenant.errcheck = check_error_code
+
     _capi.fdb_database_create_transaction.argtypes = [
         ctypes.c_void_p,
         ctypes.POINTER(ctypes.c_void_p),
@@ -1672,6 +1712,19 @@ def init_c_api():
     _capi.fdb_database_get_client_status.argtypes = [ctypes.c_void_p]
     _capi.fdb_database_get_client_status.restype = ctypes.c_void_p
 
+    _capi.fdb_tenant_destroy.argtypes = [ctypes.c_void_p]
+    _capi.fdb_tenant_destroy.restype = None
+
+    _capi.fdb_tenant_get_id.argtypes = [ctypes.c_void_p]
+    _capi.fdb_tenant_get_id.restype = ctypes.c_void_p
+
+    _capi.fdb_tenant_create_transaction.argtypes = [
+        ctypes.c_void_p,
+        ctypes.POINTER(ctypes.c_void_p),
+    ]
+    _capi.fdb_tenant_create_transaction.restype = ctypes.c_int
+    _capi.fdb_tenant_create_transaction.errcheck = check_error_code
+
     _capi.fdb_transaction_destroy.argtypes = [ctypes.c_void_p]
     _capi.fdb_transaction_destroy.restype = None