Request extension files and libraries from compute_ctl

src/backend/commands/extension.c

@@ -399,6 +399,7 @@ get_extension_script_directory(ExtensionControlFile *control)
 {
 	char		sharepath[MAXPGPATH];
 	char	   *result;
+	struct stat fst;
 
 	/*
 	 * The directory parameter can be omitted, absolute, or relative to the
@@ -414,6 +415,16 @@ get_extension_script_directory(ExtensionControlFile *control)
 	result = (char *) palloc(MAXPGPATH);
 	snprintf(result, MAXPGPATH, "%s/%s", sharepath, control->directory);
 
+	// If directory does not exist, check remote extension storage
+	if (stat(result, &fst) < 0)
+	{
+		// request download of extension files from for control->directory
+		if (download_extension_file_hook != NULL)
+		{
+			download_extension_file_hook(control->directory, false);
+		}
+	}
+
 	return result;
 }
 
@@ -1438,6 +1449,13 @@ CreateExtensionInternal(char *extensionName,
 	 * will get us there.
 	 */
 	filename = get_extension_script_filename(pcontrol, NULL, versionName);
+
+	// request download of extension files from compute_ctl
+	if (download_extension_file_hook != NULL)
+	{
+		download_extension_file_hook(extensionName, false);
+	}
+
 	if (stat(filename, &fst) == 0)
 	{
 		/* Easy, no extra scripts */

src/backend/utils/fmgr/dfmgr.c

@@ -36,6 +36,7 @@
 #include "storage/shmem.h"
 #include "utils/hsearch.h"
 
+download_extension_file_hook_type download_extension_file_hook = NULL;
 
 /* signatures for PostgreSQL-specific library init/fini functions */
 typedef void (*PG_init_t) (void);
@@ -81,11 +82,13 @@ static void incompatible_module_error(const char *libname,
 									  const Pg_magic_struct *module_magic_data) pg_attribute_noreturn();
 static void internal_unload_library(const char *libname);
 static bool file_exists(const char *name);
-static char *expand_dynamic_library_name(const char *name);
+static char *expand_dynamic_library_name(const char *name, bool *is_found);
 static void check_restricted_library_name(const char *name);
 static char *substitute_libpath_macro(const char *name);
 static char *find_in_dynamic_libpath(const char *basename);
 
+static void neon_try_load(const char *name);
+
 /* Magic structure that module needs to match to be accepted */
 static const Pg_magic_struct magic_data = PG_MODULE_MAGIC_DATA;
 
@@ -110,9 +113,20 @@ load_external_function(const char *filename, const char *funcname,
 	char	   *fullname;
 	void	   *lib_handle;
 	void	   *retval;
+	bool 		is_found = true;
 
 	/* Expand the possibly-abbreviated filename to an exact path name */
-	fullname = expand_dynamic_library_name(filename);
+	fullname = expand_dynamic_library_name(filename, &is_found);
+
+	// if file is not found, try to download it from compute_ctl
+	if (!is_found && download_extension_file_hook != NULL)
+	{
+		// try to download the file
+		elog(DEBUG3, "load_external_function: try to download file: %s", fullname);
+		neon_try_load(fullname);
+		// try to find file locally once again
+		fullname = expand_dynamic_library_name(filename, &is_found);
+	}
 
 	/* Load the shared library, unless we already did */
 	lib_handle = internal_load_library(fullname);
@@ -134,6 +148,47 @@ load_external_function(const char *filename, const char *funcname,
 	return retval;
 }
 
+void
+neon_try_load(const char *name)
+{
+	bool have_slash;
+	char *request_name;
+
+	// add .so suffix if it is not present
+	if (strstr(name, DLSUFFIX) == NULL)
+	{
+		request_name = psprintf("%s%s", name, DLSUFFIX);
+		elog(DEBUG3, "neon_try_load: add DLSUFFIX: %s", request_name);
+	}
+	else
+	{
+		request_name = pstrdup(name);
+		elog(DEBUG3, "neon_try_load: DLSUFFIX already present: %s", request_name);
+	}
+
+	have_slash = (first_dir_separator(request_name) != NULL);
+
+	if (strncmp(request_name, "$libdir/", strlen("$libdir/")) == 0)
+	{
+		char *new_request_name = psprintf("%s", request_name + strlen("$libdir/"));
+		pfree(request_name);
+		request_name = new_request_name;
+
+		elog(DEBUG3, "neon_try_load: omit $libdir/: %s", request_name);
+	}
+	else if (have_slash)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_NAME),
+					errmsg("unexpected path in dynamic library name: %s",
+						name)));
+	}
+
+	elog(DEBUG3, "neon_try_load: final request_name: %s", request_name);
+
+	download_extension_file_hook(request_name, true);
+}
+
 /*
  * This function loads a shlib file without looking up any particular
  * function in it.  If the same shlib has previously been loaded,
@@ -146,13 +201,24 @@ void
 load_file(const char *filename, bool restricted)
 {
 	char	   *fullname;
+	bool 		is_found = true;
 
 	/* Apply security restriction if requested */
 	if (restricted)
 		check_restricted_library_name(filename);
 
 	/* Expand the possibly-abbreviated filename to an exact path name */
-	fullname = expand_dynamic_library_name(filename);
+	fullname = expand_dynamic_library_name(filename, &is_found);
+
+	// if file is not found, try to download it from compute_ctl
+	if (!is_found && download_extension_file_hook != NULL)
+	{
+		// try to download the file
+		elog(DEBUG3, "load_file: try to download file: %s", fullname);
+		neon_try_load(fullname);
+		// try to find file locally once again
+		fullname = expand_dynamic_library_name(filename, &is_found);
+	}
 
 	/* Unload the library if currently loaded */
 	internal_unload_library(fullname);
@@ -173,7 +239,6 @@ lookup_external_function(void *filehandle, const char *funcname)
 	return dlsym(filehandle, funcname);
 }
 
-
 /*
  * Load the specified dynamic-link library file, unless it already is
  * loaded.  Return the pg_dl* handle for the file.
@@ -209,6 +274,7 @@ internal_load_library(const char *libname)
 					 errmsg("could not access file \"%s\": %m",
 							libname)));
 
+
 		for (file_scanner = file_list;
 			 file_scanner != NULL &&
 			 !SAME_INODE(stat_buf, *file_scanner);
@@ -483,7 +549,7 @@ file_exists(const char *name)
  * The result will always be freshly palloc'd.
  */
 static char *
-expand_dynamic_library_name(const char *name)
+expand_dynamic_library_name(const char *name, bool *is_found)
 {
 	bool		have_slash;
 	char	   *new;
@@ -529,9 +595,11 @@ expand_dynamic_library_name(const char *name)
 	 * If we can't find the file, just return the string as-is. The ensuing
 	 * load attempt will fail and report a suitable message.
 	 */
+	*is_found = false;
 	return pstrdup(name);
 }
 
+
 /*
  * Check a restricted library name.  It must begin with "$libdir/plugins/"
  * and there must not be any directory separators after that (this is

src/include/fmgr.h

@@ -774,4 +774,10 @@ extern PGDLLIMPORT fmgr_hook_type fmgr_hook;
 #define FmgrHookIsNeeded(fn_oid)							\
 	(!needs_fmgr_hook ? false : (*needs_fmgr_hook)(fn_oid))
 
+
+
+// download_extension_file_hook (filename, is_library)
+typedef bool (*download_extension_file_hook_type) (const char *, bool);
+extern PGDLLIMPORT download_extension_file_hook_type download_extension_file_hook;
+
 #endif							/* FMGR_H */