lightningd: close and reopen db across fork for daemonize

Fixes: #1092
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/lightningd.c

@@ -237,11 +237,12 @@ static void init_txfilter(struct wallet *w, struct txfilter *filter)
 	}
 }
 
-static void daemonize_but_keep_dir(void)
+static void daemonize_but_keep_dir(struct lightningd *ld)
 {
 	/* daemonize moves us into /, but we want to be here */
 	const char *cwd = path_cwd(NULL);
 
+	db_close_for_fork(ld->wallet->db);
 	if (!cwd)
 		fatal("Could not get current directory: %s", strerror(errno));
 	if (!daemonize())
@@ -252,6 +253,7 @@ static void daemonize_but_keep_dir(void)
 		fatal("Could not return to directory %s: %s",
 		      cwd, strerror(errno));
 
+	db_reopen_after_fork(ld->wallet->db);
 	tal_free(cwd);
 }
 
@@ -382,7 +384,7 @@ int main(int argc, char *argv[])
 
 	/* Now we're about to start, become daemon if desired. */
 	if (ld->daemon)
-		daemonize_but_keep_dir();
+		daemonize_but_keep_dir(ld);
 
 	/* Mark ourselves live. */
 	log_info(ld->log, "Server started with public key %s, alias %s (color #%s) and lightningd %s",

lightningd/test/run-find_my_path.c

@@ -16,12 +16,18 @@ void crashlog_activate(const char *argv0 UNNEEDED, struct log *log UNNEEDED)
 /* Generated stub for db_begin_transaction_ */
 void db_begin_transaction_(struct db *db UNNEEDED, const char *location UNNEEDED)
 { fprintf(stderr, "db_begin_transaction_ called!\n"); abort(); }
+/* Generated stub for db_close_for_fork */
+void db_close_for_fork(struct db *db UNNEEDED)
+{ fprintf(stderr, "db_close_for_fork called!\n"); abort(); }
 /* Generated stub for db_commit_transaction */
 void db_commit_transaction(struct db *db UNNEEDED)
 { fprintf(stderr, "db_commit_transaction called!\n"); abort(); }
 /* Generated stub for db_get_intvar */
 s64 db_get_intvar(struct db *db UNNEEDED, char *varname UNNEEDED, s64 defval UNNEEDED)
 { fprintf(stderr, "db_get_intvar called!\n"); abort(); }
+/* Generated stub for db_reopen_after_fork */
+void db_reopen_after_fork(struct db *db UNNEEDED)
+{ fprintf(stderr, "db_reopen_after_fork called!\n"); abort(); }
 /* Generated stub for debug_poll */
 int debug_poll(struct pollfd *fds UNNEEDED, nfds_t nfds UNNEEDED, int timeout UNNEEDED)
 { fprintf(stderr, "debug_poll called!\n"); abort(); }
@@ -35,7 +41,7 @@ void free_htlcs(struct lightningd *ld UNNEEDED, const struct channel *channel UN
 void gossip_init(struct lightningd *ld UNNEEDED)
 { fprintf(stderr, "gossip_init called!\n"); abort(); }
 /* Generated stub for handle_opts */
-bool handle_opts(struct lightningd *ld UNNEEDED, int argc UNNEEDED, char *argv[] UNUSED)
+bool handle_opts(struct lightningd *ld UNNEEDED, int argc UNNEEDED, char *argv[])
 { fprintf(stderr, "handle_opts called!\n"); abort(); }
 /* Generated stub for hash_htlc_key */
 size_t hash_htlc_key(const struct htlc_key *htlc_key UNNEEDED)
@@ -78,7 +84,7 @@ void subd_shutdown(struct subd *subd UNNEEDED, unsigned int seconds UNNEEDED)
 void timer_expired(tal_t *ctx UNNEEDED, struct timer *timer UNNEEDED)
 { fprintf(stderr, "timer_expired called!\n"); abort(); }
 /* Generated stub for txfilter_add_derkey */
-void txfilter_add_derkey(struct txfilter *filter UNNEEDED, u8 derkey[PUBKEY_DER_LEN] UNUSED)
+void txfilter_add_derkey(struct txfilter *filter UNNEEDED, u8 derkey[PUBKEY_DER_LEN])
 { fprintf(stderr, "txfilter_add_derkey called!\n"); abort(); }
 /* Generated stub for txfilter_new */
 struct txfilter *txfilter_new(const tal_t *ctx UNNEEDED)

wallet/db.c

@@ -432,6 +432,28 @@ struct db *db_setup(const tal_t *ctx, struct log *log)
 	return db;
 }
 
+void db_close_for_fork(struct db *db)
+{
+	/* https://www.sqlite.org/faq.html#q6
+	 *
+	 * Under Unix, you should not carry an open SQLite database across a
+	 * fork() system call into the child process. */
+	if (sqlite3_close(db->sql) != SQLITE_OK)
+		fatal("sqlite3_close: %s", sqlite3_errmsg(db->sql));
+	db->sql = NULL;
+}
+
+void db_reopen_after_fork(struct db *db)
+{
+	int err = sqlite3_open_v2(db->filename, &db->sql,
+				  SQLITE_OPEN_READWRITE, NULL);
+
+	if (err != SQLITE_OK) {
+		fatal("failed to re-open database %s: %s", db->filename,
+		      sqlite3_errstr(err));
+	}
+}
+
 s64 db_get_intvar(struct db *db, char *varname, s64 defval)
 {
 	int err;

wallet/db.h

@@ -113,6 +113,10 @@ bool db_exec_prepared_mayfail_(const char *caller,
 			       struct db *db,
 			       sqlite3_stmt *stmt);
 
+/* Do not keep db open across a fork: needed for --daemon */
+void db_close_for_fork(struct db *db);
+void db_reopen_after_fork(struct db *db);
+
 #define sqlite3_column_arr(ctx, stmt, col, type)			\
 	((type *)sqlite3_column_arr_((ctx), (stmt), (col),		\
 				     sizeof(type), TAL_LABEL(type, "[]"), \

wallet/test/run-wallet.c

@@ -230,9 +230,6 @@ void log_add(struct log *log UNNEEDED, const char *fmt UNNEEDED, ...)
 void log_io(struct log *log UNNEEDED, enum log_level dir UNNEEDED, const char *comment UNNEEDED,
 	    const void *data UNNEEDED, size_t len UNNEEDED)
 { fprintf(stderr, "log_io called!\n"); abort(); }
-/* Generated stub for logv_add */
-void logv_add(struct log *log UNNEEDED, const char *fmt UNNEEDED, va_list ap UNNEEDED)
-{ fprintf(stderr, "logv_add called!\n"); abort(); }
 /* Generated stub for new_json_result */
 struct json_result *new_json_result(const tal_t *ctx UNNEEDED)
 { fprintf(stderr, "new_json_result called!\n"); abort(); }