diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/postmaster/postmaster.c | 37 |
1 files changed, 20 insertions, 17 deletions
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index 5b5fc97c72d..38e2c16ac20 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -156,28 +156,32 @@ * authorization phase). This is used mainly to keep track of how many * children we have and send them appropriate signals when necessary. * - * "Special" children such as the startup, bgwriter and autovacuum launcher - * tasks are not in this list. Autovacuum worker and walsender are in it. + * As shown in the above set of backend types, this list includes not only + * "normal" client sessions, but also autovacuum workers, walsenders, and + * background workers. (Note that at the time of launch, walsenders are + * labeled BACKEND_TYPE_NORMAL; we relabel them to BACKEND_TYPE_WALSND + * upon noticing they've changed their PMChildFlags entry. Hence that check + * must be done before any operation that needs to distinguish walsenders + * from normal backends.) + * * Also, "dead_end" children are in it: these are children launched just for * the purpose of sending a friendly rejection message to a would-be client. * We must track them because they are attached to shared memory, but we know * they will never become live backends. dead_end children are not assigned a - * PMChildSlot. + * PMChildSlot. dead_end children have bkend_type NORMAL. * - * Background workers are in this list, too. + * "Special" children such as the startup, bgwriter and autovacuum launcher + * tasks are not in this list. They are tracked via StartupPID and other + * pid_t variables below. (Thus, there can't be more than one of any given + * "special" child process type. We use BackendList entries for any child + * process there can be more than one of.) */ typedef struct bkend { pid_t pid; /* process id of backend */ int32 cancel_key; /* cancel key for cancels for this backend */ int child_slot; /* PMChildSlot for this backend, if any */ - - /* - * Flavor of backend or auxiliary process. Note that BACKEND_TYPE_WALSND - * backends initially announce themselves as BACKEND_TYPE_NORMAL, so if - * bkend_type is normal, you should check for a recent transition. - */ - int bkend_type; + int bkend_type; /* child process flavor, see above */ bool dead_end; /* is it going to send an error and quit? */ bool bgworker_notify; /* gets bgworker start/stop notifications */ dlist_node elem; /* list link in BackendList */ @@ -1059,10 +1063,9 @@ PostmasterMain(int argc, char *argv[]) * only during a few moments during a standby promotion. However there is * a race condition: if pg_ctl promote is executed and creates the files * during a promotion, the files can stay around even after the server is - * brought up to be the primary. Then, if a new standby starts by using the - * backup taken from the new primary, the files can exist at the server - * startup and should be removed in order to avoid an unexpected - * promotion. + * brought up to be the primary. Then, if a new standby starts by using + * the backup taken from the new primary, the files can exist at server + * startup and must be removed in order to avoid an unexpected promotion. * * Note that promotion signal files need to be removed before the startup * process is invoked. Because, after that, they can be used by @@ -5336,8 +5339,8 @@ sigusr1_handler(SIGNAL_ARGS) /* * Tell startup process to finish recovery. * - * Leave the promote signal file in place and let the Startup - * process do the unlink. + * Leave the promote signal file in place and let the Startup process + * do the unlink. */ signal_child(StartupPID, SIGUSR2); } |