[PATCH v3/3] replication: handle replication shutdown correctly.
Vladimir Davydov
vdavydov.dev at gmail.com
Wed Aug 15 16:49:27 MSK 2018
On Wed, Aug 15, 2018 at 02:03:03PM +0300, Serge Petrenko wrote:
> diff --git a/src/box/box.cc b/src/box/box.cc
> index ae4959d6f..c5e05bc15 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -1597,9 +1597,9 @@ box_free(void)
> * initialized
> */
> if (is_box_configured) {
> + replication_free();
> #if 0
> session_free();
> - replication_free();
Nit: better move replication_free() after #endif, where all other
destructor are called.
> user_cache_free();
> schema_free();
> module_free();
> diff --git a/src/box/relay.cc b/src/box/relay.cc
> index 4cacbc840..81dc88a06 100644
> --- a/src/box/relay.cc
> +++ b/src/box/relay.cc
> @@ -198,6 +198,14 @@ relay_start(struct relay *relay, int fd, uint64_t sync,
> relay->state = RELAY_FOLLOW;
> }
>
> +void
> +relay_cancel(struct relay *relay)
> +{
> + assert(relay->state == RELAY_FOLLOW);
IMO it would be better to make this function work both if the relay
thread is running and if it is not (do nothing in the latter case).
Also relay->state is set to RELAY_FOLLOW on initial join, when
relay thread isn't running. In this case, you must not call pthread
cancel/join.
> + tt_pthread_cancel(relay->cord.id);
> + tt_pthread_join(relay->cord.id, NULL);
> +}
> +
> static void
> relay_stop(struct relay *relay)
> {
> @@ -460,6 +468,9 @@ relay_send_heartbeat(struct relay *relay)
> static int
> relay_subscribe_f(va_list ap)
> {
> + /* Allow to be cancelled. */
> + tt_pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
> + tt_pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);
These cancelstate/type are set by default for all new threads and so we
don't need to set them explicitly, no?
> struct relay *relay = va_arg(ap, struct relay *);
> struct recovery *r = relay->r;
>
> diff --git a/src/box/relay.h b/src/box/relay.h
> index 2988e6b0d..53bf68eb8 100644
> --- a/src/box/relay.h
> +++ b/src/box/relay.h
> @@ -61,6 +61,10 @@ enum relay_state {
> struct relay *
> relay_new(struct replica *replica);
>
> +/** Cancel a running relay. Called on shutdown. */
> +void
> +relay_cancel(struct relay *relay);
> +
> /** Destroy and delete the relay */
> void
> relay_delete(struct relay *relay);
> diff --git a/src/box/replication.cc b/src/box/replication.cc
> index 48956d2ed..acf20fc2c 100644
> --- a/src/box/replication.cc
> +++ b/src/box/replication.cc
> @@ -91,13 +91,6 @@ replication_init(void)
> latch_create(&replicaset.applier.order_latch);
> }
>
> -void
> -replication_free(void)
> -{
> - free(replicaset.replica_by_id);
> - fiber_cond_destroy(&replicaset.applier.cond);
> -}
> -
> void
> replica_check_id(uint32_t replica_id)
> {
> @@ -242,6 +235,47 @@ replica_clear_applier(struct replica *replica)
> trigger_clear(&replica->on_applier_state);
> }
>
> +void
> +replication_free(void)
> +{
After some consideration, I still don't think it's a good idea to add
the code that frees replicas in this patch, because it's a completely
separate change, which has nothing to do with the issue you're fixing.
The more code you add the more difficult it will be to cherry-pick this
patch, and it also increases the likelihood of introducing a bug.
Please remove this code so that replication_free only cancels relay
threads.
We will probably need to free memory on shutdown (to silence valgrind
and asan), but let's do it separately and when we get to it.
> + struct replica *replica, *next;
> +
> + replica_hash_foreach_safe(&replicaset.hash, replica, next) {
> + if (replica->id == instance_id) {
> + replica_hash_remove(&replicaset.hash, replica);
> + /*
> + * Local replica doesn't have neither applier
> + * nor relay, so free it right away.
> + */
> + TRASH(replica);
> + free(replica);
> + continue;
> + }
> + if (replica->applier != NULL) {
> + replica_clear_applier(replica);
> + /*
> + * We're exiting, so control won't be passed
> + * to appliers and we don't need to stop them.
> + */
> + }
> + if (replica->id != REPLICA_ID_NIL) {
> + if (relay_get_state(replica->relay) == RELAY_FOLLOW) {
> + replica->id = REPLICA_ID_NIL;
> + relay_cancel(replica->relay);
Please add a comment here why we need to stop relay threads on shutdown.
> + }
> + } else {
> + replica_hash_remove(&replicaset.hash, replica);
> + replica_delete(replica);
> + }
> + }
> + rlist_foreach_entry_safe(replica, &replicaset.anon, in_anon, next) {
> + replica_clear_applier(replica);
> + replica_delete(replica);
> + }
> + free(replicaset.replica_by_id);
> + fiber_cond_destroy(&replicaset.applier.cond);
> +}
> +
> static void
> replica_on_applier_sync(struct replica *replica)
> {
> diff --git a/src/box/replication.h b/src/box/replication.h
> index e8b391af2..a8baafd12 100644
> --- a/src/box/replication.h
> +++ b/src/box/replication.h
> @@ -154,6 +154,9 @@ replication_disconnect_timeout(void)
> void
> replication_init(void);
>
> +/**
> + * Stop replication and delete all replicas and replicaset.
> + */
This comment is not really needed - it's clear from the name of this
function that it is a destructor. Besides, replication_init() doesn't
have a comment so let's leave this declaration as is.
> void
> replication_free(void);
>
> diff --git a/src/tt_pthread.h b/src/tt_pthread.h
> index 60ade50ae..144425ccb 100644
> --- a/src/tt_pthread.h
> +++ b/src/tt_pthread.h
> @@ -277,6 +277,21 @@
> tt_pthread_error(e__); \
> })
>
> +#define tt_pthread_cancel(thread) \
> +({ int e__ = pthread_cancel(thread); \
> + tt_pthread_error(e__); \
> + })
Extra space.
> +
+#define tt_pthread_setcancelstate(state, ret) \
> +({ int e__ = pthread_setcancelstate(state, ret); \
> + tt_pthread_error(e__); \
> +})
> +
> +#define tt_pthread_setcanceltype(type, ret) \
> +({ int e__ = pthread_setcanceltype(type, ret); \
> + tt_pthread_error(e__); \
> +})
> +
> #define tt_pthread_key_create(key, dtor) \
> ({ int e__ = pthread_key_create(key, dtor); \
> tt_pthread_error(e__); \
> diff --git a/test/replication/gc.result b/test/replication/gc.result
> index 3f9db26ce..aa59747db 100644
> --- a/test/replication/gc.result
> +++ b/test/replication/gc.result
> @@ -152,6 +152,9 @@ box.snapshot()
> ---
> - ok
> ...
> +wait_gc(1)
> +---
> +...
I don't understand how this is relevant to the issue you're fixing.
If the test is buggy, you should fix it in a separate patch.
> #box.info.gc().checkpoints == 1 or box.info.gc()
> ---
> - true
> @@ -311,6 +314,9 @@ box.snapshot()
> ---
> - ok
> ...
> +wait_gc(1)
> +---
> +...
> #box.info.gc().checkpoints == 1 or box.info.gc()
> ---
> - true
> @@ -330,6 +336,9 @@ xlog_count == 3 or xlog_count == 2 or fio.listdir('./master')
> test_run:cleanup_cluster()
> ---
> ...
> +fiber.sleep(0.1)
> +---
> +...
Please don't use sleeps. Use wait_gc() instead.
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