From b073b0176704a8aede65d22d7b1a81e98bdadad1 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov.dev@gmail.com>
Date: Wed, 24 Oct 2018 15:42:41 +0300
Subject: [PATCH] wal: add event_mask to wal_watcher
In order to implement WAL auto-deletion, we need a notification channel
through which the WAL thread could notify TX that a WAL file was deleted
so that the latter can shoot off stale replicas. We will reuse existing
wal_watcher API for this. Currently, wal_watcher invokes the registered
callback on each WAL write so using it as is would be inefficient. To
avoid that, let's allow the caller to specify events of interest when
registering a wal_watcher.
Needed for #3397
---
src/box/relay.cc | 5 ++++-
src/box/wal.c | 19 ++++++++++++++++++-
src/box/wal.h | 9 ++++++++-
3 files changed, 30 insertions(+), 3 deletions(-)
diff --git a/src/box/relay.cc b/src/box/relay.cc
index 2a4cb41246..0034f99a04 100644
--- a/src/box/relay.cc
+++ b/src/box/relay.cc
@@ -408,6 +408,8 @@ relay_schedule_pending_gc(struct relay *relay, const struct vclock *vclock)
static void
relay_process_wal_event(struct wal_watcher_msg *msg)
{
+ assert((msg->events & (WAL_EVENT_WRITE | WAL_EVENT_ROTATE)) != 0);
+
struct relay *relay = container_of(msg->watcher, struct relay,
wal_watcher);
if (relay->state != RELAY_FOLLOW) {
@@ -505,7 +507,8 @@ relay_subscribe_f(va_list ap)
};
trigger_add(&r->on_close_log, &on_close_log);
wal_set_watcher(&relay->wal_watcher, cord_name(cord()),
- relay_process_wal_event, cbus_process);
+ relay_process_wal_event, cbus_process,
+ WAL_EVENT_WRITE | WAL_EVENT_ROTATE);
relay_set_cord_name(relay->io.fd);
diff --git a/src/box/wal.c b/src/box/wal.c
index b239acd48c..30e36d8e06 100644
--- a/src/box/wal.c
+++ b/src/box/wal.c
@@ -1027,6 +1027,12 @@ wal_watcher_notify(struct wal_watcher *watcher, unsigned events)
{
assert(!rlist_empty(&watcher->next));
+ events &= watcher->event_mask;
+ if (events == 0) {
+ /* The watcher isn't interested in this event. */
+ return;
+ }
+
if (watcher->msg.cmsg.route != NULL) {
/*
* If the notification message is still en route,
@@ -1100,7 +1106,8 @@ wal_watcher_detach(void *arg)
void
wal_set_watcher(struct wal_watcher *watcher, const char *name,
void (*watcher_cb)(struct wal_watcher_msg *),
- void (*process_cb)(struct cbus_endpoint *))
+ void (*process_cb)(struct cbus_endpoint *),
+ unsigned event_mask)
{
assert(journal_is_initialized(&wal_writer_singleton.base));
@@ -1110,6 +1117,7 @@ wal_set_watcher(struct wal_watcher *watcher, const char *name,
watcher->msg.events = 0;
watcher->msg.cmsg.route = NULL;
watcher->pending_events = 0;
+ watcher->event_mask = event_mask;
assert(lengthof(watcher->route) == 2);
watcher->route[0] = (struct cmsg_hop)
@@ -1130,6 +1138,15 @@ wal_clear_watcher(struct wal_watcher *watcher,
wal_watcher_detach, watcher, process_cb);
}
+/**
+ * Notify all interested watchers about a WAL event.
+ *
+ * XXX: Note, this function iterates over all registered watchers,
+ * including those that are not interested in the given event.
+ * This is OK only as long as the number of events/watchers is
+ * small. If this ever changes, we should consider maintaining
+ * a separate watcher list per each event type.
+ */
static void
wal_notify_watchers(struct wal_writer *writer, unsigned events)
{
diff --git a/src/box/wal.h b/src/box/wal.h
index b7edcd43f1..e8a4299cc9 100644
--- a/src/box/wal.h
+++ b/src/box/wal.h
@@ -95,6 +95,11 @@ struct wal_watcher {
struct cmsg_hop route[2];
/** Message sent to notify the watcher. */
struct wal_watcher_msg msg;
+ /**
+ * Bit mask of WAL events that this watcher is
+ * interested in.
+ */
+ unsigned event_mask;
/**
* Bit mask of WAL events that happened while
* the notification message was en route.
@@ -126,11 +131,13 @@ struct wal_watcher {
* @param process_cb Function called to process cbus messages
* while the watcher is being attached or NULL
* if the cbus loop is running elsewhere.
+ * @param event_mask Bit mask of events the watcher is interested in.
*/
void
wal_set_watcher(struct wal_watcher *watcher, const char *name,
void (*watcher_cb)(struct wal_watcher_msg *),
- void (*process_cb)(struct cbus_endpoint *));
+ void (*process_cb)(struct cbus_endpoint *),
+ unsigned event_mask);
/**
* Unsubscribe from WAL events.
--
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