[ovs-dev] [PATCH v5] ovsdb: provide raft and command interfaces with priority
anton.ivanov at cambridgegreys.com
anton.ivanov at cambridgegreys.com
Thu Jul 22 15:03:44 UTC 2021
From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
Set a soft time limit of "raft election timer"/2 on ovsdb
processing.
This improves behaviour in large heavily loaded clusters.
While it cannot fully eliminate spurious raft elections
under heavy load, it significantly decreases their number.
Processing is (to the extent possible) restarted where it
stopped on the previous iteration to ensure that sessions
towards the tail of the session list are not starved.
Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
---
ovsdb/jsonrpc-server.c | 92 ++++++++++++++++++++++++++++++++++++++++--
ovsdb/jsonrpc-server.h | 2 +-
ovsdb/ovsdb-server.c | 23 ++++++++++-
ovsdb/raft.c | 6 +++
ovsdb/raft.h | 3 ++
ovsdb/storage.c | 12 ++++++
ovsdb/storage.h | 2 +
7 files changed, 134 insertions(+), 6 deletions(-)
diff --git a/ovsdb/jsonrpc-server.c b/ovsdb/jsonrpc-server.c
index 351c39d8a..13c437811 100644
--- a/ovsdb/jsonrpc-server.c
+++ b/ovsdb/jsonrpc-server.c
@@ -60,7 +60,8 @@ static struct ovsdb_jsonrpc_session *ovsdb_jsonrpc_session_create(
struct ovsdb_jsonrpc_remote *, struct jsonrpc_session *, bool);
static void ovsdb_jsonrpc_session_preremove_db(struct ovsdb_jsonrpc_remote *,
struct ovsdb *);
-static void ovsdb_jsonrpc_session_run_all(struct ovsdb_jsonrpc_remote *);
+static void ovsdb_jsonrpc_session_run_all(struct ovsdb_jsonrpc_remote *,
+ uint64_t limit);
static void ovsdb_jsonrpc_session_wait_all(struct ovsdb_jsonrpc_remote *);
static void ovsdb_jsonrpc_session_get_memory_usage_all(
const struct ovsdb_jsonrpc_remote *, struct simap *usage);
@@ -128,6 +129,11 @@ struct ovsdb_jsonrpc_server {
bool read_only; /* This server is does not accept any
transactions that can modify the database. */
struct shash remotes; /* Contains "struct ovsdb_jsonrpc_remote *"s. */
+ struct ovsdb_jsonrpc_remote *skip_to; /* Pointer to remote where processing
+ should restart after a time
+ constraint interruption. */
+ bool must_wake_up; /* The processing loop must be re-run. It was
+ interrupted due to exceeding a time constraint. */
};
/* A configured remote. This is either a passive stream listener plus a list
@@ -137,6 +143,9 @@ struct ovsdb_jsonrpc_remote {
struct ovsdb_jsonrpc_server *server;
struct pstream *listener; /* Listener, if passive. */
struct ovs_list sessions; /* List of "struct ovsdb_jsonrpc_session"s. */
+ struct ovsdb_jsonrpc_session *skip_to; /* Session at which processing
+ should restart after an
+ interruption. */
uint8_t dscp;
bool read_only;
char *role;
@@ -279,6 +288,7 @@ ovsdb_jsonrpc_server_add_remote(struct ovsdb_jsonrpc_server *svr,
remote->dscp = options->dscp;
remote->read_only = options->read_only;
remote->role = nullable_xstrdup(options->role);
+ remote->skip_to = NULL;
shash_add(&svr->remotes, name, remote);
if (!listener) {
@@ -293,6 +303,11 @@ ovsdb_jsonrpc_server_del_remote(struct shash_node *node)
{
struct ovsdb_jsonrpc_remote *remote = node->data;
+ /* safest option - rerun all remotes */
+ if (remote->server->skip_to) {
+ remote->server->skip_to = NULL;
+ }
+
ovsdb_jsonrpc_session_close_all(remote);
pstream_close(remote->listener);
shash_delete(&remote->server->remotes, node);
@@ -378,12 +393,24 @@ ovsdb_jsonrpc_server_set_read_only(struct ovsdb_jsonrpc_server *svr,
}
void
-ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *svr)
+ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *svr, uint64_t limit)
{
struct shash_node *node;
+ uint64_t elapsed = 0;
+ uint64_t start_time = time_msec();
+
+ svr->must_wake_up = false;
SHASH_FOR_EACH (node, &svr->remotes) {
struct ovsdb_jsonrpc_remote *remote = node->data;
+ if (svr->skip_to) {
+ if (remote != svr->skip_to) {
+ continue;
+ } else {
+ svr->skip_to = NULL;
+ svr->must_wake_up = true;
+ }
+ }
if (remote->listener) {
struct stream *stream;
@@ -403,7 +430,17 @@ ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *svr)
}
}
- ovsdb_jsonrpc_session_run_all(remote);
+ /* We assume accept and session creation time to be
+ * negligible for the purposes of computing timeouts.
+ */
+ ovsdb_jsonrpc_session_run_all(remote, limit - elapsed);
+
+ elapsed = time_msec() - start_time;
+ if (elapsed > limit) {
+ svr->must_wake_up = true;
+ svr->skip_to = remote;
+ break;
+ }
}
}
@@ -412,6 +449,16 @@ ovsdb_jsonrpc_server_wait(struct ovsdb_jsonrpc_server *svr)
{
struct shash_node *node;
+ if (svr->must_wake_up) {
+ /* We have stopped processing due to a time constraint.
+ * In this case there is no point to walk all sessions
+ * and rebuild the poll structure for the poll loop.
+ */
+ poll_immediate_wake();
+ svr->must_wake_up = false;
+ return;
+ }
+
SHASH_FOR_EACH (node, &svr->remotes) {
struct ovsdb_jsonrpc_remote *remote = node->data;
@@ -583,15 +630,52 @@ ovsdb_jsonrpc_session_set_options(struct ovsdb_jsonrpc_session *session,
}
static void
-ovsdb_jsonrpc_session_run_all(struct ovsdb_jsonrpc_remote *remote)
+ovsdb_jsonrpc_session_run_all(struct ovsdb_jsonrpc_remote *remote,
+ uint64_t limit)
{
struct ovsdb_jsonrpc_session *s, *next;
+ uint64_t start_time = time_msec();
LIST_FOR_EACH_SAFE (s, next, node, &remote->sessions) {
+ if (remote->skip_to && s != remote->skip_to) {
+ /* Processing was interrupted, we skip to the point
+ * where we had to interrupt it.
+ * We cannot use the _CONTINUE macro as it is not safe
+ * if the list has been changed in the meantime.
+ */
+ continue;
+ }
+
+ /* Set ->next as skip point if we need to restart processing.
+ * This way, even if current is removed, we always have a
+ * valid pointer to continue processing.
+ */
+ remote->skip_to =
+ CONTAINER_OF(ovs_list_front(&s->node),
+ struct ovsdb_jsonrpc_session, node);
+
+ if (remote->skip_to == s) {
+ /* The list is a singleton. This is a special case, where
+ * deleting the node will invalidate the pointer.
+ */
+ remote->skip_to = NULL;
+ }
+
int error = ovsdb_jsonrpc_session_run(s);
if (error) {
ovsdb_jsonrpc_session_close(s);
}
+
+ if (time_msec() - start_time > limit) {
+ /* We bail leaving skip_to set. Next processing iteration
+ * will skip everything up to skip_to which was set to
+ * ->next earlier on.
+ */
+ break;
+ } else {
+ /* We are within time constraints, clear skip_to. */
+ remote->skip_to = NULL;
+ }
}
}
diff --git a/ovsdb/jsonrpc-server.h b/ovsdb/jsonrpc-server.h
index e0653aa39..218152e9d 100644
--- a/ovsdb/jsonrpc-server.h
+++ b/ovsdb/jsonrpc-server.h
@@ -67,7 +67,7 @@ void ovsdb_jsonrpc_server_free_remote_status(
void ovsdb_jsonrpc_server_reconnect(struct ovsdb_jsonrpc_server *, bool force,
char *comment);
-void ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *);
+void ovsdb_jsonrpc_server_run(struct ovsdb_jsonrpc_server *, uint64_t limit);
void ovsdb_jsonrpc_server_wait(struct ovsdb_jsonrpc_server *);
void ovsdb_jsonrpc_server_set_read_only(struct ovsdb_jsonrpc_server *,
diff --git a/ovsdb/ovsdb-server.c b/ovsdb/ovsdb-server.c
index 0b3d2bb71..3fcedf617 100644
--- a/ovsdb/ovsdb-server.c
+++ b/ovsdb/ovsdb-server.c
@@ -216,7 +216,28 @@ main_loop(struct server_config *config,
reconfigure_remotes(jsonrpc, all_dbs, remotes),
&remotes_error);
report_error_if_changed(reconfigure_ssl(all_dbs), &ssl_error);
- ovsdb_jsonrpc_server_run(jsonrpc);
+
+ /* Figure out current processing time limit. */
+
+ bool first_db = true;
+ uint64_t limit = UINT64_MAX;
+ SHASH_FOR_EACH (node, all_dbs) {
+ struct db *db = node->data;
+ uint64_t db_limit;
+
+ db_limit = ovsdb_storage_max_processing_time(db->db->storage);
+ if (first_db) {
+ /* reset the limit */
+ limit = db_limit;
+ first_db = false;
+ }
+ limit = MIN(db_limit, limit);
+ }
+ if (ovs_replay_is_active()) {
+ limit = UINT64_MAX;
+ }
+
+ ovsdb_jsonrpc_server_run(jsonrpc, limit);
if (*is_backup) {
replication_run();
diff --git a/ovsdb/raft.c b/ovsdb/raft.c
index 2fb515651..183463aba 100644
--- a/ovsdb/raft.c
+++ b/ovsdb/raft.c
@@ -407,6 +407,12 @@ raft_make_address_passive(const char *address_)
}
}
+uint64_t
+raft_get_election_timer(const struct raft *raft)
+{
+ return raft->election_timer;
+}
+
static struct raft *
raft_alloc(void)
{
diff --git a/ovsdb/raft.h b/ovsdb/raft.h
index 3545c41c2..575e7f609 100644
--- a/ovsdb/raft.h
+++ b/ovsdb/raft.h
@@ -188,4 +188,7 @@ void raft_take_leadership(struct raft *);
void raft_transfer_leadership(struct raft *, const char *reason);
const struct uuid *raft_current_eid(const struct raft *);
+
+uint64_t raft_get_election_timer(const struct raft *);
+
#endif /* lib/raft.h */
diff --git a/ovsdb/storage.c b/ovsdb/storage.c
index d727b1eac..58018fe6d 100644
--- a/ovsdb/storage.c
+++ b/ovsdb/storage.c
@@ -647,3 +647,15 @@ ovsdb_storage_peek_last_eid(struct ovsdb_storage *storage)
}
return raft_current_eid(storage->raft);
}
+
+uint64_t
+ovsdb_storage_max_processing_time(struct ovsdb_storage *storage)
+{
+ if (!storage->raft) {
+ return UINT64_MAX;
+ }
+ if (raft_get_election_timer(storage->raft) > 2) {
+ return raft_get_election_timer(storage->raft) / 2;
+ }
+ return 1;
+}
diff --git a/ovsdb/storage.h b/ovsdb/storage.h
index e120094d7..a8a02e0bd 100644
--- a/ovsdb/storage.h
+++ b/ovsdb/storage.h
@@ -97,4 +97,6 @@ struct ovsdb_schema *ovsdb_storage_read_schema(struct ovsdb_storage *);
const struct uuid *ovsdb_storage_peek_last_eid(struct ovsdb_storage *);
+uint64_t ovsdb_storage_max_processing_time(struct ovsdb_storage *);
+
#endif /* ovsdb/storage.h */
--
2.20.1
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