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authorVolker Lendecke <vl@samba.org>2012-03-27 14:31:04 +0200
committerVolker Lendecke <vl@samba.org>2012-04-17 10:21:00 +0200
commit94cf5cc284ba908675ed5fd573dd101d7b9bad02 (patch)
treefa3cbe066f5400c31cfa13ea149e13bada59fbdc /source3/lib
parentbd9178506ed8796a0aa7e4e757f2adc20dcae4f8 (diff)
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s3: Add dbwrap_try_fetch_locked
This is designed to spread the load on individual ctdb records to allow upper layers to do backoff mechanisms. In the ctdb case, do not get the record if a local lock is already taken. If we are not dmaster, do at most one migrate attempt. For the tdb case, this is a nonblocking fetch_locked. If someone else has the lock, give up.
Diffstat (limited to 'source3/lib')
-rw-r--r--source3/lib/dbwrap/dbwrap.c27
-rw-r--r--source3/lib/dbwrap/dbwrap.h3
-rw-r--r--source3/lib/dbwrap/dbwrap_cache.c1
-rw-r--r--source3/lib/dbwrap/dbwrap_ctdb.c36
-rw-r--r--source3/lib/dbwrap/dbwrap_file.c1
-rw-r--r--source3/lib/dbwrap/dbwrap_private.h3
-rw-r--r--source3/lib/dbwrap/dbwrap_rbt.c1
-rw-r--r--source3/lib/dbwrap/dbwrap_tdb.c41
8 files changed, 97 insertions, 16 deletions
diff --git a/source3/lib/dbwrap/dbwrap.c b/source3/lib/dbwrap/dbwrap.c
index 11ab5d91f0..cfd15a976b 100644
--- a/source3/lib/dbwrap/dbwrap.c
+++ b/source3/lib/dbwrap/dbwrap.c
@@ -141,9 +141,10 @@ static struct dbwrap_lock_order_state *dbwrap_check_lock_order(
return state;
}
-struct db_record *dbwrap_fetch_locked(struct db_context *db,
- TALLOC_CTX *mem_ctx,
- TDB_DATA key)
+static struct db_record *dbwrap_fetch_locked_internal(
+ struct db_context *db, TALLOC_CTX *mem_ctx, TDB_DATA key,
+ struct db_record *(*db_fn)(struct db_context *db, TALLOC_CTX *mem_ctx,
+ TDB_DATA key))
{
struct db_record *rec;
struct dbwrap_lock_order_state *lock_order;
@@ -152,7 +153,7 @@ struct db_record *dbwrap_fetch_locked(struct db_context *db,
if (lock_order == NULL) {
return NULL;
}
- rec = db->fetch_locked(db, mem_ctx, key);
+ rec = db_fn(db, mem_ctx, key);
if (rec == NULL) {
TALLOC_FREE(lock_order);
return NULL;
@@ -161,6 +162,24 @@ struct db_record *dbwrap_fetch_locked(struct db_context *db,
return rec;
}
+struct db_record *dbwrap_fetch_locked(struct db_context *db,
+ TALLOC_CTX *mem_ctx,
+ TDB_DATA key)
+{
+ return dbwrap_fetch_locked_internal(db, mem_ctx, key,
+ db->fetch_locked);
+}
+
+struct db_record *dbwrap_try_fetch_locked(struct db_context *db,
+ TALLOC_CTX *mem_ctx,
+ TDB_DATA key)
+{
+ return dbwrap_fetch_locked_internal(
+ db, mem_ctx, key,
+ db->try_fetch_locked
+ ? db->try_fetch_locked : db->fetch_locked);
+}
+
struct dbwrap_fetch_state {
TALLOC_CTX *mem_ctx;
TDB_DATA data;
diff --git a/source3/lib/dbwrap/dbwrap.h b/source3/lib/dbwrap/dbwrap.h
index 386a9fa2a4..9981b6dfd9 100644
--- a/source3/lib/dbwrap/dbwrap.h
+++ b/source3/lib/dbwrap/dbwrap.h
@@ -34,6 +34,9 @@ NTSTATUS dbwrap_record_delete(struct db_record *rec);
struct db_record *dbwrap_fetch_locked(struct db_context *db,
TALLOC_CTX *mem_ctx,
TDB_DATA key);
+struct db_record *dbwrap_try_fetch_locked(struct db_context *db,
+ TALLOC_CTX *mem_ctx,
+ TDB_DATA key);
NTSTATUS dbwrap_delete(struct db_context *db, TDB_DATA key);
NTSTATUS dbwrap_store(struct db_context *db, TDB_DATA key,
diff --git a/source3/lib/dbwrap/dbwrap_cache.c b/source3/lib/dbwrap/dbwrap_cache.c
index 43c85f7b09..ded85258a3 100644
--- a/source3/lib/dbwrap/dbwrap_cache.c
+++ b/source3/lib/dbwrap/dbwrap_cache.c
@@ -194,6 +194,7 @@ struct db_context *db_open_cache(TALLOC_CTX *mem_ctx,
dbwrap_cache_validate(ctx);
db->fetch_locked = dbwrap_cache_fetch_locked;
+ db->try_fetch_locked = NULL;
db->traverse = dbwrap_cache_traverse;
db->traverse_read = dbwrap_cache_traverse_read;
db->get_seqnum = dbwrap_cache_get_seqnum;
diff --git a/source3/lib/dbwrap/dbwrap_ctdb.c b/source3/lib/dbwrap/dbwrap_ctdb.c
index 47d5dc6929..fe2af3609c 100644
--- a/source3/lib/dbwrap/dbwrap_ctdb.c
+++ b/source3/lib/dbwrap/dbwrap_ctdb.c
@@ -1028,13 +1028,15 @@ static bool db_ctdb_own_record(TDB_DATA ctdb_data, bool read_only)
static struct db_record *fetch_locked_internal(struct db_ctdb_ctx *ctx,
TALLOC_CTX *mem_ctx,
- TDB_DATA key)
+ TDB_DATA key,
+ bool tryonly)
{
struct db_record *result;
struct db_ctdb_rec *crec;
NTSTATUS status;
TDB_DATA ctdb_data;
int migrate_attempts = 0;
+ int lockret;
if (!(result = talloc(mem_ctx, struct db_record))) {
DEBUG(0, ("talloc failed\n"));
@@ -1072,7 +1074,10 @@ again:
TALLOC_FREE(keystr);
}
- if (tdb_chainlock(ctx->wtdb->tdb, key) != 0) {
+ lockret = tryonly
+ ? tdb_chainlock_nonblock(ctx->wtdb->tdb, key)
+ : tdb_chainlock(ctx->wtdb->tdb, key);
+ if (lockret != 0) {
DEBUG(3, ("tdb_chainlock failed\n"));
TALLOC_FREE(result);
return NULL;
@@ -1098,6 +1103,12 @@ again:
tdb_chainunlock(ctx->wtdb->tdb, key);
talloc_set_destructor(result, NULL);
+ if (tryonly && (migrate_attempts != 0)) {
+ DEBUG(5, ("record migrated away again\n"));
+ TALLOC_FREE(result);
+ return NULL;
+ }
+
migrate_attempts += 1;
DEBUG(10, ("ctdb_data.dptr = %p, dmaster = %u (%u) %u\n",
@@ -1163,7 +1174,25 @@ static struct db_record *db_ctdb_fetch_locked(struct db_context *db,
return db_ctdb_fetch_locked_persistent(ctx, mem_ctx, key);
}
- return fetch_locked_internal(ctx, mem_ctx, key);
+ return fetch_locked_internal(ctx, mem_ctx, key, false);
+}
+
+static struct db_record *db_ctdb_try_fetch_locked(struct db_context *db,
+ TALLOC_CTX *mem_ctx,
+ TDB_DATA key)
+{
+ struct db_ctdb_ctx *ctx = talloc_get_type_abort(db->private_data,
+ struct db_ctdb_ctx);
+
+ if (ctx->transaction != NULL) {
+ return db_ctdb_fetch_locked_transaction(ctx, mem_ctx, key);
+ }
+
+ if (db->persistent) {
+ return db_ctdb_fetch_locked_persistent(ctx, mem_ctx, key);
+ }
+
+ return fetch_locked_internal(ctx, mem_ctx, key, true);
}
/*
@@ -1559,6 +1588,7 @@ struct db_context *db_open_ctdb(TALLOC_CTX *mem_ctx,
result->private_data = (void *)db_ctdb;
result->fetch_locked = db_ctdb_fetch_locked;
+ result->try_fetch_locked = db_ctdb_try_fetch_locked;
result->parse_record = db_ctdb_parse_record;
result->traverse = db_ctdb_traverse;
result->traverse_read = db_ctdb_traverse_read;
diff --git a/source3/lib/dbwrap/dbwrap_file.c b/source3/lib/dbwrap/dbwrap_file.c
index a8a31e3750..ebe768528b 100644
--- a/source3/lib/dbwrap/dbwrap_file.c
+++ b/source3/lib/dbwrap/dbwrap_file.c
@@ -367,6 +367,7 @@ struct db_context *db_open_file(TALLOC_CTX *mem_ctx,
result->private_data = ctx;
result->fetch_locked = db_file_fetch_locked;
+ result->try_fetch_locked = NULL;
result->traverse = db_file_traverse;
result->traverse_read = db_file_traverse;
result->persistent = ((tdb_flags & TDB_CLEAR_IF_FIRST) == 0);
diff --git a/source3/lib/dbwrap/dbwrap_private.h b/source3/lib/dbwrap/dbwrap_private.h
index 111f02dc6b..f95e305a00 100644
--- a/source3/lib/dbwrap/dbwrap_private.h
+++ b/source3/lib/dbwrap/dbwrap_private.h
@@ -36,6 +36,9 @@ struct db_context {
struct db_record *(*fetch_locked)(struct db_context *db,
TALLOC_CTX *mem_ctx,
TDB_DATA key);
+ struct db_record *(*try_fetch_locked)(struct db_context *db,
+ TALLOC_CTX *mem_ctx,
+ TDB_DATA key);
int (*traverse)(struct db_context *db,
int (*f)(struct db_record *rec,
void *private_data),
diff --git a/source3/lib/dbwrap/dbwrap_rbt.c b/source3/lib/dbwrap/dbwrap_rbt.c
index 4fbb0bc1a0..95cd3e82e8 100644
--- a/source3/lib/dbwrap/dbwrap_rbt.c
+++ b/source3/lib/dbwrap/dbwrap_rbt.c
@@ -426,6 +426,7 @@ struct db_context *db_open_rbt(TALLOC_CTX *mem_ctx)
}
result->fetch_locked = db_rbt_fetch_locked;
+ result->try_fetch_locked = NULL;
result->traverse = db_rbt_traverse;
result->traverse_read = db_rbt_traverse;
result->get_seqnum = db_rbt_get_seqnum;
diff --git a/source3/lib/dbwrap/dbwrap_tdb.c b/source3/lib/dbwrap/dbwrap_tdb.c
index 46d6cdb8d1..ffad39bed8 100644
--- a/source3/lib/dbwrap/dbwrap_tdb.c
+++ b/source3/lib/dbwrap/dbwrap_tdb.c
@@ -101,20 +101,13 @@ static int db_tdb_fetchlock_parse(TDB_DATA key, TDB_DATA data,
return 0;
}
-static struct db_record *db_tdb_fetch_locked(struct db_context *db,
- TALLOC_CTX *mem_ctx, TDB_DATA key)
+static struct db_record *db_tdb_fetch_locked_internal(
+ struct db_context *db, TALLOC_CTX *mem_ctx, TDB_DATA key)
{
struct db_tdb_ctx *ctx = talloc_get_type_abort(db->private_data,
struct db_tdb_ctx);
struct tdb_fetch_locked_state state;
- db_tdb_log_key("Locking", key);
-
- if (tdb_chainlock(ctx->wtdb->tdb, key) != 0) {
- DEBUG(3, ("tdb_chainlock failed\n"));
- return NULL;
- }
-
state.mem_ctx = mem_ctx;
state.result = NULL;
@@ -140,6 +133,35 @@ static struct db_record *db_tdb_fetch_locked(struct db_context *db,
return state.result;
}
+static struct db_record *db_tdb_fetch_locked(
+ struct db_context *db, TALLOC_CTX *mem_ctx, TDB_DATA key)
+{
+ struct db_tdb_ctx *ctx = talloc_get_type_abort(db->private_data,
+ struct db_tdb_ctx);
+
+ db_tdb_log_key("Locking", key);
+ if (tdb_chainlock(ctx->wtdb->tdb, key) != 0) {
+ DEBUG(3, ("tdb_chainlock failed\n"));
+ return NULL;
+ }
+ return db_tdb_fetch_locked_internal(db, mem_ctx, key);
+}
+
+static struct db_record *db_tdb_try_fetch_locked(
+ struct db_context *db, TALLOC_CTX *mem_ctx, TDB_DATA key)
+{
+ struct db_tdb_ctx *ctx = talloc_get_type_abort(db->private_data,
+ struct db_tdb_ctx);
+
+ db_tdb_log_key("Trying to lock", key);
+ if (tdb_chainlock_nonblock(ctx->wtdb->tdb, key) != 0) {
+ DEBUG(3, ("tdb_chainlock_nonblock failed\n"));
+ return NULL;
+ }
+ return db_tdb_fetch_locked_internal(db, mem_ctx, key);
+}
+
+
static int db_tdb_exists(struct db_context *db, TDB_DATA key)
{
struct db_tdb_ctx *ctx = talloc_get_type_abort(
@@ -373,6 +395,7 @@ struct db_context *db_open_tdb(TALLOC_CTX *mem_ctx,
}
result->fetch_locked = db_tdb_fetch_locked;
+ result->try_fetch_locked = db_tdb_try_fetch_locked;
result->traverse = db_tdb_traverse;
result->traverse_read = db_tdb_traverse_read;
result->parse_record = db_tdb_parse;