loading_shared_values/loading_cache'es iterators interface is dangerous/fragile because
iterator doesn't "lock" the entry it points to and if there is a
preemption point between aquiring non-end() iterator and its
dereferencing the corresponding cache entry may had already got evicted (for
whatever reason, e.g. cache size constraints or expiration) and then
dereferencing may end up in a use-after-free and we don't have any
protection against it in the value_extractor_fn today.
And this is in addition to #8920.
So, instead of trying to fix the iterator interface this patch kills two
birds in a single shot: we are ditching the iterators interface
completely and return value_ptr from find(...) instead - the same one we
are returning from loading_cache::get_ptr(...) asyncronous APIs.
A similar rework is done to a loading_shared_values loading_cache is
based on: we drop iterators interface and return
loading_shared_values::entry_ptr from find(...) instead.
loading_cache::value_ptr already takes care of "lock"ing the returned value so that it
would relain readable even if it's evicted from the cache by the time
one tries to read it. And of course it also takes care of updating the
last read time stamp and moving the corresponding item to the top of the
MRU list.
Fixes#8920
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
Message-Id: <20210817222404.3097708-1-vladz@scylladb.com>
In order to implement service level cql queries, the queries objects
needs access to the service_level_controller object when processing.
This patch adds this access by embedding it into the query state object.
In order to accomplish the above the query processor object needs an
access to service_level_controller in order to instantiate the query state.
Message-Id: <68f5a7796068a49d9cd004f1cbf34bdf93b418bc.1609234193.git.sarna@scylladb.com>
The query processor sits upper than the migration manager,
in the services layering, it's started after and (will be)
stopped before the migration manager.
The migration manager is needed in schema altering statements
which are called with query processor argument. They will
later get the migration manager from the query processor.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Timeout config is now stored in each connection, so there's no point
in tracking it inside each query as well. This patch removes
timeout_config from query_options and follows by removing now
unnecessary parameters of many functions and constructors.
The `query_processor::query` method allowed internal paged queries.
However, it was quite limited, hardcoding a number of parameters:
consistency level, timeout config, page size.
This commit does the following improvements:
1. Rename `query` to `query_internal` to make it obvious that this API
is supposed to be used for internal queries only
2. Extend the method to take consistency level, timeout config, and page
size as parameters
3. Remove unused overloads of `query_internal`
4. Fix a bunch of typos / grammar issues in the docstring
Executing internal CQL queries needs to be done with caution,
since they were designed to be used mainly for local tables
and have very specific semantics wrt. propagating
schema changes. A short comment is added in order to prevent
future misuse of this interface.
This patch adds a new `LWT` flag to `cql3::prepared_metadata`.
That allows clients to clearly distinguish betwen lwt and
non-lwt statements without need to execute some custom parsing
logic (e.g. parsing the prepared query with regular expressions),
which is obviously quite fragile.
The feature is meant to be further utilized by client drivers
to use primary replicas consistently when dealing with conditional
statements.
Whether to use lwt optimization flag or not is handled by negotiation
procedure between scylla server and client library via SUPPORTED/STARTUP
messages (`LWT_ADD_METADATA_MARK` extension).
Tests: unit(dev, debug), manual testing with modified scylla/gocql driver
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Change CQL parsing routine to return std::unique_ptr
instead of seastar::shared_ptr.
This can help reduce redundant shared_ptr copies even further.
Make some supplementary changes necessary for this transition:
* Remove enabled_shared_from_this base class from the following
classes: truncate_statement, authorization_statement,
authentication_statement: these were previously constructing
prepared_statement instance in `prepare` method using
`shared_from_this`.
Make `prepare` methods implementation of inheriting classes
mirror implementation from other statements (i.e.
create a shallow copy of the object when prepairing into
`prepared_statement`; this could be further refactored
to avoid copies as much as possible).
* Remove unused fields in create_role_statement which led to
error while using compiler-generated copy ctor (copying
uninitialied bool values via ctor).
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
raw_cql_statement is a member of prepared_statement which
is not set in its constructor because prepared_statement
constructor has too many call sites inside cql_statement
hierarchy.
cql_statement and prepared_statement dependency form a
cycle and long term it obviously should be fixed.
As a quick fix to query processor tracing, consistently
assign raw_cql_statement in all prepared_statement
usage sites.
All internal execution always uses query text as a key in the
cache of internal prepared statements. There is no need
to publish API for executing an internal prepared statement object.
The folded execute_internal() calls an internal prepare() and then
internal execute().
execute_internal(cache=true) does exactly that.
Rename an overloaded function process() to execute_direct().
Execute direct is a common term for executing a statement
that was not previously prepared. See, for example
SQLExecuteDirect in ODBC/SQL CLI specification,
mysql_stmt_execute_direct() in MySQL C API or EXECUTE DIRECT
in Postgres XC.
query_processor is a central class, so reducing its includes
can reduce dependencies treewite. This patch removes includes
for parsed_statement, cf_statement, and untyped_result_set and
fixes up the rest of the tree to include what it lacks as a result
of these removals.
This patch breaks one (probably harmless but still) dependency
loop. The query_processor -> migration_manager -> storage_proxy
-> tracing -> query_processor.
The first link is not not needed, as the query_processor needs the
migration_manager purely to (ub)subscribe on notifications.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
_user cannot outlive client_state class instance, so there is no point
in holding it in shared_ptr.
Tested: debug test.py and dtest auth_test.py
Message-Id: <20191128131217.26294-5-gleb@scylladb.com>
query and for_each_cql_result accept a function that reads a row and
return a stop_iterator.
This implementation of those functions gets a function that returns a
future stop_iterator allowing preemption between calls.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Replace stdx::optional and stdx::string_view with the C++ std
counterparts.
Some instances of boost::variant were also replaced with std::variant,
namely those that called seastar::visit.
Scylla now requires GCC 8 to compile.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20190108111141.5369-1-duarte@scylladb.com>
query_processor uses storage_proxy to access data, and the local
database object to access replicated metadata. While it seems strange
that the database object is not used to access data, it is logical
when you consider that a sharded<database> only contain's this node's
data, not the cluster data.
Take advantage of this to replace sharded<database> with a single database
shard.
sprint() recently became more strict, throwing on sprint("%s", 5). Replace
with the more modern format().
Mechanically converted with https://github.com/avikivity/unsprint.
"
This patchset makes all users of query_processor specify their timeouts
explicitly, in preparation for the removal of
cql_statement::execute_internal() (whose main function was to override
timeouts).
"
* tag 'cql-explicit-timeouts/v1' of https://github.com/avikivity/scylla:
query_processor: require clients to specify timeout configuration
query_processor: un-default consistency level in make_internal_options
Like with the EXECUTE command avoid authorizing the same prepared
statement twice - this time in the context of processing the BATCH
command.
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
Add a cache that would store the checked weak pointer to already authorized prepared statements
and which key is a tuple of an authenticated_user and key of the prepared_statements_cache.
The entries will be held as long as the corresponding prepared statement is valid (cached)
and will be discarded with the period equal to the refresh period of the permissions cache.
Entries are also going to be discarded after 60 minutes if not used.
The purpose of this new cache is to save the lookup in the permissions cache for already authenticated
resource (whatever is needed to be authenticated for the particular prepared statement).
This is meant to improve the cache coherency as well (since we are going to look in a single cache
instead of two).
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
Remove implicit timeouts and replace with caller-specified timeouts.
This allows removing the ambiguity about what timeout a statement is
executed with, and allows removing cql_statement::execute_internal(),
which mostly overrode timeouts and consistency levels.
Timeout selection is now as follows:
query_processor::*_internal: infinite timeout, CL=ONE
query_processor::process(), execute(): user-specified consisistency level and timeout
All callers were adjusted to specify an infinite timeout. This can be
further adjusted later to use the "other" timeout for DCL and the
read or write timeout (as needed) for authentication in the normal
query path.
Note that infinite timeouts don't mean that the query will hang; as
soon as the failure detector decides that the node is down, RPC
responses will termiante with a failure and the query will fail.
Make the consistency level explicit in the caller in order to clarify
what is going on.
An "internal" query used to mean that it was accessing local tables,
so infinite timeouts and a consistency level of ONE were indicated,
but authentication accesses non-local tables so explicit consistency
level and timeouts are needed.
Since storage_proxy provides access to the entire cluster, a local shard
reference is sufficient. Adjust query_processor to store a reference to
just the local shard, rather than a seastar::sharded<storage_proxy> and
adjust callers.
This simplifies the code a little.
Message-Id: <20180415142656.25370-3-avi@scylladb.com>
"
The original motivation for the "utils: introduce a loading_shared_values" series was a hinted handoff work where
I needed an on-demand asynchronously loading key-value container (a replica address to a commitlog instance map).
It turned out that we already have the classes that do almost what I needed:
- utils::loading_cache
- sstables::shared_index_lists
Therefore it made sense to find a common ground, unify this functionality and reuse the code both in the classes above and in the
new hinted handoff code.
This series introduces the utils::loading_shared_values that generalizes the sstables::shared_index_lists
API on top of bi::unordered_set with the rehashing logic from the utils::loading_cache triggered by an addition
of an entry to the set (PATCH1).
Then it reworks the sstables::shared_index_lists and utils::loading_cache on top of the new class (PATCH2 and PATCH3).
PATCH4 optimizes the loading_cache for the long timer period use case.
But then we have discovered that we have another "customer" for the loading_cache. Apparently our prepared statements cache
had a birth flaw - it was unlimited in size - unless the corresponding keyspace and/or table are modified/dropped the entries
are never evicted. We clearly need to limit its size and it would also make sense to evict the cache entries that haven't been
used long enough.
This seems like a perfect match for a utils::loading_cache except for prepared statements don't need to be reloaded after
they are created.
Patches starting from PATCH5 are dealing with adding the utils::loading_cache the missing functionality (like making the "reloading"
conditional and adding the synchronous methods like find(key)) and then transitioning the CQL and Thrift prepared statements
caches to utils::loading_cache.
This also fixes #2474."
* 'evict_unused_prepared-v5' of https://github.com/vladzcloudius/scylla:
tests: loading_cache_test: initial commit
cql3::query_processor: implement CQL and Thrift prepared statements caches using cql3::prepared_statements_cache
cql3: prepared statements cache on top of loading_cache
utils::loading_cache: make the size limitation more strict
utils::loading_cache: added static_asserts for checking the callbacks signatures
utils::loading_cache: add a bunch of standard synchronous methods
utils::loading_cache: add the ability to create a cache that would not reload the values
utils::loading_cache: add the ability to work with not-copy-constructable values
utils::loading_cache: add EntrySize template parameter
utils::loading_cache: rework on top of utils::loading_shared_values
sstables::shared_index_list: use utils::loading_shared_values
utils: introduce loading_shared_values
Forward-declare untyped_result_set and untyped_result_set_row, and remove
the include from query_processor.hh.
Message-Id: <20170916170859.27612-3-avi@scylladb.com>
- Transition the prepared statements caches for both CQL and Trhift to the cql3::prepared_statements_cache class.
- Add the corresponding metrics to the query_processor:
- Evictions count.
- Current entries count.
- Current memory footprint.
Fixes#2474
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
Usually, internal queries are used for short queries. Sometimes though,
like in the case of get compaction history, there could be a large
amount of results. Without paging it will overload the system.
This patch adds the ability to use paging internally.
Using paging will be done explicitely, all the relevant information
would be store in an internal_query_state, that would hold both the
paging state but also the query so consecutive calls can be made.
To use paging use the query method with a function.
The function gets beside a statement and its parameters a function that
will be used for each of the returned rows.
For example if qp is a query_processor:
qp.query("SELECT * from system.compaction_history", [] (const cql3::untyped_result_set::row& row) {
....
// do something with row
...
return stop_iteration::no; // keep on reading
});
Will run the function on each of the compaction history table rows.
To stop the iteration, the function can return stop_iteration::yes.
- introcduced "seastarx.hh" header, which does a "using namespace seastar";
- 'net' namespace conflicts with seastar::net, renamed to 'netw'.
- 'transport' namespace conflicts with seastar::transport, renamed to
cql_transport.
- "logger" global variables now conflict with logger global type, renamed
to xlogger.
- other minor changes
Use seastar::checked_ptr<weak_ptr<pepared_statement>> instead of shared_ptr for passing prepared statements around.
This allows an easy tracking and handling of statements invalidation.
This implementation will throw an exception every time an invalidated
statement reference is dereferenced.
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
