"This series adds more information (i.e. keys and tombstones) to the
query result digest in order to ensure correctness and increase the
chances of early detection of disagreement between replicas.
The digest is no longer computed by hashing query::result but build
using the query result builder. That is necessary since the query
result itself doesn't contain all information required to compute
the digest. Another consequence of this is that now replicas asked
for a result need to send both the result and the digest to
the coordinator as it won't be able to compute the digest itself.
Unfortunately, these patches change our on wire communication:
1) hash computation is different
2) format of query::result is changed (and it is made non-final)
Fixes #182."
This patch makes sure that every time we need to create a new generation number -
the very first step in the creation of a new SSTable, the respective CF is already
initialized and populated. Failure to do so can lead to data being overwritten.
Extensive details about why this is important can be found
in Scylla's Github Issue #1014
Nothing should be writing to SSTables before we have the chance to populate the
existing SSTables and calculate what should the next generation number be.
However, if that happens, we want to protect against it in a way that does not
involve overwriting existing tables. This is one of the ways to do it: every
column family starts in an unwriteable state, and when it can finally be written
to, we mark it as writeable.
Note that this *cannot* be a part of add_column_family. That adds a column family
to a db in memory only, and if anybody is about to write to a CF, that was most
likely already called. We need to call this explicitly when we are sure we're ready
to issue disk operations safely.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
We are no longer using the in_flight_seals gate, but forgot to remove it.
To guarantee that all seal operations will have finished when we're done,
we are using the memtable_flush_queue, which also guarantees order. But
that gate was never removed.
The FIXME code should also be removed, since such interface does exist now.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
We already have a function that wraps this, re-use it. This FIXME is still
relevant, so just move it there. Let's not lose it.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
We use memory usage as a threshold these days, and nowhere is _mutation_count
checked. Get rid of it.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Store the "incremental_backups" configuration value in the database
class (and use it when creating a keyspace::config) in order to be
able to modify it in runtime.
Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
To report disk usage, scylla was only taking into account size of
sstable data component. Other components such as index and filter
may be relatively big too. Therefore, 'nodetool status' would
report an innacurate disk usage. That can be fixed by taking into
account size of all sstable components.
Fixes#943.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <08453585223570006ac4d25fe5fb909ad6c140a5.1456762244.git.raphaelsc@scylladb.com>
Fixes#934 - faulty assert in discard_sstables
run_with_compaction_disabled clears out a CF from compaction
mananger queue. discard_sstables wants to assert on this, but looks
at the wrong counters.
pending_compactions is an indicator on how much interested parties
want a CF compacted (again and again). It should not be considered
an indicator of compactions actually being done.
This modifies the usage slightly so that:
1.) The counter is always incremented, even if compaction is disallowed.
The counters value on end of run_with_compaction_disabled is then
instead used as an indicator as to whether a compaction should be
re-triggered. (If compactions finished, it will be zero)
2.) Document the use and purpose of the pending counter, and add
method to re-add CF to compaction for r_w_c_d above.
3.) discard_sstables now asserts on the right things.
Message-Id: <1456332824-23349-1-git-send-email-calle@scylladb.com>
Fixes#937
In fixing #884, truncation not truncating memtables properly,
time stamping in truncate was made shard-local. This however
breaks the snapshot logic, since for all shards in a truncate,
the sstables should snapshot to the same location.
This patch adds a required function argument to truncate (and
by extension drop_column_family) that produces a time stamp in
a "join" fashion (i.e. same on all shards), and utilizes the
joinpoint type in caller to do so.
Message-Id: <1456332856-23395-2-git-send-email-calle@scylladb.com>
Avi says:
"Something like unordered_set<unsigned long> is error prone, because ints
tend to mix up (also, need to use a sized type, unsigned long varies among
machines)."
With that in mind, it's better if we keep track of compacting sstables in
a unordered_set<shared_sstable>.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <249f0fd4cfcf786cf3c37a79978f7743d07f48ad.1455120811.git.raphaelsc@scylladb.com>
Fixes#884
Time stamps for truncation must be generated after flush, either by
splitting the truncate into two (or more) for-each-shard operations,
or simply by doing time stamping per shard (this solution).
We generate TS on each shard after flushing, and then rely on the
actual stored value to be the highest time point generated.
This should however, from batch replay point of view, be functionally
equivalent. And not a problem.
SSTables already have a priority argument wired to their read path. However,
most of our reads do not call that interface directly, but employ the services
of a mutation reader instead.
Some of those readers will be used to read through a mutation_source, and those
have to patched as well.
Right now, whenever we need to pass a class, we pass Seastar's default priority
class.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Compaction manager was initially created at utils because it was
more generic, and wasn't only intended for compaction.
It was more like a task handler based on futures, but now it's
only intended to manage compaction tasks, and thus should be
moved elsewhere. /sstables is where compaction code is located.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Cleanup is a procedure that will discard irrelevant keys from
all sstables of a column family, thus saving disk space.
Scylla will clean up a sstable by using compaction code, in
which this sstable will be the only input used.
Compaction manager was changed to become aware of cleanup, such
that it will be able to schedule cleanup requests and also know
how to handle them properly.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
The implementation is about storing generation of compacting sstables
in an unordered set per column family, so before strategy is called,
compaction manager will filter out compacting sstables.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Currently, compaction strategy is the responsible for both getting the
sstables selected for compaction and running compaction.
Moving the code that runs compaction from strategy to manager is a big
improvement, which will also make possible for the compaction manager
to keep track of which sstables are being compacted at a moment.
This change will also be needed for cleanup and concurrent compaction
on the same column family.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
That code will be used by column family cleanup, so let's put
that code into a function. This change also improves the code
readability.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Replicates https://issues.apache.org/jira/browse/CASSANDRA-7910 :
"Prepare a statement with a wildcard in the select clause.
2. Alter the table - add a column
3. execute the prepared statement
Expected result - get all the columns including the new column
Actual result - get the columns except the new column"
There is one current schema for given column_family. Entries in
memtables and cache can be at any of the previous schemas, but they're
always upgraded to current schema on access.
The intent is to make data returned by queries always conform to a
single schema version, which is requested by the client. For CQL
queries, for example, we want to use the same schema which was used to
compile the query. The other node expects to receive data conforming
to the requested schema.
Interface on shard level accepts schema_ptr, across nodes we use
table_schema_version UUID. To transfer schema_ptr across shards, we
use global_schema_ptr.
Because schema is identified with UUID across nodes, requestors must
be prepared for being queried for the definition of the schema. They
must hold a live schema_ptr around the request. This guarantees that
schema_registry will always know about the requested version. This is
not an issue because for queries the requestor needs to hold on to the
schema anyway to be able to interpret the results. But care must be
taken to always use the same schema version for making the request and
parsing the results.
Schema requesting across nodes is currently stubbed (throws runtime
exception).
Schema is tracked in memtable and cache per-entry. Entries are
upgraded lazily on access. Incoming mutations are upgraded to table's
current schema on given shard.
Mutating nodes need to keep schema_ptr alive in case schema version is
requested by target node.
service::storage_service::clear_snapshot() was built around _db.local()
calls so it makes more sense to move its code into the 'database' class
instead of calling _db.local().bla_bla() all the time.
Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
"When a node gain or regain responsibility for certain token ranges, streaming
will be performed, upon receiving of the stream data, the row cache
is invalidated for that range.
Refs #484."
The add interface of the estimated histogram is confusing as it is not
clear what units are used.
This patch removes the general add method and replace it with a add_nano
that adds nanoseconds or add that gets duration.
To be compatible with origin, nanoseconds vales are translated to
microseconds.
When analyzing a recent performance issue, I found helpful to keep track of
the amount of memtables that are currently in flight, as well as how much memory
they are consuming in the system.
Although those are memtable statistics, I am grouping them under the "cf_stats"
structure: being the column family a central piece of the puzzle, it is reasonable
to assume that a lot of metrics about it would be potentially welcome in the future.
Note that we don't want to reuse the "stats" structure in the column family: for once,
the fields not always map precisely (pending flushes, for instance, only tracks explicit
flushes), and also the stats structure is a lot more complex than we need.
Signed-off-by: Glauber Costa <glommer@scylladb.com>
Get initial tokens specified by the initial_token in scylla.conf.
E.g.,
--initial-token "-1112521204969569328,1117992399013959838"
--initial-token "1117992399013959838"
It can be multiple tokens split by comma.
"The snapshots API need to expose GET methods so people can
query information on them. Now that taking snapshots is supported,
this relatively simple series implement get_snapshot_details, a
column family method, and wire that up through the storage_service."
"This patchset implements load_new_sstables, allowing one to move tables inside the
data directory of a CF, and then call "nodetool refresh" to start using them.
Keep in mind that for Cassandra, this is deemed an unsafe operation:
https://issues.apache.org/jira/browse/CASSANDRA-6245
It is still for us something we should not recommend - unless the CF is totally
empty and not yet used, but we can do a much better job in the safety front.
To guarantee that, the process works in four steps:
1) All writes to this specific column family are disabled. This is a horrible thing to
do, because dirty memory can grow much more than desired during this. Throughout out
this implementation, we will try to keep the time during which the writes are disabled
to its bare minimum.
While disabling the writes, each shard will tell us about the highest generation number
it has seen.
2) We will scan all tables that we haven't seen before. Those are any tables found in the
CF datadir, that are higher than the highest generation number seen so far. We will link
them to new generation numbers that are sequential to the ones we have so far, and end up
with a new generation number that is returned to the next step
3) The generation number computed in the previous step is now propagated to all CFs, which
guarantees that all further writes will pick generation numbers that won't conflict with
the existing tables. Right after doing that, the writes are resumed.
4) The tables we found in step 2 are passed on to each of the CFs. They can now load those
tables while operations to the CF proceed normally."
This series adds a histogrm to the column family for live scanned and
tombstone scaned.
It expose those histogram via the API instead of the stub implmentation,
currently exist.
The implementation update of the histogram will be added in a different
series.
Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
CF-level code to load new SSTables. There isn't really a lot of complication
here. We don't even need to repopulate the entire SSTable directory: by
requiring that the external service who is coordinating this tell us explicitly
about the new SSTables found in the scan process, we can just load them
specifically and add them to the SSTable map.
All new tables will start their lifes as shared tables, and will be unshared
if it is possible to do so: this all happens inside add_sstable and there isn't
really anything special in this front.
Signed-off-by: Glauber Costa <glommer@scylladb.com>
Before loading new SSTables into the node, we need to make sure that their
generation numbers are sequential (at least if we want to follow Cassandra's
footsteps here).
Note that this is unsafe by design. More information can be found at:
https://issues.apache.org/jira/browse/CASSANDRA-6245
However, we can already to slightly better in two ways:
Unlike Cassandra, this method takes as a parameter a generation number. We
will not touch tables that are before that number at all. That number must be
calculated from all shards as the highest generation number they have seen themselves.
Calling load_new_sstables in the absence of new tables will therefore do nothing,
and will be completely safe.
It will also return the highest generation number found after the reshuffling
process. New writers should start writing after that. Therefore, new tables
that are created will have a generation number that is higher than any of this,
and will therefore be safe.
Signed-off-by: Glauber Costa <glommer@scylladb.com>
During certain operations we need to stop writing SSTables. This is needed when
we want to load new SSTables into the system. They will have to be scanned by all
shards, agreed upon, and in most cases even renamed. Letting SSTables be written
at that point makes it inherently racy - specially with the rename.
Signed-off-by: Glauber Costa <glommer@scylladb.com>
Avoid using long for it, and let's use a fixed size instead. Let's do signed
instead of unsigned to avoid upsetting any code that we may have converted.
Signed-off-by: Glauber Costa <glommer@scylladb.com>
