Currently, whole topology description for CDC is stored in a single row.
This means that for a large cluster of strong machines (say 100 nodes 64
cpus each), the size of the topology description can reach 32MB.
This causes multiple problems. First of all, there's a hard limit on
mutation size that can be written to Scylla. It's related to commit log
block size which is 16MB by default. Mutations bigger than that can't be
saved. Moreover, such big partitions/rows cause reactor stalls and
negatively influence latency of other requests.
This patch limits the size of topology description to about 4MB. This is
done by reducing the number of CDC streams per vnode and can lead to CDC
data not being fully colocated with Base Table data on shards. It can
impact performance and consistency of data.
This is just a quick fix to make it easily backportable. A full solution
to the problem is under development.
For more details see #7961, #7993 and #7985.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Closes#8048
* github.com:scylladb/scylla:
cdc: Limit size of topology description
cdc: Extract create_stream_ids from topology_description_generator
Currently, whole topology description for CDC is stored in a single row.
This means that for a large cluster of strong machines (say 100 nodes 64
cpus each), the size of the topology description can reach 32MB.
This causes multiple problems. First of all, there's a hard limit on
mutation size that can be written to Scylla. It's related to commit log
block size which is 16MB by default. Mutations bigger than that can't be
saved. Moreover, such big partitions/rows cause reactor stalls and
negatively influence latency of other requests.
This patch limits the size of topology description to about 4MB. This is
done by reducing the number of CDC streams per vnode and can lead to CDC
data not being fully colocated with Base Table data on shards. It can
impact performance and consistency of data.
This is just a quick fix to make it easily backportable. A full solution
to the problem is under development.
For more details see #7961, #7993 and #7985.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Commit aab6b0ee27 introduced the
controversial new IMR format, which relied on a very template-heavy
infrastructure to generate serialization and deserialization code via
template meta-programming. The promise was that this new format, beyond
solving the problems the previous open-coded representation had (working
on linearized buffers), will speed up migrating other components to this
IMR format, as the IMR infrastructure reduces code bloat, makes the code
more readable via declarative type descriptions as well as safer.
However, the results were almost the opposite. The template
meta-programming used by the IMR infrastructure proved very hard to
understand. Developers don't want to read or modify it. Maintainers
don't want to see it being used anywhere else. In short, nobody wants to
touch it.
This commit does a conceptual revert of
aab6b0ee27. A verbatim revert is not
possible because related code evolved a lot since the merge. Also, going
back to the previous code would mean we regress as we'd revert the move
to fragmented buffers. So this revert is only conceptual, it changes the
underlying infrastructure back to the previous open-coded one, but keeps
the fragmented buffers, as well as the interface of the related
components (to the extent possible).
Fixes: #5578
1. It's unused since cbe510d1b8
2. It's unsafe to keep a reference to token_metadata&
potentially across yield points.
The higher-level motivation is to make
storage_service::get_token_metadata() private so we
can control better how it's used.
For cdc, if the token_metadata is going to be needed
to the future, it'd be better get it from
db_context::_proxy.get_token_metadata_ptr().
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20201213162351.52224-2-bhalevy@scylladb.com>
There are 3 callers of this helper (cdc, migration manager and tests)
and all of them already have the database object at hands.
The argument will be used by next patch to remove call for global
storage proxy instance from make_update_indices_mutations.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
When a row was inserted into a table with no regular columns, and no
such row existed in the first place, postimage would not be produced.
Fix this.
Fixes#7716.
Closes#7723
Now that CDC is GA, it should be enabled in all the tests by default.
To achieve that the PR adds a special db::config::add_cdc_extension()
helper which is used in cql_test_envm to make sure CDC is usable in
all the tests that use cql_test_env.m As a result, cdc_tests can be
simplified.
Finally, some trailing whitespaces are removed from cdc_tests.
Tests: unit(dev)
Closes#7657
* github.com:scylladb/scylla:
cdc: Remove trailing whitespaces from cdc_tests
cdc: Remove mk_cdc_test_config from tests
config: Add add_cdc_extension function for testing
cdc: Add missing includes to cdc_extension.hh
The meaning of the parameter changes from defining whether the function
is called in testing environment to deciding whether a delay should be
added to a timestamp of a newly created CDC generation.
This is a preparation for improvement in the following patch that does
not always add delay to every node but only to non-first node.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Following patch enables CDC by default and this means CDC has to work
will all the clusters now.
There is a problematic case when existing cluster with no CDC support
is stopped, all the binaries are updated to newer version with
CDC enabled by default. In such case, nodes know that they are already
members of the cluster but they can't find any CDC generation so they
will try to create one. This creation may fail due to lack of QUORUM
for the write.
Before this patch such situation would lead to node failing to start.
After the change, the node will start but CDC generation will be
missing. This will mean CDC won't be able to work on such cluster before
nodetool checkAndRepairCdcStreams is run to fix the CDC generation.
We still fail to bootstrap if the creation of CDC generation fails.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Fixes#7435
Adds an "eor" (end-of-record) column to cdc log. This is non-null only on
last-in-timestamp group rows, i.e. end of a singular source "event".
A client can use this as a shortcut to knowing whether or not he has a
full cdc "record" for a given source mutation (single row change).
Closes#7436
Clang does not yet implement p1091r3, which allows lambdas
to capture structured bindings. To accomodate it, don't
use structured bindings for variables that are later
captured.
Fixes#7345Fixes#7346
Do a more efficient collection skip when doing paging, instead of
iterating the full sets.
Ensure some semblance of sanity in the parent-child relationship
between shards by ensuring token order sorting and finding the
apparent previous ID coverting the approximate range of new gen.
Fix endsequencenumber generation by looking at whether we are
last gen or not, instead of the (not filled in) 'expired' column.
Due to a bug, clang does not decay a type to a reference, failing
the concept evaluation on correct input. Add parentheses to force
it to decay the type.
Commit a6ad70d3da changed the format of
stream IDs: the lower 8 bytes were previously generated randomly, now
some of them have semantics. In particular, the least significant byte
contains a version (stream IDs might evolve with further releases).
This is a backward-incompatible change: the code won't properly handle
stream IDs with all lower 8 bytes generated randomly. To protect us from
subtle bugs, the code has an assertion that checks the stream ID's
version.
This means that if an experimental user used CDC before the change and
then upgraded, they might hit the assertion when a node attempts to
retrieve a CDC generation with old stream IDs from the CDC description
tables and then decode it.
In effect, the user won't even be able to start a node.
Similarly as with the case described in
d89b7a0548, the simplest fix is to rename
the tables. This fix must get merged in before CDC goes out of
experimental.
Now, if the user upgrades their cluster from a pre-rename version, the
node will simply complain that it can't obtain the CDC generation
instead of preventing the cluster from working. The user will be able to
use CDC after running checkAndRepairCDCStreams.
Since a new table is added to the system_distributed keyspace, the
cluster's schema has changed, so sstables and digests need to be
regenerated for schema_digest_test.
Refs #7095
CDC delta!=full both relied on post-filtering
to remove generated log row and/or cells. This is inefficient.
Instead, simply check if the data should be created in the
visitors.
v2:
* Fixed delta logs rows created (empty) even when delta == off
v3:
* Killed delta == off
v4:
* Move checks into (const) member var(s)
Fixes#7128
CDC logs are not useful without at least delta_mode==keys, since
pre/post image data has no info on _what_ was actually done to
base table in source mutation.
Fixes#7119Fixes#7120
If preimage select came up empty - i.e. the row did not exist, either
due to never been created, or once delete, we should not bother creating
a log preimage row for it. Esp. since it makes it harder to interpret the
cdc log.
If an operation in a cdc batch did a row delete (ranged, ck, etc), do
not generate postimage data, since the row does no longer exist.
Note that we differentiate deleting all (non-pk/ck) columns from actual
row delete.
Fixes#6900
Clustered range deletes did not clear out the "row_states" data associated
with affected rows (might be many).
Adds a sweep through and erases relevant data. Since we do pre- and
postimage in "order", this should only affect postimage.
Use a different getter for a token_metadata& that
may be changed so we can better synchronize readers
and writers of token_metadata and eventually allow
them to yield in asynchronous loops.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
This is an abstraction for walking over mutations created by a write
coordinator, deconstructing them into ,,atomic'' pieces (,,changes''),
and consuming these pieces.
Read the big comment in cdc/change_visitor.hh for more details.
Before this patch, modifying cdc/cdc_options.hh required recompiling 264
source files. This is because this header file was included by a couple
other header files - most notably schema.hh, where a forward declaration
would have been enough. Only the handful of source files which really
need to access the CDC options should include "cdc/cdc_options.hh" directly.
After this patch, modifying cdc/cdc_options.hh requires only 6 source files
to be recompiled.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20200813070631.180192-1-nyh@scylladb.com>
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
`count` function was often used in various ways.
`contains` does not only express the intend of the code better but also
does it in more unified way.
This commit replaces all the occurences of the `count` with the
`contains`.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <b4ef3b4bc24f49abe04a2aba0ddd946009c9fcb2.1597314640.git.piotr@scylladb.com>
Makes the "preimage" option for cdc non-binary, i.e. it can now
be "true"/"on", "false"/"off" or "full. The two former behaving like
previously, the latter obviously including all columns in pre image.
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
the code pattern looked like:
<collection>.find(<element>) != <collection>.end()
In C++20 the same can be expressed with:
<collection>.contains(<element>)
This is not only more concise but also expresses the intend of the code
more clearly.
This commit replaces all the occurences of the old pattern with the new
approach.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <f001bbc356224f0c38f06ee2a90fb60a6e8e1980.1597132302.git.piotr@scylladb.com>
Fixes#6948
Changes the stream_id format from
<token:64>:<rand:64>
to
<token:64>:<rand:38><index:22><version:4>
The code will attempt to assert version match when
presented with a stored id (i.e. construct from bytes).
This means that ID:s created by previous (experimental)
versions will break.
Moves the ID encoding fully into the ID class, and makes
the code path private for the topology generation code
path.
Removes some superflous accessors but adds accessors for
token, version and index. (For alternator etc).
Merged pull request https://github.com/scylladb/scylla/pull/6910
by Wojciech Mitros:
This patch enables selecting more than 2^32 rows from a table. The change
becomes active after upgrading whole cluster - until then old limits are
used.
Tested reading 4.5*10^9 rows from a virtual table, manually upgrading a
cluster with ccm and performing cql SELECT queries during the upgrade,
ran unit tests in dev mode and cql and paging dtests.
tests: add large paging state tests
increase the maximum size of query results to 2^64
This commit takes out some responsibilities of `cdc::transformer`
(which is currently a big ball of mud) into a separate class.
This class is a simple abstraction for creating entries in a CDC log
mutation.
Low-level calls to the mutation API (such as `set_cell`) inside
`cdc::transformer` were replaced by higher-level calls to the builder
abstraction, removing some duplication of logic.
Refs #6864
When booting a clean scylla, CDC stream ID:s will not be availble until
a n*ring delay time period has passed. Before this, writing to a CDC
enabled table will fail hard.
For alternator (and its tests), we can report the stream(s) for tables as not yet
available (ENABLING) until such time as id:s are
computed.
v2:
* Keep storage service ref in executor
Currently, we cannot select more than 2^32 rows from a table because we are limited by types of
variables containing the numbers of rows. This patch changes these types and sets new limits.
The new limits take effect while selecting all rows from a table - custom limits of rows in a result
stay the same (2^32-1).
In classes which are being serialized and used in messaging, in order to be able to process queries
originating from older nodes, the top 32 bits of new integers are optional and stay at the end
of the class - if they're absent we assume they equal 0.
The backward compatibility was tested by querying an older node for a paged selection, using the
received paging_state with the same select statement on an upgraded node, and comparing the returned
rows with the result generated for the same query by the older node, additionally checking if the
paging_state returned by the upgraded node contained new fields with correct values. Also verified
if the older node simply ignores the top 32 bits of the remaining rows number when handling a query
with a paging_state originating from an upgraded node by generating and sending such a query to
an older node and checking the paging_state in the reply(using python driver).
Fixes#5101.
Merged pull request https://github.com/scylladb/scylla/pull/6914
by By Juliusz Stasiewicz:
The goal is to have finer control over CDC "delta" rows, i.e.:
disable them totally (mode off);
record only base PK+CK columns (mode keys);
make them behave as usual (mode full, default).
The editing of log rows is performed at the stage of finishing CDC mutation.
Fixes#6838
tests: Added CQL test for `delta mode`
cdc: Implementations of `delta_mode::off/keys`
cdc: Infrastructure for controlling `delta_mode`
This field will replace max size which is currently passed once per
established rpc connection via the CLIENT_ID verb and stored as an
auxiliary value on the client_info. For now it is unused, but we update
all sites creating a read command to pass the correct value to it. In the
next patch we will phase out the old max size and use this field to pass
max size on each verb instead.
The convenience constructor of read_command now has two integer
parameter next to each other. In the next patch we intend to add another
one. This is recipe for disaster, so to avoid mistakes this patch
converts these parameters to tagged integers. This makes sure callers
pass what they meant to pass. As a matter of fact, while fixing up
call-sites, I already found several ones passing `query::max_partitions`
to the `row_limit` parameter. No harm done yet, as
`query::max_partitions` == `query::max_rows` but this shows just how
easy it is to mix up parameters with the same type.
The goal is to have finer control over CDC "delta" rows, i.e.:
- disable them totally (mode `off`);
- record only PK+CK (mode `keys`);
- make them behave as usual (mode `full`, default).
This commit adds the necessary infrastructure to `cdc_options`.
If ring_delay == 0, something fishy is going on, e.g. single-node tests
are being performed. In this case we want the CDC generation to start
operating immediately. There is no need to wait until it propagates to
the cluster.
You should not use ring_delay == 0 in production.
Fixes https://github.com/scylladb/scylla/issues/6864.
It is legal for a user to create a table with name that has a
_scylla_cdc_log suffix. In such case, the table won't be treated as a
cdc log table, and does not require a corresponding base table to exist.
During refactoring done as a part of initial implemetation of of
Alternator streams (#6694), `is_log_for_some_table` started throwing
when trying to check a name like `X_scylla_cdc_log` when there was no
table with name `X`. Previously, it just returned false.
The exception originates inside `get_base_table`, which tries to return
the base table schema, not checking for its existence - which may throw.
It makes more sense for this function to return nullptr in such case (it
already does when provided log table name does not have the cdc log
suffix), so this patch adds an explicit check and returns nullptr when
necessary.
A similar oversight happened before (see #5987), so this patch also adds
a comment which explains why existence of `X_scylla_cdc_log` does not
imply existence of `X`.
Fixes: #6852
Refs: #5724, #5987
