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v16.0.0

vitessio/vitess

版本发布时间: 2023-02-28 23:15:28

vitessio/vitess最新发布版本:v21.0.0-rc2(2024-10-23 13:13:47)

Release of Vitess v16.0.0

Summary

Table of Contents

Known Issues

MySQL & Xtrabackup known issue

There is a known issue with MySQL's INSTANT DDL combined with Percona XtraBackup, that affects users of Vitess 16.0. The problem is described in https://docs.percona.com/percona-xtrabackup/8.0/em/instant.html, and the immediate impact is you may not be able to backup your database using XtraBackup under certain conditions.

As of MySQL 8.0.12, the default ALGORITHM for InnoDB's ALTER TABLE is INSTANT. In 8.0.12 only a small number of operations were eligible for INSTANT, but MySQL 8.0.29 added support for more common cases. Unfortunately, the changes in 8.0.29 affect XtraBackup as follows: if you ALTER TABLE in MySQL 8.0.29, and that ALTER is eligible for INSTANT DDL (e.g. add new table column), then as of that moment, XtraBackup is unable to backup that table, hence your entire database.

It is important to note that even if you then upgrade your MySQL server to, e.g. 8.0.32, the table still cannot be backed up.

Versions where XtraBackup is unable to backup such tables: MySQL 8.0.29 - 8.0.31. This does not apply to Percona Server flavor.

The issue is resolved with Percona XtraBackup 8.0.32 combined with MySQL 8.0.32.

You might be affected if:

A futures Vitess patch release v16.0.1 will address the issue via Online DDL migrations.

Mitigations

Workarounds

If you have already been affected, these are the options to be able to backup your database:

$ vtctldclient ApplySchema --skip_preflight --ddl_strategy "vitess" --sql "ALTER TABLE your_table ENGINE=InnoDB" your_keyspace

or

> SET @@ddl_strategy='vitess';
> ALTER TABLE your_table ENGINE=InnoDB;

VTTablet Restore Metrics

As part of the VTTablet Sidecar Schema Maintenance Refactor in v16.0.0, we dropped the local_metadata table from the sidecar database schema. This table was storing a couple of metrics related to restores from backup, which have now been lost. They have been re-introduced in v17.0.0 as metrics that can be accessed from /debug/vars.

The original issue can be found here.

Schema-initialization stuck on semi-sync ACKs while upgrading to v16.0.0

During upgrades from <= v15.x.x to v16.0.0, as part of PromoteReplica call, the schema-init realizes that there are schema diffs to apply and ends up writing to the database. The issue is that if semi-sync is enabled, all of these writes get blocked indefinitely. Eventually, PromoteReplica fails, and this fails the entire PRS call.

A fix for this issue was merged on release-16.0 in PR#13441, read the corresponding bug report to learn more.

This issue is fixed in v16.0.3 and later patch releases.

Broken downgrade from v17.x.x when super_read_only turned on by default

In v17.x.x super_read_only is turned on by default meaning that downgrading from v17 to v16.0.0 breaks due to init_db.sql needing write access.

This issue is fixed in >= v16.0.3 thanks to PR #13525

Major Changes

Breaking Changes

VTGate Advertised MySQL Version

Since Pull Request #11989, VTGate advertises MySQL version 8.0.30. This is a breaking change for clients that rely on the VTGate advertised MySQL version and still use MySQL 5.7. The users can set the mysql_server_version flag to advertise the correct version.

It is worth noting that the feature to avoid using reserved connections depends on the mysql_server_version CLI flag, which default value has been changed from 5.7.9-vitess to 8.0.30-vitess. We recommend that users running MySQL 5.7 set vtgate's mysql_server_version CLI flag to 5.7.9-vitess to prevent the queries from being unexpectedly rewritten.

Default MySQL version on Docker

The default major MySQL version used by our vitess/lite:latest image is going from 5.7 to 8.0. Additionally, the patch version of MySQL80 has been upgraded from 8.0.23 to 8.0.30. This change was brought by Pull Request #12252.

⚠️Upgrading to this release with vitess-operator

If you are using the vitess-operator and want to remain on MySQL 5.7, you are required to use the vitess/lite:v16.0.0-mysql57 Docker Image, otherwise the vitess/lite:v16.0.0 image will be on MySQL 80.

However, if you are running MySQL 8.0 on the vitess-operator, with for instance vitess/lite:v15.0.2-mysql80, considering that we are bumping the patch version of MySQL 80 from 8.0.23 to 8.0.30, you will have to manually upgrade:

  1. Add innodb_fast_shutdown=0 to your extra cnf in your YAML file.
  2. Apply this file.
  3. Wait for all the pods to be healthy.
  4. Then change your YAML file to use the new Docker Images (vitess/lite:v16.0.0, defaults to mysql80).
  5. Remove innodb_fast_shutdown=0 from your extra cnf in your YAML file.
  6. Apply this file.

<a id="flag-deletions-and-deprecations">Flag Deletions and Deprecations

VTCtld

With the removal of the vtctld UI, the following vtctld flags have been deprecated:

The following deprecated flags have also been removed:

MySQLCtld

The mysqlctl command-line client had some leftover (ignored) server flags after the v15 pflag work. Those unused flags have now been removed. If you are using any of the following flags with mysqlctl in your scripts or other tooling, they will need to be removed prior to upgrading to v16: --port --grpc_auth_static_client_creds --grpc_compression --grpc_initial_conn_window_size --grpc_initial_window_size --grpc_keepalive_time --grpc_keepalive_timeout

VTTablet

The following flags were removed in v16:

The flag --disable-replication-manager is deprecated and will be removed in a future release.

VTBackup

The VTBackup flag --backup_storage_hook has been removed, use one of the builtin compression algorithms or --external-compressor and --external-decompressor instead.

VTOrc

The flag --lock-shard-timeout has been deprecated. Please use the newly introduced --lock-timeout flag instead. More detail here.

lock-timeout and remote_operation_timeout Changes

Before the changes made in Pull Request #11881, the shard and keyspace locks used to be capped by the remote_operation_timeout. This is no longer the case and instead a new flag called lock-timeout is introduced. For backward compatibility, if lock-timeout is unspecified and remote_operation_timeout flag is provided, then its value will also be used for lock-timeout. The default value for remote_operation_timeout has also changed from 30 seconds to 15 seconds. The default for the new flag lock-timeout is 45 seconds.

During upgrades, if the users want to preserve the same behaviour as previous releases, then they should provide the remote_operation_timeout flag explicitly before upgrading. After the upgrade, they should then alter their configuration to also specify lock-timeout explicitly.

Orchestrator Integration Deletion

Orchestrator integration in vttablet was deprecated in the previous release and is deleted in this release. VTOrc should be deployed instead. You can read more on how VTOrc is designed and on how to run VTOrc in production.

vtctld web UI Removal

In v13, the vtctld UI was deprecated. As of this release, the web/vtctld2 directory is deleted and the UI will no longer be included in any Vitess images going forward. All build scripts and the Makefile have been updated to reflect this change, which was done in Pull Request #11851

However, the vtctld HTTP API will remain at {$vtctld_web_port}/api.

Query Serving Errors

In Pull Request #10738 we are introducing a new way to report errors from Vitess through the query interface. Errors will now have an error code for each error, which will make it easy to search for more information on the issue. For instance, the following error:

aggregate functions take a single argument 'count(user_id, name)'

Will be transformed into:

VT03001: aggregate functions take a single argument 'count(user_id, name)'

The error code VT03001 can then be used to search or ask for help and report problems.

If you have code searching for error strings from Vitess, this is a breaking change. Many error strings have been tweaked. If your application is searching for specific errors, you might need to update your code.

Logstats Table and Keyspace removed

Information about which tables are used is now reported by the field TablesUsed added in v15, that is a string array, listing all tables and which keyspace they are in. The Table/Keyspace fields were deprecated in v15 and are now removed in the v16 release, more information can be found on Pull Request #12083.

Removed Stats

The stat QueryRowCounts is removed in v16 as part of Pull Request #12083. QueryRowsAffected and QueryRowsReturned can be used instead to gather the same information.

Deprecated Stats

The stats QueriesProcessed and QueriesRouted are deprecated in v16 as part of Pull Request #12083. The same information can be inferred from the stats QueriesProcessedByTable and QueriesRoutedByTable respectively. These stats will be removed in the next release.

Normalized labels in the Prometheus Exporter

The Prometheus metrics exporter now properly normalizes all label names into their snake_case form, as it is idiomatic for Prometheus metrics. Previously, Vitess instances were emitting inconsistent labels for their metrics, with some of them being CamelCase and others being snake_case. More information about this change can be found on Pull Request #12057.

For example, vtgate_topology_watcher_errors{Operation="GetTablet"} 0 will become vtgate_topology_watcher_errors{operation="GetTablet"} 0

Some more of these changes are listed here -

Previous metric New Metric
vtgate_topology_watcher_operations{Operation="AddTablet"} vtgate_topology_watcher_operations{operation="AddTablet"}
vtgate_queries_processed{Plan="Reference"} vtgate_queries_processed{plan="Reference"}
vtgate_queries_routed{Plan="Reference"} vtgate_queries_routed{plan="Reference"}
vttablet_table_allocated_size{Table="corder"} vttablet_table_allocated_size{table="corder"}
vttablet_table_file_size{Table="corder"} vttablet_table_file_size{table="corder"}
vttablet_topology_watcher_errors{Operation="GetTablet"} vttablet_topology_watcher_errors{operation="GetTablet"}
vttablet_topology_watcher_operations{Operation="AddTablet"} vttablet_topology_watcher_operations{operation="AddTablet"}

Replication manager removal and VTOrc becomes mandatory

VTOrc is now a required component of Vitess starting from v16. If the users want Vitess to manage replication, then they must run VTOrc. Replication manager is removed from vttablets since the responsibility of fixing replication lies entirely with VTOrc now. The flag disable-replication-manager is deprecated and will be removed in a future release.

VReplication

VStream Copy Resume

In Pull Request #11103 we introduced the ability to resume a VTGate VStream copy operation. This is useful when a VStream copy operation is interrupted due to e.g. a network failure or a server restart. The VStream copy operation can be resumed by specifying each table's last seen primary key value in the VStream request. Please see the VStream docs for more details.

VDiff2 GA

We are marking VDiff v2 as production-ready in v16. We now recommend that you use v2 rather than v1 going forward. V1 will be deprecated and eventually removed in future releases. If you wish to use v1 for any reason, you will now need to specify the --v1 flag.

Tablet throttler

The tablet throttler can now be configured dynamically. Configuration is now found in the topo service, and applies to all tablets in all shards and cells of a given keyspace. It is possible to enable or disable throttling, and to change the throttling threshold as well as the throttler query.

Please note that this feature is considered experimental in this release. For backwards compatibility v16 still supports vttablet-based command line flags for throttler configuration.

More information can be found on Pull Request #11604.

Incremental backup and point in time recovery

In Pull Request #11097 we introduced native incremental backup and point in time recovery:

New command line flags and behavior

VTGate: Support query timeout --query-timeout

--query-timeout allows you to specify a timeout for queries. This timeout is applied to all queries. It can be overridden by setting the query_timeout session variable. Setting it as query comment directive with QUERY_TIMEOUT_MS will override other values.

VTTablet: VReplication parallel insert workers --vreplication-parallel-insert-workers

--vreplication-parallel-insert-workers=[integer] enables parallel bulk inserts during the copy phase of VReplication (disabled by default). When set to a value greater than 1 the bulk inserts — each executed as a single transaction from the vstream packet contents — may happen in-parallel and out-of-order, but the commit of those transactions are still serialized in order.

Other aspects of the VReplication copy-phase logic are preserved:

  1. All statements executed when processing a vstream packet occur within a single MySQL transaction.
  2. Writes to _vt.copy_state always follow their corresponding inserts from within the vstream packet.
  3. The final commit for the vstream packet always follows the corresponding write to _vt.copy_state.
  4. The vstream packets are committed in the order seen in the stream. So for any PK1 and PK2, the write to _vt.copy_state and commit steps (steps 2 and 3 above) for PK1 will both precede the _vt.copy_state write and commit steps of PK2.

Other phases, catchup, fast-forward, and replicating/"running", are unchanged.

VTTablet: --queryserver-config-pool-conn-max-lifetime

--queryserver-config-pool-conn-max-lifetime=[integer] allows you to set a timeout on each connection in the query server connection pool. It chooses a random value between its value and twice its value, and when a connection has lived longer than the chosen value, it'll be removed from the pool the next time it's returned to the pool.

vttablet --throttler-config-via-topo

The flag --throttler-config-via-topo switches throttler configuration from vttablet-flags to the topo service. This flag is false by default, for backwards compatibility. It will default to true in future versions.

vtctldclient UpdateThrottlerConfig

Tablet throttler configuration is now supported in topo. Updating the throttler configuration is done via vtctldclient UpdateThrottlerConfig and applies to all tablet in all cells for a given keyspace.

Examples:

# disable throttler; all throttler checks will return with "200 OK"
$ vtctldclient UpdateThrottlerConfig --disable commerce

# enable throttler; checks are responded with appropriate status per current metrics
$ vtctldclient UpdateThrottlerConfig --enable commerce

# Both enable and set threshold in same command. Since no query is indicated, we assume the default check for replication lag
$ vtctldclient UpdateThrottlerConfig --enable --threshold 5.0 commerce

# Change threshold. Does not affect enabled/disabled state of the throttler
$ vtctldclient UpdateThrottlerConfig --threshold 1.5 commerce

# Use a custom query
$ vtctldclient UpdateThrottlerConfig --custom_query "show global status like 'threads_running'" --check_as_check_self --threshold 50 commerce

# Restore default query and threshold
$ vtctldclient UpdateThrottlerConfig --custom_query "" --check_as_check_shard --threshold 1.5 commerce

See https://github.com/vitessio/vitess/pull/11604

vtctldclient Backup --incremental_from_pos

The Backup command now supports --incremental_from_pos flag, which can receive a valid position or the value auto. For example:

$ vtctlclient -- Backup --incremental_from_pos "MySQL56/16b1039f-22b6-11ed-b765-0a43f95f28a3:1-615" zone1-0000000102
$ vtctlclient -- Backup --incremental_from_pos "auto" zone1-0000000102

When the value is auto, the position is evaluated as the last successful backup's Position. The idea with incremental backups is to create a contiguous (overlaps allowed) sequence of backups that store all changes from last full backup.

The incremental backup copies binary log files. It does not take MySQL down nor places any locks. It does not interrupt traffic on the MySQL server. The incremental backup copies complete binlog files. It initially rotates binary logs, then copies anything from the requested position and up to the last completed binary log.

The backup thus does not necessarily start exactly at the requested position. It starts with the first binary log that has newer entries than requested position. It is OK if the binary logs include transactions prior to the requested position. The restore process will discard any duplicates.

Normally, you can expect the backups to be precisely contiguous. Consider an auto value: due to the nature of log rotation and the fact we copy complete binlog files, the next incremental backup will start with the first binay log not covered by the previous backup, which in itself copied the one previous binlog file in full. Again, it is completely valid to enter any good position.

The incremental backup fails if it is unable to attain binary logs from given position (ie binary logs have been purged).

The manifest of an incremental backup has a non-empty FromPosition value, and a Incremental = true value.

vtctldclient RestoreFromBackup --restore_to_pos

Examples:

$ vtctlclient -- RestoreFromBackup  --restore_to_pos  "MySQL56/16b1039f-22b6-11ed-b765-0a43f95f28a3:1-220" zone1-0000000102

The restore process seeks a restore path: a sequence of backups (handles/manifests) consisting of one full backup followed by zero or more incremental backups, that can bring the server up to the requested position, inclusive.

The command fails if it cannot evaluate a restore path. Possible reasons:

The command outputs the restore path.

There may be multiple restore paths, the command prefers a path with the least number of backups. This has nothing to say about the amount and size of binary logs involved.

The RestoreFromBackup --restore_to_pos ends with:

New vexplain command

A new vexplain command has been introduced with the following syntax:

VEXPLAIN [ALL|QUERIES|PLAN] explainable_stmt

This command will help users look at the plan that vtgate comes up with for the given query (PLAN type), see all the queries that are executed on all the MySQL instances (QUERIES type), and see the vtgate plan along with the MySQL explain output for the executed queries (ALL type).

The formats VTEXPLAIN and VITESS for EXPLAIN queries are deprecated, and these newly introduced commands should be used instead.

Important bug fixes

Corrupted results for non-full-group-by queries with JOINs

An issue in versions <= v14.0.3 and <= v15.0.0 that generated corrupted results for non-full-group-by queries with a JOIN is now fixed. The full issue can be found here, and its fix here.

Deprecations and Removals

MySQL Compatibility

Transaction Isolation Level

In Pull Request #11704 we are adding support for set [session] transaction isolation level <transaction_characteristic>

transaction_characteristic: {
    ISOLATION LEVEL level
  | access_mode
}

level: {
     REPEATABLE READ
   | READ COMMITTED
   | READ UNCOMMITTED
   | SERIALIZABLE
}

This will set the transaction isolation level for the current session. This will be applied to any shard where the session will open a transaction.

Transaction Access Mode

In Pull Request #11704 we are adding support for start transaction with transaction characteristic.

START TRANSACTION
    [transaction_characteristic [, transaction_characteristic] ...]

transaction_characteristic: {
    WITH CONSISTENT SNAPSHOT
  | READ WRITE
  | READ ONLY
}

This will allow users to start a transaction with these characteristics.

Support For Views

Views sharded support is released as an experimental feature in v16.0.0. Views are not enabled by default in your Vitess cluster, but they can be turned on using the --enable-views flag on VTGate, and --queryserver-enable-views flag on VTTablet.

To read more on how views are implemented you can read the Views Support RFC. And if you want to learn more on how to use views and its current limitations, you can read the Views Documentation.

VTTestServer

Performance Improvement

Creating a database with vttestserver was taking ~45 seconds. This can be problematic in test environments where testcases do a lot of create and drop database. In an effort to minimize the database creation time, in Pull Request #11918 we have changed the value of tablet_refresh_interval to 10s while instantiating vtcombo during vttestserver initialization. We have also made this configurable so that it can be reduced further if desired. For any production cluster the default value of this flag is still 1 minute. Reducing this value might put more stress on Topo Server (since we now read from Topo server more often) but for testing purposes this shouldn't be a concern.

Minor changes

Backup Compression Benchmarks

Compression benchmarks have been added to the mysqlctl package.

The benchmarks fetch and compress a ~6 GiB tar file containing 3 InnoDB files using different built-in and external compressors.

Here are sample results from a 2020-era Mac M1 with 16 GiB of memory:

$ go test -bench=BenchmarkCompress ./go/vt/mysqlctl -run=NONE -timeout=12h -benchtime=1x -v
goos: darwin
goarch: arm64
pkg: vitess.io/vitess/go/vt/mysqlctl
BenchmarkCompressLz4Builtin
    compression_benchmark_test.go:310: downloading data from https://www.dropbox.com/s/raw/smmgifsooy5qytd/enwiki-20080103-pages-articles.ibd.tar.zst
    BenchmarkCompressLz4Builtin-8                  1        11737493087 ns/op        577.98 MB/s             2.554 compression-ratio
    BenchmarkCompressPargzipBuiltin
    BenchmarkCompressPargzipBuiltin-8              1        31083784040 ns/op        218.25 MB/s             2.943 compression-ratio
    BenchmarkCompressPgzipBuiltin
    BenchmarkCompressPgzipBuiltin-8                1        13325299680 ns/op        509.11 MB/s             2.910 compression-ratio
    BenchmarkCompressZstdBuiltin
    BenchmarkCompressZstdBuiltin-8                 1        18683863911 ns/op        363.09 MB/s             3.150 compression-ratio
    BenchmarkCompressZstdExternal
    BenchmarkCompressZstdExternal-8                1        10795487675 ns/op        628.41 MB/s             3.093 compression-ratio
    BenchmarkCompressZstdExternalFast4
    BenchmarkCompressZstdExternalFast4-8           1        7139319009 ns/op         950.23 MB/s             2.323 compression-ratio
    BenchmarkCompressZstdExternalT0
    BenchmarkCompressZstdExternalT0-8              1        4393860434 ns/op        1543.97 MB/s             3.093 compression-ratio
    BenchmarkCompressZstdExternalT4
    BenchmarkCompressZstdExternalT4-8              1        4389559744 ns/op        1545.49 MB/s             3.093 compression-ratio
    PASS
    cleaning up "/var/folders/96/k7gzd7q10zdb749vr02q7sjh0000gn/T/ee7d47b45ef09786c54fa2d7354d2a68.dat"

Refactor

VTTablet Sidecar Schema Maintenance Refactor

This is an internal refactor and should not change the behavior of Vitess as seen by users.

Developers will see a difference though: v16 changes the way we maintain vttablet's sidecar database schema (also referred to as the _vt database). Instead of using the WithDDL package, introduced in PR #6348, we use a declarative approach. Developers will now have to update the desired schema in the go/vt/sidecardb/schema directory.

The desired schema is specified, one per table. A new module sidecardb, compares this to the existing schema and performs the required create or alter to reach it. This is done whenever a primary vttablet starts up.

The sidecar tables local_metadata and shard_metadata are no longer in use and all references to them are removed as part of this refactor. They were used previously for Orchestrator support, which has been superseded by vtorc.

The entire changelog for this release can be found here.

The release includes 378 commits (excluding merges)

Thanks to all our contributors: @EmadMokhtar, @GuptaManan100, @Weijun-H, @WilliamLu99, @ajm188, @arthurschreiber, @arvind-murty, @brendar, @brirams, @dbussink, @deepthi, @dependabot[bot], @draftcode, @ejortegau, @frouioui, @harshit-gangal, @jjh-kim, @johanoskarsson, @kbslvsk, @mattlord, @maxenglander, @mdlayher, @notfelineit, @pbibra, @pudiva, @rohit-nayak-ps, @rsajwani, @shlomi-noach, @systay, @timvaillancourt, @vitess-bot[bot], @vmg, @yoheimuta

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