Conduit Connector for MySQL

Source

A source connector pulls data from an external resource and pushes it to downstream resources via Conduit.

Snapshot mode

Snapshot mode is the first stage of the source sync process. It reads all rows from the configured tables as record snapshots.

In snapshot mode, the record payload consists of opencdc.StructuredData, with each key being a column and each value being that column's value.

Change Data Capture mode

When the connector switches to CDC mode, it starts streaming changes from the obtained position at the start of the snapshot. It uses the row-based binlog format to capture detailed changes at the individual row level.

Unsafe snapshot

By default, the connector will error out if it finds a table that has no primary key and no specified sorting column specified, as we can't guarantee that the snapshot will be consistent. Table changes during the snapshot will be however captured by CDC mode.

As of writing, the unsafe snapshot is implemented using batches with LIMIT and OFFSET, so expect it to be slow for large tables. You can optimize the snapshot by specifying a sorting column (see source configuration parameters). The position of the table is currently not recorded, so the unsafe snapshot will restart from zero every time.

Schema

The source connector uses avro to decode mysql rows. Here's the MySQL datatype to avro datatype equivalence that the connector uses:

MySQL Type	Avro Type
TINYINT	int
SMALLINT	int
MEDIUMINT	int
INT	int
BIGINT	long
DECIMAL	double
NUMERIC	double
FLOAT	double
DOUBLE	double
BIT	bytes
CHAR	string
VARCHAR	string
TINYTEXT	string
TEXT	string
MEDIUMTEXT	string
LONGTEXT	string
BINARY	bytes
VARBINARY	bytes
TINYBLOB	bytes
BLOB	bytes
MEDIUMBLOB	bytes
LONGBLOB	bytes
DATE	string
TIME	string
DATETIME	string
TIMESTAMP	string
YEAR	long
ENUM	string
SET	string
JSON	string

Record structure

Records produced by the MySQL source connector contain the following opencdc record structure:

• Operation: Indicates the type of change (create, update, delete, snapshot).
• Payload:
  • Before: (Only present on CDC update operations) opencdc.StructuredData representing the row state before the change.
  • After: opencdc.StructuredData representing the row state after the change (or the current state for snapshot and create).
• Key: Identifies the specific row. See Snapshot/CDC sections below for details.
• Position: Represents the point in the data stream. It's a JSON object containing either a snapshot_position field or a cdc_position field, structured as described below.
• Metadata: Contains standard OpenCDC fields plus:
  • mysql.server.id: (CDC only) The originating MySQL server ID from the replication event header.
  • Key and payload schema registry data.

Snapshot Records

• Operation: snapshot.
• Payload After: opencdc.StructuredData with all column values.
• Key:
  • With Primary Key(s): opencdc.StructuredData using primary key columns and values.
  • Without Primary Key(s) (using LIMIT/OFFSET): opencdc.RawData string "<table_name>_<row_offset>".
• Position (snapshot_position field): A JSON object containing:
  • snapshots: (object) Maps table names to their specific snapshot position object.
    • (Single Primary Key Table): Contains last_read (any) and snapshot_end (any).
    • (Multiple Primary Key Table): Contains an array of objects, each with key_name (string), last_read (any), and snapshot_end (any).
    • (No Primary Key Table): Table entry might be missing or empty (offset is not persisted).

CDC Records

• Operation: Either create, update or delete.
• Key:
  • With Primary Key(s): opencdc.StructuredData using primary key columns and values (from the After state).
  • Without Primary Key(s): opencdc.RawData string "<binlog_file_name>_<log_position>".
• Payload:
  • Before: (For update only) opencdc.StructuredData with pre-update column values.
  • After: opencdc.StructuredData with post-change column values (for create, update) or pre-deletion values (for delete).
• Position (cdc_position field): Encodes the binlog location in a JSON object with the following fields.
  • name: (string) Binlog file name.
  • pos: (uint32) Position within the binlog file.
  • prev: (object, optional) Position of the preceding event, containing name (string) and pos (uint32). Omitted if not applicable.
  • idx: (int, optional) Row index within a potentially multi-row MySQL replication event. Omitted if zero or not applicable.

Destination

The MySQL destination takes a slice of opencdc.Record and writes them in batches to MySQL. It will use the opencdc.collection field in the metadata to determine the table to write to.

Upsert Behavior

If the target table contains a column with a unique constraint (this includes PRIMARY KEY and UNIQUE indexes), records will be upserted. Otherwise, they will be appended. Support for updating tables without unique constraints is tracked here.

If the target table already contains a record with the same key, the Destination will upsert with its current received values. Because Keys must be unique, this can overwrite and thus potentially lose data, so keys should be assigned correctly from the Source.

If a unique key is not present in the target table, the record will be simply appended.

Requirements and compatibility

The connector is tested against MySQL v8.0. Compatibility with older versions isn't guaranteed.

MySQL Server Requirements:

• Binary Log (binlog) must be enabled.
• Binlog format must be set to ROW.
• Binlog row image must be set to FULL.
• Tables must have sortable primary keys.

MySQL User Privileges:

For Snapshot and CDC modes, the following privileges are required:

• SELECT
• LOCK TABLES
• RELOAD
• REPLICATION CLIENT
• REPLICATION SLAVE

Source Configuration Parameters

version: 2.2
pipelines:
  - id: example
    status: running
    connectors:
      - id: example
        plugin: "mysql"
        settings:
          # The connection string for the MySQL database.
          # Type: string
          # Required: yes
          dsn: ""
          # Represents the tables to read from. - By default, no tables are
          # included, but can be modified by adding a comma-separated string of
          # regex patterns. - They are applied in the order that they are
          # provided, so the final regex supersedes all previous ones. - To
          # include all tables, use "*". You can then filter that list by adding
          # a comma-separated string of regex patterns. - To set an "include"
          # regex, add "+" or nothing in front of the regex. - To set an
          # "exclude" regex, add "-" in front of the regex. - e.g. "-.*meta$,
          # wp_postmeta" will exclude all tables ending with "meta" but include
          # the table "wp_postmeta".
          # Type: string
          # Required: yes
          tables: ""
          # Disables verbose cdc driver logs.
          # Type: bool
          # Required: no
          cdc.disableLogs: "false"
          # Controls whether the snapshot is done.
          # Type: bool
          # Required: no
          snapshot.enabled: "true"
          # Limits how many rows should be retrieved on each database fetch on
          # snapshot mode.
          # Type: int
          # Required: no
          snapshot.fetchSize: "10000"
          # Allows a snapshot of a table with neither a primary key nor a
          # defined sorting column. The opencdc.Position won't record the last
          # record read from a table.
          # Type: bool
          # Required: no
          snapshot.unsafe: "false"
          # Allows to force using a custom column to sort the snapshot.
          # Type: string
          # Required: no
          tableConfig.*.sortingColumn: ""
          # Maximum delay before an incomplete batch is read from the source.
          # Type: duration
          # Required: no
          sdk.batch.delay: "1s"
          # Maximum size of batch before it gets read from the source.
          # Type: int
          # Required: no
          sdk.batch.size: "10000"
          # Specifies whether to use a schema context name. If set to false, no
          # schema context name will be used, and schemas will be saved with the
          # subject name specified in the connector (not safe because of name
          # conflicts).
          # Type: bool
          # Required: no
          sdk.schema.context.enabled: "true"
          # Schema context name to be used. Used as a prefix for all schema
          # subject names. If empty, defaults to the connector ID.
          # Type: string
          # Required: no
          sdk.schema.context.name: ""
          # Whether to extract and encode the record key with a schema.
          # Type: bool
          # Required: no
          sdk.schema.extract.key.enabled: "true"
          # The subject of the key schema. If the record metadata contains the
          # field "opencdc.collection" it is prepended to the subject name and
          # separated with a dot.
          # Type: string
          # Required: no
          sdk.schema.extract.key.subject: "key"
          # Whether to extract and encode the record payload with a schema.
          # Type: bool
          # Required: no
          sdk.schema.extract.payload.enabled: "true"
          # The subject of the payload schema. If the record metadata contains
          # the field "opencdc.collection" it is prepended to the subject name
          # and separated with a dot.
          # Type: string
          # Required: no
          sdk.schema.extract.payload.subject: "payload"
          # The type of the payload schema.
          # Type: string
          # Required: no
          sdk.schema.extract.type: "avro"

Destination Configuration Parameters

version: 2.2
pipelines:
  - id: example
    status: running
    connectors:
      - id: example
        plugin: "mysql"
        settings:
          # The connection string for the MySQL database.
          # Type: string
          # Required: yes
          dsn: ""
          # Maximum delay before an incomplete batch is written to the
          # destination.
          # Type: duration
          # Required: no
          sdk.batch.delay: "0"
          # Maximum size of batch before it gets written to the destination.
          # Type: int
          # Required: no
          sdk.batch.size: "0"
          # Allow bursts of at most X records (0 or less means that bursts are
          # not limited). Only takes effect if a rate limit per second is set.
          # Note that if `sdk.batch.size` is bigger than `sdk.rate.burst`, the
          # effective batch size will be equal to `sdk.rate.burst`.
          # Type: int
          # Required: no
          sdk.rate.burst: "0"
          # Maximum number of records written per second (0 means no rate
          # limit).
          # Type: float
          # Required: no
          sdk.rate.perSecond: "0"
          # The format of the output record. See the Conduit documentation for a
          # full list of supported formats
          # (https://conduit.io/docs/using/connectors/configuration-parameters/output-format).
          # Type: string
          # Required: no
          sdk.record.format: "opencdc/json"
          # Options to configure the chosen output record format. Options are
          # normally key=value pairs separated with comma (e.g.
          # opt1=val2,opt2=val2), except for the `template` record format, where
          # options are a Go template.
          # Type: string
          # Required: no
          sdk.record.format.options: ""
          # Whether to extract and decode the record key with a schema.
          # Type: bool
          # Required: no
          sdk.schema.extract.key.enabled: "true"
          # Whether to extract and decode the record payload with a schema.
          # Type: bool
          # Required: no
          sdk.schema.extract.payload.enabled: "true"

Testing

Run make test to run all tests.

The Docker compose file at test/docker-compose.yml can be used to run the required resource locally. It includes adminer for database management.

Use the TRACE=true environment variable to enable trace logs when running tests.