showed {"type": "STATE", "value": {"currently_syncing": null}} even though table rows not empty

tap-mysql

Singer tap that extracts data from a MySQL database and produces JSON-formatted data following the Singer spec.

$ mkvirtualenv -p python3 tap-mysql
$ pip install tap-mysql
$ tap-mysql --config config.json --discover
$ tap-mysql --config config.json --properties properties.json --state state.json

Usage
Replication methods and state file
- Full Table
- Incremental
  - Example

Usage

This section dives into basic usage of tap-mysql by walking through extracting data from a table. It assumes that you can connect to and read from a MySQL database.

Install

$ mkvirtualenv -p python3 tap-mysql
$ pip install tap-mysql

or

$ git clone [email protected]:singer-io/tap-mysql.git
$ cd tap-mysql
$ mkvirtualenv -p python3 tap-mysql
$ python install .

Have a source database

There's some important business data siloed in this MySQL database -- we need to extract it. Here's the table we'd like to sync:

mysql> select * from example_db.animals;
+----|----------|----------------------+
| id | name     | likes_getting_petted |
+----|----------|----------------------+
|  1 | aardvark |                    0 |
|  2 | bear     |                    0 |
|  3 | cow      |                    1 |
+----|----------|----------------------+
3 rows in set (0.00 sec)

Create the configuration file

Create a config file containing the database connection credentials, e.g.:

{
  "host": "localhost",
  "port": "3306",
  "user": "root",
  "password": "password"
}

These are the same basic configuration properties used by the MySQL command-line client (mysql).

Discovery mode

The tap can be invoked in discovery mode to find the available tables and columns in the database:

$ tap-mysql --config config.json --discover

A discovered catalog is output, with a JSON-schema description of each table. A source table directly corresponds to a Singer stream.

{
  "streams": [
    {
      "tap_stream_id": "example_db-animals",
      "table_name": "animals",
      "schema": {
        "type": "object",
        "properties": {
          "name": {
            "inclusion": "available",
            "type": [
              "null",
              "string"
            ],
            "maxLength": 255
          },
          "id": {
            "inclusion": "automatic",
            "minimum": -2147483648,
            "maximum": 2147483647,
            "type": [
              "null",
              "integer"
            ]
          },
          "likes_getting_petted": {
            "inclusion": "available",
            "type": [
              "null",
              "boolean"
            ]
          }
        }
      },
      "metadata": [
        {
          "breadcrumb": [],
          "metadata": {
            "row-count": 3,
            "table-key-properties": [
              "id"
            ],
            "database-name": "example_db",
            "selected-by-default": false,
            "is-view": false,
          }
        },
        {
          "breadcrumb": [
            "properties",
            "id"
          ],
          "metadata": {
            "sql-datatype": "int(11)",
            "selected-by-default": true
          }
        },
        {
          "breadcrumb": [
            "properties",
            "name"
          ],
          "metadata": {
            "sql-datatype": "varchar(255)",
            "selected-by-default": true
          }
        },
        {
          "breadcrumb": [
            "properties",
            "likes_getting_petted"
          ],
          "metadata": {
            "sql-datatype": "tinyint(1)",
            "selected-by-default": true
          }
        }
      ],
      "stream": "animals"
    }
  ]
}

Field selection

In sync mode, tap-mysql consumes the catalog and looks for tables and fields have been marked as selected in their associated metadata entries.

Redirect output from the tap's discovery mode to a file so that it can be modified:

$ tap-mysql -c config.json --discover > properties.json

Then edit properties.json to make selections. In this example we want the animals table. The stream's metadata entry (associated with "breadcrumb": []) gets a top-level selected flag, as does its columns' metadata entries. Additionally, we will mark the animals table to replicate using a FULL_TABLE strategy. For more, information, see Replication methods and state file.

[
  {
    "breadcrumb": [],
    "metadata": {
      "row-count": 3,
      "table-key-properties": [
        "id"
      ],
      "database-name": "example_db",
      "selected-by-default": false,
      "is-view": false,
      "selected": true,
      "replication-method": "FULL_TABLE"
    }
  },
  {
    "breadcrumb": [
      "properties",
      "id"
    ],
    "metadata": {
      "sql-datatype": "int(11)",
      "selected-by-default": true,
      "selected": true
    }
  },
  {
    "breadcrumb": [
      "properties",
      "name"
    ],
    "metadata": {
      "sql-datatype": "varchar(255)",
      "selected-by-default": true,
      "selected": true
    }
  },
  {
    "breadcrumb": [
      "properties",
      "likes_getting_petted"
    ],
    "metadata": {
      "sql-datatype": "tinyint(1)",
      "selected-by-default": true,
      "selected": true
    }
  }
]

Sync mode

With a properties catalog that describes field and table selections, the tap can be invoked in sync mode:

$ tap-mysql -c config.json --properties properties.json

Messages are written to standard output following the Singer specification. The resultant stream of JSON data can be consumed by a Singer target.

{"value": {"currently_syncing": "example_db-animals"}, "type": "STATE"}

{"key_properties": ["id"], "stream": "animals", "schema": {"properties": {"name": {"inclusion": "available", "maxLength": 255, "type": ["null", "string"]}, "likes_getting_petted": {"inclusion": "available", "type": ["null", "boolean"]}, "id": {"inclusion": "automatic", "minimum": -2147483648, "type": ["null", "integer"], "maximum": 2147483647}}, "type": "object"}, "type": "SCHEMA"}

{"stream": "animals", "version": 1509133344771, "type": "ACTIVATE_VERSION"}

{"record": {"name": "aardvark", "likes_getting_petted": false, "id": 1}, "stream": "animals", "version": 1509133344771, "type": "RECORD"}

{"record": {"name": "bear", "likes_getting_petted": false, "id": 2}, "stream": "animals", "version": 1509133344771, "type": "RECORD"}

{"record": {"name": "cow", "likes_getting_petted": true, "id": 3}, "stream": "animals", "version": 1509133344771, "type": "RECORD"}

{"stream": "animals", "version": 1509133344771, "type": "ACTIVATE_VERSION"}

{"value": {"currently_syncing": "example_db-animals", "bookmarks": {"example_db-animals": {"initial_full_table_complete": true}}}, "type": "STATE"}

{"value": {"currently_syncing": null, "bookmarks": {"example_db-animals": {"initial_full_table_complete": true}}}, "type": "STATE"}

Replication methods and state file

In the above example, we invoked tap-mysql without providing a state file and without specifying a replication method. The two ways to replicate a given table are FULL_TABLE and INCREMENTAL.

Full Table

Full-table replication extracts all data from the source table each time the tap is invoked.

Incremental

Incremental replication works in conjunction with a state file to only extract new records each time the tap is invoked. This requires a replication key to be specified in the table's metadata as well.

Example

Let's sync the animals table again, but this time using incremental replication. The replication method and replication key are set in the table's metadata entry in properties file:

{
  "streams": [
    {
      "tap_stream_id": "example_db-animals",
      "table_name": "animals",
      "schema": { ... },
      "metadata": [
        {
          "breadcrumb": [],
          "metadata": {
            "row-count": 3,
            "table-key-properties": [
              "id"
            ],
            "database-name": "example_db",
            "selected-by-default": false,
            "is-view": false,
            "replication-method": "INCREMENTAL",
            "replication-key": "id"
          }
        },
        ...
      ],
      "stream": "animals"
    }
  ]
}

We have no meaningful state so far, so just invoke the tap in sync mode again without a state file:

$ tap-mysql -c config.json --properties properties.json

The output messages look very similar to when the table was replicated using the default FULL_TABLE replication method. One important difference is that the STATE messages now contain a replication_key_value -- a bookmark or high-water mark -- for data that was extracted:

{"type": "STATE", "value": {"currently_syncing": "example_db-animals"}}

{"stream": "animals", "type": "SCHEMA", "schema": {"type": "object", "properties": {"id": {"type": ["null", "integer"], "minimum": -2147483648, "maximum": 2147483647, "inclusion": "automatic"}, "name": {"type": ["null", "string"], "inclusion": "available", "maxLength": 255}, "likes_getting_petted": {"type": ["null", "boolean"], "inclusion": "available"}}}, "key_properties": ["id"]}

{"stream": "animals", "type": "ACTIVATE_VERSION", "version": 1509135204169}

{"stream": "animals", "type": "RECORD", "version": 1509135204169, "record": {"id": 1, "name": "aardvark", "likes_getting_petted": false}}

{"stream": "animals", "type": "RECORD", "version": 1509135204169, "record": {"id": 2, "name": "bear", "likes_getting_petted": false}}

{"stream": "animals", "type": "RECORD", "version": 1509135204169, "record": {"id": 3, "name": "cow", "likes_getting_petted": true}}

{"type": "STATE", "value": {"bookmarks": {"example_db-animals": {"version": 1509135204169, "replication_key_value": 3, "replication_key": "id"}}, "currently_syncing": "example_db-animals"}}

{"type": "STATE", "value": {"bookmarks": {"example_db-animals": {"version": 1509135204169, "replication_key_value": 3, "replication_key": "id"}}, "currently_syncing": null}}

Note that the final STATE message has a replication_key_value of 3, reflecting that the extraction ended on a record that had an id of 3. Subsequent invocations of the tap will pick up from this bookmark.

Normally, the target will echo the last STATE after it's finished processing data. For this example, let's manually write a state.json file using the STATE message:

{
  "bookmarks": {
    "example_db-animals": {
      "version": 1509135204169,
      "replication_key_value": 3,
      "replication_key": "id"
    }
  },
  "currently_syncing": null
}

Let's add some more animals to our farm:

mysql> insert into animals (name, likes_getting_petted) values ('dog', true), ('elephant', true), ('frog', false);

$ tap-mysql -c config.json --properties properties.json --state state.json

This invocation extracts any data since (and including) the replication_key_value:

{"type": "STATE", "value": {"bookmarks": {"example_db-animals": {"replication_key": "id", "version": 1509135204169, "replication_key_value": 3}}, "currently_syncing": "example_db-animals"}}

{"key_properties": ["id"], "schema": {"properties": {"name": {"maxLength": 255, "inclusion": "available", "type": ["null", "string"]}, "id": {"maximum": 2147483647, "minimum": -2147483648, "inclusion": "automatic", "type": ["null", "integer"]}, "likes_getting_petted": {"inclusion": "available", "type": ["null", "boolean"]}}, "type": "object"}, "type": "SCHEMA", "stream": "animals"}

{"type": "ACTIVATE_VERSION", "version": 1509135204169, "stream": "animals"}

{"record": {"name": "cow", "id": 3, "likes_getting_petted": true}, "type": "RECORD", "version": 1509135204169, "stream": "animals"}
{"record": {"name": "dog", "id": 4, "likes_getting_petted": true}, "type": "RECORD", "version": 1509135204169, "stream": "animals"}
{"record": {"name": "elephant", "id": 5, "likes_getting_petted": true}, "type": "RECORD", "version": 1509135204169, "stream": "animals"}
{"record": {"name": "frog", "id": 6, "likes_getting_petted": false}, "type": "RECORD", "version": 1509135204169, "stream": "animals"}

{"type": "STATE", "value": {"bookmarks": {"example_db-animals": {"replication_key": "id", "version": 1509135204169, "replication_key_value": 6}}, "currently_syncing": "example_db-animals"}}

{"type": "STATE", "value": {"bookmarks": {"example_db-animals": {"replication_key": "id", "version": 1509135204169, "replication_key_value": 6}}, "currently_syncing": null}}

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tap-mysql's Introduction

tap-mysql

Usage

Install

Have a source database

Create the configuration file

Discovery mode

Field selection

Sync mode

Replication methods and state file

Full Table

Incremental

Example

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