Flink: Not able to sink a stream into csv

[Yik San Chan]

The question is cross posted on Stack Overflow https://stackoverflow.com/questions/67195207/flink-not-able-to-sink-a-stream-into-csv.

I am trying to sink a stream into filesystem in csv format using PyFlink, however it does not work.

```python
# stream_to_csv.py
from pyflink.table import EnvironmentSettings, StreamTableEnvironment

env_settings = EnvironmentSettings.new_instance().in_streaming_mode().use_blink_planner().build()
table_env = StreamTableEnvironment.create(environment_settings=env_settings)

table_env.execute_sql("""
    CREATE TABLE datagen (
        id INT,
        data STRING
    ) WITH (
        'connector' = 'datagen',
        'rows-per-second' = '1'
    )
""")

table_env.execute_sql("""
    CREATE TABLE print (
        id INT,
        data STRING
    ) WITH (
        'connector' = 'filesystem',
        'format' = 'csv',
        'path' = '/tmp/output'
    )
""")

table_env.execute_sql("""
INSERT INTO print
SELECT id, data
FROM datagen
""").wait()
```

To run the script:

```
$ python stream_to_csv.py
```

I expect records go to /tmp/output folder, however that doesn't happen.

```
$ ~ ls /tmp/output
(nothing shown here)
```

Anything I miss?

Best,

Yik San

[Dian Fu]

Hi Yik San,

You need to set the rolling policy for filesystem. You could refer to the Rolling Policy section [1] for more details.

Actually there are output and you could execute command `ls -la /tmp/output/`, then you will see several files named “.part-xxx”.

For your job, you need to set the `execution.checkpointing.interval` in the configuration and `sink.rolling-policy.rollover-interval` in the property of Filesystem connector.

The job will look like the following:

```

from pyflink.table import EnvironmentSettings, StreamTableEnvironment

env_settings = EnvironmentSettings.new_instance().in_streaming_mode().use_blink_planner().build()

table_env = StreamTableEnvironment.create(environment_settings=env_settings)

table_env.get_config().get_configuration().set_string("execution.checkpointing.interval", "10s")

table_env.execute_sql("""

    CREATE TABLE datagen (

        id INT,

        data STRING

    ) WITH (

        'connector' = 'datagen',

        'rows-per-second' = '1'

    )

""")

table_env.execute_sql("""

    CREATE TABLE print (

        id INT,

        data STRING

    ) WITH (

        'connector' = 'filesystem',

        'format' = 'csv',

        'path' = '/tmp/output',

        'sink.rolling-policy.rollover-interval' = '10s'

    )

""")

table_env.execute_sql("""

INSERT INTO print

SELECT id, data

FROM datagen

""").wait()

```

[1] https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/connectors/filesystem.html#rolling-policy

2021年4月21日 下午7:44，Yik San Chan <[hidden email]> 写道：

The question is cross posted on Stack Overflow https://stackoverflow.com/questions/67195207/flink-not-able-to-sink-a-stream-into-csv.

I am trying to sink a stream into filesystem in csv format using PyFlink, however it does not work.

```python
# stream_to_csv.py
from pyflink.table import EnvironmentSettings, StreamTableEnvironment

env_settings = EnvironmentSettings.new_instance().in_streaming_mode().use_blink_planner().build()
table_env = StreamTableEnvironment.create(environment_settings=env_settings)

table_env.execute_sql("""
    CREATE TABLE datagen (
        id INT,
        data STRING
    ) WITH (
        'connector' = 'datagen',
        'rows-per-second' = '1'
    )
""")

table_env.execute_sql("""
    CREATE TABLE print (
        id INT,
        data STRING
    ) WITH (
        'connector' = 'filesystem',
        'format' = 'csv',
        'path' = '/tmp/output'
    )
""")

table_env.execute_sql("""
INSERT INTO print
SELECT id, data
FROM datagen
""").wait()
```

To run the script:

```
$ python stream_to_csv.py
```

I expect records go to /tmp/output folder, however that doesn't happen.

```
$ ~ ls /tmp/output
(nothing shown here)
```

Anything I miss?

Best,

Yik San

[Yik San Chan]

Hi Dian,

Thanks for your help, again!

Best,

Yik San

On Wed, Apr 21, 2021 at 8:39 PM Dian Fu <[hidden email]> wrote:

Hi Yik San,

You need to set the rolling policy for filesystem. You could refer to the Rolling Policy section [1] for more details.

Actually there are output and you could execute command `ls -la /tmp/output/`, then you will see several files named “.part-xxx”.

For your job, you need to set the `execution.checkpointing.interval` in the configuration and `sink.rolling-policy.rollover-interval` in the property of Filesystem connector.

The job will look like the following:

```

from pyflink.table import EnvironmentSettings, StreamTableEnvironment

env_settings = EnvironmentSettings.new_instance().in_streaming_mode().use_blink_planner().build()

table_env = StreamTableEnvironment.create(environment_settings=env_settings)

table_env.get_config().get_configuration().set_string("execution.checkpointing.interval", "10s")

table_env.execute_sql("""

    CREATE TABLE datagen (

        id INT,

        data STRING

    ) WITH (

        'connector' = 'datagen',

        'rows-per-second' = '1'

    )

""")

table_env.execute_sql("""

    CREATE TABLE print (

        id INT,

        data STRING

    ) WITH (

        'connector' = 'filesystem',

        'format' = 'csv',

        'path' = '/tmp/output',

        'sink.rolling-policy.rollover-interval' = '10s'

    )

""")

table_env.execute_sql("""

INSERT INTO print

SELECT id, data

FROM datagen

""").wait()

```

[1] https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/connectors/filesystem.html#rolling-policy

2021年4月21日 下午7:44，Yik San Chan <[hidden email]> 写道：

The question is cross posted on Stack Overflow https://stackoverflow.com/questions/67195207/flink-not-able-to-sink-a-stream-into-csv.

I am trying to sink a stream into filesystem in csv format using PyFlink, however it does not work.

```python
# stream_to_csv.py
from pyflink.table import EnvironmentSettings, StreamTableEnvironment

env_settings = EnvironmentSettings.new_instance().in_streaming_mode().use_blink_planner().build()
table_env = StreamTableEnvironment.create(environment_settings=env_settings)

table_env.execute_sql("""
    CREATE TABLE datagen (
        id INT,
        data STRING
    ) WITH (
        'connector' = 'datagen',
        'rows-per-second' = '1'
    )
""")

table_env.execute_sql("""
    CREATE TABLE print (
        id INT,
        data STRING
    ) WITH (
        'connector' = 'filesystem',
        'format' = 'csv',
        'path' = '/tmp/output'
    )
""")

table_env.execute_sql("""
INSERT INTO print
SELECT id, data
FROM datagen
""").wait()
```

To run the script:

```
$ python stream_to_csv.py
```

I expect records go to /tmp/output folder, however that doesn't happen.

```
$ ~ ls /tmp/output
(nothing shown here)
```

Anything I miss?

Best,

Yik San