@Marvin I have the following function in my code. If the code fails at execute statement it is not throwing error but rather showing success in prefect cloud ui. How to capture error and raise an error

@flow(name="Push Records to Database", log_prints=True)
def github_pipeline():
 
    try:
        # connector = SnowflakeConnector.load(SNOWFLAKE_BLOCK_NAME)
        with SnowflakeConnector.load(SNOWFLAKE_BLOCK_NAME) as conn:
            
            # Execute the query
            # cursor = conn.cursor()
            print('creating cursor')
            conn.execute("TRUNCATE TABLE GITHUB_DATA;")
            print('execute the query')

            # Commit the transaction
            # connection.commit()
            # conn.close()

It appears that your Prefect flow is not capturing the failure because the exception handling provided in your Python code is suppressing any errors that might occur. According to the Prefect documentation, if an exception is raised within the flow function, the flow is immediately marked as failed. As such, if you want the flow to report a failure in the Prefect Cloud UI, you should allow exceptions to surface, or re-raise exceptions after logging them. Here's a snippet from the Prefect documentation about raising an exception within a flow to ensure a failure is reported:

python
from prefect import flow

@flow
def always_fails_flow():
    raise ValueError("This flow immediately fails")

always_fails_flow()

Running this flow will mark the flow as failed in Prefect. If you have additional error handling, ensure that it either re-raises the exception or that you set the flow state to

Failed

explicitly. For more information on how to handle exceptions in your flow, you can visit the following link to Prefect documentation: Prefect Flows - Handling Exceptions. To address the specific issue with your code, you may consider modifying your function to include error handling that re-raises any exceptions caught during the

try

block. Here is an example of how you might modify your flow function:

python
from prefect import flow
from prefect.engine import signals

@flow(name="Push Records to Database", log_prints=True)
def github_pipeline():
 
    try:
        with SnowflakeConnector.load(SNOWFLAKE_BLOCK_NAME) as conn:
            print('creating cursor')
            conn.execute("TRUNCATE TABLE GITHUB_DATA;")
            print('execute the query')
    except Exception as e:
        print('An error occurred:', e)
        # You can either directly raise the original exception or use Prefect signals.
        # raise e  # Re-raises the original exception, marking the flow as failed.
        raise signals.FAIL('Task failed due to an error: ' + str(e))  # Uses a Prefect signal to fail the task.

Make sure that any try-except blocks inside tasks are either re-raising exceptions or that tasks are signaling failure to Prefect. If you need a further detailed example, please let me know.

@Marvin How to get status of sql statement execution in snowflake. Need to check whether it is succeeded or failed and if dfailed raise an error

To get the status of an SQL statement execution in Snowflake and raise an error if it failed, you can use the cursor's

execute

method within your Prefect flow. This method will raise an exception if the SQL query fails, which you can then catch to handle the error accordingly. Here is an example to demonstrate this:

python
from prefect import flow, task
from snowflake.connector import ProgrammingError
from your_package import SnowflakeConnector  # Replace with your actual import

@task
def execute_sql(sql: str):
    try:
        with SnowflakeConnector.load("your_snowflake_connection_block_name") as conn:
            with conn.cursor() as cursor:
                cursor.execute(sql)
                # If the execution is successful, you can get the number of affected rows if necessary
                affected_rows = cursor.rowcount
                print(f"The SQL statement was executed successfully, {affected_rows} rows affected.")
    except ProgrammingError as e:
        # This example error handling simply prints and re-raises the error, 
        # but you could handle it in a way that's appropriate for your use case.
        print(f"An error occurred during SQL statement execution: {e}")
        raise

@flow(name="Run SQL in Snowflake")
def run_sql_flow():
    sql_statement = "TRUNCATE TABLE GITHUB_DATA;"
    execute_sql(sql_statement)

run_sql_flow()

In this snippet, the

execute_sql

task within the flow will attempt to run the SQL statement. If the

execute

method encounters any issues while running the statement, it will throw a

ProgrammingError

, which is handled in the

except

block. The error is logged, and then re-raised to signal the task (and flow) failure to Prefect. Remember to adapt the example by importing the

SnowflakeConnector

from your actual package and using your Snowflake connection block name. You can consult the Prefect and Snowflake connector documentation for more details: - Prefect documentation - Prefect Snowflake integration These links will provide further guidance on working with Snowflake within Prefect flows. If you have further queries or need more code examples, feel free to ask.

@Marvin encountered an exception: ImportError("cannot import name 'signals' from 'prefect.engine'

It seems there are no direct issues in the Prefect GitHub repository that match the exception

ImportError("cannot import name 'signals' from 'prefect.engine'

. However, the error message suggests that you're trying to import a module or object named

signals

from the

prefect.engine

namespace, which might not exist in your installed version of Prefect. It's possible that the code you are referencing is outdated, or it was meant for a previous version of Prefect. In Prefect Core 1.x, there used to be a module called

prefect.engine.signals

, which included various signal exceptions to control flow execution, such as

FAIL

or

SKIP

. If you migrated from Prefect 1.x to Prefect 2.x (Orion), you should be aware that the API has changed significantly. In Prefect 2.x, you could use

prefect.exceptions

to raise exceptions such as

PAUSE

,

FAIL

, or custom exceptions in your flow or tasks. Here's how you might use it:

python
from prefect import flow
from prefect.exceptions import FAIL

@flow
def failing_flow():
    # ... some code ...
    if error_condition:
        raise FAIL("An error occurred, stopping the flow")

Make sure to update your calls to use the appropriate exception handling mechanisms provided by the version of Prefect you are using. If you've recently upgraded Prefect or the information provided doesn't resolve your issue, it might be worth consulting: - Prefect 2.0 (Orion) documentation for the latest guidance on exception signaling in flows. - Your installed version of Prefect to ensure you are referring to the correct version of the documentation. If you need further assistance or clarification, please don't hesitate to reach out.

@Marvin 'SnowflakeConnector' object has no attribute 'cursor'

The error

'SnowflakeConnector' object has no attribute 'cursor'

suggests that you're trying to use a

cursor

attribute on an instance of

SnowflakeConnector

, which apparently does not exist. This could be an indication that the usage pattern you're employing is not aligned with the API of the

SnowflakeConnector

object you're working with. The

SnowflakeConnector

might be part of an integration library for Prefect which abstracts the connection to Snowflake, and it may have a different interface compared to the raw

snowflake-connector-python

library. In a typical usage of the

snowflake-connector-python

library, you would obtain a cursor from a connection object, not directly from the connector. For example:

python
import snowflake.connector

# Connect to Snowflake
conn = snowflake.connector.connect(
    user='<user>',
    password='<password>',
    account='<account>'
)

# Create a cursor object
cursor = conn.cursor()

However, if you're using a Prefect integration for Snowflake, you should refer to the documentation for the proper usage. Prefect integrations usually come with tasks that can execute queries for you, or methods that help in obtaining the raw connection. If you can specify the precise library or version of

SnowflakeConnector

you're using, or provide more context surrounding the error, I could offer a more targeted solution. Otherwise, you should refer to the documentation of the specific Prefect integration or the library from which you're obtaining the

SnowflakeConnector

to find the correct way to execute queries against Snowflake. For custom integrations or connectors, reviewing the source code or any usage examples provided by the library is typically the best way to understand how to correctly use the connector object. If you're working with the

prefect-snowflake

integration, then you should be able to find examples and documentation specifically for Prefect's usage patterns here.