Hvuj
02/25/2024, 6:59 AMScout
02/25/2024, 6:59 AM@success_hook
and @failure_hook
decorators that can be used to define hooks that run after an op has completed successfully or failed, respectively. If you are looking to perform actions before an op runs, you might consider using other mechanisms provided by Dagster, such as custom logic within the op itself or using resources to set up necessary preconditions before the op execution. For any functionality that is not explicitly covered in the documentation, it's possible that it may not be supported directly by Dagster. If you have a specific use case or requirement for a pre-hook feature, you could consider reaching out to the Dagster community or checking the GitHub issues and discussions for any updates or workarounds that other users might have shared.Hvuj
02/25/2024, 7:03 AMScout
02/25/2024, 7:03 AM@success_hook
and @failure_hook
decorators provided by Dagster. These decorators allow you to define hooks that will be triggered on the success or failure of ops within a job. Here's a step-by-step guide on how to create custom hooks based on the documentation: 1. Define the Hook Function: You start by defining a Python function that will act as your hook. This function will take a single argument, context
, which is an instance of HookContext
. The HookContext
provides information about the op, job, and resources available to the hook. 2. Decorate the Function: You then decorate this function with either @success_hook
or @failure_hook
, depending on when you want the hook to be triggered. 3. Specify Required Resources: If your hook requires any resources (like a Slack client to send messages), you can specify these using the required_resource_keys
parameter in the decorator. Here's an example of how you might define a custom hook that sends a message to Slack when an op succeeds: python from dagster import HookContext, success_hook, ResourceDefinition # Define a resource for Slack def slack_resource(_): # Here you would create and return your Slack client pass # Define the hook function @success_hook(required_resource_keys={"slack"}) def slack_message_on_success(context: HookContext): message = f"Op {context.op.name} finished successfully" context.resources.slack.chat_postMessage(channel="#foo", text=message)
And here's an example of a custom hook that sends a message when an op fails: python from dagster import HookContext, failure_hook # Define the hook function @failure_hook(required_resource_keys={"slack"}) def slack_message_on_failure(context: HookContext): message = f"Op {context.op.name} failed" context.resources.slack.chat_postMessage(channel="#foo", text=message)
4. Apply the Hook to Ops or Jobs: After defining your hooks, you can apply them to individual ops using the .with_hooks
method or to an entire job by passing a set of hook definitions to the hooks
parameter of the @job
decorator. Here's how you might apply the slack_message_on_success
hook to a job: python from dagster import job @job(resource_defs={"slack": slack_resource}, hooks={slack_message_on_success}) def my_job(): # Define your ops here pass
Remember to provide the necessary configuration for any resources your hooks use when you execute the job. This is a basic example, and your actual implementation might vary depending on the specifics of your use case and the resources you're interacting with. Always refer to the latest Dagster documentation for the most up-to-date guidance on creating and using hooks.Hvuj
02/25/2024, 7:23 AMScout
02/25/2024, 7:23 AMrun_launcher
or executor
to perform actions before the pipeline run starts. This is more advanced and requires a deeper integration with Dagster's execution system. 4. Sensors: Sensors in Dagster are used to trigger pipeline runs in response to external events. While they are not pre-hooks, you can use a sensor to perform checks or set up conditions before triggering a pipeline run. If none of these options suit your needs and you specifically require a pre-run hook, you might consider reaching out to the Dagster community for advice or to propose a feature request. The community and maintainers could provide insights into whether such a feature is on the roadmap or suggest alternative approaches. For now, the recommended approach is to use the existing mechanisms within Dagster to perform any necessary actions before a pipeline run. Always refer to the latest Dagster documentation for the most up-to-date guidance and best practices.Hvuj
02/25/2024, 7:23 AMScout
02/25/2024, 7:23 AM@success_hook
and @failure_hook
decorators and then attach them to your ops or jobs. These hooks will be triggered during the pipeline run when the corresponding events occur (i.e., when an op succeeds or fails). Here's how you can define and use hooks in a Dagster pipeline: 1. Define the Hook: Create a Python function and decorate it with either @success_hook
or @failure_hook
, depending on when you want the hook to be triggered. python from dagster import success_hook, failure_hook, HookContext @success_hook def my_success_hook(context: HookContext): # Logic to run when an op succeeds pass @failure_hook def my_failure_hook(context: HookContext): # Logic to run when an op fails pass
2. Attach the Hook to Ops: Use the .with_hooks
method to attach the hook to individual ops within your job. python from dagster import op, job @op def my_op(context): # Your op logic here pass @job def my_job(): my_op.with_hooks(hook_defs={my_success_hook})
3. Attach the Hook to Jobs: Alternatively, you can attach hooks to the entire job by passing a set of hook definitions to the hooks
parameter of the @job
decorator. python @job(hooks={my_success_hook, my_failure_hook}) def my_job(): my_op()
When you execute the job, Dagster will run the hooks at the appropriate times during the pipeline execution: - my_success_hook
will be executed after any op within the job completes successfully. - my_failure_hook
will be executed after any op within the job fails. Remember that hooks are a powerful way to add custom behavior to your pipeline runs, such as notifications, metrics collection, or cleanup tasks. Always refer to the latest Dagster documentation for the most up-to-date guidance on creating and using hooks.Hvuj
02/25/2024, 7:30 AMScout
02/25/2024, 7:30 AMpython from dagster import op, job, HookContext, success_hook # Define a dummy op @op def start_pipeline_op(): pass # This op does nothing # Define a hook that will run after the dummy op succeeds @success_hook def pipeline_start_hook(context: HookContext): # Logic to run at the start of the pipeline pass # Attach the hook to the dummy op @job def my_pipeline(): start_pipeline_op.with_hooks(hook_defs={pipeline_start_hook}) # Rest of your pipeline ops
In this example, start_pipeline_op
is a dummy op that does nothing, and pipeline_start_hook
is a hook that contains the logic you want to run at the start of the pipeline. When you execute my_pipeline
, the start_pipeline_op
will run, and upon its success, the pipeline_start_hook
will be triggered. While this approach does not hide the dummy op from the UI, it allows you to execute custom logic at the beginning of your pipeline run. If you have a specific requirement for ops not to be shown in the UI, you might consider reaching out to the Dagster community or checking the GitHub issues and discussions for any updates or workarounds that other users might have shared.Hvuj
02/25/2024, 7:39 AMScout
02/25/2024, 7:39 AM@success_hook
is triggered after an op completes successfully, and @failure_hook
is triggered if an op fails. There is no built-in mechanism for hooks to run during the execution of an op. Here's a brief overview of how hooks work in Dagster: - Success Hook: A success hook is executed after an op completes without any errors. It allows you to define logic that should run only when the op is successful. - Failure Hook: A failure hook is executed if an op raises an exception during its execution. This allows you to handle errors or perform cleanup actions. Both types of hooks are defined as functions and decorated with @success_hook
or @failure_hook
. They receive a HookContext
object, which provides information about the op and the job. If you need to perform actions during the execution of an op, you should include that logic within the body of the op itself. Hooks are not intended for use during an op's execution; they are meant to respond to the op's outcome. For example, if you want to log something or perform a check in the middle of an op's execution, you would do so directly within the op's function: python from dagster import op @op def my_op(context): # Logic before the check ... # Perform some check or action during the op <http://context.log.info|context.log.info>("Performing a check") if some_condition: # Handle the condition ... # Logic after the check ...
In this example, the check is performed as part of the op's execution flow, not as a separate hook. If you have a use case that requires monitoring or interacting with an op during its execution, you would need to implement that logic within the op itself.Hvuj
02/25/2024, 7:41 AMScout
02/25/2024, 7:41 AM@success_hook
will not trigger the hook during the op's execution. In Dagster, hooks are not designed to be nested within ops, and the @success_hook
decorator is intended to be used at the top level to define hooks that respond to the completion of ops. Hooks in Dagster are triggered by the Dagster framework after an op has finished executing. They are not called like regular functions within the op's code. Instead, they are registered with the framework, and the framework calls them when the appropriate event (success or failure of an op) occurs. If you want to execute some logic during an op's execution, you should simply include that logic as part of the op's function body. Here's an example of how to include additional logic within an op: python from dagster import op @op def my_op(context): # Your op logic here do_something() # Additional logic you want to run during the op do_additional_thing() # More op logic do_something_else()
In this example, do_additional_thing()
is a regular function call that occurs as part of the op's execution. It is not a hook and does not need to be decorated with @success_hook
. To use hooks properly, you define them outside of ops and then attach them to ops or jobs using the @job
decorator or the .with_hooks
method on ops. Here's an example of defining and using a success hook: python from dagster import op, success_hook, HookContext, job # Define a success hook @success_hook def my_success_hook(context: HookContext): # Logic to run after an op succeeds <http://context.log.info|context.log.info>(f"Op {context.op.name} succeeded.") # Define an op @op def my_op(): # Op logic pass # Attach the hook to the job @job(hooks={my_success_hook}) def my_job(): my_op()
In this example, my_success_hook
will be triggered after my_op
completes successfully when my_job
is executed. The hook is not part of the op's internal logic; it is a separate function that responds to the op's success event.Hvuj
02/25/2024, 7:42 AMfrom dagster._core.definitions.decorators.hook_decorator import _validate_hook_fn_params,event_list_hook
from dagster._core.definitions.events import HookExecutionResult
import dagster._check as check
StartHookFn = Callable[["HookContext"], Any]
@overload
def start_hook(hook_fn: StartHookFn) -> HookDefinition:
...
@overload
def start_hook(
*,
name: Optional[str] = ...,
required_resource_keys: Optional[AbstractSet[str]] = ...,
) -> Callable[[StartHookFn], HookDefinition]:
...
def start_hook(
hook_fn: Optional[StartHookFn] = None,
*,
name: Optional[str] = None,
required_resource_keys: Optional[AbstractSet[str]] = None,
) -> Union[HookDefinition, Callable[[StartHookFn], HookDefinition]]:
"""Create a hook on step success events with the specified parameters from the decorated function.
Args:
name (Optional[str]): The name of this hook.
required_resource_keys (Optional[AbstractSet[str]]): Keys for the resources required by the
hook.
Examples:
.. code-block:: python
@start_hook(required_resource_keys={'slack'})
def slack_message_on_success(context):
message = 'op {} succeeded'.format(context.op.name)
context.resources.slack.send_message(message)
@start_hook
def do_something_on_success(context):
do_something()
"""
def wrapper(fn: StartHookFn) -> HookDefinition:
check.callable_param(fn, "fn")
expected_positionals = ["context"]
_validate_hook_fn_params(fn, expected_positionals)
if name is None or callable(name):
_name = fn.__name__
else:
_name = name
@event_list_hook(name=_name, required_resource_keys=required_resource_keys, decorated_fn=fn)
def _start_hook(
context: "HookContext", event_list: Sequence["DagsterEvent"]
) -> HookExecutionResult:
for event in event_list:
if event.is_step_start:
fn(context)
return HookExecutionResult(hook_name=_name, is_skipped=False)
# hook is skipped when fn didn't run
return HookExecutionResult(hook_name=_name, is_skipped=True)
return _start_hook
# This case is for when decorator is used bare, without arguments, i.e. @start_hook
if hook_fn is not None:
check.invariant(required_resource_keys is None)
return wrapper(hook_fn)
return wrapper
Scout
02/25/2024, 7:42 AM@success_hook
and @failure_hook
decorators to create hooks that trigger after an op has completed successfully or failed, respectively. There is no public API support for a "start hook" that triggers before an op's execution. Using internal APIs, as shown in your snippet, can lead to unexpected behavior and compatibility issues, especially when upgrading Dagster to newer versions, as internal implementations may change without notice. If you need to run logic at the start of an op, the recommended approach is to include that logic within the op itself. If you need to run logic at the start of a pipeline, consider using resources or custom initialization logic in your job definition. For any functionality that is not explicitly covered in the official documentation, you might consider reaching out to the Dagster community for advice or to propose a feature request. The community and maintainers could provide insights into whether such a feature is on the roadmap or suggest alternative approaches. It's important to follow the practices and patterns recommended by the official Dagster documentation to ensure that your pipelines are stable, maintainable, and compatible with future Dagster releases.Hvuj
02/25/2024, 7:44 AMconsider using resources or custom initialization logic in your job definition.
please elaborateScout
02/25/2024, 7:44 AMpython from dagster import resource @resource def my_resource(init_context): # Perform initialization logic here # For example, set up a database connection db_connection = connect_to_database(init_context.resource_config['connection_string']) return db_connection
2. Attach the Resource to a Job: When defining your job, you can attach the resource using the resource_defs
argument. This will ensure that the resource is initialized when the job starts. python from dagster import job @job(resource_defs={'my_resource': my_resource}) def my_job(): # Define your ops here pass
3. Use the Resource in Ops: Within your ops, you can access the resource via the context object. This allows you to use the initialized resource as part of your op logic. python from dagster import op @op(required_resource_keys={'my_resource'}) def my_op(context): # Use the initialized resource db_connection = context.resources.my_resource # Perform operations using the resource ...
When my_job
is executed, Dagster will first initialize the my_resource
resource, running any setup logic you've defined. Then, it will proceed to execute the ops within the job. This approach allows you to perform initialization logic at the start of your job, ensuring that all necessary preconditions are met before your ops begin executing. It's a clean and idiomatic way to manage setup tasks in Dagster.Hvuj
02/25/2024, 8:01 AMScout
02/25/2024, 8:01 AMInvokedNodeOutputHandle
, which is not valid. An InvokedNodeOutputHandle
represents the output of an op that has already been executed, and hooks cannot be directly applied to these outputs. This error often arises from a misunderstanding of how to apply hooks within a graph. Hooks should be applied to ops or to the entire job, not to the outputs of ops. Here's an example of how to correctly apply a hook to an op within a graph: python from dagster import graph, op, success_hook, HookContext # Define a success hook @success_hook def my_success_hook(context: HookContext): # Logic to run after an op succeeds pass # Define an op @op def my_op(): # Op logic pass # Define a graph @graph def my_graph(): # Apply the hook to the op within the graph my_op.with_hooks(hook_defs={my_success_hook}) # Convert the graph to a job my_job = my_graph.to_job()
In this example, the my_success_hook
is applied to my_op
within the definition of my_graph
. When my_job
is executed, the hook will be triggered after my_op
completes successfully. If you're encountering this error, review your graph and job definitions to ensure that hooks are being applied correctly. Make sure that you're not trying to attach hooks to the outputs of ops, but rather to the ops themselves or to the entire job. If you need further assistance, please provide the relevant portion of your code where you're defining your graph and applying hooks, and I can help you identify the specific issue.Hvuj
02/25/2024, 8:06 AMScout
02/25/2024, 8:06 AMpipeline_end
is being referenced without being invoked, and that there are hook definitions provided (slack_message_hook_on_success
, slack_message_hook_on_start
) that may be related to this issue. In Dagster, when you define a graph and reference ops within it, you need to invoke the ops by calling them as functions. If you reference an op without invoking it (i.e., without calling it with parentheses ()
), you'll receive a warning like the one you've described. Here's an example of how to correctly invoke an op within a graph: python from dagster import graph, op @op def pipeline_start(): # Logic for starting the pipeline pass @op def pipeline_end(): # Logic for ending the pipeline pass @graph def pipeline_exit(): # Invoke the ops by calling them with parentheses pipeline_start() pipeline_end() # Convert the graph to a job pipeline_exit_job = pipeline_exit.to_job()
In this example, both pipeline_start
and pipeline_end
are invoked within the pipeline_exit
graph by calling them with parentheses. This is the correct way to include ops within a graph. If you're seeing the warning message, it's likely that you have something like this in your code: python @graph def pipeline_exit(): # Incorrectly referencing an op without invoking it pipeline_end # Missing parentheses
To resolve the warning, ensure that you invoke all ops within your graph by calling them with parentheses. If you have hooks that you want to apply to specific ops, you can do so using the .with_hooks
method on the op when you invoke it: python @graph def pipeline_exit(): pipeline_start.with_hooks(hook_defs={slack_message_hook_on_start})() pipeline_end.with_hooks(hook_defs={slack_message_hook_on_success})()
Review your graph definition and make sure that all ops are correctly invoked, and that hooks are applied to the ops, not to the graph itself. If you continue to experience issues, please provide the relevant code snippet, and I can offer more specific guidance.Hvuj
02/25/2024, 9:43 AMScout
02/25/2024, 9:43 AMNothing
type. The Nothing
type is a special Dagster type that indicates an op has a dependency on another op without needing to pass any data between them. Here's how you can create a dependency from your dummy op to the other four ops using the Nothing
type: 1. Define your dummy op to return Nothing
. python from dagster import op, Nothing, Out @op(out=Out(Nothing)) def start_pipeline(): # This op does nothing but starts the pipeline pass
2. Define the other ops to have an input of type Nothing
. This input will be used to establish the dependency. python from dagster import op, In @op(ins={"start": In(Nothing)}) def op1(start): # Logic for op1 pass @op(ins={"start": In(Nothing)}) def op2(start): # Logic for op2 pass @op(ins={"start": In(Nothing)}) def op3(start): # Logic for op3 pass @op(ins={"start": In(Nothing)}) def op4(start): # Logic for op4 pass
3. In your graph or job, connect the dummy op to the other ops using the Nothing
dependency. python from dagster import graph @graph def my_pipeline(): start = start_pipeline() op1(start=start) op2(start=start) op3(start=start) op4(start=start)
When you execute my_pipeline
, Dagster will first run start_pipeline
, and then it will run op1
, op2
, op3
, and op4
in any order since they all depend on the completion of start_pipeline
but do not depend on each other's outputs. This setup ensures that start_pipeline
runs before the other four ops, and since it returns Nothing
, it does not pass any data to them. The other ops wait for start_pipeline
to complete before they begin execution.Hvuj
02/25/2024, 9:46 AMstart = start_pipeline()
op1(start=start)
Scout
02/25/2024, 9:46 AMstart
dependency in the graph, you can use the after
parameter in the @op
decorator to specify dependencies. This parameter allows you to declare that an op should run after certain other ops have completed, without needing to pass the Nothing
type between them. Here's how you can define the dependency using the after
parameter: 1. Define your dummy op without any outputs: python from dagster import op @op def start_pipeline(): # This op does nothing but starts the pipeline pass
2. Define the other ops with the after
parameter to indicate they should run after `start_pipeline`: python from dagster import op @op def op1(): # Logic for op1 pass @op def op2(): # Logic for op2 pass @op def op3(): # Logic for op3 pass @op def op4(): # Logic for op4 pass
3. In your graph or job, use the after
parameter when invoking the ops: python from dagster import graph @graph def my_pipeline(): start = start_pipeline() op1(after=[start]) op2(after=[start]) op3(after=[start]) op4(after=[start])
By using the after
parameter, you're telling Dagster that op1
, op2
, op3
, and op4
should not start until after start_pipeline
has completed. This way, you don't need to pass the start
output explicitly when constructing the graph. Please note that the after
parameter is used within the graph or job definition when you're invoking the ops, not in the @op
decorator itself. This allows you to establish execution order dependencies without passing data.Hvuj
02/25/2024, 9:49 AMScout
02/25/2024, 9:49 AMafter
parameter when invoking the exit op within your graph or job definition. This parameter allows you to specify that the exit op should run after the completion of the specified ops. Here's how you can set up the pipeline exit dummy op to run after a few independent ops: 1. Define your independent ops and the pipeline exit dummy op: python from dagster import op @op def independent_op1(): # Logic for independent_op1 pass @op def independent_op2(): # Logic for independent_op2 pass @op def independent_op3(): # Logic for independent_op3 pass @op def pipeline_exit(): # This op does nothing but signifies the pipeline exit pass
2. In your graph or job, invoke the independent ops and then the pipeline exit dummy op with the after
parameter, listing all the independent ops: python from dagster import graph @graph def my_pipeline(): op1 = independent_op1() op2 = independent_op2() op3 = independent_op3() # Specify that pipeline_exit should run after op1, op2, and op3 have completed pipeline_exit(after=[op1, op2, op3])
By using the after
parameter when invoking pipeline_exit
, you're telling Dagster that pipeline_exit
should not start until after independent_op1
, independent_op2
, and independent_op3
have completed. This ensures that pipeline_exit
runs at the end of your pipeline, after the specified independent ops, even though they do not have data dependencies between them. Remember to convert your graph to a job if you want to execute it as a pipeline: python my_pipeline_job = my_pipeline.to_job()
This setup will maintain the desired execution order within your Dagster pipeline.Hvuj
02/25/2024, 9:50 AMScout
02/25/2024, 9:50 AMpython from dagster import graph, op @op def inner_op1(): # Logic for inner_op1 pass @op def inner_op2(): # Logic for inner_op2 pass @graph def inner_graph(): inner_op1() inner_op2()
2. Define your outer graph that includes the inner graph: python from dagster import graph, op @op def outer_op1(): # Logic for outer_op1 pass @op def outer_op2(): # Logic for outer_op2 pass @graph def outer_graph(): # Invoke the inner graph inner_graph() # Define additional ops or graphs outer_op1() outer_op2()
3. If you want to run an op after the inner graph has completed, you can capture the outputs of the inner graph's ops (if any) and use them as dependencies for the subsequent ops: python @graph def outer_graph(): # Invoke the inner graph and capture its outputs if needed inner_results = inner_graph() # Use the outputs of the inner graph as dependencies for outer ops outer_op1(after=[inner_results]) outer_op2(after=[inner_results])
4. If the inner graph does not return any outputs, or if you simply want to ensure that certain ops run after the inner graph without considering outputs, you can use the after
parameter as before: python @graph def outer_graph(): # Invoke the inner graph inner = inner_graph() # Specify that outer ops should run after the inner graph has completed outer_op1(after=[inner]) outer_op2(after=[inner])
5. Convert the outer graph to a job to execute it as a pipeline: python outer_pipeline_job = outer_graph.to_job()
By structuring your graphs and jobs in this way, you can create complex pipelines with nested graphs while still maintaining clear execution order and dependencies.Hvuj
02/25/2024, 9:53 AMstart = pipeline_init()
the next step is 4 graphs that run in parallel, i would like to run them after the startScout
02/25/2024, 9:53 AMafter
parameter when invoking the graphs within your outer graph. This parameter allows you to specify that the graphs should run after the start
op has completed. Here's an example of how you can set up your outer graph to run four inner graphs in parallel after the start
op: 1. Define your start op: python from dagster import op @op def pipeline_init(): # Logic for pipeline initialization pass
2. Define your inner graphs: python from dagster import graph @graph def graph1(): # Define ops for graph1 pass @graph def graph2(): # Define ops for graph2 pass @graph def graph3(): # Define ops for graph3 pass @graph def graph4(): # Define ops for graph4 pass
3. Define your outer graph and use the after
parameter to ensure the inner graphs run after the start
op: python from dagster import graph @graph def outer_graph(): start = pipeline_init() # Invoke the inner graphs with the `after` parameter graph1(after=[start]) graph2(after=[start]) graph3(after=[start]) graph4(after=[start])
4. Convert the outer graph to a job: python outer_pipeline_job = outer_graph.to_job()
When you execute outer_pipeline_job
, Dagster will first run the pipeline_init
op. After it completes, it will run graph1
, graph2
, graph3
, and graph4
in parallel, since they do not have dependencies on each other and only depend on the completion of the start
op. This setup ensures that your initialization logic runs first, followed by the parallel execution of your four graphs.Hvuj
02/25/2024, 9:55 AMScout
02/25/2024, 9:55 AMafter
parameter is not used in Dagster to specify execution order for graphs. Instead, you should use the after
parameter within the definitions of the ops inside the graphs if you want to specify execution order dependencies between ops. To run four graphs in parallel after a start op, you can simply invoke the graphs within your outer graph after the start op, without any explicit dependency. Since there is no data dependency between the start op and the graphs, Dagster will not enforce any execution order, and the graphs will run as soon as they are ready. Here's how you can structure your outer graph: python from dagster import graph @graph def outer_graph(): start = pipeline_init() # Invoke the inner graphs without specifying any dependencies graph1() graph2() graph3() graph4()
In this setup, start
is not used to enforce any execution order, and the four graphs are free to run in parallel. If you want to ensure that the graphs run only after the start
op has completed, you would need to include a dummy op with a Nothing
dependency in each graph that is triggered by the start
op. Here's an example of how you can modify one of the inner graphs to include a dummy op with a Nothing
dependency: python from dagster import graph, op, Nothing, In @op def dummy_op(start: Nothing): pass @graph def graph1(): start = pipeline_init() dummy_op(start=start) # Rest of the ops for graph1
Repeat this pattern for graph2
, graph3
, and graph4
, ensuring that each graph has a dummy op that depends on the start
op. Then, in your outer graph, you can invoke these graphs without any additional parameters: python @graph def outer_graph(): start = pipeline_init() # Invoke the modified inner graphs graph1(start=start) graph2(start=start) graph3(start=start) graph4(start=start)
Now, when you execute outer_graph
, Dagster will run the start
op first, followed by the dummy ops in each graph, which will enforce the execution order you desire.Hvuj
02/25/2024, 9:58 AMScout
02/25/2024, 9:58 AMpython from dagster import op @op def pipeline_init(): # Logic for pipeline initialization pass
2. Define your inner graphs: These are the graphs that you want to run in parallel after the start op. python from dagster import graph @graph def graph1(): # Define ops for graph1 pass @graph def graph2(): # Define ops for graph2 pass @graph def graph3(): # Define ops for graph3 pass @graph def graph4(): # Define ops for graph4 pass
3. Define your outer graph: This graph will include the start op and the four inner graphs. python from dagster import graph @graph def outer_graph(): # First, invoke the start op pipeline_init() # Then, invoke the inner graphs. These will run in parallel after the start op. graph1() graph2() graph3() graph4()
4. Convert the outer graph to a job: This allows you to execute the entire pipeline. python outer_pipeline_job = outer_graph.to_job()
When you run outer_pipeline_job
, Dagster will execute the pipeline_init
op first. After pipeline_init
completes, Dagster will proceed to execute graph1
, graph2
, graph3
, and graph4
. Since there are no data dependencies between pipeline_init
and the inner graphs, Dagster will run the inner graphs in parallel by default. If you want to enforce that the inner graphs only start after pipeline_init
has completed, you would need to create a dependency from pipeline_init
to each of the inner graphs. However, as of my knowledge cutoff in early 2023, Dagster does not support direct dependencies between graphs. Instead, you would need to establish dependencies at the op level within each graph, potentially using a Nothing
dependency as I described earlier. If the behavior you're looking for is not supported by the current version of Dagster, I recommend reaching out to the Dagster community for assistance or to check if there have been any updates that provide this functionality.Hvuj
02/25/2024, 9:59 AMfrom dagster import graph
@graph
def outer_graph():
# First, invoke the start op
pipeline_init()
# Then, invoke the inner graphs. These will run in parallel after the start op.
graph1()
graph2()
graph3()
graph4()
it runs all 5 graphs in parallel but i want to run first pipeline_init graph and then the other 4Scout
02/25/2024, 9:59 AMpipeline_init
runs before the other four graphs, you can use the @graph
decorator to define a new graph that encapsulates the logic of running pipeline_init
followed by the other graphs. However, you will need to establish dependencies between the ops within pipeline_init
and the ops within the other graphs. Here's a revised approach: 1. Define your pipeline_init
graph and ensure it has an op that represents the completion of the initialization: python from dagster import graph, op, Nothing, Out @op(out=Out(Nothing)) def start_op(): # Logic for pipeline initialization pass @graph def pipeline_init(): start_op()
2. Define your four graphs that should run after pipeline_init
. Each graph should have an initial op that depends on a Nothing
input, which will be used to establish the dependency on `pipeline_init`: python from dagster import graph, op, In @op(ins={"start": In(Nothing)}) def graph1_start(start): # Logic for the start of graph1 pass @graph def graph1(): graph1_start() # Repeat for graph2, graph3, and graph4
3. Define your outer graph that first invokes pipeline_init
and then invokes the other graphs, passing the output of pipeline_init
to the initial op of each graph: python from dagster import graph @graph def outer_graph(): # Invoke the pipeline_init graph and capture its output start = pipeline_init() # Pass the output of pipeline_init to the initial ops of the other graphs graph1(start=start) graph2(start=start) graph3(start=start) graph4(start=start)
4. Convert the outer graph to a job: python outer_pipeline_job = outer_graph.to_job()
When you run outer_pipeline_job
, Dagster will execute the pipeline_init
graph first. The output of pipeline_init
(which is of type Nothing
) will then be passed to the initial ops of graph1
, graph2
, graph3
, and graph4
, enforcing that they run after pipeline_init
has completed. This approach ensures that pipeline_init
runs first, followed by the other four graphs in parallel, while respecting the dependency established by the Nothing
type.Hvuj
02/25/2024, 10:03 AMScout
02/25/2024, 10:03 AMDagsterInvalidDefinitionError
, indicates that there is an unmapped input 'start' in the @graph
'read_data'. This means that the graph read_data
expects an input named 'start', but it is not being provided or passed to any op or graph within the read_data
graph. To resolve this issue, you need to ensure that the 'start' input is correctly passed to the ops within the read_data
graph that require it. If the 'start' input is of type Nothing
, it is used to establish execution order rather than to pass data. Here's an example of how you might define a graph that requires a 'start' input: python from dagster import graph, op, In, Nothing @op(ins={"start": In(Nothing)}) def my_op(start): # Your op logic here @graph def read_data(start): my_op(start=start)
When you invoke the read_data
graph from another graph or job, you need to provide the 'start' input: python from dagster import graph, op, Nothing, Out @op(out=Out(Nothing)) def start_op(): # Logic for pipeline initialization @graph def outer_graph(): start = start_op() read_data(start=start) # ... invoke other graphs similarly, passing 'start' as needed
In this example, start_op
is an op that returns Nothing
, and read_data
is a graph that takes a 'start' input of type Nothing
. When outer_graph
is invoked, it calls start_op
and then passes its output to read_data
as the 'start' input. Make sure that all graphs and ops that require the 'start' input are correctly receiving it when invoked. If an op or graph does not require the 'start' input, you should not include it in the definition or invocation. If you continue to experience issues, please check the definitions of your graphs and ops to ensure that inputs are correctly mapped and provided where necessary. If you need further assistance, please provide the relevant code snippets, and I can offer more specific guidance.Hvuj
02/25/2024, 10:07 AMScout
02/25/2024, 10:07 AMpython from dagster import graph, op, In # Define an op that requires an input @op def process_data(data): # Perform some processing on the data pass # Define a graph that takes an input and passes it to the op @graph def my_graph(input_data): process_data(input_data) # When invoking the graph, you pass the input to it result = my_graph(input_data="some data")
In this example, my_graph
takes an input called input_data
and passes it to the process_data
op within the graph. When you invoke my_graph
, you must provide the input_data
argument, which is then used by the process_data
op. If your graph contains multiple ops that require the same input, you must pass the input to each op that needs it: python @op def op1(data): pass @op def op2(data): pass @graph def my_graph(input_data): op1(input_data) op2(input_data)
If an op within the graph does not require the input, you do not need to pass it to that op. Inputs are only passed to the ops that have explicitly defined them as parameters. Remember that the names of the inputs in the ops must match the names used when passing the inputs within the graph. If the names do not match, you will encounter an error indicating that an input is unmapped or missing.Hvuj
02/25/2024, 10:57 AMScout
02/25/2024, 10:57 AMHvuj
02/25/2024, 11:44 AMScout
02/25/2024, 11:44 AMSTEP_FAILURE
through the event log, which records all the events that occur during pipeline execution. The event log includes various event types, such as STEP_START
, STEP_SUCCESS
, and STEP_FAILURE
, among others. To access STEP_FAILURE
events, you can query the event log for a specific pipeline run. Here's an example of how you might do this programmatically: python from dagster import DagsterEventType def get_step_failure_events(run_id, instance): """ Retrieve all step failure events for a given run ID. Args: run_id (str): The ID of the pipeline run. instance (DagsterInstance): The instance of the Dagster pipeline. Returns: List[EventLogEntry]: A list of EventLogEntry objects representing step failure events. """ # Fetch the event log entries for the given run ID event_records = instance.all_logs(run_id) # Filter the event log entries to only include step failure events step_failure_events = [ event_record for event_record in event_records if event_record.dagster_event and event_record.dagster_event.event_type == DagsterEventType.STEP_FAILURE ] return step_failure_events
In this function, run_id
is the ID of the pipeline run you're interested in, and instance
is an instance of DagsterInstance
that represents the Dagster pipeline's runtime environment. You can obtain the run_id
from the context of a pipeline run, and you typically have access to the instance
object within the context of your Dagster system. Please note that the exact method of accessing the event log and filtering for STEP_FAILURE
events may vary depending on the version of Dagster you are using and the context in which you are trying to access these events. Always refer to the latest Dagster documentation for the most up-to-date guidance on interacting with the event log and handling events.Hvuj
02/25/2024, 1:25 PMScout
02/25/2024, 1:25 PMSTEP_FAILURE
are represented by an enumeration, specifically the DagsterEventType
enum. To convert an event type to a string, you can access the value
attribute of the enum member, which will give you the string representation of the event type. You do not need to use the str()
function directly on the enum member. Here's an example of how to get the string representation of the STEP_FAILURE
event type: python from dagster import DagsterEventType # Get the string representation of the STEP_FAILURE event type step_failure_str = DagsterEventType.STEP_FAILURE.value print(step_failure_str) # Output: "STEP_FAILURE"
In this example, DagsterEventType.STEP_FAILURE.value
will give you the string "STEP_FAILURE"
, which is the string representation of the event type. If you have an EventLogEntry
object that represents a step failure event, you can also convert the event type to a string as follows: python from dagster import DagsterInstance # Assuming you have a run_id and a DagsterInstance run_id = "your_run_id_here" instance = DagsterInstance.get() # Get the event log entries for the given run ID event_records = instance.all_logs(run_id) # Find the first STEP_FAILURE event and convert its type to a string for event_record in event_records: if event_record.dagster_event and event_record.dagster_event.event_type == DagsterEventType.STEP_FAILURE: step_failure_str = event_record.dagster_event.event_type.value print(step_failure_str) # Output: "STEP_FAILURE" break
In this code snippet, we iterate over the event log entries, check if an entry is a step failure event, and then print the string representation of the event type. Remember to always refer to the latest Dagster documentation for the most accurate and up-to-date information on handling events and their properties.