@Marvin We have an ECS that creates a container to run the flows. We have two things, a Prefect Agent and a Prefect Executor. What is each of them for and what's the difference between them? Why locally there isn't an executor?

Let's clarify the concepts and the functions of Prefect agents and executors, keeping in mind that in Prefect 2.x, agents have been deprecated in favor of workers. ### Prefect Agents (Deprecated in 2.x, replaced by Workers) - Role: Agents were responsible for polling for flow runs that are ready to be executed and deploying them in the appropriate execution environment. - Environment: They would start the execution of flow runs on various infrastructure types (e.g., ECS, Kubernetes, Local). - Flow Run Triggering: Agents essentially acted as a bridge between Prefect Cloud or Prefect Server and the chosen execution environment. ### Prefect Workers (Replacement for Agents in Prefect 2.x) - Role: Workers are now the entities that poll for and execute flow runs. They handle the orchestration and management of the infrastructure where flows are executed. - Flexible and Pluggable: Workers support various infrastructure blocks like Docker, Kubernetes, ECS, etc. They offer more flexibility and are designed to be more modular. - More Control: Workers provide more granular control over how and where your flow runs get deployed and processed. ### Prefect Executors - Role: Executors are responsible for the execution of tasks within a flow. They determine how tasks are run, whether sequentially, in parallel, using Dask, etc. - Context: Executors run within the context of a flow run, which means they manage the individual tasks of a flow. - Configuration: Executors can be configured to use different strategies to run tasks like

LocalDaskExecutor

,

DaskExecutor

, or the default

SyncExecutor

. ### Locally Running Prefect When running Prefect flows locally: - No Agent/Worker Needed: There's no need for an agent or worker because the local environment itself is executing the flow. The local Python environment serves the purpose of managing and running the flow. - Direct Execution: The flow and its tasks are executed directly within the local process without needing an intermediary to trigger and manage the execution. ### Summary - Agents (or Workers in 2.x): Manage and trigger flow executions on various infrastructures. - Executors: Handle how individual tasks within a flow are executed (parallel, sequential, etc.). - Local Execution: Directly runs the flow without an intermediary. For further details on the newer worker constructs in Prefect 2.x, I could check the documentation or specific GitHub issues if you need more specific details.

@Marvin I just updated the image that my prefect executor is using in ECS and now a flow is failing with the following error: Finished in state Failed('Flow run encountered an exception. LibraryNotFoundError: Error detecting the version of libcrypto') What's going on?

The error

LibraryNotFoundError: Error detecting the version of libcrypto

indicates that the updated image your Prefect executor is using in ECS is not able to locate or properly interact with the

libcrypto

library, which is commonly part of the OpenSSL library suite. This library is often required for various cryptographic operations that Python libraries (like

cryptography

,

pyopenssl

, etc.) rely on. Here are the steps to diagnose and potentially resolve the issue: ### Step 1: Verify Library Installation Ensure that

libcrypto

is installed in your updated Docker image:

shell
$ docker run --rm -it <your_image> bash
# Check if libcrypto is present
$ ls /usr/lib | grep libcrypto
# or
$ ls /usr/lib64 | grep libcrypto

### Step 2: Install OpenSSL If

libcrypto

is not installed or is missing, you can install OpenSSL which includes `libcrypto`:

Dockerfile
RUN apt-get update && \
    apt-get install -y openssl
# For Alpine images:
RUN apk add --no-cache openssl

### Step 3: Rebuild the Docker Image Rebuild and push the Docker image with the necessary libraries:

shell
$ docker build -t <your_image> .
$ docker push <your_image>

### Step 4: Verify Python Dependencies Ensure that your Python environment within the Docker image has the appropriate dependencies that rely on `libcrypto`:

Dockerfile
# Example to install python dependencies in your Dockerfile
COPY requirements.txt .
RUN pip install -r requirements.txt

### Step 5: Testing Test your flow locally with the Docker image to make sure everything works, or update your ECS configuration to use the updated image and run a flow to verify. ### Further Assistance To provide more targeted assistance based on specific issues that might have been discussed in Prefect’s community or GitHub, let me search Prefect documentation and relevant GitHub issues for more information. Let's see if there's something specific related to the

libcrypto

or similar issues. I'll perform searches now. It appears the documents and GitHub issues searches did not return specific results related to the

LibraryNotFoundError

for

libcrypto

. However, the likely cause is still related to the absence or misconfiguration of the

libcrypto

library in the updated Docker image. ### Next Steps in Troubleshooting 1. Check OpenSSL Installation: Double-check the OpenSSL installation within your Docker image. Explicitly install OpenSSL and verify that

libcrypto

is present. 2. Verify OpenSSL Version: Ensure the installed version of OpenSSL is compatible with the Python libraries used in your flow.

Dockerfile
   RUN apt-get update && \
       apt-get install -y openssl
   # For Alpine images:
   RUN apk add --no-cache openssl

3. Library Paths: Sometimes the library paths might cause issues. Verify and ensure that the library paths are correctly set up. 4. Debugging: Run a simple Python script within your image to check if

libcrypto

can be found. Here’s a quick test script:

python
   import ctypes
   try:
       lib = ctypes.CDLL("libcrypto.so")
       print("libcrypto loaded successfully")
   except OSError as e:
       print(f"libcrypto not found: {e}")

5. Update Dependencies: Ensure that any dependencies requiring

libcrypto

are updated to be compatible with the new OpenSSL version. ### Resources - OpenSSL Installation: Refer to the ECS documentation for any specific instructions if needed. - Docker Hub: Check for base images that come pre-packaged with OpenSSL. - Prefect Documentation: Although not specifically helpful in this case, you can always check back for newer updates: Prefect Docs - Installation. Should you require more detailed searches or queries on this, feel free to ask!