> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cognite.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Troubleshooting
> Resolve common issues with Cognite Functions, including folder structure errors, failed calls, logging problems, and deployment issues.
## Incorrect folder structure when deploying a function as a zip file
Cognite Functions expects `handler.py` to be at the root of the zipped folder or at a path relative to the root as pointed to by the [`function_path`](/cdf/functions/index#create-a-function-from-an-uploaded-zip-file) attribute.
The following errors occur when `handler.py` isn't found at either of these locations.
**Error messages:**
When using the API to publish the function, you may see this error message in Cognite Data Fusion (CDF) if the function deployment fails:
`No Python module found at location "handler.py" in zip-file`
If you use the Cognite SDK to publish the function, you may see this error message if the function deployment fails:
`No file found at location`
This typically occurs when the root folder is zipped and not the folder content.
Here's an example of a wrong folder structure:
```commandline theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
func/
├── handler.py
└── requirements.txt
```
If you run the zip command outside the `func/` folder, the folder structure becomes wrong.
```commandline theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
# pwd: ~/tmp
> zip -r func.zip func/
adding: func/ (stored 0%)
adding: func/handler.py (stored 0%)
adding: func/requirements.txt (stored 0%)
```
The `requirements.txt` must be at the root of the zip-file.
**Solution**:
`cd` into the `func` folder before you zip the contents:
```commandline theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
# pwd: ~/tmp/func
> zip -r func.zip *
adding: handler.py (stored 0%)
adding: requirements.txt (stored 0%)
```
## Failed calls without logs
A function call returns with the status `Failed`, and there are no logs to explain why it `Failed`.
**Cause:**
Cognite Functions doesn't support the Python `logging` module, and importing it can sometimes hide the stack trace of failed calls.
**Solution**
Rerun the function after replacing logging statements with print statements. Remove all imports of the logging module.
**Cause:**
Don't place `__init__.py` files in the root folder. The file marks a directory as a Python package and can interfere with the function's run.
**Solution:**
Remove the `__init__.py` file from the root folder. You can include `__init__.py` files in subdirectories if you want to mark those as Python packages.
## Multithreading isn't behaving as expected
Avoid using **multithreading** from within the function as this may break the internal structure of the function such as function status reporting and error detection.
## Faulty requirements.txt
A faulty `requirements.txt` usually results in error messages from pip. These occur in the `error` attribute of the object returned by the function `create` operation. If the function deployment fails, the error also occurs in the CDF user interface.
We've experienced cases where the pip installation failed, but no error messages occurred in the pip log.
**Solution:**
Test the installation locally: `pip install -r requirements.txt`
For Cognite Functions on Azure, the `requirements.txt`-file must be compatible with:
```text theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
azure-functions
azure-identity
azure-keyvault-keys
azure-storage-blob
cryptography
```
## Incorrectly named requirements.txt
Your function call fails with the following message in the logs.
**Error message:**
`ModuleNotFoundError: No module named ...`
**Solution:**
Make sure the file `requirements.txt` is correctly named. If the file name is **misspelled**, the packages listed in the file will **not be installed**.
## Default version of `cognite-sdk`
By default, the function is deployed with the latest version of cognite-sdk. If a specific version is desired, it can be specified in the requirements.txt file uploaded with the function source code.
## Absolute versus relative imports
If the following message occurs in the function call logs, a relative import has failed.
**Error message:**
`ImportError: attempted relative import with no known parent package`
**Cause:**
The user is attempting to use relative imports within their handler.py.
**Solution:**
Use absolute imports instead of relative imports to avoid ambiguity about where the package should be imported from. See RealPython: [Absolute vs Relative Python Imports.](https://realpython.com/absolute-vs-relative-python-imports)
## Scheduled function call fails/times out
The following error message in the function call logs can indicate a problem with the session used to instantiate `CogniteClient`:
**Error message**:
`Could not fetch a valid token or a valid API key. Unable to instantiate a CogniteClient. Please verify your credentials.`
**Solution:**
Check CDF to see if the OpenID Connect (OIDC) settings have been updated. This revokes all existing sessions, and all schedules will fail. Recreate the function schedules to solve this problem.
## Switching from API keys to OIDC tokens
If functions authenticate with API keys, you can use the function's `external_id` to link a schedule to the Cognite Function. If you delete the Cognite Function, the linked schedule will persist and can be relinked to a new function with the same `external_id`.
If functions authenticate with OIDC-tokens, you must link a schedule to a Cognite Function via the function's ID. If you delete the Cognite Function, the schedule can never be relinked to any function since the ID never repeats. Thus, all schedules attached to a function are deleted together with the function.
## Connecting to databases outside CDF
Although connecting to databases outside CDF is technically possible, Cognite doesn't provide an IP range/CIDR to add to an **allowlist**. This makes your database publicly available for any IP, making it highly insecure.
Cognite Functions is intended to be used with CDF data. Solutions such as Azure Functions or AWS Lambdas may be a better fit for generic or arbitrary code execution.
## Download files to the function
If you are trying to download/create files from within a Cognite Function, you may see this error:
**Error message**
`OSError: [Errno 30] Read-only file system`
**Solution:**
The function code only has `write` access to the `/tmp` directory.
For example, the following snippet creates a temporary directory inside `tmp`. Use this directory to create temporary files required during function execution.
```commandline theme={"languages":{"custom":["/_languages/kuiper.json","../_languages/kuiper.json"]}}
with tempfile.TemporaryDirectory() as tmpdirname:
print('created temporary directory', tmpdirname)
```
You can't rely on files created during the execution of a function to be persisted and available in the next execution.