Azure CosmosDB - pymongo.errors.ServerSelectionTimeoutError: encoding with 'idna' codec failed

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Azure CosmosDB - pymongo.errors.ServerSelectionTimeoutError: encoding with 'idna' codec failed

saurabh pophare 0

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I am following the official Azure documentation to build a Travel AI Agent using Python, FastAPI, and Azure CosmosDB (MongoDB API) as the database. The project involves storing and retrieving travel-related data using CosmosDB as the vector store. However, when executing the main.py script responsible for loading data into CosmosDB, the process fails with a Server Selection Timeout Error due to an IDNA (Internationalized Domain Name) encoding issue.

The error message suggests that the CosmosDB hostname is too long, leading to a Unicode encoding failure when pymongo attempts to process it. The pymongo.errors.ServerSelectionTimeoutError occurs when the MongoDB client is unable to establish a connection within the allocated timeout (30 seconds). The traceback indicates that the root cause is:

pymongo.errors.ServerSelectionTimeoutError: encoding with 'idna' codec failed (UnicodeError: label too long)

Python version: 3.11

pymongo version: (output of pip show pymongo)
Azure CosmosDB API: MongoDB API
Connection string: Using MongoClient(connection_string)

Steps Taken:

I verified the CosmosDB connection string is correct.
I tried replacing the MongoClient connection with connect=False.
I ensured my database and collection exist in CosmosDB.
- Python version: 3.11
  - pymongo version: (output of pip show pymongo)
    - Azure CosmosDB API: MongoDB API
      - Connection string: Using MongoClient(connection_string)
Steps Taken:
1. I verified the CosmosDB connection string is correct.
2. I tried replacing the MongoClient connection with connect=False.
I ensured my database and collection exist in CosmosDB.

Vijayalaxmi Kattimani 1,720 Reputation points Microsoft External Staff

2025-03-07T15:29:43.1466667+00:00
Hi saurabh pophare,

Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.

As we understand that, you are encountering an issue with the IDNA encoding when trying to connect to Azure CosmosDB using pymongo.

Please find below the steps and suggestions that may help resolve the issue:

Ensure that the hostname in your CosmosDB connection string is not exceeding the maximum length allowed by the IDNA encoding. If it is, you might need to shorten it or use a different hostname.

Make sure you are using the latest version of pymongo. Sometimes, updating to the latest version can resolve compatibility issues.

As you mentioned, you have already tried using connect=False when creating the MongoClient. This is a good step as it defers the connection until the first operation is attempted, which can sometimes help avoid race conditions.

Ensure that there are no network issues preventing your client from reaching the CosmosDB server. You can try pinging the server or using other network diagnostic tools to verify connectivity.

Double-check your connection string for any typos or errors. Ensure that it follows the correct format for CosmosDB with the MongoDB API.

You can try increasing the server selection timeout to give pymongo more time to establish a connection. You can do this by setting the serverSelectionTimeoutMS parameter when creating the MongoClien. Example:
from pymongo import MongoClient client = MongoClient(connection_string, serverSelectionTimeoutMS=5000)

I hope this information helps. Please do let us know if you have any further queries.
Sai Raghunadh M 2,880 Reputation points Microsoft External Staff

2025-03-10T02:37:08.51+00:00

Hi saurabh pophare,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Sai Raghunadh M 2,880 Reputation points Microsoft External Staff

2025-03-10T10:54:39.3733333+00:00

Hi saurabh pophare,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
saurabh pophare 0 Reputation points

2025-03-11T06:19:40.57+00:00

thankyou for your response but it still doesnt work , trying to fix / understand what is going wrong , reach here if have any other advice.
saurabh pophare 0 Reputation points

2025-03-11T06:55:59.3733333+00:00

that issue is resolve we have to enter the password by replacing the special characters like @ as %40 for the string to work

1 answer

Your answer

Vijayalaxmi Kattimani 1,720 Reputation points Microsoft External Staff

2025-03-07T15:29:43.1466667+00:00

Hi saurabh pophare,

Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.

As we understand that, you are encountering an issue with the IDNA encoding when trying to connect to Azure CosmosDB using pymongo.

Please find below the steps and suggestions that may help resolve the issue:

Ensure that the hostname in your CosmosDB connection string is not exceeding the maximum length allowed by the IDNA encoding. If it is, you might need to shorten it or use a different hostname.

Make sure you are using the latest version of pymongo. Sometimes, updating to the latest version can resolve compatibility issues.

As you mentioned, you have already tried using connect=False when creating the MongoClient. This is a good step as it defers the connection until the first operation is attempted, which can sometimes help avoid race conditions.

Ensure that there are no network issues preventing your client from reaching the CosmosDB server. You can try pinging the server or using other network diagnostic tools to verify connectivity.

Double-check your connection string for any typos or errors. Ensure that it follows the correct format for CosmosDB with the MongoDB API.

You can try increasing the server selection timeout to give pymongo more time to establish a connection. You can do this by setting the serverSelectionTimeoutMS parameter when creating the MongoClien. Example:
from pymongo import MongoClient client = MongoClient(connection_string, serverSelectionTimeoutMS=5000)

I hope this information helps. Please do let us know if you have any further queries.
Sai Raghunadh M 2,880 Reputation points Microsoft External Staff

2025-03-10T02:37:08.51+00:00

Hi saurabh pophare,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Sai Raghunadh M 2,880 Reputation points Microsoft External Staff

2025-03-10T10:54:39.3733333+00:00

Hi saurabh pophare,

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
saurabh pophare 0 Reputation points

2025-03-11T06:19:40.57+00:00

thankyou for your response but it still doesnt work , trying to fix / understand what is going wrong , reach here if have any other advice.
saurabh pophare 0 Reputation points

2025-03-11T06:55:59.3733333+00:00

that issue is resolve we have to enter the password by replacing the special characters like @ as %40 for the string to work

Answer 1

Hi saurabh pophare,

Glad to see you resolve the issue posting it as an answer to help other community members.

pymongo.errors.ServerSelectionTimeoutError: encoding with 'idna' codec failed (UnicodeError: label too long)

The error can cause because of many reasons but one of the reasons is if you have special characters like @,/ in your username and password these need to be escaped before it could be used normally.

special characters such as those that may be used in the user and password need to be URL encoded to be parsed correctly. This includes the @ sign.

Below is an example :

Here password : "kx@jj5/g", where the "@" sign and "/"characters are Present

Which can be escaped bu repenteng %40 as @ and %2F as / respectively

Reference : https://blog.csdn.net/qq_41878442/article/details/141337484

Please feel free to click the 'Upvote' (Thumbs-up) button and 'Accept as Answer'. This helps the community by allowing others with similar queries to easily find the solution.

PratikLad 240 Reputation points Microsoft External Staff

2025-03-12T04:46:11.2133333+00:00

Hi saurabh pophare, Please feel free to click the 'Upvote' (Thumbs-up) button and 'Accept as Answer'. This helps the community by allowing others with similar queries to easily find the solution.

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Azure CosmosDB - pymongo.errors.ServerSelectionTimeoutError: encoding with 'idna' codec failed

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