Thanos sidecar: failed to upload block

What is Thanos sidecar: failed to upload block

Understanding Thanos and Its Purpose

Thanos is an open-source project that provides highly available Prometheus setup with long term storage capabilities. It is designed to scale out Prometheus by providing a global query view, unlimited storage, and downsampling capabilities. Thanos Sidecar is a component that runs alongside Prometheus, enabling it to upload data to object storage and query data from it.

Identifying the Symptom: Sidecar Failed to Upload Block

When using Thanos, you might encounter an error message stating: sidecar: failed to upload block. This indicates that the Sidecar component is unable to upload a block of data to the configured object storage.

What You Observe

In your logs, you may see entries similar to:

level=error ts=2023-10-01T12:34:56.789Z caller=sidecar.go:123 msg="failed to upload block" err="upload failed: access denied"

Delving into the Issue

The error typically arises due to network connectivity problems or insufficient permissions to access the object storage. The Sidecar component needs to communicate with the storage backend to upload blocks, and any disruption in this process can lead to the error.

Common Root Causes

Network connectivity issues between the Sidecar and the object storage.Incorrect or insufficient permissions for the Sidecar to write to the storage.Misconfigured storage endpoint or credentials.

Steps to Fix the Issue

To resolve the issue, follow these steps:

1. Verify Network Connectivity

Ensure that the network path between the Thanos Sidecar and the object storage is open. You can use tools like ping or curl to test connectivity:

ping your-object-storage-endpoint.comcurl -v http://your-object-storage-endpoint.com

2. Check Access Permissions

Ensure that the credentials used by the Sidecar have the necessary permissions to upload data. This typically involves checking the IAM roles or access keys:

For AWS S3, ensure the IAM policy allows s3:PutObject and s3:PutObjectAcl.For GCS, ensure the service account has the Storage Object Creator role.

3. Validate Configuration

Double-check the configuration of the Sidecar to ensure that the storage endpoint and credentials are correctly set. Refer to the Thanos Sidecar documentation for configuration details.

Conclusion

By ensuring network connectivity and verifying permissions, you can resolve the sidecar: failed to upload block error. Proper configuration and access rights are crucial for the seamless operation of Thanos Sidecar. For further assistance, consult the Thanos troubleshooting guide.