Duplicate log entries with Google Cloud Stackdriver logging of Python code on Kubernetes Engine

Question

I have a simple Python app running in a container on Google Kubernetes Engine. I am trying to connect the standard Python logging to Google Stackdriver logging using this guide. I have almost succeeded, but I am getting duplicate log entries with one always at the 'error' level...

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Screenshot of Stackdriver logs showing duplicate entries

This is my python code that set's up the logging according to the above guide:

import webapp2
from paste import httpserver
import rpc

# Imports the Google Cloud client library
import google.cloud.logging
# Instantiates a client
client = google.cloud.logging.Client()
# Connects the logger to the root logging handler; by default this captures
# all logs at INFO level and higher
client.setup_logging()

app = webapp2.WSGIApplication([('/rpc/([A-Za-z]+)', rpc.RpcHandler),], debug=True)
httpserver.serve(app, host='0.0.0.0', port='80')

Here's the code that triggers the logs from the screenshot:

import logging

logging.info("INFO Entering PostEchoPost...")
logging.warning("WARNING Entering PostEchoPost...")
logging.error("ERROR Entering PostEchoPost...")
logging.critical("CRITICAL Entering PostEchoPost...")

Here is the full Stackdriver log, expanded from the screenshot, with an incorrectly interpreted ERROR level:

{
 insertId:  "1mk4fkaga4m63w1"  
 labels: {
  compute.googleapis.com/resource_name:  "gke-alg-microservice-default-pool-xxxxxxxxxx-ttnz"   
  container.googleapis.com/namespace_name:  "default"   
  container.googleapis.com/pod_name:  "esp-alg-xxxxxxxxxx-xj2p2"   
  container.googleapis.com/stream:  "stderr"   
 }
 logName:  "projects/projectname/logs/algorithm"  
 receiveTimestamp:  "2018-01-03T12:18:22.479058645Z"  
 resource: {
  labels: {
   cluster_name:  "alg-microservice"    
   container_name:  "alg"    
   instance_id:  "703849119xxxxxxxxxx"   
   namespace_id:  "default"    
   pod_id:  "esp-alg-xxxxxxxxxx-xj2p2"    
   project_id:  "projectname"    
   zone:  "europe-west1-b"    
  }
  type:  "container"   
 }
 severity:  "ERROR"  
 textPayload:  "INFO Entering PostEchoPost...
"  
 timestamp:  "2018-01-03T12:18:20Z"  
}

Here is the the full Stackdriver log, expanded from the screenshot, with a correctly interpreted INFO level:

{
 insertId:  "1mk4fkaga4m63w0"  
 jsonPayload: {
  message:  "INFO Entering PostEchoPost..."   
  thread:  140348659595008   
 }
 labels: {
  compute.googleapis.com/resource_name:  "gke-alg-microservi-default-pool-xxxxxxxxxx-ttnz"   
  container.googleapis.com/namespace_name:  "default"   
  container.googleapis.com/pod_name:  "esp-alg-xxxxxxxxxx-xj2p2"   
  container.googleapis.com/stream:  "stderr"   
 }
 logName:  "projects/projectname/logs/algorithm"  
 receiveTimestamp:  "2018-01-03T12:18:22.479058645Z"  
 resource: {
  labels: {
   cluster_name:  "alg-microservice"    
   container_name:  "alg"    
   instance_id:  "703849119xxxxxxxxxx"    
   namespace_id:  "default"    
   pod_id:  "esp-alg-xxxxxxxxxx-xj2p2"    
   project_id:  "projectname"    
   zone:  "europe-west1-b"    
  }
  type:  "container"   
 }
 severity:  "INFO"  
 timestamp:  "2018-01-03T12:18:20.260099887Z"  
}

So, this entry might be the key:

container.googleapis.com/stream:  "stderr" 

It looks like in addition to my logging set-up working, all logs from the container are being send to stderr in the container, and I believe that by default, at least on Kubernetes Container Engine, all stdout/stderr are picked up by Google Stackdriver via FluentD... Having said that, I'm out of my depth at this point.

Any ideas why I am getting these duplicate entries?

Answer 1

I solved this problem by overwriting the handlers property on my root logger immediately after calling the setup_logging method

import logging
from google.cloud import logging as gcp_logging
from google.cloud.logging.handlers import CloudLoggingHandler, ContainerEngineHandler, AppEngineHandler

logging_client = gcp_logging.Client()
logging_client.setup_logging(log_level=logging.INFO)
root_logger = logging.getLogger()
# use the GCP handler ONLY in order to prevent logs from getting written to STDERR
root_logger.handlers = [handler
                        for handler in root_logger.handlers
                        if isinstance(handler, (CloudLoggingHandler, ContainerEngineHandler, AppEngineHandler))]

To elaborate on this a bit, the client.setup_logging method sets up 2 handlers, a normal logging.StreamHandler and also a GCP-specific handler. So, logs will go to both stderr and Cloud Logging. You need to remove the stream handler from the handlers list to prevent the duplication.

EDIT: I have filed an issue with Google to add an argument to to make this less hacky.