google-fluentd-sidecar.conf

@include config.d/*.conf

# Do not collect fluentd's own logs to avoid infinite loops.
<match fluent.**>
  @type null
</match>

# Add k8s_container label from environment variables K8S_NAMESPACE, K8S_POD, K8S_CONTAINER
<filter **>
  @type record_transformer
  enable_ruby true
  <record>
    "logging.googleapis.com/local_resource_id" ${"k8s_container.#{ENV['K8S_NAMESPACE']}.#{ENV['K8S_POD']}.#{ENV['K8S_CONTAINER']}"}
  </record>
</filter>

# Add Kubernetes metadata labels from DownwardApiVolume /k8s/labels
# This enables searching/aggregating logs using k8s labels.
<filter **>
  @type record_transformer
  enable_ruby true
  <record>
    "logging.googleapis.com/labels" ${File.foreach("/k8s/labels").map{ |line| /^(.*)=\"(.*)\"$/.match(line)[1..2] }.map{ |k,v| [ "k8s-pod/#{k}", v] }.to_h }
  </record>
</filter>

# Add a unique insertId to each log entry that doesn't already have it.
# This helps guarantee the order and prevent log duplication.
<filter **>
  @type add_insert_ids
</filter>

# Configure all sources to output to Google Cloud Logging
<match **>
  @type google_cloud
  buffer_type file
  buffer_path /var/log/google-fluentd/buffers

  # Set the chunk limit conservatively to avoid exceeding the recommended
  # chunk size of 5MB per write request.
  buffer_chunk_limit 512KB

  # Flush logs every 5 seconds, even if the buffer is not full.
  flush_interval 5s

  # Enforce some limit on the number of retries.
  disable_retry_limit false

  # After 3 retries, a given chunk will be discarded.
  retry_limit 3

  # Wait 10 seconds before the first retry. The wait interval will be doubled on
  # each following retry (20s, 40s...) until it hits the retry limit.
  retry_wait 10

  # Never wait longer than 5 minutes between retries. If the wait interval
  # reaches this limit, the exponentiation stops.
  # Given the default config, this limit should never be reached, but if
  # retry_limit and retry_wait are customized, this limit might take effect.
  max_retry_wait 300

  # Use multiple threads for processing.
  num_threads 8
  detect_json true

  # Use the gRPC transport.
  use_grpc true
</match>