Stackdriver

Stackdriver output plugin allows to ingest your records into the Google Cloud Stackdriver Logging service.

Before getting started with the plugin configuration, make sure to obtain the proper credentials to get access to the service. We strongly recommend using a common JSON credentials file, reference link:

• Creating a Google Service Account for Stackdriver

Your goal is to obtain a credentials JSON file that will be used later by Fluent Bit Stackdriver output plugin.

Refer to the Google Cloud LogEntry API documentation for information on the meaning of some of the parameters below.

Configuration Parameters

Key	Description	default
google_service_credentials	Absolute path to a Google Cloud credentials JSON file	Value of environment variable $GOOGLE_APPLICATION_CREDENTIALS
service_account_email	Account email associated to the service. Only available if no credentials file has been provided.	Value of environment variable $SERVICE_ACCOUNT_EMAIL
service_account_secret	Private key content associated with the service account. Only available if no credentials file has been provided.	Value of environment variable $SERVICE_ACCOUNT_SECRET
metadata_server	Prefix for a metadata server.	Value of environment variable $METADATA_SERVER, or http://metadata.google.internal if unset.
location	The GCP or AWS region in which to store data about the resource. If the resource type is one of the generic_node or generic_task, then this field is required.
namespace	A namespace identifier, such as a cluster name or environment. If the resource type is one of the generic_node or generic_task, then this field is required.
node_id	A unique identifier for the node within the namespace, such as hostname or IP address. If the resource type is generic_node, then this field is required.
job	An identifier for a grouping of related task, such as the name of a microservice or distributed batch. If the resource type is generic_task, then this field is required.
task_id	A unique identifier for the task within the namespace and job, such as a replica index identifying the task within the job. If the resource type is generic_task, then this field is required.
export_to_project_id	The GCP project that should receive these logs.	The project_id in the google_service_credentials file, or the project_id from Google's metadata.google.internal server.
resource	Set resource type of data. Supported resource types: k8s_container, k8s_node, k8s_pod, global, generic_node, generic_task, and gce_instance.	global, gce_instance
k8s_cluster_name	The name of the cluster that the container (node or pod based on the resource type) is running in. If the resource type is one of the k8s_container, k8s_node or k8s_pod, then this field is required.
k8s_cluster_location	The physical location of the cluster that contains (node or pod based on the resource type) the container. If the resource type is one of the k8s_container, k8s_node or k8s_pod, then this field is required.
labels_key	The name of the key from the original record that contains the LogEntry's labels.	logging.googleapis.com/labels
labels	Optional list of comma-separated of strings specifying key=value pairs. The resulting labels will be combined with the elements obtained from labels_key to set the LogEntry Labels. Elements from labels will override duplicate values from labels_key.
log_name_key	The name of the key from the original record that contains the logName value.	logging.googleapis.com/logName
tag_prefix	Set the tag_prefix used to validate the tag of logs with k8s resource type. Without this option, the tag of the log must be in format of k8s_container(pod/node).* in order to use the k8s_container resource type. Now the tag prefix is configurable by this option (note the ending dot).	k8s_container., k8s_pod., k8s_node.
severity_key	The name of the key from the original record that contains the severity.	logging.googleapis.com/severity
project_id_key	The value of this field is used by the Stackdriver output plugin to find the gcp project id from jsonPayload and then extract the value of it to set the PROJECT_ID within LogEntry logName, which controls the gcp project that should receive these logs.	logging.googleapis.com/projectId. See Stackdriver Special Fields for more info.
autoformat_stackdriver_trace	Rewrite the trace field to include the projectID and format it for use with Cloud Trace. When this flag is enabled, the user can get the correct result by printing only the traceID (usually 32 characters).	false
workers	The number of workers to perform flush operations for this output.	1
custom_k8s_regex	Set a custom regex to extract field like pod_name, namespace_name, container_name and docker_id from the local_resource_id in logs. This is helpful if the value of pod or node name contains dots.	(?<pod_name>[a-z0-9](?:[-a-z0-9]*[a-z0-9])?(?:\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)_(?<namespace_name>[^_]+)_(?<container_name>.+)-(?<docker_id>[a-z0-9]{64})\.log$
resource_labels	An optional list of comma-separated strings specifying resource label plaintext assignments (new=value) and/or mappings from an original field in the log entry to a destination field (destination=$original). Nested fields and environment variables are also supported using the record accessor syntax. If configured, all resource labels will be assigned using this API only, with the exception of project_id. See Resource Labels for more details.
http_request_key	The name of the key from the original record that contains the LogEntry's httpRequest. Note that the default value erroneously uses an underscore; users will likely need to set this to logging.googleapis.com/httpRequest.	logging.googleapis.com/http_request
compress	Set payload compression mechanism. The only available option is gzip. Default = "", which means no compression.
cloud_logging_base_url	Set the base Cloud Logging API URL to use for the /v2/entries:write API request.	https://logging.googleapis.com

Configuration File

If you are using a Google Cloud Credentials File, the following configuration is enough to get started:

fluent-bit.yaml

pipeline:
  inputs:
    - name: cpu
      tag: cpu

  outputs:
    - name: stackdriver
      match: '*'

fluent-bit.conf

[INPUT]
  Name  cpu
  Tag   cpu

[OUTPUT]
  Name        stackdriver
  Match       *

Example configuration file for k8s resource type:

local_resource_id is used by the Stackdriver output plugin to set the labels field for different k8s resource types. Stackdriver plugin will try to find the local_resource_id field in the log entry. If there is no field logging.googleapis.com/local_resource_id in the log, the plugin will then construct it by using the tag value of the log.

The local_resource_id should be in format:

• k8s_container.<namespace_name>.<pod_name>.<container_name>

• k8s_node.<node_name>

• k8s_pod.<namespace_name>.<pod_name>

This implies that if there is no local_resource_id in the log entry then the tag of logs should match this format. Note that we have an option tag_prefix so it is not mandatory to use k8s_container(node/pod) as the prefix for tag.

fluent-bit.yaml

pipeline:
  inputs:
    - name: tail
      tag_regex: 'var.log.containers.(?<pod_name>[a-z0-9](?:[-a-z0-9]*[a-z0-9])?(?:\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)_(?<namespace_name>[^_]+)_(?<container_name>.+)-(?<docker_id>[a-z0-9]{64})\.log$'
      tag: custom_tag.<namespace_name>.<pod_name>.<container_name>
      path: /var/log/containers/*.log
      parser: docker
      db: /var/log/fluent-bit-k8s-container.db

  outputs:
    - name: stackdriver
      match: 'custom_tag.*'
      resource: k8s_container
      k8s_cluster_name: test_cluster_name
      k8s_cluster_location: test_cluster_location
      tag_prefix: 'custom_tag.'

fluent-bit.conf

[INPUT]
  Name               tail
  Tag_Regex          var.log.containers.(?<pod_name>[a-z0-9](?:[-a-z0-9]*[a-z0-9])?(?:\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*)_(?<namespace_name>[^_]+)_(?<container_name>.+)-(?<docker_id>[a-z0-9]{64})\.log$
  Tag                custom_tag.<namespace_name>.<pod_name>.<container_name>
  Path               /var/log/containers/*.log
  Parser             docker
  DB                 /var/log/fluent-bit-k8s-container.db

[OUTPUT]
  Name                  stackdriver
  Match                 custom_tag.*
  Resource              k8s_container
  k8s_cluster_name      test_cluster_name
  k8s_cluster_location  test_cluster_location
  tag_prefix            custom_tag.

Resource Labels

Currently, there are four ways which fluent-bit uses to assign fields into the resource/labels section.

1. Resource Labels API

2. Monitored Resource API

3. Local Resource ID

4. Credentials / Config Parameters

If resource_labels is correctly configured, then fluent-bit will attempt to populate all resource/labels using the entries specified. Otherwise, fluent-bit will attempt to use the monitored resource API. Similarly, if the monitored resource API cannot be used, then fluent-bit will attempt to populate resource/labels using configuration parameters and/or credentials specific to the resource type. As mentioned in the Configuration File section, fluent-bit will attempt to use or construct a local resource ID for a K8s resource type which does not use the resource labels or monitored resource API.

Note that the project_id resource label will always be set from the service credentials or fetched from the metadata server and cannot be overridden.

Using the resource_labels parameter

The resource_labels configuration parameter offers an alternative API for assigning the resource labels. To use, input a list of comma separated strings specifying resource labels plaintext assignments (new=value), mappings from an original field in the log entry to a destination field (destination=$original) and/or environment variable assignments (new=${var}).

For instance, consider the following log entry:

{
  "keyA": "valA",
  "toplevel": {
    "keyB": "valB"
  }
}

Combined with the following Fluent Bit Stackdriver output plugin configuration:

fluent-bit.yaml

pipeline:

  outputs:
    - name: stackdriver
      match: '*'
      resource_labels: keyC=$keyA,keyD=$toplevel['keyB'],keyE=valC

fluent-bit.conf

[OUTPUT]
  Name             stackdriver
  Match            *
  Resource_Labels  keyC=$keyA,keyD=$toplevel['keyB'],keyE=valC

This will produce the following log:

{
  "resource": {
    "type": "global",
    "labels": {
      "project_id": "fluent-bit",
      "keyC": "valA",
      "keyD": "valB",
      "keyE": "valC"
    }
  },
  "entries": [
    {
      "jsonPayload": {
        "keyA": "valA",
        "toplevel": {
           "keyB": "valB"
        }
      }
    }
  ]
}

This makes the resource_labels API the recommended choice for supporting new or existing resource types that have all resource labels known before runtime or available on the payload during runtime.

For instance, for a K8s resource type, resource_labels can be used in tandem with the Kubernetes filter to pack all six resource labels. Below is an example of what this could look like for a k8s_container resource:

fluent-bit.yaml

pipeline:

  outputs:
    - name: stackdriver
      match: '*'
      resource: k8s_container
      resource_labels: cluster_name=my-cluster,location=us-central1-c,container_name=$kubernetes['container_name'],namespace_name=$kubernetes['namespace_name'],pod_name=$kubernetes['pod_name']

fluent-bit.conf

[OUTPUT]
  Name            stackdriver
  Match           *
  Resource        k8s_container
  Resource_Labels cluster_name=my-cluster,location=us-central1-c,container_name=$kubernetes['container_name'],namespace_name=$kubernetes['namespace_name'],pod_name=$kubernetes['pod_name']

resource_labels also supports validation for required labels based on the input resource type. This allows fluent-bit to check if all specified labels are present for a given configuration before runtime. If validation is not currently supported for a resource type that you would like to use this API with, we encourage you to open a pull request for it. Adding validation for a new resource type is simple - all that is needed is to specify the resources associated with the type alongside the required labels here.

Log Name

By default, the plugin will write to the following log name:

/projects/<project ID>/logs/<log tag>

You may be in a scenario where being more specific about the log name is important (for example integration with Log Router rules or controlling cardinality of log based metrics). You can control the log name directly on a per-log basis by using the logging.googleapis.com/logName special field. You can configure a log_name_key if you'd like to use something different from logging.googleapis.com/logName, i.e. if the log_name_key is set to mylognamefield will extract the log name from mylognamefield in the log.

Troubleshooting Notes

Upstream connection error

An upstream connection error means Fluent Bit was not able to reach Google services, the error looks like this:

[2019/01/07 23:24:09] [error] [oauth2] could not get an upstream connection

This is due to a network issue in the environment where Fluent Bit is running. Make sure that the Host, Container or Pod can reach the following Google end-points:

• https://www.googleapis.com

• https://logging.googleapis.com

For more details, see GitHub reference: #761

Fail to process local_resource_id

The error looks like this:

[2020/08/04 14:43:03] [error] [output:stackdriver:stackdriver.0] fail to process local_resource_id from log entry for k8s_container

Check the following:

• If the log entry does not contain the local_resource_id field, does the tag of the log match for format?

• If tag_prefix is configured, does the prefix of tag specified in the input plugin match the tag_prefix?

Other Implementations

Stackdriver officially supports a logging agent based on Fluentd.

We plan to support some special fields in structured payloads. Use cases of special fields is here.