Routing and storage overview

This page explains how Cloud Logging processes log entries, and describes the key components of Logging routing and storage.

At a high level, this is how Cloud Logging routes and stores log entries:

Figure illustrating how Cloud Logging routes logs entries.

Ingesting and routing logs with the Log Router

The following sections explain how logs are ingested by Logging and routed through the Log Router using sinks.

Log Router

A log entry is sent to the Google Cloud resource specified in its logName field during its entries.write call.

Cloud Logging receives log entries through the Cloud Logging API where they pass through the Log Router. The sinks in the Log Router check each log entry against the existing inclusion filter and exclusion filters that determine which destinations, including Cloud Logging buckets, that the log entry should be sent to. You can use combinations of sinks to route logs to multiple destinations.

To reliably route logs, the Log Router also stores the logs temporarily (not depicted in the image), which buffers against temporary disruptions on any sink. Note that the Log Router's temporary storage is distinct from the longer term storage provided by Logging buckets.

Sinks

Sinks control how Cloud Logging routes logs. Using sinks, you can route some or all of your logs to supported destinations. Some of the reasons that you might want to control how your logs are routed include the following:

  • To store logs that are unlikely to be read but that must be retained for compliance purposes.
  • To organize your logs in buckets in a format that is useful to you.
  • To use big-data analysis tools on your logs.
  • To stream your logs to other applications, other repositories, or third parties.

Sinks belong to a given Google Cloud resource: Cloud projects, billing accounts, folders, and organizations. When the resource receives a log entry, it routes the log entry according to the sinks contained by that resource and, if enabled, any ancestral sinks belonging under the resource hierarchy. The log entry is sent to the destination associated with each matching sink.

Cloud Logging provides two predefined sinks for each Cloud project, billing account, folder, and organization: _Required and _Default. All logs that are generated in a resource are automatically processed through these two sinks and then are stored either in the correspondingly named _Required or _Default buckets.

Sinks act independently of each other. Regardless of how the predefined sinks process your log entries, you can create your own sinks to route some or all of your logs to various supported destinations or to exclude them from being stored by Cloud Logging.

The routing behavior for each sink is controlled by configuring the inclusion filter and exclusion filters for that sink. Depending on the sink's configuration, every log entry received by Cloud Logging falls into one or more of these categories:

  • Stored in Cloud Logging and not routed elsewhere.

  • Stored in Cloud Logging and routed to a supported destination.

  • Not stored in Cloud Logging but routed to a supported destination.

  • Neither stored in Cloud Logging nor routed elsewhere.

You usually create sinks at the Cloud project level, but if you want to combine and route logs from the resources contained by a Google Cloud organization or folder, you can create aggregated sinks.

You can't route log entries that Logging received before your sink was created because routing happens as logs pass through the Logging API, and new routing rules only apply to logs written after those rules have been created. If you need to route log entries retroactively, see Copy logs.

Inclusion filters

For any new sink, if you don't specify filters, all logs match and are routed to the sink's destination. You can configure the sink to select specific logs by setting an inclusion filter. You can also set one or more exclusion filters to exclude logs from the sink's destination.

When you configure sinks, you create inclusion filters by using the Logging query language. Sinks can also contain multiple exclusion filters.

Every log entry received by Logging is routed based on these filtering rules:

  • The sink's exclusion filters override any of its defined inclusion filters. If a log matches any exclusion filter in the sink, then it doesn't match the sink regardless of any inclusion filters defined. The log entry isn't routed to that sink's destination.

  • If the sink doesn't contain an inclusion filter, then the following happens:

    • If the log entry matches any exclusion filter, it isn't routed to the sink's destination.
    • If the log entry doesn't match any exclusion filter, it is routed to the sink's destination. An empty inclusion filter selects all logs.
  • If the sink contains an inclusion filter, then the following happens:

    • If the log entry matches the inclusion filter, it is routed to the sink's destination.
    • If the log entry doesn't match the inclusion filter, it isn't routed to the sink's destination.

Exclusion filters

When you create a sink, you can set multiple exclusion filters, letting you exclude matching log entries from being routed to the sink's destination or from being ingested by Cloud Logging. You create exclusion filters by using the Logging query language.

Logs are excluded after they are received by the Logging API. Therefore, excluding logs doesn't reduce the number of entries.write API calls.

Excluded log entries aren't available in the Logs Explorer or Cloud Debugger.

Log entries that aren't routed to at least one log bucket, either explicitly with exclusion filters or because they don't match any sinks with a Logging storage destination, are also excluded from Error Reporting.

User-defined log-based metrics are computed from log entries in both included and excluded logs. For more information, see Monitor your logs.

Supported destinations

You can use the Log Router to route certain logs to supported destinations in any Cloud project. Logging supports the following sink destinations:

  • Cloud Storage: JSON files stored in Cloud Storage buckets; provides inexpensive, long-term storage.
  • BigQuery: Tables created in BigQuery datasets; provides big data analysis capabilities.
  • Pub/Sub: JSON-formatted messages delivered to Pub/Sub topics; supports third-party integrations, such as Splunk, with Logging.
  • Cloud Logging: Log entries held in log buckets; provides storage in Cloud Logging with customizable retention periods.

For more information on routing logs to supported destinations, see Configure sinks.

Storing, viewing, and managing logs

The following section details how logs are stored in Cloud Logging, and how you can view and manage them.

Log buckets

Cloud Logging uses log buckets as containers in your Google Cloud projects, billing accounts, folders, and organizations to store and organize your logs data. The logs that you store in Cloud Logging are indexed, optimized, and delivered to let you analyze your logs in real time. Cloud Logging buckets are different storage entities than the similarly named Cloud Storage buckets.

For each Cloud project, billing account, folder, and organization, Logging automatically creates two log buckets: _Required and _Default. Logging automatically creates sinks named _Required and _Default that, in the default configuration, route logs to the correspondingly named buckets.

You can disable the logs that are routed to the _Default log bucket. You can't change routing rules for the _Required bucket.

Additionally, you can create user-defined buckets for any Cloud project.

You create sinks to route all, or just a subset, of your logs to any log bucket. This flexibility allows you to choose the Cloud project in which your logs are stored and what other logs are stored with them.

For more information, see Configure log buckets.

_Required log bucket

Cloud Logging automatically routes the following types of logs to the _Required bucket:

Cloud Logging retains the logs in this bucket for 400 days; you can't change this retention period.

You can't modify or delete the _Required bucket. You can't disable the _Required sink, which routes logs to the _Required bucket.

Neither ingestion pricing nor storage pricing applies to the logs data stored in the _Required log bucket.

_Default log bucket

Any log entry that isn't ingested by the _Required bucket is routed by the _Default sink to the _Default bucket, unless you disable or otherwise edit the _Default sink. For instructions on modifying sinks, see Manage sinks.

You can't delete the _Default bucket.

Logs held in the _Default bucket are retained for 30 days, unless you configure custom retention for the bucket.

Cloud Logging pricing applies to the logs data held in the _Default bucket.

User-defined log buckets

You can also create user-defined log buckets in any Cloud project. By applying sinks to your user-defined log buckets, you can route any subset of your logs to any log bucket, letting you choose which Cloud project your logs are stored in and which other logs are stored with them.

For example, for any log generated in Project-A, you can configure a sink to route that log to user-defined buckets in Project-A or Project-B.

Cloud Logging pricing applies to the logs data held in this bucket, regardless of the log type.

You can configure custom retention for the bucket.

For information on managing your user-defined log buckets, including deleting or updating them, see Configure and manage log buckets.

Regionalization

Log buckets are regional resources. The infrastructure that stores, indexes, and searches your logs is located in a specific geographical location. Google manages that infrastructure so that your applications are available redundantly across the zones within that region.

For more information on logs data location, see Data regionality for Cloud Logging.

When you create your log bucket, you can choose to store your logs in any of the following regions:

Continent Regions
Asia asia-east1
asia-east2
asia-northeast1
asia-northeast2
asia-northeast3
asia-south1
asia-south2
asia-southeast1
asia-southeast2
Australia australia-southeast1
australia-southeast2
Europe europe-central2
europe-north1
europe-west1
europe-west2
europe-west3
europe-west4
europe-west6
North America northamerica-northeast1
northamerica-northeast2
us-central1
us-east1
us-east4
us-west1
us-west2
us-west3
us-west4
South America southamerica-east1

In addition to these regions, you also have the option to set the location to global, which means that you don't need to specify where your logs are physically stored.

Organization policy

You can create an organization policy to ensure that your organization meets your compliance and regulatory needs. Using an organization policy, you can specify in which regions your organization can create new log buckets. You can also restrict your organization from creating new log buckets in specified regions.

Cloud Logging doesn't enforce your newly created organization policy on your existing log bucket; it only enforces the policy on new log buckets.

For information on creating a location-based organization policy, refer to Restrict resource locations.

Retention

Cloud Logging retains logs according to retention rules applying to the log bucket type where the logs are held.

You can configure Cloud Logging to retain logs between 1 day and 3650 days. Custom retention rules apply to all the logs in a bucket, regardless of the log type or whether that log has been copied from another location.

For information on setting retention rules for a log bucket, see Configure custom retention.

Log views

Log views let you control who has access to the logs within your log buckets.

Cloud Logging automatically creates the _AllLogs view for every bucket, which shows all logs. Cloud Logging also creates a view for the _Default bucket called _Default, which shows all logs except Data Access audit logs.

Because log buckets can contain logs from multiple Cloud projects, you might want to control which Cloud projects different users can view logs from. You can create custom log views, which give you more granular access control for those buckets.

For more information, see Manage log views.

Using logs in the Google Cloud ecosystem

The following section provides information on using logs in the broader Google Cloud.

Log-based metrics

Log-based metrics are Cloud Monitoring metrics that are based on the content of log entries. If Cloud Logging receives a log entry for a Cloud project that matches the filters of one of the Cloud project's metrics, then that log entry is reflected in the metric data.

Sink exclusion filters apply to system-defined user metrics, which count only logs that are included for ingestion by the Cloud project.

Sink exclusion filters don't apply to user-defined log-based metrics. Even if you exclude logs from being ingested by Cloud Logging API and the logs aren't stored in any Logging buckets, you could see those logs counted in these metrics.

Log-based metrics apply at the Cloud project level. These metrics are calculated by the Log Router and apply to logs only in the Cloud project in which they're received.

For more information, see Log-based metrics overview.

Finding logs in supported destinations

To learn about the format of routed log entries and how the logs are organized in destinations, see View logs in sink destinations.

Common use cases

To address common use cases for routing and storing logs, see the following documents and tutorials:

Compliance needs

For best practices on using routing for data governance, see the following documents:

Access control with IAM

For information on how you use Identity and Access Management (IAM) roles and permissions to control access to Cloud Logging data, see the Access control with IAM.

Pricing

To understand ingestion and storage pricing, see the Cloud Logging pricing information.

Cloud Logging doesn't charge to route logs, but destination charges might apply. For details, review the appropriate service's pricing details:

Note also that if you send and then exclude your Virtual Private Cloud flow logs from Cloud Logging, VPC flow log generation charges apply in addition to the destination charges.

What's next

To help you route and store Cloud Logging data, see the following documents: