Storage Analytics logs detailed information about successful and failed requests to a storage service. This information can be used to monitor individual requests and to diagnose issues with a storage service. Requests are logged on a best-effort basis.
Storage Analytics logging is not enabled by default for your storage account. You can enable it in the Azure portal; for details, see Monitor a storage account in the Azure portal. You can also enable Storage Analytics programmatically via the REST API or the client library. Use the Get Blob Service Properties, Get Queue Service Properties, and Get Table Service Properties operations to enable Storage Analytics for each service.
Log entries are created only if there are requests made against the service endpoint. For example, if a storage account has activity in its Blob endpoint but not in its Table or Queue endpoints, only logs pertaining to the Blob service will be created.
Storage Analytics logging is currently available only for the Blob, Queue, and Table services.
Logging Authenticated Requests
The following types of authenticated requests are logged:
Failed requests, including timeout, throttling, network, authorization, and other errors
Requests using a Shared Access Signature (SAS), including failed and successful requests
Requests to analytics data
Requests made by Storage Analytics itself, such as log creation or deletion, are not logged. A full list of the logged data is documented in the Storage Analytics Logged Operations and Status Messages and Storage Analytics Log Format topics.
Logging Anonymous Requests
The following types of anonymous requests are logged:
Timeout errors for both client and server
Failed GET requests with error code 304 (Not Modified)
All other failed anonymous requests are not logged. A full list of the logged data is documented in the Storage Analytics Logged Operations and Status Messages and Storage Analytics Log Format topics.
How Logs are Stored
All logs are stored in block blobs in a container named
$logs, which is automatically created when Storage Analytics is enabled for a storage account. The
$logs container is located in the blob namespace of the storage account, for example:
http://<accountname>.blob.core.windows.net/$logs. This container cannot be deleted once Storage Analytics has been enabled, though its contents can be deleted.
$logs container is not displayed when a container listing operation is performed, such as the List Containers operation. It must be accessed directly. For example, you can use the List Blobs operation to access the blobs in the
As requests are logged, Storage Analytics will upload intermediate results as blocks. Periodically, Storage Analytics will commit these blocks and make them available as a blob.
Duplicate records may exist for logs created in the same hour. You can determine if a record is a duplicate by checking the RequestId and Operation number.
Log Naming Conventions
Each log will be written in the following format:
The following table describes each attribute in the log name:
||The name of the storage service. For example:
||The four digit year for the log. For example:
||The two digit month for the log. For example:
||The two digit day for the log. For example:
||The two digit hour that indicates the starting hour for the logs, in 24 hour UTC format. For example:
||The two digit number that indicates the starting minute for the logs. Note: This value is unsupported in the current version of Storage Analytics, and its value will always be
||A zero-based counter with six digits that indicates the number of log blobs generated for the storage service in an hour time period. This counter starts at
The following is a complete sample log name that combines the above examples:
The following is a sample URI that can be used to access the above log:
When a storage request is logged, the resulting log name correlates to the hour when the requested operation completed. For example, if a GetBlob request was completed at 6:30PM on 7/31/2011, the log would be written with the following prefix:
All log blobs are stored with metadata that can be used to identify what logging data the blob contains. The following table describes each metadata attribute:
||Describes whether the log contains information pertaining to read, write, or delete operations. This value can include one type or a combination of all three, separated by commas.
||The earliest time of an entry in the log, in the form of
||The latest time of an entry in the log, in the form of
||The version of the log format. Currently the only supported value is:
The following list displays complete sample metadata using the above examples:
Accessing Logging Data
All data in the
$logs container can be accessed by using the Blob service APIs, including the .NET APIs provided by the Azure managed library. The storage account administrator can read and delete logs, but cannot create or update them. Both the log’s metadata and log name can be used when querying for a log. It is possible for a given hour’s logs to appear out of order, but the metadata always specifies the timespan of log entries in a log. Therefore, you can use a combination of log names and metadata when searching for a particular log.