UDFS_STATISTICS
Records aggregate information about file-system and object-store operations.
Records aggregate information about file-system and object-store operations. For access through LibHDFS++, the table records information about metadata but not data.
An operation can be made up of many individual read, write, or retry requests. SUCCESSFUL_OPERATIONS and FAILED_OPERATIONS count operations; the other counters count individual requests. When an operation finishes, one of the OPERATIONS counters is incremented once, but several other counters could be incremented several times each.
| Column Name | Data Type | Description |
|---|---|---|
| FILESYSTEM | VARCHAR | Name of the file system, such as S3 or Libhdfs++. |
| SUCCESSFUL_OPERATIONS | INTEGER | Number of successful file-system operations. |
| FAILED_OPERATIONS | INTEGER | Number of failed file-system operations. |
| RETRIES | INTEGER | Number of retry events. |
| METADATA_READS | INTEGER | Number of requests to read metadata. For example, S3 list bucket and HEAD requests are metadata reads. |
| METADATA_WRITES | INTEGER | Number of requests to write metadata. For example, S3 POST and DELETE requests are metadata writes. |
| DATA_READS | INTEGER | Number of read operations, such as S3 GET requests to download files. |
| DATA_WRITES | INTEGER | Number of write operations, such as S3 PUT requests to upload files. |
| DOWNSTREAM_BYTES | INTEGER | Number of bytes received. |
| UPSTREAM_BYTES | INTEGER | Number of bytes sent. |
| OPEN_FILES | INTEGER | Number of files that are currently open. |
| MAPPED_FILES | INTEGER | Number of currently-mapped files on S3 file systems. This value shows the number of streaming connections for reading data from S3. This value will be 0 for non-S3 file systems. |
| READING | INTEGER | The number of currently-running read operations. |
| WRITING | INTEGER | The number of currently-running writer operations. |
Examples
The following query gets the total number of metadata RPCs for Libhdfs++ operations:
=> SELECT SUM(metadata_reads) FROM UDFS_STATISTICS WHERE filesystem = 'Libhdfs++';