# `BeamExport.Telemetry`
[🔗](https://github.com/HataluliRandima/beam_export/blob/v0.1.0/lib/beam_export/telemetry.ex#L1)

`:telemetry` events emitted by BeamExport.

Events are emitted by `BeamExport.to_file/3` (`destination: :file`, including
`BeamExport.Plug.send_staged_export/4`) and `BeamExport.to_iodata/2`
(`destination: :iodata`). `BeamExport.to_stream/2` and
`BeamExport.Plug.send_chunked_export/4` emit no events.

Handlers run synchronously in the process performing the export.

  * `[:beam_export, :export, :start]` - an export begins (after option validation).
    * Measurements: `%{system_time: integer()}`
    * Metadata: `%{destination: :file | :iodata, format: :csv}`
  * `[:beam_export, :export, :chunk]` - a chunk was written (`:file` only).
    * Measurements: `%{rows: integer(), bytes: integer()}` - `bytes` are uncompressed
    * Metadata: `%{destination: :file}`
  * `[:beam_export, :export, :stop]` - the export completed successfully.
    * Measurements: `%{duration: integer(), rows: integer(), bytes: integer()}`.
      `duration` is in `:native` time units (convert with `System.convert_time_unit/3`),
      `rows` includes the header row, and `bytes` is the size on disk (compressed
      size for gzip files).
    * Metadata: `%{destination: :file | :iodata, format: :csv}`
  * `[:beam_export, :export, :exception]` - the export failed.
    * Measurements: `%{duration: integer()}` (`:native` time units)
    * Metadata: `%{destination: atom(), kind: :error, reason: Exception.t(),
      stacktrace: list(), format: :csv}`

Exception metadata never contains record contents: `BeamExport.MappingError`s are
always redacted (even with `include_record_in_errors: true`), and stacktrace
entries carry arities instead of arguments. Exceptions raised by your own source or
database driver are passed through unchanged.

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*Consult [api-reference.md](api-reference.md) for complete listing*