Introduction¶

Reference Documents¶

[RD1]: Central Control System Development Standards;

ESO-366378 v1

Metadata Acquisition Interface¶

Metadata acquisition interface, metadaqif, is a relatively small interface used by components that provide metadata to FITS data products created by OCM and DPM.

The following sections document the interface in a language agnostic manner. For data structures only the data members are documented, not the accessors generated by MAL. Similarly names are not fully qualified as it is different across the supported languages.

Interfaces¶

class metadaqif.MetaDaq¶

Metadata acquisition interface.

StartDaq(id) → DaqReply¶

Start new data acquisition that is eventually stopped with StopDaq() or aborted with AbortDaq().

Note

If id is not provided (left empty) it is expected that the server implementing the interface will generate a unique identifier automatically.

If the same id is reused it should be considered a fatal error.

Parameters: id (str) – Optional (may be empty) unique identifier of data acquisition.
Returns: If id was provided that is returned as an acknowledgement, otherwise the id generated by server is returned.
Return type: DaqReply
Raises: DaqException – On fatal error.

StopDaq(id) → DaqStopReply¶

Stops data acquisition and returns created FITS filenames and/or keywords. Produced files should be closed so it is safe to immediately read them.

If an error occurrsed such that the acquisition has failed this is communicated by throwing an exception.

Parameters: id (str) – Id of data acquisition to stop.
Returns: Structure containing produced FITS files and/or FITS keywords.
Return type: DaqStopReply
Raises: DaqException – On fatal error.

AbortDaq(id) → DaqReply¶

Aborts data acquisition and discards any data that has been acquired.

Parameters: id (str) – Id of data acquisition to abort.
Return type: DaqReply
Raises: DaqException – On fatal error.

GetDaqStatus(id) → DaqStatus¶

Get status of current or past Data Acquisitions.

It is unspecified exactly how far back the history should go. But the bare minimum is to be able to provide status for last two (e.g. any current and previous).

Parameters: id (str) – Id of data acquisition to get status for.
Return type: DaqStatus
Raises: DaqException – On fatal error.

Data Structures¶

class metadaqif.DaqState¶

Enumeration of data acquisition states. The expected state transitions are as follows:

$digraph DaqStates { # Config node [shape=Mrecord,fontname=helvetica,fontsize=11]; graph [fontname = "helvetica", bgcolor=transparent]; # States NotStarted [label="{NotStarted|\l}"]; Acquiring [label="{Acquiring|\l}"]; Succeeded [label="{Succeeded|\l}"]; Aborted [label="{Aborted|\l}"]; Failed [label="{Failed|\l}"]; # Transitions NotStarted -> Acquiring; Acquiring -> Succeeded; edge [weight=0]; Acquiring -> {Aborted, Failed}; }$

Note

There may be more internal (transitional states) but this enumeration covers the ones that are observable with metadaqif.

NotStarted¶: Data Acquisition is created but not yet started.

Acquiring¶: Data is being acquired.

Succeeded¶: Final state for a successful Data Acquisition. All data has been acquired and any FITS files are completed and closed.

Aborted¶: Final state for an aborted Data Acquisition.

Failed¶: Final state for failed Data Acquisition.

class metadaqif.DaqException¶

Exception used by MetaDaq.

id: str¶: Data Acquisition identifier.

message: str¶: Exception message.

class metadaqif.DaqStatus¶

Contains the Data Acquisition reply.

id: str¶: Data Acquisition identifier.

state: DaqState¶: Data Acquisition state at the time the reply was sent.

message: str¶: Message, if any.

files: List[str]¶: List of FITS files created for this Data Acquisition in the format [user@]host:/absolute/path.

keywords: str¶

JSON-encoded FITS keywords, or empty.

Example:

[
   {
      "type":"valueKeyword",
      "name":"OBJECT",
      "value":"OBJECT,SKY"
   },
   {
      "type":"esoKeyword",
      "name":"OBS TPLNO",
      "value":2
   }
]

timestamp: double¶: Timestamp of last status update in number of seconds in TAI time standard with epoch set to 1 January 1970 00:00:00 TAI, which is 31 December 1969 23:59:51.999918 UTC [RD1].

class metadaqif.DaqReply¶

Common reply type.

id: str¶: Data Acquisition identifier.

class metadaqif.DaqStopReply¶

Reply structure for DaqStop.

id: str¶: Data Acquisition identifier.

files: List[str]¶: List of FITS files created for this Data Acquisition in the format [user@]host:/absolute/path.

keywords: str¶

JSON-encoded FITS keywords, or empty.

Example:

[
   {
      "type":"valueKeyword",
      "name":"OBJECT",
      "value":"OBJECT,SKY"
   },
   {
      "type":"esoKeyword",
      "name":"OBS TPLNO",
      "value":2
   }
]