Temporary archive unavailability mechanism

An archive will be set to status “temporarily unavailable” by ImageMaster for a number of minutes, if problems occur during read or write access to  the archive.

For instance if an archive A1 is accessed by ImageMaster during archiving a document attachment into A1 and A1 responds with a network error, A1 is set to temporarily unavailable for 10 minutes (this is the default value) by ImageMaster. This means on subsequent archiving requests or retrievals A1 will not be accessed for archiving attachments or retrieving attachments to or from it. After 10 minutes ImageMaster will set A1 automatically to “available”, i.e. then ImageMaster includes A1 again into the read/write cycles of ImageMaster archiving and retrieval requests.

The parameter which sets the duration of the temporary unavailability of the archive is called “OnlineCheckingInterval”. The parameter can be configured in the configuration tab of the given archive in the AdminClient. The default value is 10 minutes.

An archive can be immediately reset to “available” via the AdminClient by successfully performing a ping to the archive in the configuration tab of the given archive.

Furthermore, there are three reasons why an archive can be set to temporarily unavailable by ImageMaster:

  1. A network error occurred while accessing the archive.

  2. A ping to the archive failed.

  3. Access to the archive resulted in an error and the overall request response time exceeded a timeout.

The timeout duration from reason 3 can be configured and the default value for the timeout is -1 which disables the timeout. Recommended timeout values that are often used in practice are 60 or 90 seconds.

The timeout only applies if the access to the archive resulted in an error: For instance a request accessing an archive took 32 seconds and no error occurred. If the timeout is set to 30 seconds the timeout does not apply as the request did not result in an error while accessing the archive. The archive is not set to temporarily unavailable in this case. But for instance if a request accessing an archive took 32 seconds and resulted in an error while accessing the archive such as ‘GeneralError’, the archive will be set to temporarily unavailable as the timeout of 30 seconds is exceeded.

In the third example assume that a request accessing an archive took 1 second and resulted in an error such as ‘Archive Host not found’. In this case the archive is not  set to temporarily unavailable as the request response time did not exceed the timeout of 30 seconds. The timeout is rather intended to catch all long running requests resulting eventually in an error. If many requests of this kind occur, the server is likely to experience a congestion. If the corresponding archive is set to temporarily unavailable, requests will be able to succeed with a shorter response time preventing a congestion of the system.

The timeout duration is configured in the AdminClient in the configuration tab of the given archive.

In multi-node ImageMaster systems, setting an archive to temporarily unavailable is done per application server. This means if an ImageMaster system has two application servers AS1 ans AS2, it is possible that an archive B1 is ‘available’ from AS1 and is set to temporarily unavailable on application server AS2. This means AS1 will access B1 for read and write operations while application server AS2 will not. This reflects the possibility that AS1 has a working network connection to B1 while application server AS2 has a broken network connection to B1.