Integrity service

The integrity services purpose is to monitor the state of integrity on a per collection basis. This is done by periodically collecting information about files and their checksums on each pillar. Based on the collected information the state of integrity can be determined.
As a side effect, statistics about number of files and collection sizes is also generated.

A collection is considered to be consistent and in a good state of integrity if pillars all agree on the full set of files and their checksums. Therefore the state of integrity is described by:

• Missing files: Files not present on all pillars in a collection.
• Missing checksums: Files missing a checksum on one or more pillars.
• Obsolete checksums: Files on a pillar where the checksum have become outdated. How old a checksum can be before it is considered obsolete, depends on configuration and is specificed for a collection. As pillars use different storage teniques and media it is possible to configure specific maximum age per pillar.
• Inconsistent checksums: Files which checksums does not agree across all pillars in a collection.

Integrity checks

The current service supports two types of integrity checking: full and incremental. Common for both checks is that they rely on the same database, in which they store the collected information about files and their checksums. After finished collection, the content of the database serves as a snapshot of the state of the collection and is used to determine if there are any of the mentioned integrity issues.

As the outcome of a integrity check is a report containing the (if any) found issues. Also in case of discovered issues an alarm is sent, containing a summary of the issues.

Full integrity check

The full integrity check collects all file ids and checksums and removes those that are no longer reported to be present on a pillar before carrying on to running the checks listed above.

Incremental integrity check

The incremental check collects fileids and checksums from the point where an earlier check had collected and forward. This enables quick discovery of new or updated files, but cannot discover files no longer present.

Correcting integrity issues

The integrity service does not provide means to automatically correct issues found. The information that the service provides is intended for supporting a human being (or purposely written software) in the decision on how to act on issues.