Separating Adapters

An entire discovery could be defined in a single adapter. But good design demands that a complex system be separated into simpler, more manageable components.

The following are guidelines and best practices for dividing the adapter process:

• Discovery should be done in stages. Each stage should be represented by an adapter that should map an area or tier of the system. Adapters should rely on the previous stage or tier to be discovered, to continue discovery of the system. For example, Adapter A is triggered by an application server TQL result and maps the application server tier. As part of this mapping, a JDBC connection component is mapped. Adapter B registers a JDBC connection component as a trigger TQL and uses the results of adapter A to access the database tier (for example, through the JDBC URL attribute) and maps the database tier.

• The two-phase connect paradigm: Most systems require credentials to access their data. This means that a user/password combination needs to be tried against these systems. The DFM administrator supplies credentials information in a secure way to the system and can give several, prioritized login credentials. This is referred to as the Protocol Dictionary. If the system is not accessible (for whatever reason) there is no point in performing further discovery. If the connection is successful, there needs to be a way to indicate which credential set was successfully used, for future discovery access.

  These two phases lead to a separation of the two adapters in the following cases:

  • Connection Adapter: This is an adapter that accepts an initial trigger and looks for the existence of a remote agent on that trigger. It does so by trying all entries in the Protocol Dictionary which match this agent's type. If successful, this adapter provides as its result a remote agent CI (SNMP, WMI, and so on), which also points to the correct entry in the Protocol Dictionary for future connections. This agent CI is then part of a trigger for the content adapter.

  • Content Adapter: This adapter's precondition is the successful connection of the previous adapter (preconditions specified by the TQLs). These types of adapters no longer need to look through all of the Protocol Dictionary since they have a way to obtain the correct credentials from the remote agent CI and use them to log in to the discovered system.

• Different scheduling considerations can also influence discovery division. For example, a system may only be queried during off hours, so even though it would make sense to join the adapter to the same adapter discovering another system, the different schedules mean that you need to create two adapters.

• Discovery of different management interfaces or technologies to discover the same system should be placed in separate adapters. This is so that you can activate the access method appropriate for each system or organization. For example, some organizations have WMI access to machines but do not have SNMP agents installed on them.

Parent topic: Developing Discovery Content