9.2. Detecting Errors During Normal Processing
Protect server performance by detecting errors during the normal chaining operation between the database link and the remote server. The database link has two attributes —
nsMaxResponseDelay and nsMaxTestResponseDelay — which work together to determine if the remote server is no longer responding.
The first attribute,
nsMaxResponseDelay, sets a maximum duration for an LDAP operation to complete. If the operation takes more than the amount of time specified in this attribute, the database link's server suspects that the remote server is no longer online.
Once the
nsMaxResponseDelay period has been met, the database link pings the remote server. During the ping, the database link issues another LDAP request, a simple search request for an object that does not exist in the remote server. The duration of the ping is set using the nsMaxTestResponseDelay.
If the remote server does not respond before the
nsMaxTestResponseDelay period has passed, then an error is returned, and the connection is flagged as down. All connections between the database link and remote server will be blocked for 30 seconds, protecting the server from a performance degradation. After 30 seconds, operation requests made by the database link to the remote server continue as normal.
Both attributes are stored in the
cn=config,cn=chaining database,cn=plugins,cn=config entry. The following table describes the attributes in more detail:
Table 9.1. Database Link Processing Error Detection Parameters
| Attribute Name | Description |
|---|---|
| nsMaxResponseDelay | Maximum amount of time it can take a remote server to respond to an LDAP operation request made by a database link before an error is suspected. This period is given in seconds. The default delay period is 60 seconds. Once this delay period has been met, the database link tests the connection with the remote server. |
| nsMaxTestResponseDelay | Duration of the test issued by the database link to check whether the remote server is responding. If a response from the remote server is not returned before this period has passed, the database link assumes the remote server is down, and the connection is not used for subsequent operations. This period is given in seconds. The default test response delay period is 15 seconds. |
