Configuration: Server group with 4 servers. How long after performing an admin operation (on the Primary Administration server) will it take before the secondary servers reload the cache from the database? |
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Once an admin operation takes place, the primary administration server posts the types of changes into the Server Group Bulletin Board (servgrp_board table) in the pendingSignals column for the other servers in the group. The admin server will wait the Delay-Recache-Time before it promotes the new cache. In that timeframe, all threads are still using the old copy of the cache up until the Delay-Recache-Time has elapsed. If Delay-Recache-Time is set to a higher value on the admin server than on the other servers, the other servers in the group may be using the new changes before the admin server cache (with the changes) has been promoted. In most environments, the same Delay-Recache-Time is used on all servers in the group; therefore, the admin server will use the new cache first since the other servers still need to wait at least 2 intervals in addition to the Delay-Recache-Time. The Bulletin Board will be updated as soon as the admin change is complete (not waiting for the Delay-Recache-Time). If there are subsequent admin changes, the Bulletin Board table will get updated again. All of the non-admin servers in the group read the Bulletin Board every Server Group Interval, which defaults to 1 minute. Each server reads the types of changes via the pendingSignals column, which is a bitmasked field. So it knows what type of admin operation was performed. On the next Interval, each server reads the value of the pendingSignals again. If the values indicate an additional change was made, then it continues to wait until an interval occurs where there are no new changes.
If Server-Group-Signal-Option is set to T, then the Bulletin Board is not updated. Rather, ARSignal is used to directly signal the other servers Setting Disable-ARSignals: T will prevent signaling and will also prevent posts to the Bulletin Board. If this is used, it is expected that arsignal be manually used to trigger the other servers to reload the cache at a specific time. When running arsignal to reload the cache (-r), the Delay-Recache-Time must elapse before the cache is reloaded. |