[AMQ-2504] Synchronize time without modifying the system date.

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 5.6.0
• Component/s: JMS client
• Assignee: Unassigned
• Reporter: Adam Walczak
• Created: 22/Nov/09 12:29
• Updated: 20/Sep/11 11:01
• Resolved: 20/Sep/11 11:01

Description

I have a proposal to create a global variable in ActiveMQ's internals which alters the value of System.getCurrentMillis(). Thanks to this we should be able to synchronize clients connected to a JMS server (equipped with an additional NTP server for example) with out modifying their system dates.

Scenario:

1. Servers system date is sync'ed with an NTP server.

2. Clients retrieve their time difference from the NTP server

3. The client set ActiveMq...setTimeDifferenceToServer(...)

4. Every call for system millis in ActiveMQ sources looks like this: System.getCurrentMillis() + ActiveMq...getTimeDifferenceToServer()

I think it also would be an good idea to wrapper the System.getCurrentMillis() in a internal ActiveMQ method and never call it again directly. This would allow the above modifications and perhaps a to transit to System.nanoTime() to indicate millis in the future which is far more accurate (getCurrentMillis() has a 0-20ms error range).