JIRA Data Center Start Generates Large Network Traffic
Platform Notice: Data Center Only - This article only applies to Atlassian products on the Data Center platform.
Note that this KB was created for the Data Center version of the product. Data Center KBs for non-Data-Center-specific features may also work for Server versions of the product, however they have not been tested. Support for Server* products ended on February 15th 2024. If you are running a Server product, you can visit the Atlassian Server end of support announcement to review your migration options.
*Except Fisheye and Crucible
Summary
Symptoms
When starting up a JIRA node in Data Center, while other nodes are running, there is a large spike in network traffic between all currently running nodes.
Diagnosis
Reviewing network traffic indicates there are spikes on all nodes when a startup, or restart of one of the nodes occurs. For example Node A, B and C are running. When D is started, there are spikes of traffic on Nodes A, B, C & D.
Cause
JIRA Data Center uses a caching library called EHCache, and contains an in-memory cache of certain project, user and group data. On the very first node start (if no others are running) this cache is built from querying the database. When additional nodes are started, the cache is built from querying the existing nodes in-memory cache and propagating that data into the node that is starting up. Other caches are built only locally by filling the node's own copy of the cache directly from the database.
Additionally when JIRA Data Center restarts a node reindex thread runs which is designed to synchronise changes between the nodes - this can also contribute to the increase in network traffic.
Solution
Resolution
There is no resolution for this issue - it is expected behaviour of JIRA Data Center.
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