Bug ID 659899: Rare, intermittent system instability observed in dynamic load-balancing modes

Last Modified: Oct 10, 2018

Bug Tracker

Affected Product:  See more info
BIG-IP TMOS(all modules)

Known Affected Versions:
11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1, 11.5.4 HF2, 11.5.4 HF3, 11.5.4 HF4, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 11.6.1, 11.6.1 HF1, 11.6.1 HF2, 11.6.2, 11.6.2 HF1, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1

Fixed In:
13.1.0, 12.1.3, 11.6.3, 11.5.5

Opened: Apr 21, 2017
Severity: 2-Critical
Related AskF5 Article:
K10589537

Symptoms

The dynamic pool member load-balancing modes require a precision measurement of active connection counts and/or rates. Rare, intermittent system instability has been observed in dynamic pool member selection when a new connection arrives. TMM may restart, leaving a core file.

Impact

TMM restarts and leaves a core file. Traffic disrupted while tmm restarts.

Conditions

LTM pool configured to use a dynamic load-balancing mode ('ltm pool NAME load-balancing-mode MODE' where MODE is one of the dynamic load-balancing modes, such as dynamic-ratio-member, least-connections-node, predictive-node, etc.). The dynamic modes use the session database to share data among all TMM instances, and under extremely rare conditions, the session database may become unreliable.

Workaround

None.

Fix Information

The dynamic load-balancing modes are now more tolerant of errors from the underlying session database.

Behavior Change