One server with nwaf installed had nginx stalled with the following in the nginx error log
2021/05/19 12:30:48 [alert] 1042#1042: worker process 17236 exited on signal 11
2021/05/19 12:30:48 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17236
2021/05/19 12:30:48 [alert] 1042#1042: worker process 17301 exited on signal 11
2021/05/19 12:30:48 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17301
2021/05/19 12:30:48 [alert] 1042#1042: worker process 17368 exited on signal 11
2021/05/19 12:30:48 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17368
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17434 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17434
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17500 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17500
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17566 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17566
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17633 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17633
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17698 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17698
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17764 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17764
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17829 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17829
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17895 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17895
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17960 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17960
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18025 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18025
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18090 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18090
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18156 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18156
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18222 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18222
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18288 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18288
A restart of nginx fixed it. But why this error happened and could it be prevented?
2021/05/19 12:30:48 [alert] 1042#1042: worker process 17236 exited on signal 11
2021/05/19 12:30:48 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17236
2021/05/19 12:30:48 [alert] 1042#1042: worker process 17301 exited on signal 11
2021/05/19 12:30:48 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17301
2021/05/19 12:30:48 [alert] 1042#1042: worker process 17368 exited on signal 11
2021/05/19 12:30:48 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17368
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17434 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17434
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17500 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17500
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17566 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17566
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17633 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17633
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17698 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17698
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17764 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17764
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17829 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17829
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17895 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17895
2021/05/19 12:30:49 [alert] 1042#1042: worker process 17960 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 17960
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18025 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18025
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18090 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18090
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18156 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18156
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18222 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18222
2021/05/19 12:30:49 [alert] 1042#1042: worker process 18288 exited on signal 11
2021/05/19 12:30:49 [alert] 1042#1042: shared memory zone "nwaf_shared" was locked by 18288
A restart of nginx fixed it. But why this error happened and could it be prevented?