Add more notes for 2015-12

Signed-off-by: Alan Orth <alan.orth@gmail.com>

content/2015-12.md

@@ -20,3 +20,37 @@ image = "../images/bg.jpg"
 
 - I had used lrzip once, but it needs more memory and is harder to use as it requires the lrztar wrapper
 - Need to remember to go check if everything is ok in a few days and then change CGSpace
+- CGSpace went down again (due to PostgreSQL idle connections of course)
+- Current database settings for DSpace are `db.maxconnections = 30` and `db.maxidle = 8`, yet idle connections are exceeding this:
+
+```
+$ psql -c 'SELECT * from pg_stat_activity;' | grep cgspace | grep -c idle
+39
+```
+
+- I restarted PostgreSQL and Tomcat and it's back
+- On a related note of why CGSpace is so slow, I decided to finally try the `pgtune` script to tune the postgres settings:
+
+```
+# apt-get install pgtune
+# pgtune -i /etc/postgresql/9.3/main/postgresql.conf -o postgresql.conf-pgtune
+# mv /etc/postgresql/9.3/main/postgresql.conf /etc/postgresql/9.3/main/postgresql.conf.orig 
+# mv postgresql.conf-pgtune /etc/postgresql/9.3/main/postgresql.conf
+```
+
+- It introduced the following new settings:
+
+```
+default_statistics_target = 50
+maintenance_work_mem = 480MB
+constraint_exclusion = on
+checkpoint_completion_target = 0.9
+effective_cache_size = 5632MB
+work_mem = 48MB
+wal_buffers = 8MB
+checkpoint_segments = 16
+shared_buffers = 1920MB
+max_connections = 80
+```
+
+- Now I need to go read PostgreSQL docs about these options, and watch memory settings in munin etc