On most Unix platforms, LightDB modifies its
command title as reported by ps
, so that individual server
processes can readily be identified. A sample display is
$ ps auxww | grep ^lightdb lightdb 15551 0.0 0.1 57536 7132 pts/0 S 18:02 0:00 lightdb -i lightdb 15554 0.0 0.0 57536 1184 ? Ss 18:02 0:00 lightdb: background writer lightdb 15555 0.0 0.0 57536 916 ? Ss 18:02 0:00 lightdb: checkpointer lightdb 15556 0.0 0.0 57536 916 ? Ss 18:02 0:00 lightdb: walwriter lightdb 15557 0.0 0.0 58504 2244 ? Ss 18:02 0:00 lightdb: autovacuum launcher lightdb 15558 0.0 0.0 17512 1068 ? Ss 18:02 0:00 lightdb: stats collector lightdb 15582 0.0 0.0 58772 3080 ? Ss 18:04 0:00 lightdb: joe runbug 127.0.0.1 idle lightdb 15606 0.0 0.0 58772 3052 ? Ss 18:07 0:00 lightdb: tgl regression [local] SELECT waiting lightdb 15610 0.0 0.0 58772 3056 ? Ss 18:07 0:00 lightdb: tgl regression [local] idle in transaction
(The appropriate invocation of ps
varies across different
platforms, as do the details of what is shown. This example is from a
recent Linux system.) The first process listed here is the
master server process. The command arguments
shown for it are the same ones used when it was launched. The next five
processes are background worker processes automatically launched by the
master process. (The “stats collector” process will not be present
if you have set the system not to start the statistics collector; likewise
the “autovacuum launcher” process can be disabled.)
Each of the remaining
processes is a server process handling one client connection. Each such
process sets its command line display in the form
lightdb:user
database
host
activity
The user, database, and (client) host items remain the same for
the life of the client connection, but the activity indicator changes.
The activity can be idle
(i.e., waiting for a client command),
idle in transaction
(waiting for client inside a BEGIN
block),
or a command type name such as SELECT
. Also,
waiting
is appended if the server process is presently waiting
on a lock held by another session. In the above example we can infer
that process 15606 is waiting for process 15610 to complete its transaction
and thereby release some lock. (Process 15610 must be the blocker, because
there is no other active session. In more complicated cases it would be
necessary to look into the
pg_locks
system view to determine who is blocking whom.)
If cluster_name has been configured the
cluster name will also be shown in ps
output:
$ ltsql -c 'SHOW cluster_name' cluster_name -------------- server1 (1 row) $ ps aux|grep server1 lightdb 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 lightdb: server1: background writer ...
If you have turned off update_process_title then the activity indicator is not updated; the process title is set only once when a new process is launched. On some platforms this saves a measurable amount of per-command overhead; on others it's insignificant.
Solaris requires special handling. You must
use /usr/ucb/ps
, rather than
/bin/ps
. You also must use two w
flags, not just one. In addition, your original invocation of the
lightdb
command must have a shorter
ps
status display than that provided by each
server process. If you fail to do all three things, the ps
output for each server process will be the original lightdb
command line.