From 0cd21c3bdc1f5028738023bd93cb13596d8f0460 Mon Sep 17 00:00:00 2001 From: Greg Smith Date: Sat, 30 Oct 2010 14:31:58 -0400 Subject: [PATCH] Add intro to lag monitoring to the docs --- README.rst | 37 +++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) diff --git a/README.rst b/README.rst index b88e6786..e297f463 100644 --- a/README.rst +++ b/README.rst @@ -1,11 +1,11 @@ -===================================================== -repmgr: Replication Manager for PostgreSQL's clusters -===================================================== +=================================================== +repmgr: Replication Manager for PostgreSQL clusters +=================================================== Introduction ============ -PostgreSQL 9.0 allow us to have replicated hot standby servers +PostgreSQL 9.0 allow us to have replicated Hot Standby servers which we can query and/or use for high availability. While the main components of the feature are included with @@ -105,6 +105,8 @@ the full path of the binary instead, such as:: /usr/pgsql-9.0/bin/repmgr --version /usr/pgsql-9.0/bin/repmgr --version +Below this base binary installation directory is referred to as PGDIR. + Set up trusted copy between postgres accounts --------------------------------------------- @@ -270,7 +272,7 @@ If now we want to add a new node we can a prepare a new server (node4) and run:: repmgr -D /var/lib/postgresql/9.0 standby clone node2 -NOTE: yu need to have PGDIR/bin in your path, if you don't want that as a +NOTE: you need to have PGDIR/bin in your path, if you don't want that as a permanent setting you can do it this way:: PATH=$PGDIR/bin:$PATH repmgr standby promote @@ -285,19 +287,38 @@ To use the repmgrd (repmgr daemon) to monitor standby so we know how is going the replication and how far they are from primary, you need to execute the ``repmgr.sql`` script in the postgres database. -You also need to add a row for every node in the repl_node table +You also need to add a row for every node in the ``repl_node`` table. This work +may be done for you by the daemon itself, as described below. + +Lag monitoring +-------------- + +To look at the current lag between primary and each node listed +in ``repl_node``, consult the repl_status view:: + + psql -d postgres -c "SELECT * FROM repl_status" + +This view shows the latest monitor info from every node. + +* replication_lag: in bytes. This is how far the latest xlog record + we have received is from master. + +* apply_lag: in bytes. This is how far the latest xlog record + we have applied is from the latest record we have received. + +* time_lag: in seconds. How many seconds behind the master is this node. Usage ----- -It reads the repmgr.conf file in current directory or as indicated with -f +repmgrd reads the ``repmgr.conf`` file in current directory or as indicated with -f parameter looks if the standby is in repl_nodes and if it is not add it. Before you can run the repmgr daemon (repmgrd) you need to register a master and at least a standby in a cluster, for that you need to use the MASTER REGISTER and STANDBY REGISTER commands. -For example, following last example and assuming that repmgr.conf is in postgres +For example, following last example and assuming that ``repmgr.conf`` is in postgres home directory you will run this on the master:: repmgr -f /home/postgres/repmgr.conf master register