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Add intro to lag monitoring to the docs

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Greg Smith
2010-10-30 14:31:58 -04:00
parent 915eae9c12
commit 0cd21c3bdc
1 changed files with 29 additions and 8 deletions
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37
README.rst
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@@ -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