Metadata-Version: 2.1
Name: couchdb-cluster-admin
Version: 0.7.2
Summary: Utility for managing multi-node couchdb 2.x clusters
Home-page: https://github.com/dimagi/couchdb-cluster-admin
Maintainer: Dimagi
Maintainer-email: dev@dimagi.com
License: BSD License
Platform: UNKNOWN
Classifier: Development Status :: 3 - Alpha
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: BSD License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.6
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Description-Content-Type: text/x-rst
License-File: LICENSE

couchdb-cluster-admin
=====================

utility for managing multi-node couchdb 2.x clusters

First, put together a config file for your setup
================================================

This will make the rest of the commands simpler to run. Copy the example

::

   cp config/conf.example.yml config/mycluster.yml

and then edit it with the details of your cluster.

Setting up a local cluster to test on
=====================================

If you have docker installed you can just run

.. code:: bash

   docker build -t couchdb-cluster - < docker-couchdb-cluster/Dockerfile

to build the cluster image (based on klaemo/couchdb:2.0-dev) and then
run

.. code:: bash

   docker run --name couchdb-cluster \
     -p 15984:15984 \
     -p 15986:15986 \
     -p 25984:25984 \
     -p 25986:25986 \
     -p 35984:35984 \
     -p 35986:35986 \
     -p 45984:45984 \
     -p 45986:45986 \
     -v $(pwd)/data:/usr/src/couchdb/dev/lib/ \
     -t couchdb-cluster \
     --with-admin-party-please \
     -n 4

to start a cluster with 4 nodes. The nodes’ data will be persisted to
``./data``.

To run the tests (which require this docker setup), download and install
https://github.com/sstephenson/bats

.. code:: bash

   git clone https://github.com/sstephenson/bats.git
   cd bats
   ./install.sh /usr/local  # or wherever on your PATH you want to install this

and then

.. code:: bash

   docker start couchdb-cluster  # make sure this is running and localhost:15984 is receiving pings
   bats test/

Optional: Set password in environment
=====================================

If you do not wish to specify your password every time you run a
command, you may put its value in the ``COUCHDB_CLUSTER_ADMIN_PASSWORD``
environment variable like so:

::

   read -sp Password: PW

Then, for all commands below prefex the command with
``COUCHDB_CLUSTER_ADMIN_PASSWORD=$PW``, e.g.

::

   COUCHDB_CLUSTER_ADMIN_PASSWORD=$PW python couchdb-admin-cluster/describe.py --conf mycluster.yml

Get a quick overview of your cluster
====================================

Now you can run

::

   python couchdb_cluster_admin/describe.py --conf config/mycluster.yml

to see an overview of your cluster nodes and shard allocation. For
example, in the following output:

::

   Membership
       cluster_nodes:  couch3  couch1  couch4  couch2
       all_nodes:  couch3  couch1  couch4  couch2
   Shards
                          00000000-1fffffff  20000000-3fffffff  40000000-5fffffff  60000000-7fffffff  80000000-9fffffff  a0000000-bfffffff  c0000000-dfffffff  e0000000-ffffffff
       mydb                    couch1             couch1             couch1             couch1             couch1             couch1             couch1             couch1
       my_second_database      couch1             couch1             couch1             couch1             couch1             couch1             couch1             couch1

you can see that while there are four nodes, all shards are currently
assigned only to the first node.

Help estimating shard allocation
================================

In order to plan out a shard reallocation, you can run the following
command:

.. code:: bash

   python couchdb_cluster_admin/suggest_shard_allocation.py --conf config/mycluster.yml --allocate couch1:1 couch2,couch3,couch4:2

The values for the ``--allocate`` arg in the example above should be
interpreted as “Put 1 copy on couch1, and put 2 copies spread across
couch2, couch3, and couch4”.

The output looks like this:

::

   couch1  57.57 GB
   couch2  42.15 GB
   couch3  36.5 GB
   couch4  36.5 GB
                        00000000-1fffffff     20000000-3fffffff     40000000-5fffffff     60000000-7fffffff     80000000-9fffffff     a0000000-bfffffff     c0000000-dfffffff     e0000000-ffffffff
   mydb                couch1,couch2,couch4  couch1,couch2,couch3  couch1,couch3,couch4  couch1,couch2,couch4  couch1,couch2,couch3  couch1,couch3,couch4  couch1,couch2,couch4  couch1,couch2,couch3
   my_second_database  couch1,couch3,couch4  couch1,couch3,couch4  couch1,couch3,couch4  couch1,couch3,couch4  couch1,couch3,couch4  couch1,couch3,couch4  couch1,couch3,couch4  couch1,couch3,couch4

Note, the reallocation does not take into account the current location
of shards, so it is much more useful in the situation that you’re moving
from a single-node cluster to a multi-node cluster than it is in the
situation where you’re adding one more node to a multi-node cluster. In
the example above, couch1 would be the single-node cluster and couch2,
couch3, and couch4 form are the multi-node cluster–to-be. You can
imagine that after implementing the shard allocation suggested here, we
might remove all shards from couch1 and remove it from the cluster.

Note also that there is no guarantee that the “same” shard of different
databases will go to the same node; each (db, shard)-pair is treated as
an independent unit when making computing an even shard allocation. In
this example there are only a few dbs and shards; when shards \* dbs is
high, this process can be quite good at evenly balancing your data
across nodes.


