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CHT Data Migration tool

Facilitates migrating data from a CHT 3.x installation to a CHT 4.x installation. Also, facilitates moving data within a CHT 4.x CouchDb cluster.

Installation

Check out this repository. Run:

docker-compose up

API:

get-env

Requires COUCH_URL and CHT_NETWORK environment variable to be set. Run this while running 3.x CouchDb. Outputs list of environment variables that are required by 4.x CouchDb.

Usage:

export COUCH_URL=http://admin:pass@<couchdb-host>:5984
export CHT_NETWORK=<network_name>
docker-compose run couch-migration get-env

You can save the output in an env file:

docker-compose run couch-migration get-env > .env

or export every line for usage in the current terminal:

export $(docker-compose run couch-migration get-env | xargs)

move-node

Used when running 4.x CouchDb in single node.

Requires COUCH_URL and CHT_NETWORK environment variable to be set. If your CouchDb Cluster port is different from the default (5986), export this port as COUCH_CLUSTER_PORT. Run this after starting 4.x CouchDb. Updates every databases' metadata to assign shards to the correct node.

Usage

export COUCH_URL=http://admin:pass@couchdbhost:5984
export COUCH_CLUSTER_PORT=5986
export CHT_NETWORK=<network_name>
docker-compose run couch-migration move-node

generate-shard-distribution-matrix

Used when running 4.x CouchDb in clustered mode, with multiple nodes.

Requires COUCH_URL and CHT_NETWORK environment variable to be set. If your CouchDb Cluster port is different from the default (5984), export this port as COUCH_CLUSTER_PORT. Outputs a JSON object representing redistribution of existent shards among CouchDb nodes. The matrix should be followed when moving shard data files among nodes, and should be passed to the mode-shards command. Run this after starting 4.x CouchDb.

Usage:

shard_matrix=$(docker-compose run couch-migration generate-shard-distribution-matrix)
echo $shard_matrix

Example Output:

{
  "00000000-15555554": "couchdb@couchdb-1.local",
  "15555555-2aaaaaa9": "couchdb@couchdb-2.local",
  "2aaaaaaa-3ffffffe": "couchdb@couchdb-3.local",
  "3fffffff-55555553": "couchdb@couchdb-1.local",
  "55555554-6aaaaaa8": "couchdb@couchdb-2.local",
  "6aaaaaa9-7ffffffd": "couchdb@couchdb-3.local",
  "7ffffffe-95555552": "couchdb@couchdb-1.local",
  "95555553-aaaaaaa7": "couchdb@couchdb-2.local",
  "aaaaaaa8-bffffffc": "couchdb@couchdb-3.local",
  "bffffffd-d5555551": "couchdb@couchdb-1.local",
  "d5555552-eaaaaaa6": "couchdb@couchdb-2.local",
  "eaaaaaa7-ffffffff": "couchdb@couchdb-3.local"
}

shard-move-instructions

Used when running 4.x CouchDb in clustered mode, with multiple nodes. Requires output from generate-shard-distribution-matrix to be passed as a parameter. Will output instructions on which shard folders to move, and to what locations.

Usage: 

shard_matrix=$(docker-compose run couch-migration generate-shard-distribution-matrix)
docker-compose run couch-migration shard-move-instructions $shard_matrix

Example Output:

Move the following shard folders to the corresponding nodes data folders:
If your shard folder is already in the correct location, on your main node, no move is necessary.
Move <mainNode-Path>/shards/00000000-1fffffff to <couchdb@couchdb-1.local-path>/shards/00000000-1fffffff
Move <mainNode-Path>/.shards/00000000-1fffffff to <couchdb@couchdb-1.local-path>/.shards/00000000-1fffffff
Move <mainNode-Path>/shards/20000000-3fffffff to <couchdb@couchdb-2.local-path>/shards/20000000-3fffffff
Move <mainNode-Path>/.shards/20000000-3fffffff to <couchdb@couchdb-2.local-path>/.shards/20000000-3fffffff
Move <mainNode-Path>/shards/40000000-5fffffff to <couchdb@couchdb-3.local-path>/shards/40000000-5fffffff
Move <mainNode-Path>/.shards/40000000-5fffffff to <couchdb@couchdb-3.local-path>/.shards/40000000-5fffffff
Move <mainNode-Path>/shards/60000000-7fffffff to <couchdb@couchdb-1.local-path>/shards/60000000-7fffffff
Move <mainNode-Path>/.shards/60000000-7fffffff to <couchdb@couchdb-1.local-path>/.shards/60000000-7fffffff
Move <mainNode-Path>/shards/80000000-9fffffff to <couchdb@couchdb-2.local-path>/shards/80000000-9fffffff
Move <mainNode-Path>/.shards/80000000-9fffffff to <couchdb@couchdb-2.local-path>/.shards/80000000-9fffffff
Move <mainNode-Path>/shards/a0000000-bfffffff to <couchdb@couchdb-3.local-path>/shards/a0000000-bfffffff
Move <mainNode-Path>/.shards/a0000000-bfffffff to <couchdb@couchdb-3.local-path>/.shards/a0000000-bfffffff
Move <mainNode-Path>/shards/c0000000-dfffffff to <couchdb@couchdb-1.local-path>/shards/c0000000-dfffffff
Move <mainNode-Path>/.shards/c0000000-dfffffff to <couchdb@couchdb-1.local-path>/.shards/c0000000-dfffffff
Move <mainNode-Path>/shards/e0000000-ffffffff to <couchdb@couchdb-2.local-path>/shards/e0000000-ffffffff
Move <mainNode-Path>/.shards/e0000000-ffffffff to <couchdb@couchdb-2.local-path>/.shards/e0000000-ffffffff

move-shards

Used when running 4.x CouchDb in clustered mode, with multiple nodes.

Requires COUCH_URL and CHT_NETWORK environment variable to be set. If your CouchDb Cluster port is different from the default (5984), export this port as COUCH_CLUSTER_PORT. Requires output from generate-shard-distribution-matrix to be passed as a parameter. Updates every databases' metadata to assign shards to the correct node, according to the distribution matrix.

Usage

shard_matrix=$(generate-shard-distribution-matrix)
docker-compose run couch-migration move-shards $shard_matrix

pre-index-views

Used to pre-index target 4.x CouchDb views while still running 3.x CouchDb. This will reduce downtime when you launch 4.x. Requires COUCH_URL and CHT_NETWORK environment variable to be set. Requires that target 4.x version to be passed as the first parameter (for example: 4.0.1).

Usage

docker-compose run couch-migration pre-index-views <target 4.x version>

Runtime of this command will depend on the size of the database, as it will install and index all design documents and views from the target 4.x CHT version. The command will output view indexing progress. Interrupting this command will not interrupt view indexing (that can only be achieved by restarting CouchDb). The design documents installed by this command will not overwrite the design documents that are used by your 3.x CHT installation.

Single Node example

Note

When starting 4.x CouchDb, you should mount the same data volume that 3.x CouchDb was using.

<start 3.x CouchDb>
docker-compose run couch-migration pre-index-views 4.1.0
docker-compose run couch-migration get-env > /path/to/docker-compose/.env
<stop 3.x CouchDb>
docker-compose -f ./path/to/docker-compose/couchdb-single.yml up -d
<wait for CouchDb to be up>
docker-compose run couch-migration move-node

Clustered example

Note

When clustering, your 4.x CouchDb cluster will have one main node and multiple secondary nodes. The main node is defined in your docker-compose file, and is the one that receives the environment variable: CLUSTER_PEER_IPS, while your secondary nodes will receive a different environment variable: COUCHDB_SYNC_ADMINS_NODE. When starting 4.x CouchDb, you should mount the 3.x CouchDb data volume to the main CouchDb node, and create two more folders/volumes for the secondary nodes. The couch-migration script does not know which of the nodes is the main node. 

<start 3.x CouchDb>
docker-compose run couch-migration pre-index-views 4.2.0
docker-compose run couch-migration get-env > /path/to/docker-compose/.env
<stop 3.x Couchdb>
docker-compose -f ./path/to/docker-compose/couchdb-cluster.yml up -d
<wait for CouchDb to be up>
shard_matrix=$(docker-compose run couch-migration generate-shard-distribution-matrix)
docker-compose run couch-migration shard-move-instructions $shard_matrix
<move shard and .shard folders to seconday nodes according to the instructions from the step above>
docker-compose run couch-migration move-shards $shard_matrix