Cassandra-migrate

Simple Cassandra schema migration tool.

Installation

Run pip install cassandra-migrate, or python ./setup.py

Reasoning

Unlike other available tools, this one:

• Written in Python for easy installation
• Does not require cqlsh, just the Python driver
• Supports baselining existing database to given versions
• Supports partial advancement
• Supports locking for concurrent instances using Lightweight Transactions
• Verifies stored migrations against configured migrations
• Stores content, checksum, date and state of every migration
• Supports deploying with different keyspace configurations for different environments

Configuration

Databases are configured through YAML files. For example:

keyspace: herbie
profiles:
  prod:
    replication:
      class: SimpleStrategy
      replication_factor: 3
migrations_path: ./migrations

Where the migrations folder (relative to the config file). contains .cql files. The files are loaded in lexical order.

The default convention is to name them in the form: v001_my_migration.cql. A custom naming scheme can be specified with the new_migration_name option. For example

# Date-based migration names
new_migration_name: "v{date:YYYYMMDDHHmmss}_{desc}"

# Default migration names
new_migration_name: "v{next_version:03d}_{desc}"

# Custom initial migration content
new_migration_text: |
  /* Cassandra migration for keyspace {keyspace}.
     Version {next_version} - {date}

     {full_desc} */

new_migration_name is a new-style Python format string, which can use the following parameters:

• next_version: Number of the newly generated migration (as an int).
• desc: filename-clean description of the migration, as specified by the user.
• full_desc: unmodified description, possibly containing special characters.
• date: current date in UTC. Pay attention to the choice of formatting, otherwise you might include spaces in the file name. The above example should be a good starting point.
• keyspace: name of the configured keyspace.

The format string should not contain the .cql extension, as it is added automatically.

new_migraton_text is handled with the same rules outline above, but defines the initial content of the migration file.

Profiles

Profiles can be defined in the configuration file. They can configure the replication and durable_writes parameters for CREATE KEYSPACE. A default dev profile is implicitly defined using a replication factor of 1.

Usage

Common parameters:

-H HOSTS, --hosts HOSTS
                      Comma-separated list of contact points
-p PORT, --port PORT  Connection port
-u USER, --user USER  Connection username
-P PASSWORD, --password PASSWORD
                      Connection password
-c CONFIG_FILE, --config-file CONFIG_FILE
                      Path to configuration file
-m PROFILE, --profile PROFILE
                      Name of keyspace profile to use

migrate

Advances a database to the latest (or chosen) version of migrations. Creates the keyspace and migrations table if necessary.

Migrate will refuse to run if a previous attempt failed. To override that after cleaning up any leftovers (as Cassandra has no DDL transactions), use the --force option.

Examples:

# Migrate to the latest database version using the default configuration file,
# connecting to Cassandra in the local machine.
cassandra-migrate -H 127.0.0.1 migrate

# Migrate to version 2 using a specific config file.
cassandra-migrate -c mydb.yml migrate 2

# Migrate to a version by name.
cassandra-migrate migrate v005_my_changes.cql

# Force migration after a failure
cassandra-migrate migrate 2 --force

reset

Reset the database by dropping an existing keyspace, then running a migration.

Examples:

# Reset the database to the latest version
cassandra-migrate reset

# Reset the database to a specifis version
cassandra-migrate reset 3

baseline

Advance an existing database version without actually running the migrations.

Useful for starting to manage a pre-existing database without recreating it from scratch.

Examples:

# Baseline the existing database to the latest version
cassandra-migrate baseline

# Baseline the existing database to a specific version
cassandra-migrate baseline 5

status

Print the current status of the database.

Example:

cassandra-migrate status

generate

Generate a new migration file with the appropriate name and a basic header template, in the configured migrations_path.

When running the command interactively, the file will be opened by the default editor. The newly-generated file name will be printed to stdout.

See the configuration section for details on migration naming.

Example:

cassandra-migrate generate "My migration description"

TODO

• Ask for confirmation before applying dangerous commands
• Support Python migrations (instead of just CQL)

License (MIT)

Copyright (C) 2017 Cobli

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.