Management API for Apache Cassandra®

Introduction

Cassandra operations have historically been command line driven. The management of operational tools for Apache Cassandra have been mostly outsourced to teams who manage their specific environments.

The result is a fragmented and tribal set of best practices, workarounds, and edge cases.

The Management API is a sidecar service layer that attempts to build a well supported set of operational actions on Cassandra nodes that can be administered centrally. It currently works with official Apache Cassandra 3.11.x and 4.0 via a drop in java agent.

• Lifecycle Management
  • Start Node
  • Stop Node
• Configuration Management (alpha)
  • Change YAML
  • Change jvm-opts
• Health Checks
  • Kubernetes liveness/readiness checks
  • Consistency level checks
• Per node actions
  • All nodetool commands

Design Principles

• Secure by default
• Simple to use and extend
• CQL Only for all C* interactions
  • Operations: Use CALL method for invoking via CQL
  • Observations: Rely on System Views

The Management API has no configuration file. Rather, it can only be configured from a small list of command line flags. Communication by default can only be via unix socket or via a http(s) endpoint with optional TLS client auth.

In a containerized setting the Management API represents PID 1 and will be responsible for the lifecycle of Cassandra via the API.

Communication between the Management API and Cassandra is via a local unix socket using CQL as it's only protocol. This means, out of the box Cassandra can be started securely with no open ports! Also, using CQL only means operators can execute operations via CQL directly if they wish.

Each Management API is responsible for the local node only. Coordination across nodes is up to the caller. That being said, complex health checks can be added via CQL.

Building

Containers

First you need to build the Management API base image

(Deprecated: For Cassandra 3.11 and 4.0 images, as well as DSE 6.8 images, you do not need to build the Management API builder image):

docker build -t management-api-for-apache-cassandra-builder -f ./Dockerfile-build .

Then you need to build the image based on the actual Cassandra version, either the 3.11 or 4.0:

NOTE: For building 3.11 and 4.0 images, you will need to have the Docker buildx plugin installed.

#Create a docker image with management api and C* 3.11 (version 3.11.7 and newer are supported, replace `3.11.11` with the version you want below)
docker buildx build --load --build-arg CASSANDRA_VERSION=3.11.11 --tag mgmtapi-3_11 --file Dockerfile-oss --target oss311 --platform linux/amd64 .

#Create a docker image with management api and C* 4.0 (version 4.0.0 and 4.0.1 are supported)
docker buildx build --load --build-arg CASSANDRA_VERSION=4.0.1 --tag mgmtapi-4_0 --file Dockerfile-4_0 --target oss40 --platform linux/amd64 .

You can also build an image based on Datastax Astra Cassandra 4.0 sources. First checkout sources and build a tgz distribution:

ant artifacts

Then copy the tgz archive into the astra-4.0 directory of the Management API sources and run:

cd astra-4.0
docker build -t datastax/astra:4.0 .

Finally build the Management API image:

cd ..
docker build -t mgmtapi-astra-4_0 -f Dockerfile-astra-4_0 .

Standalone

mvn -DskipTests package
mvn test
mvn integration-test -Drun311tests=true -Drun40tests=true

NOTE 1: Running integration-tests will also run unit tests.

NOTE 2: Running integration-tests requires at least one of -Drun311tests, -Drun40tests or -DrunDSEtests to be set to true (you can set any combination of them to true).

NOTE 3: In order to run DSE integration tests, you must also enable the dse profile:

mvn integration-test -P dse -DrunDSEtests=true

REST API

The current Swagger/OpenAPI documentation

Also readable from url root: /openapi.json

Usage

As of v0.1.24, Management API Docker images for Apache Cassandra are consolidated into a single image repository here:

• Management API for Apache Cassandra

For different Cassandra versions, you will need to specify the Cassandra version as an image tag. The following lists the currently supported versions

  k8ssandra/cass-management-api:3.11.7
  k8ssandra/cass-management-api:3.11.8
  k8ssandra/cass-management-api:3.11.9 (**Deprecated: last version is v0.1.27**)
  k8ssandra/cass-management-api:3.11.10 (**Deprecated: last version is v0.1.27**)
  k8ssandra/cass-management-api:3.11.11
  k8ssandra/cass-management-api:4.0.0
  k8ssandra/cass-management-api:4.0.1

Each of the above examples will always point to the latest Management API version for the associated Cassandra version. If you want a specific Management API version, you can append the desired version to the Cassandra version tag. For example, if you want v0.1.24 of Management API for Cassandra version 3.11.9:

 docker pull k8ssandra/cass-management-api:3.11.9-v0.1.24

For Management API versions v0.1.23 and lower, you will need to use the old Docker repositories, which are Cassandra version specific:

• Management API for Apache Cassandra 3.11.7
• Management API for Apache Cassandra 3.11.8
• Management API for Apache Cassandra 3.11.9
• Management API for Apache Cassandra 3.11.10
• Management API for Apache Cassandra 4.0-beta4.

For DSE Docker images, the location remains unchanged

• Management API for DSE 6.8

For running standalone the jars can be downloaded from the github release: Management API Releases Zip

The Management API can be run as a standalone service or along with the Kubernetes cass-operator.

The Management API is configured from the CLI. To start the service with a C* version built above, run:

 > docker run -p 8080:8080 -it --rm mgmtapi-4_0

 > curl http://localhost:8080/api/v0/probes/liveness
 OK

 # Check service and C* are running
 > curl http://localhost:8080/api/v0/probes/readiness
 OK

Usage with DSE

A DSE jar must be locally available before running the Management API with DSE. Details are described in the DSE README. Once you have DSE jars published locally, follow these steps:

# The builder image needs to have Maven settings.xml (that provides access to Artifactory):
cp $HOME/.m2/settings.xml $PWD

docker build -t mgmtapi-dse -f Dockerfile-dse-68 .

docker run -p 8080:8080 -it --rm mgmtapi-dse

Using the Service with a locally installed C* or DSE instance

To start the service with a locally installed C* or DSE instance, you would run the below commands. The Management API will figure out through --db-home whether it points to a C* or DSE folder

# REQUIRED: Add management api agent to C*/DSE startup
> export JVM_EXTRA_OPTS="-javaagent:$PWD/management-api-agent/target/datastax-mgmtapi-agent-0.1.0-SNAPSHOT.jar"

> alias mgmtapi="java -jar management-api-server/target/datastax-mgmtapi-server-0.1.0-SNAPSHOT.jar"

# Start the service with a local unix socket only, you could also pass -H http://localhost:8080 to expose a port
> mgmtapi --db-socket=/tmp/db.sock --host=unix:///tmp/mgmtapi.sock --db-home=<pathToCassandraOrDseHome>

# Cassandra/DSE will be started by the service by default unless you pass --explicit-start flag

# Check the service is up
> curl --unix-socket /tmp/mgmtapi.sock http://localhost/api/v0/probes/liveness
OK

# Check C*/DSE is up
> curl --unix-socket /tmp/mgmtapi.sock http://localhost/api/v0/probes/readiness
OK

# Stop C*/DSE
curl -XPOST --unix-socket /tmp/mgmtapi.sock http://localhost/api/v0/lifecycle/stop
OK

Making changes

Design Summary

The architecture of this repository is laid as follows, front-to-back:

1. The management-api-server/doc/openapi.json documents the API.
2. The server implements the HTTP verbs/endpoints under the management-api-server/src/main/java/com/datastax/mgmtapi/resources folder (e.g. NodeOpsresources.java).
3. The server methods communicate back to the agents using cqlService.executePreparedStatement() calls which are routed as plaintext through a local socket. These calls return ResultSet objects, and to acess scalar values within these you are best to call .one() before checking for nulls and .getObject(0). This java objectcan then be serialised into JSON for return to the client.
4. The server communicates only with the management-api-agent-common subproject, which holds the unversioned CassandraAPI interface.
5. The management-api-agent-common/src/main/java/com/datastax/mgmtapi/NodeOpsProvider.java routes commands through to specific versioned instances of CassandraAPI which is implemented in the version 3x/4x subprojects as CassandraAPI4x/CassandraAPI3x.

Any change to add endpoints or features will need to make modifications in each of the above components to ensure that they propagate through.

Changes to API endpoints

If you are adding a new endpoint, removing an endpoint, or otherwise changing the public API of an endpoint, you will need to re-generate the OpenAPI/Swagger document. The document lives at management-api-server/doc/openapi.json and is regenerated during the build's compile phase. If your changes to code cause the API to change, you will need to perform a local mvn compile to regenerate the document and then add the change to your git commit.

mvn clean compile
git add management-api-server/doc/openapi.json
git commit

API Client Generation

In addition to automatic OpenAPI document generation, a Golang client can be generated during the build by enabling the clientgen Maven profile. The client is built using the OpenAPI Tools generator Maven plugin and can be used by Go projects to interact with the Management API. The client generation happens during the process-classes phase of the Maven build so that changes to the API implementation can be compiled into an OpenAPI document spec file during the compile phase of the build. The client code is generated in the target directory under the management-api-server sub-module and should be located at

management-api-server/target/generated-sources/openapi

To generate the client, run the following from the root of the project:

mvn clean process-classes -Pclientgen

Published Docker images

When PRs are merged into the master branch, if all of the integration tests pass, the CI process will build and publish all supported Docker images with GitHub commit SHA tags. These images are not intended to be used in production. They are meant for facilitating testing with dependent projects.

The format of the Docker image tag for OSS Cassandra based images will be <Cassandra version>-<git commit sha>. For example, if the SHA for the commit to master is 3e99e87, then the Cassandra 3.11.11 image tag would be 3.11.11-3e99e87. The full docker coordinates would be k8ssandra/cass-management-api:3.11.11-3e99e87. Once published, these images can be used for testing in dependent projects (such as cass-operator). Testing in dependent projects is a manual process at this time and is not automated.

Official Release process

When the master branch is ready for release, all that needs to be done is to create a git tag and push the tag. When a git tag is pushed, a GitHub Action will kick off that builds the release versions of the Docker images and publish the to DockerHub. The release tag should be formatted as:

v0.1.X

where X is incremental for each release. If the most recent release version is v0.1.32, then to cut the next (v0.1.33) release, do the following:

git checkout master
git pull
git tag v0.1.33
git push origin refs/tags/v0.1.33

Once the tag is pushed, the release process will start and build the Docker images as well as the Maven artifacts. The images are automatically pushed to DockerHub and the Maven artifacts are published and attached to the GitHub release.

CLI Help

The CLI help covers the different options:

mgmtapi --help

NAME
        cassandra-management-api - REST service for managing an Apache
        Cassandra or DSE node

SYNOPSIS
        cassandra-management-api
                [ {-C | --cassandra-home | --db-home} <db_home> ]
                [ --explicit-start <explicit_start> ] [ {-h | --help} ]
                {-H | --host} <listen_address>...
                [ {-K | --no-keep-alive} <no_keep_alive> ]
                [ {-p | --pidfile} <pidfile> ]
                {-S | --cassandra-socket | --db-socket} <db_unix_socket_file>
                [ --tlscacert <tls_ca_cert_file> ]
                [ --tlscert <tls_cert_file> ] [ --tlskey <tls_key_file> ]

OPTIONS
        -C <db_home>, --cassandra-home <db_home>, --db-home <db_home>
            Path to the Cassandra or DSE root directory, if missing will use
            $CASSANDRA_HOME/$DSE_HOME respectively

            This options value must be a path on the file system that must be
            readable, writable and executable.


        --explicit-start <explicit_start>
            When using keep-alive, setting this flag will make the management
            api wait to start Cassandra/DSE until /start is called via REST

        -h, --help
            Display help information

        -H <listen_address>, --host <listen_address>
            Daemon socket(s) to listen on. (required)

        -K <no_keep_alive>, --no-keep-alive <no_keep_alive>
            Setting this flag will stop the management api from starting or
            keeping Cassandra/DSE up automatically

        -p <pidfile>, --pidfile <pidfile>
            Create a PID file at this file path.

            This options value must be a path on the file system that must be
            readable and writable.


        -S <db_unix_socket_file>, --cassandra-socket <db_unix_socket_file>,
        --db-socket <db_unix_socket_file>
            Path to Cassandra/DSE unix socket file (required)

            This options value must be a path on the file system that must be
            readable and writable.


        --tlscacert <tls_ca_cert_file>
            Path to trust certs signed only by this CA

            This options value must be a path on the file system that must be
            readable.


        --tlscert <tls_cert_file>
            Path to TLS certificate file

            This options value must be a path on the file system that must be
            readable.


        --tlskey <tls_key_file>
            Path to TLS key file

            This options value must be a path on the file system that must be
            readable.


COPYRIGHT
        Copyright (c) DataStax 2020

LICENSE
        Please see https://www.apache.org/licenses/LICENSE-2.0 for more
        information

Roadmap

• CQL based configuration changes
• Configuration as system table

License

Copyright DataStax, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Dependencies

For information on the packaged dependencies of the Management API for Apache Cassandra® and their licenses, check out our open source report.