cql-proxy

cql-proxy

Table of Contents

• What is the cql-proxy?
• When to use cql-proxy
• Configuration
• Getting started
  • Locally build and run
  • Run a cql-proxy docker image
  • Use Kubernetes
• Tracking Metrics
• Known issues
  • Token-aware load balancing

What is cql-proxy?

cql-proxy is designed to forward your application's CQL traffic to an appropriate database service. It listens on a local address and securely forwards that traffic.

When to use cql-proxy

The cql-proxy sidecar enables unsupported CQL drivers to work with DataStax Astra. These drivers include both legacy DataStax drivers and community-maintained CQL drivers, such as the gocql driver and the rust-driver.

cql-proxy also enables applications that are currently using Apache Cassandra or DataStax Enterprise (DSE) to use Astra without requiring any code changes. Your application just needs to be configured to use the proxy.

If you're building a new application using DataStax drivers, cql-proxy is not required, as the drivers can communicate directly with Astra. DataStax drivers have excellent support for Astra out-of-the-box, and are well-documented in the driver-guide guide.

Configuration

Use the -h or --help flag to display a listing all flags and their corresponding descriptions and environment variables (shown below as items starting with $):

$ ./cql-proxy -h
Usage: cql-proxy

Flags:
  -h, --help                                               Show context-sensitive help.
  -b, --astra-bundle=STRING                                Path to secure connect bundle for an Astra database. Requires '--username' and '--password'. Ignored if using the token or contact points option ($ASTRA_BUNDLE).
  -t, --astra-token=STRING                                 Token used to authenticate to an Astra database. Requires '--astra-database-id'. Ignored if using the bundle path or contact points option ($ASTRA_TOKEN).
  -i, --astra-database-id=STRING                           Database ID of the Astra database. Requires '--astra-token' ($ASTRA_DATABASE_ID)
      --astra-api-url="https://api.astra.datastax.com"     URL for the Astra API ($ASTRA_API_URL)
      --astra-timeout=10s                                  Timeout for contacting Astra when retrieving the bundle and metadata ($ASTRA_TIMEOUT)
  -c, --contact-points=CONTACT-POINTS,...                  Contact points for cluster. Ignored if using the bundle path or token option ($CONTACT_POINTS).
  -u, --username=STRING                                    Username to use for authentication ($USERNAME)
  -p, --password=STRING                                    Password to use for authentication ($PASSWORD)
  -r, --port=9042                                          Default port to use when connecting to cluster ($PORT)
  -n, --protocol-version="v4"                              Initial protocol version to use when connecting to the backend cluster (default: v4, options: v3, v4, v5, DSEv1, DSEv2) ($PROTOCOL_VERSION)
  -m, --max-protocol-version="v4"                          Max protocol version supported by the backend cluster (default: v4, options: v3, v4, v5, DSEv1, DSEv2) ($MAX_PROTOCOL_VERSION)
  -a, --bind=":9042"                                       Address to use to bind server ($BIND)
  -f, --config=CONFIG                                      YAML configuration file ($CONFIG_FILE)
      --debug                                              Show debug logging ($DEBUG)
      --health-check                                       Enable liveness and readiness checks ($HEALTH_CHECK)
      --http-bind=":8000"                                  Address to use to bind HTTP server used for health checks ($HTTP_BIND)
      --heartbeat-interval=30s                             Interval between performing heartbeats to the cluster ($HEARTBEAT_INTERVAL)
      --idle-timeout=60s                                   Duration between successful heartbeats before a connection to the cluster is considered unresponsive and closed ($IDLE_TIMEOUT)
      --readiness-timeout=30s                              Duration the proxy is unable to connect to the backend cluster before it is considered not ready ($READINESS_TIMEOUT)
      --idempotent-graph                                   If true it will treat all graph queries as idempotent by default and retry them automatically. It may be dangerous to retry some graph queries -- use with caution ($IDEMPOTENT_GRAPH).
      --num-conns=1                                        Number of connection to create to each node of the backend cluster ($NUM_CONNS)
      --proxy-cert-file=STRING                             Path to a PEM encoded certificate file with its intermediate certificate chain. This is used to encrypt traffic for proxy clients ($PROXY_CERT_FILE)
      --proxy-key-file=STRING                              Path to a PEM encoded private key file. This is used to encrypt traffic for proxy clients ($PROXY_KEY_FILE)
      --cluster-ca-file=STRING                             Path to a PEM encoded file with CA certificates and their intermediate certificate chains. This is used to encrypt traffic between the proxy and the backend cluster ($CLUSTER_CA_FILE)
      --rpc-address=STRING                                 Address to advertise in the 'system.local' table for 'rpc_address'. It must be set if configuring peer proxies ($RPC_ADDRESS)
      --data-center=STRING                                 Data center to use in system tables ($DATA_CENTER)
      --tokens=TOKENS,...                                  Tokens to use in the system tables. It's not recommended ($TOKENS)
      --track-usage                                        Enable usage tracking for Astra Serverless estimation ($TRACK_USAGE).
      --usage-track-system                                 Include system tables in usage tracking ($USAGE_TRACK_SYSTEM).
      --usage-keyspace=STRING                              Specify the keyspace where the usage table will be created ($USAGE_KEYSPACE).
      --usage-rru-bytes=4096                               Specify the size of a read-request unit ($USAGE_RRU_BYTES)
      --usage-wru-bytes=1024                               Specify the size of a write-request unit ($USAGE_WRU_BYTES)
      --usage-flush-seconds=60                             Specify how frequently the accumulated stats should be made durable ($USAGE_FLUSH_SECONDS)
      --usage-table="astra_usage_stats"                    Specify the name of the table where usage data will be stored. Defaults to astra_usage_stats ($USAGE_TABLE).
      --usage-histograms-table="astra_usage_histograms"    Specify the name of the table where usage histograms will be stored. Defaults to astra_usage_histograms ($USAGE_HISTOGRAMS_TABLE).

To pass configuration to cql-proxy, either command-line flags, environment variables, or a configuration file can be used. Using the docker method as an example, the following samples show how the token and database ID are defined with each method.

Using flags

docker run -p 9042:9042 \
  --rm datastax/cql-proxy:v0.1.4 \
  --astra-token <astra-token> --astra-database-id <astra-datbase-id>

Using environment variables

docker run -p 9042:9042  \
  --rm datastax/cql-proxy:v0.1.4 \
  -e ASTRA_TOKEN=<astra-token> -e ASTRA_DATABASE_ID=<astra-datbase-id>

Using a configuration file

Proxy settings can also be passed using a configuration file with the --config /path/to/proxy.yaml flag. This can be mixed and matched with command-line flags and environment variables. Here are some example configuration files:

contact-points:
  - 127.0.0.1
username: cassandra
password: cassandra
port: 9042
bind: 127.0.0.1:9042
# ...

or with a Astra token:

astra-token: <astra-token>
astra-database-id: <astra-database-id>
bind: 127.0.0.1:9042
# ...

All configuration keys match their command-line flag counterpart, e.g. --astra-bundle is astra-bundle:, --contact-points is contact-points: etc.

Setting up peer proxies

Multi-region failover with DC-aware load balancing policy is the most useful case for a multiple proxy setup.

When configuring peers: it is required to set --rpc-address (or rpc-address: in the yaml) for each proxy and it must match is corresponding peers: entry. Also, peers: is only available in the configuration file and cannot be set using a command-line flag.

Here's an example of configuring multi-region failover with two proxies. A proxy is started for each region of the cluster connecting to it using that region's bundle. They all share a common configuration file that contains the full list of proxies.

Note: Only bundles are supported for multi-region setups.

cql-proxy --astra-bundle astra-region1-bundle.zip --username token --password <astra-token> \
  --bind 127.0.0.1:9042 --rpc-address 127.0.0.1 --data-center dc-1 --config proxy.yaml

cql-proxy ---astra-bundle astra-region2-bundle.zip --username token --password <astra-token> \
  --bind 127.0.0.2:9042 --rpc-address 127.0.0.2 --data-center dc-2 --config proxy.yaml

The peers settings are configured using a yaml file. It's a good idea to explicitly provide the --data-center flag, otherwise; these values are pulled from the backend cluster and would need to be pulled from the system.local and system.peers table to properly setup the peers data-center: values. Here's an example proxy.yaml:

peers:
  - rpc-address: 127.0.0.1
    data-center: dc-1
  - rpc-address: 127.0.0.2
    data-center: dc-2

Note: It's okay for the peers: to contain entries for the current proxy itself because they'll just be omitted.

Getting started

There are three methods for using cql-proxy:

• Locally build and run cql-proxy
• Run a docker image that has cql-proxy installed
• Use a Kubernetes container to run cql-proxy

Locally build and run

1. Build cql-proxy.

   go build
   

2. Run with your desired database.

   • DataStax Astra cluster:

     ./cql-proxy --astra-token <astra-token> --astra-database-id <astra-database-id>
     

     The <astra-token> can be generated using these instructions. The proxy also supports using the Astra Secure Connect Bundle along with a client ID and secret generated using these instructions:

     ./cql-proxy --astra-bundle <your-secure-connect-zip> \
     --username <astra-client-id> --password <astra-client-secret>
     

   • Apache Cassandra cluster:

     ./cql-proxy --contact-points <cluster node IPs or DNS names> [--username <username>] [--password <password>]
     

Run a cql-proxy docker image

1. Run with your desired database.

   • DataStax Astra cluster:

     docker run -p 9042:9042 \
       datastax/cql-proxy:v0.1.4 \
       --astra-token <astra-token> --astra-database-id <astra-database-id>
     

     The <astra-token> can be generated using these instructions. The proxy also supports using the Astra Secure Connect Bundle, but it requires mounting the bundle to a volume in the container:

     docker run -v <your-secure-connect-bundle.zip>:/tmp/scb.zip -p 9042:9042 \
     --rm datastax/cql-proxy:v0.1.4 \
     --astra-bundle /tmp/scb.zip --username <astra-client-id> --password <astra-client-secret>
     

   • Apache Cassandra cluster:

     docker run -p 9042:9042 \
       datastax/cql-proxy:v0.1.4 \
       --contact-points <cluster node IPs or DNS names> [--username <username>] [--password <password>]
     

If you wish to have the docker image removed after you are done with it, add --rm before the image name datastax/cql-proxy:v0.1.4.

Use Kubernetes

Using Kubernetes with cql-proxy requires a number of steps:

1. Generate a token following the Astra instructions. This step will display your Client ID, Client Secret, and Token; make sure you download the information for the next steps. Store the secure bundle in /tmp/scb.zip to match the example below.

2. Create cql-proxy.yaml. You'll need to add three sets of information: arguments, volume mounts, and volumes. A full example can be found here.

• Argument: Modify the local bundle location, username and password, using the client ID and client secret obtained in the last step to the container argument.

  command: ["./cql-proxy"]
  args: ["--astra-bundle=/tmp/scb.zip","--username=Client ID","--password=Client Secret"]
  

• Volume mounts: Modify /tmp/ as a volume mount as required.

  volumeMounts:
    - name: my-cm-vol
    mountPath: /tmp/
  

• Volume: Modify the configMap filename as required. In this example, it is named cql-proxy-configmap. Use the same name for the volumes that you used for the volumeMounts.

  volumes:
    - name: my-cm-vol
      configMap:
        name: cql-proxy-configmap        
  

1. Create a configmap. Use the same secure bundle that was specified in the cql-proxy.yaml.

   kubectl create configmap cql-proxy-configmap --from-file /tmp/scb.zip 
   

2. Check the configmap that was created.

   kubectl describe configmap cql-proxy-configmap
   
     Name:         cql-proxy-configmap
     Namespace:    default
     Labels:       <none>
     Annotations:  <none>
   
     Data
     ====
   
     BinaryData
     ====
     scb.zip: 12311 bytes
   

3. Create a Kubernetes deployment with the YAML file you created:

   kubectl create -f cql-proxy.yaml
   

4. Check the logs:

   kubectl logs <deployment-name>
   

Track Metrics

CQL-Proxy can track and summarize counts and latency of queries/statements passing through it. This can make it useful for diagnostics or to quantify your traffic in the way that DBaaS providers, such as DataStax Astra do. When you enable --track-usage and specify --usage-keyspace, cql-proxy will create two tables in the designated keyspace. By default they will be named astra_usage_stats and astra_usage_histograms.

NOTE: The user/token must have sufficient permissions to create these tables.

DataStax Astra counts each 4KB of a read request and each 1KB of a write request as a "read request unit" and a "write request unit" respectively. These unit sizes are configurable with the --usage-rru-bytes and --usage-wru-bytes options.

CQL Proxy will accumulate metrics internally and flush them to the tables every 60 seconds by default (configurable with the --usage-flush-seconds option). The data model of the stats and histograms tables will track metrics per table, per hour.

The metrics tracking feature is not intended to run indefinitely. It is intended to run for days up to a few months in order to collect data for a representative usage pattern and then it should be disabled and the data extracted and analyzed.

Known issues

Please be aware that CQL Proxy works downstream of the DataStax Astra billing engine and any metrics captured by CQL-Proxy are only intended to give an indication of the number of credits that are / may be used. There are some known limitations due to this separation If a read request involves server-side filtering or aggregation of data, the data is measured before the filtering or aggregation takes place. Some examples of queries where this can happen are:

• Queries that use the ALLOW FILTERING clause.
• Queries that use the COUNT function.
• Queries that use the GROUP BY clause.
• Queries that do not request all columns from a row be returned. In these cases the CQL-Proxy will only capture the data passed back to the client.

CQL Proxy is similarly unable to understand the billing implication of the use of features like secondary indexes and SAI, or operations similar to ORDER BY ... LIMIT, or client pagination that abandons query results, or other more complex scenarios.

Token-aware load balancing

Drivers that use token-aware load balancing may print a warning or may not work when using cql-proxy. Because cql-proxy abstracts the backend cluster as a single endpoint this doesn't always work well with token-aware drivers that expect there to be at least "replication factor" number of nodes in the cluster. Many drivers print a warning (which can be ignored) and fallback to something like round-robin, but other drivers might fail with an error. For the drivers that fail with an error it is required that they disable token-aware or configure the round-robin load balancing policy.