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es-simple-cluster

A multi-container cluster using docker-compose, including the basic services that are part of the EarthScope environment.

See docs for general documentation.

Running in Docker Compose

From the root of this project run:

docker compose up -d

See Installation for more. See Notes for MacOS for MacOS variations.

Services

Ideally, every available service should be included in this project, but for any particular bit of development most of them should probably be commented out for size/performance.

  • broker (core)
    • Kafka broker
  • zookeeper (core)
    • Kafka zookeeper
  • schema-registry (core)
    • Kafka schema registry
  • landoop topics UI (core)
    • Kafka topics UI
  • landoop schema registry UI (core)
    • Kafka schema registry UI
  • nginx (core)
    • external web interface
  • vouch-proxy
    • provides CILogon authentication for the nginx server
  • postgres
    • postgres database
  • redis
    • redis key/value store
  • localstack
  • prometheus
    • metrics backend
  • grafana
    • metrics front end
  • examples

Volumes

For the most part, you only need volumes when you want persistent or shared data.

  • web-static
    • Static web content produced by Django, surfaced by nginx
  • kafka-data
    • Data backend for the broker
    • Disabled by default to avoid kafka errors
  • postgres-data
    • Storage for postgres
  • prometheus
    • Storage for prometheus
  • grafana
    • Storage for grafana (ie. user accounts, dashboards)

/avro_schemas

For now, AVRO schemas are shared through a file mount.

This path typically gets passed to components like:

volumes:
  - ./avro_schemas:/avro_schemas:ro
environment:
  - AVRO_SCHEMAS_ROOT=/avro_schemas

Kafka brokers and schema registry

Use the following to connect to kafka.

For code running internal to docker-compose network BOOTSTRAP_SERVERS="broker:9092" SCHEMA_REGISTRY_URL="http://schema-registry:8081"

Code running on local machine, not in docker-compose env BOOTSTRAP_SERVERS='localhost:19092' SCHEMA_REGISTRY_URL='http://localhost:8081'

Kafka UIs

topics UI landoop free UI, shows topics and messages localhost:8093

schema registry UI landoop free UI, shows schemas localhost:8094

Data collection prototype components so far

strain-producer - image contains sample gtsm bottle files, which it reads in and produces to topic 'gtsm_etl' based on the schema 'gtsm_etl.avsc'. container exits when done reading files.

ggkx-producer - container connects to RT-GNSS GGKX stream (NTRIP Castor) for station P225 and produces 1 sample per second messages containing an epoch of data. Uses all_GNSS_position_metadata.avsc schema, and includes original ggkx data and also maps to unified 'position' schema.

slink-producer - connects to rtserve and produces packets from network code HL to topic 'binarypackets'

Flink Components

jobmanager - the endpoint to which apache flink jobs are submitted. the web frontend runs on port 8083 that you can access on the host machine (outside the docker network) via http://localhost:8083

taskmanager - the container to which the jobmanager farms out flink jobs. the parallelism of jobs is dictated by the number of slots made available

sql-client - a vanilla flink container that serves as a standalone client to submit jobs to flink. In our setup, we use it to invoke flink-sql-client.sh after logging in to get the flink sql command line client interface.

Using Flink to query from Kafka topic using Flink SQL Client

$ docker-compose  exec  sql-client /bin/bash

root@4a339a52acba:/opt/flink# ls
LICENSE  NOTICE  README.txt  bin  conf	examples  lib  licenses  log  opt  plugins  update_flink_install.sh

We now have to run a script that will update the flink install to download the relevant kafka jars that enable us to query kafka topics and also do schema registry validation

root@4a339a52acba:/opt/flink# ./update_flink_install.sh 
...
Saving to: ‘/opt/flink/lib/flink-sql-connector-kafka_2.11-1.14.2.jar’
Saving to: ‘/opt/flink/lib/flink-sql-avro-confluent-registry-1.14.2.jar’

Now we can run the sql client to bring up the sql interface

root@4a339a52acba:/opt/flink# /opt/flink/bin/flink-sql-client.sh
Command history file path: /root/.flink-sql-history

                                   ...
          
    ______ _ _       _       _____  ____  _         _____ _ _            _  BETA   
   |  ____| (_)     | |     / ____|/ __ \| |       / ____| (_)          | |  
   | |__  | |_ _ __ | | __ | (___ | |  | | |      | |    | |_  ___ _ __ | |_ 
   |  __| | | | '_ \| |/ /  \___ \| |  | | |      | |    | | |/ _ \ '_ \| __|
   | |    | | | | | |   <   ____) | |__| | |____  | |____| | |  __/ | | | |_ 
   |_|    |_|_|_| |_|_|\_\ |_____/ \___\_\______|  \_____|_|_|\___|_| |_|\__|
          
        Welcome! Enter 'HELP;' to list all available commands. 'QUIT;' to exit.


Flink SQL>

We will now first create a SQL table that maps to the kafka topic gtsm_etl that we have . To do issue the following commands in flink sql interface

Flink SQL> CREATE TABLE gtsm_etl (
    
    -- one column mapped to the 'id' Avro field of the Kafka key
    `key_site` STRING,
    
    -- a few columns mapped to the Avro fields of the Kafka value
    `timestamp` STRING
    
  ) WITH (
  
    'connector' = 'kafka',
    'topic' = 'gtsm_etl',
    'properties.bootstrap.servers' = 'broker:9092',
  
    -- Watch out: schema evolution in the context of a Kafka key is almost never backward nor
    -- forward compatible due to hash partitioning.
    'key.format' = 'avro-confluent',
    'key.avro-confluent.url' = 'http://schema-registry:8081',
    'key.fields' = 'key_site',
  
    -- In this example, we want the Avro types of both the Kafka key and value to contain the field 'id'
    -- => adding a prefix to the table column associated to the Kafka key field avoids clashes
    'key.fields-prefix' = 'key_',
  
    'value.format' = 'avro-confluent',
    'value.avro-confluent.url' = 'http://schema-registry:8081',
    'value.fields-include' = 'EXCEPT_KEY',
    'properties.group.id' = 'testGroup',
    'scan.startup.mode' = 'earliest-offset'
     
    -- subjects have a default value since Flink 1.13, though can be overriden:
    -- 'key.avro-confluent.schema-registry.subject' = 'user_events_example2-key2',
    -- 'value.avro-confluent.schema-registry.subject' = 'user_events_example2-value2'
  );
[INFO] Execute statement succeed.

Now we have a Flink SQL table that maps directly to query the Kafka topic gtsm_etl Lets query the table and retrieve the data from this topic

Flink SQL> select * from gtsm_etl;

                      key_site                      timestamp
                           B009            2021-07-01 16:50:00
                           B009            2021-07-01 17:00:00
                           B009            2021-07-01 17:10:00
                           B009            2021-07-01 17:20:00
                           B009            2021-07-01 17:30:00
                           ....

Behind the scenes.

When we issued the select command, a flink job gets launched by the jobmanager, and the jobs run in the task manager container

You can navigate to http://localhost:8083 in your local web browser

Apache Flink Dashboard

There you will see a job running. You can click on the job to get futher details Apache Flink Dashboard