Summing over Multiplexed File Chunks

This example application implements a SHA-summing consumer which incrementally sums file “chunks” and publishes their final sum. It’s implemented using the Gazette consumer framework.

The complete implementation can be found in package stream-sum.


A number of “chunker” jobs will randomly create and publish “chunks” of number of files. Each chunker will publish incremental chunks of many simultaneous files. A “summer” consumer must accumulate the running SHA-sum of each file and, when the file is completed, it must emit a final SHA-sum of its content. Each chunker job will independently verify that a final and correct SHA-sum is published in a timely fashion.

This is a fully self-contained example, and also serves as a soak test for Gazette. Chunkers and summers run continuously, and each verifies expected guarantees of Gazette brokers and consumers: that all messages are delivered exactly one time, within a bounded SLA. If any of these guarantees are violated, the summer or chunker process will crash with an error.

These guarantees are further tested by a suite of crash tests which crash and partition components of the application, like Etcd, gazette brokers, and consumer processes.

Deploy the Example to Kubernetes

Deploy the example to the stream-sum namespace of a test Kubernetes cluster, such as Minikube or Docker for Desktop:

$ kubectl apply -k  ./kustomize/test/deploy-stream-sum/
namespace/stream-sum created
serviceaccount/minio created
configmap/etcd-scripts-24t872gm88 created
configmap/example-journal-specs created
configmap/gazette-zonemap created
configmap/generate-shards-stream-sum-9k96chk9cg created
configmap/minio-create-bucket-mm6f469cbt created
configmap/postgres-init created
secret/gazette-aws-credentials created
secret/minio-credentials-fgdm8fkm5m created
service/consumer-stream-sum created
service/etcd created
service/gazette created
service/minio created
deployment.apps/consumer-stream-sum created
deployment.apps/gazette created
deployment.apps/minio created
statefulset.apps/etcd created
job.batch/apply-journal-specs created
job.batch/apply-shard-specs-stream-sum created
job.batch/chunker-stream-sum created
job.batch/minio-create-bucket created