Merge branch 'main' of https://github.com/stackabletech/demos into bump/nifi-2.2.0-git-registry-client

Author: dervoeti

.pre-commit-config.yaml

@@ -2,6 +2,8 @@
 default_language_version:
   node: system
 
+exclude: '^stacks/_templates/minio-tls/rendered-chart\.yaml$'
+
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: 2c9f875913ee60ca25ce70243dc24d5b6415598c # 4.6.0

docs/modules/demos/pages/signal-processing.adoc

@@ -65,6 +65,9 @@ image::signal-processing/notebook.png[]
 
 The notebook reads the measurement data in windowed batches using a loop, computes some predictions for each batch and persists the scores in a separate timescale table.
 
+NOTE: Re-running the notebook *will* result in errors, due to collisions in indexed data created by these batch scores.
+Nifi is used to simulate the ingestion of streamed data by performing a one-off import and then re-calibrating the timestamps so that each batch created by the notebook will always "find" new data. Re-running the notebook will mean that batched (but *not* aggregated i.e. the timestamps are not altered) data will be written to the database a second time, resulting in a violation of a unique index constraint.
+
 === Adding libraries
 
 There are two ways of doing this:

stacks/_templates/minio-tls/README.md

@@ -0,0 +1,16 @@
+# MinIO with TLS from secret-operator
+
+MinIO has a severe limitation whereby the TLS certificates must be named `public.crt`
+and `private.key`. This goes against Kubernetes naming of `tls.crt` and `tls.key`.
+
+The upstream minio chart is also too limited:
+
+- No way to add initContainers (to rename cert files in a shared volume).
+- No way to edit the container command (to rename cert files before starting minio).
+
+Therefore, we will render the upstream chart here, and then apply the necessary
+customizations on top.
+
+```yaml
+helm template minio minio/minio -f values.yaml > rendered-chart.yaml
+```