Add k8ssecret strategy for cross-namespace secret watching

Dockerfile.integrationtest

@@ -1,10 +1,10 @@
-FROM golang:1.23 AS builder
+FROM golang:1.24 AS builder
 WORKDIR /go/src/github.com/infobloxopen/hotload/
 COPY . .
 
 # build integration test binary
 RUN make build-test
 
-FROM golang:1.23 AS runner
+FROM golang:1.24 AS runner
 COPY --from=builder /go/src/github.com/infobloxopen/hotload/integrationtests.test .
 

Dockerfile.test

@@ -1,4 +1,4 @@
-FROM golang:1.23
+FROM golang:1.24
 WORKDIR /go/src/github.com/infobloxopen/hotload
 COPY . .
 RUN make ci-test

k8ssecret/README.md

@@ -0,0 +1,124 @@
+# hotload/k8ssecret
+
+A [hotload](https://github.com/infobloxopen/hotload) strategy that watches Kubernetes Secrets for connection string changes via the K8s API.
+
+Use this when the Secret containing your database credentials is in a **different namespace** than your application — where a volume mount isn't possible.
+
+## Installation
+
+```bash
+go get github.com/infobloxopen/hotload/k8ssecret
+```
+
+This is a separate Go module. It pulls in `k8s.io/client-go` but does **not** add those dependencies to the root `hotload` module.
+
+## Usage
+
+```go
+import (
+    "database/sql"
+
+    _ "github.com/infobloxopen/hotload"
+    _ "github.com/infobloxopen/hotload/k8ssecret"
+    _ "github.com/jackc/pgx/v5/stdlib" // or any sql driver
+)
+
+func main() {
+    // The Secret "orders-db" in namespace "orders-ns" has a key "dsn.txt"
+    // containing: postgres://statexfer:s3cret@orders-pg:5432/orders?sslmode=require
+    db, err := sql.Open("hotload", "k8ssecret://pgx/orders-db?namespace=orders-ns&dsn=dsn.txt")
+    if err != nil {
+        log.Fatal(err)
+    }
+    db.Query("SELECT 1")
+}
+```
+
+When the Secret is updated (e.g., credential rotation), hotload detects the change and transparently creates new connections with the updated DSN.
+
+## DSN Format
+
+```
+k8ssecret://<driver>/<secret-name>?namespace=<ns>&dsn=<key>
+```
+
+| Component | Description |
+|-----------|-------------|
+| `<driver>` | The registered database driver name (e.g., `pgx`, `postgres`, `mysql`) |
+| `<secret-name>` | Kubernetes Secret name |
+| `namespace` | Namespace containing the Secret. Defaults to the pod's namespace (from service account mount) or `"default"`. |
+| `dsn` | Data key within the Secret that holds the connection string. Defaults to `"dsn.txt"`. |
+
+## Kubernetes Secret
+
+The Secret holds connection strings as data keys. Each key is a file when volume-mounted, or a watchable field via this strategy:
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: orders-db
+  namespace: orders-ns
+type: Opaque
+stringData:
+  dsn.txt: "postgres://statexfer:s3cret@orders-pg:5432/orders?sslmode=require"
+```
+
+The `dsn` parameter selects which key to read:
+
+```
+k8ssecret://pgx/orders-db?namespace=orders-ns&dsn=dsn.txt
+```
+
+## When to Use This vs fsnotify
+
+| Scenario | Strategy | Why |
+|----------|----------|-----|
+| Secret in the **same** namespace | `fsnotify` | Mount the Secret as a volume. Cheaper — no API calls. |
+| Secret in a **different** namespace | `k8ssecret` | Volume mounts can't cross namespaces. This strategy watches via the K8s API. |
+
+For same-namespace Secrets mounted as volumes:
+
+```go
+// Secret mounted at /var/run/secrets/myapp/dsn.txt
+db, err := sql.Open("hotload", "fsnotify://pgx/var/run/secrets/myapp/dsn.txt")
+```
+
+## RBAC
+
+The service account running your application needs `get` and `watch` permissions on the target Secret:
+
+```yaml
+apiVersion: rbac.authorization.k8s.io/v1
+kind: Role
+metadata:
+  name: secret-reader
+  namespace: orders-ns
+rules:
+  - apiGroups: [""]
+    resources: ["secrets"]
+    resourceNames: ["orders-db"]
+    verbs: ["get", "watch"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: RoleBinding
+metadata:
+  name: statexd-reads-orders-db
+  namespace: orders-ns
+subjects:
+  - kind: ServiceAccount
+    name: statexd
+    namespace: statexfer-system
+roleRef:
+  kind: Role
+  name: secret-reader
+  apiGroup: rbac.authorization.k8s.io
+```
+
+## How It Works
+
+1. On first `Watch()` call, the strategy fetches the Secret via `Secrets(namespace).Get()`.
+2. It reads the value of the specified `key` and returns it as the initial connection string.
+3. A background goroutine establishes a K8s watch on the Secret.
+4. When the Secret is modified, the new value is pushed to hotload, which transparently rotates connections.
+5. If the watch is interrupted (API server restart, network partition), it reconnects automatically with a 2-second backoff.

k8ssecret/go.mod

@@ -0,0 +1,59 @@
+module github.com/infobloxopen/hotload/k8ssecret
+
+go 1.23.0
+
+require (
+	github.com/infobloxopen/hotload v1.7.4
+	k8s.io/api v0.32.3
+	k8s.io/apimachinery v0.32.3
+	k8s.io/client-go v0.32.3
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/colega/gaugefuncvec v0.1.0 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/emicklei/go-restful/v3 v3.11.0 // indirect
+	github.com/fxamacker/cbor/v2 v2.7.0 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
+	github.com/go-openapi/jsonpointer v0.21.0 // indirect
+	github.com/go-openapi/jsonreference v0.20.2 // indirect
+	github.com/go-openapi/swag v0.23.0 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/protobuf v1.5.4 // indirect
+	github.com/google/gnostic-models v0.6.8 // indirect
+	github.com/google/go-cmp v0.7.0 // indirect
+	github.com/google/gofuzz v1.2.0 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/josharian/intern v1.0.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/kylelemons/godebug v1.1.0 // indirect
+	github.com/mailru/easyjson v0.7.7 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/prometheus/client_golang v1.20.0 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.55.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	github.com/teivah/onecontext v1.3.0 // indirect
+	github.com/x448/float16 v0.8.4 // indirect
+	golang.org/x/net v0.43.0 // indirect
+	golang.org/x/oauth2 v0.23.0 // indirect
+	golang.org/x/sys v0.35.0 // indirect
+	golang.org/x/term v0.34.0 // indirect
+	golang.org/x/text v0.28.0 // indirect
+	golang.org/x/time v0.7.0 // indirect
+	google.golang.org/protobuf v1.36.7 // indirect
+	gopkg.in/evanphx/json-patch.v4 v4.12.0 // indirect
+	gopkg.in/inf.v0 v0.9.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+	k8s.io/klog/v2 v2.130.1 // indirect
+	k8s.io/kube-openapi v0.0.0-20241105132330-32ad38e42d3f // indirect
+	k8s.io/utils v0.0.0-20241104100929-3ea5e8cea738 // indirect
+	sigs.k8s.io/json v0.0.0-20241010143419-9aa6b5e7a4b3 // indirect
+	sigs.k8s.io/structured-merge-diff/v4 v4.4.2 // indirect
+	sigs.k8s.io/yaml v1.4.0 // indirect
+)