feat(sdk): add contrib/viper remote config provider

- Go applications using Viper for configuration had no way to read OpenDecree values without custom glue code.
- Added sdk/contrib/viper — implements Viper's remote config provider interface backed by configclient.GetAll.
- Converts flat field paths into nested JSON structures that Viper's key lookup traverses naturally.

Closes #14

Author: zeevdr

.github/workflows/ci.yml

@@ -257,6 +257,7 @@ jobs:
           cd sdk/configwatcher && go test ./... -count=1 -coverprofile=../../cov-configwatcher.out -covermode=atomic & pids+=($!)
           cd sdk/grpctransport && go test ./... -count=1 -coverprofile=../../cov-grpctransport.out -covermode=atomic & pids+=($!)
           cd sdk/tools && go test ./... -count=1 -coverprofile=../../cov-tools.out -covermode=atomic & pids+=($!)
+          cd sdk/contrib/viper && go test ./... -count=1 -coverprofile=../../cov-contrib-viper.out -covermode=atomic & pids+=($!)
           cd cmd/decree && go test ./... -count=1 -coverprofile=../../cov-decree.out -covermode=atomic & pids+=($!)
           fail=0
           for pid in "${pids[@]}"; do wait "$pid" || fail=1; done
@@ -276,7 +277,7 @@ jobs:
       - name: Merge coverage profiles
         run: |
           echo "mode: atomic" > coverage.out
-          for f in coverage-internal.out cov-configclient.out cov-adminclient.out cov-configwatcher.out cov-grpctransport.out cov-tools.out cov-decree.out; do
+          for f in coverage-internal.out cov-configclient.out cov-adminclient.out cov-configwatcher.out cov-grpctransport.out cov-tools.out cov-contrib-viper.out cov-decree.out; do
             [ -f "$f" ] && grep -v "^mode:" "$f" >> coverage.out || true
           done
 

Makefile

@@ -22,7 +22,7 @@ SERVER_LDFLAGS := -X github.com/opendecree/decree/internal/version.Version=$(GIT
 CLI_LDFLAGS := -X main.cliVersion=$(GIT_VERSION) -X main.cliCommit=$(GIT_COMMIT)
 
 # Module list for multi-module operations.
-SDK_MODULES := sdk/retry sdk/configclient sdk/adminclient sdk/configwatcher sdk/grpctransport sdk/tools
+SDK_MODULES := sdk/retry sdk/configclient sdk/adminclient sdk/configwatcher sdk/grpctransport sdk/tools sdk/contrib/viper
 
 .PHONY: all generate generate-proto generate-sqlc deps test lint lint-go lint-proto lint-migrations build image ui migrate e2e e2e-jwt examples bench bench-e2e stress chaos docs docs-api docs-cli docs-man docs-serve docs-deploy pre-commit clean tools help demo-gif validate-meta-schemas
 

sdk/contrib/viper/README.md

@@ -0,0 +1,60 @@
+# decree contrib/viper
+
+A [Viper](https://github.com/spf13/viper) remote config provider backed by an OpenDecree `configclient`. It allows Go applications that use Viper for configuration to transparently read values from OpenDecree without changing their existing Viper-based code.
+
+> **Alpha**: This module is part of the OpenDecree alpha release. The API may change.
+
+## Installation
+
+```sh
+go get github.com/opendecree/decree/sdk/contrib/viper
+```
+
+## Usage
+
+```go
+import (
+    "github.com/opendecree/decree/sdk/configclient"
+    "github.com/opendecree/decree/sdk/grpctransport"
+    vipercontrib "github.com/opendecree/decree/sdk/contrib/viper"
+    "github.com/spf13/viper"
+)
+
+func main() {
+    // Create a configclient backed by the gRPC transport.
+    conn, _ := grpc.Dial("localhost:9090", grpc.WithTransportCredentials(insecure.NewCredentials()))
+    transport := grpctransport.NewConfigTransport(conn)
+    client := configclient.New(transport)
+
+    // Create and register the provider for your tenant.
+    p := vipercontrib.New(client, "my-tenant")
+    vipercontrib.Register("decree", p)
+
+    // Configure Viper to use the provider.
+    viper.SetConfigType("json")
+    viper.AddRemoteProvider("decree", "decree://local", "")
+    if err := viper.ReadRemoteConfig(); err != nil {
+        log.Fatal(err)
+    }
+
+    // Use Viper as normal.
+    fmt.Println(viper.GetString("app.name"))
+    fmt.Println(viper.GetBool("feature.flag"))
+}
+```
+
+Decree field paths use dot notation (e.g. `"app.name"`, `"feature.flag"`). These are mapped to Viper's hierarchical key model, so `viper.GetString("app.name")` works as expected.
+
+## Options
+
+```go
+// WithTimeout sets the per-fetch request timeout (default: 5s).
+p := vipercontrib.New(client, "my-tenant", vipercontrib.WithTimeout(10*time.Second))
+```
+
+## Limitations
+
+- **Read-only**: this provider does not support writing config values back to OpenDecree. Use `configclient.Client` directly for writes.
+- **No real-time watch**: `WatchRemoteConfig` and `WatchRemoteConfigOnChannel` use polling (30-second interval) rather than a live subscription. For real-time updates use `configwatcher`.
+- **All values are strings**: `GetAll` returns string representations of all field types. Use `configclient` typed getters (`GetInt`, `GetBool`, etc.) when type fidelity matters.
+- **Single tenant per provider**: each `Provider` is scoped to one tenant. Register multiple providers under different names if you need to read from multiple tenants.

sdk/contrib/viper/go.mod

@@ -0,0 +1,35 @@
+module github.com/opendecree/decree/sdk/contrib/viper
+
+go 1.22.0
+
+require (
+	github.com/opendecree/decree/sdk/configclient v0.1.2
+	github.com/spf13/viper v1.19.0
+)
+
+require (
+	github.com/fsnotify/fsnotify v1.7.0 // indirect
+	github.com/hashicorp/hcl v1.0.0 // indirect
+	github.com/magiconair/properties v1.8.7 // indirect
+	github.com/mitchellh/mapstructure v1.5.0 // indirect
+	github.com/opendecree/decree/sdk/retry v0.0.0 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
+	github.com/sagikazarmark/locafero v0.4.0 // indirect
+	github.com/sagikazarmark/slog-shim v0.1.0 // indirect
+	github.com/sourcegraph/conc v0.3.0 // indirect
+	github.com/spf13/afero v1.11.0 // indirect
+	github.com/spf13/cast v1.6.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/subosito/gotenv v1.6.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	go.uber.org/multierr v1.9.0 // indirect
+	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
+	golang.org/x/sys v0.18.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	gopkg.in/ini.v1 v1.67.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+replace github.com/opendecree/decree/sdk/configclient => ../../../sdk/configclient
+
+replace github.com/opendecree/decree/sdk/retry => ../../../sdk/retry

sdk/contrib/viper/go.sum

@@ -0,0 +1,71 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
+github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
+github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
+github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0VQdvPDY=
+github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
+github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=
+github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
+github.com/pelletier/go-toml/v2 v2.2.2 h1:aYUidT7k73Pcl9nb2gScu7NSrKCSHIDE89b3+6Wq+LM=
+github.com/pelletier/go-toml/v2 v2.2.2/go.mod h1:1t835xjRzz80PqgE6HHgN2JOsmgYu/h4qDAS4n929Rs=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
+github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+github.com/sagikazarmark/locafero v0.4.0 h1:HApY1R9zGo4DBgr7dqsTH/JJxLTTsOt7u6keLGt6kNQ=
+github.com/sagikazarmark/locafero v0.4.0/go.mod h1:Pe1W6UlPYUk/+wc/6KFhbORCfqzgYEpgQ3O5fPuL3H4=
+github.com/sagikazarmark/slog-shim v0.1.0 h1:diDBnUNK9N/354PgrxMywXnAwEr1QZcOr6gto+ugjYE=
+github.com/sagikazarmark/slog-shim v0.1.0/go.mod h1:SrcSrq8aKtyuqEI1uvTDTK1arOWRIczQRv+GVI1AkeQ=
+github.com/sourcegraph/conc v0.3.0 h1:OQTbbt6P72L20UqAkXXuLOj79LfEanQ+YQFNpLA9ySo=
+github.com/sourcegraph/conc v0.3.0/go.mod h1:Sdozi7LEKbFPqYX2/J+iBAM6HpqSLTASQIKqDmF7Mt0=
+github.com/spf13/afero v1.11.0 h1:WJQKhtpdm3v2IzqG8VMqrr6Rf3UYpEF239Jy9wNepM8=
+github.com/spf13/afero v1.11.0/go.mod h1:GH9Y3pIexgf1MTIWtNGyogA5MwRIDXGUr+hbWNoBjkY=
+github.com/spf13/cast v1.6.0 h1:GEiTHELF+vaR5dhz3VqZfFSzZjYbgeKDpBxQVS4GYJ0=
+github.com/spf13/cast v1.6.0/go.mod h1:ancEpBxwJDODSW/UG4rDrAqiKolqNNh2DX3mk86cAdo=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/spf13/viper v1.19.0 h1:RWq5SEjt8o25SROyN3z2OrDB9l7RPd3lwTWU8EcEdcI=
+github.com/spf13/viper v1.19.0/go.mod h1:GQUN9bilAbhU/jgc1bKs99f/suXKeUMct8Adx5+Ntkg=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/subosito/gotenv v1.6.0 h1:9NlTDc1FTs4qu0DDq7AEtTPNw6SVm7uBMsUCUjABIf8=
+github.com/subosito/gotenv v1.6.0/go.mod h1:Dk4QP5c2W3ibzajGcXpNraDfq2IrhjMIvMSWPKKo0FU=
+go.uber.org/atomic v1.9.0 h1:ECmE8Bn/WFTYwEW/bpKD3M8VtR/zQVbavAoalC1PYyE=
+go.uber.org/atomic v1.9.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
+go.uber.org/multierr v1.9.0 h1:7fIwc/ZtS0q++VgcfqFDxSBZVv/Xo49/SYnDFupUwlI=
+go.uber.org/multierr v1.9.0/go.mod h1:X2jQV1h+kxSjClGpnseKVIxpmcjrj7MNnI0bnlfKTVQ=
+golang.org/x/exp v0.0.0-20230905200255-921286631fa9 h1:GoHiUyI/Tp2nVkLI2mCxVkOjsbSXD66ic0XW0js0R9g=
+golang.org/x/exp v0.0.0-20230905200255-921286631fa9/go.mod h1:S2oDrQGGwySpoQPVqRShND87VCbxmc6bL1Yd2oYrm6k=
+golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
+golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
+golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
+gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

sdk/contrib/viper/viper.go

@@ -0,0 +1,171 @@
+// Package vipercontrib provides a Viper remote config provider backed by a
+// decree configclient. It allows Go applications using Viper for configuration
+// to transparently read values from OpenDecree.
+//
+// Usage:
+//
+//	transport := grpctransport.NewConfigTransport(conn)
+//	client := configclient.New(transport)
+//	p := vipercontrib.New(client, "my-tenant")
+//	vipercontrib.Register("decree", p)
+//
+//	// Then use Viper normally:
+//	viper.SetConfigType("json")
+//	viper.AddRemoteProvider("decree", "", "")
+//	viper.ReadRemoteConfig()
+package vipercontrib
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"time"
+
+	"github.com/opendecree/decree/sdk/configclient"
+	"github.com/spf13/viper"
+)
+
+// Provider is a Viper remote config provider backed by a decree configclient.
+// It fetches all config fields for the tenant and maps them to Viper keys.
+type Provider struct {
+	client   *configclient.Client
+	tenantID string
+	timeout  time.Duration
+}
+
+// New creates a new Provider for the given tenant.
+func New(client *configclient.Client, tenantID string, opts ...Option) *Provider {
+	p := &Provider{
+		client:   client,
+		tenantID: tenantID,
+		timeout:  5 * time.Second,
+	}
+	for _, opt := range opts {
+		opt(p)
+	}
+	return p
+}
+
+// Option configures a Provider.
+type Option func(*Provider)
+
+// WithTimeout sets the request timeout for config reads.
+func WithTimeout(d time.Duration) Option {
+	return func(p *Provider) { p.timeout = d }
+}
+
+// Register registers this provider with Viper under the given provider name and
+// appends that name to viper.SupportedRemoteProviders so that
+// viper.AddRemoteProvider accepts it.
+//
+// Call Register before viper.AddRemoteProvider.
+func Register(name string, p *Provider) {
+	viper.SupportedRemoteProviders = append(viper.SupportedRemoteProviders, name)
+	viper.RemoteConfig = &configProvider{p: p}
+}
+
+type configProvider struct {
+	p *Provider
+}
+
+func (cp *configProvider) Get(_ viper.RemoteProvider) (io.Reader, error) {
+	return cp.p.fetch()
+}
+
+func (cp *configProvider) Watch(_ viper.RemoteProvider) (io.Reader, error) {
+	return cp.p.fetch()
+}
+
+func (cp *configProvider) WatchChannel(_ viper.RemoteProvider) (<-chan *viper.RemoteResponse, chan bool) {
+	ch := make(chan *viper.RemoteResponse)
+	quit := make(chan bool)
+	go func() {
+		for {
+			select {
+			case <-quit:
+				return
+			default:
+				r, err := cp.p.fetch()
+				if err == nil {
+					b, _ := io.ReadAll(r)
+					ch <- &viper.RemoteResponse{Value: b}
+				}
+				time.Sleep(30 * time.Second)
+			}
+		}
+	}()
+	return ch, quit
+}
+
+// fetch retrieves all config values for the tenant and encodes them as JSON.
+// Viper parses JSON from remote providers. Field paths with dot separators
+// (e.g. "app.name") are converted to nested JSON objects so that Viper's
+// hierarchical key lookup works correctly:
+//
+//	"app.name" → {"app": {"name": "..."}}
+func (p *Provider) fetch() (io.Reader, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), p.timeout)
+	defer cancel()
+
+	m, err := p.client.GetAll(ctx, p.tenantID)
+	if err != nil {
+		return nil, err
+	}
+
+	nested := toNestedMap(m)
+
+	b, err := json.Marshal(nested)
+	if err != nil {
+		return nil, err
+	}
+	return bytes.NewReader(b), nil
+}
+
+// toNestedMap converts a flat map with dot-separated keys into a nested
+// map[string]any suitable for Viper's hierarchical key lookup.
+//
+// Example:
+//
+//	{"app.name": "myapp", "app.debug": "true"} →
+//	{"app": {"name": "myapp", "debug": "true"}}
+func toNestedMap(flat map[string]string) map[string]any {
+	out := make(map[string]any)
+	for key, val := range flat {
+		setNested(out, key, val)
+	}
+	return out
+}
+
+// setNested inserts val into m at the path described by the dot-separated key.
+func setNested(m map[string]any, key, val string) {
+	for {
+		dot := -1
+		for i := 0; i < len(key); i++ {
+			if key[i] == '.' {
+				dot = i
+				break
+			}
+		}
+		if dot < 0 {
+			m[key] = val
+			return
+		}
+		prefix := key[:dot]
+		key = key[dot+1:]
+		child, ok := m[prefix]
+		if !ok {
+			next := make(map[string]any)
+			m[prefix] = next
+			m = next
+			continue
+		}
+		next, ok := child.(map[string]any)
+		if !ok {
+			// Conflict: existing leaf at prefix — prefer the deeper key.
+			next = make(map[string]any)
+			m[prefix] = next
+		}
+		m = next
+	}
+}