storage/oasis: Cache init failure is not longer fatal

storage/oasis/client.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/oasisprotocol/nexus/common"
 	"github.com/oasisprotocol/nexus/config"
+	"github.com/oasisprotocol/nexus/log"
 	"github.com/oasisprotocol/nexus/storage/oasis/nodeapi"
 	"github.com/oasisprotocol/nexus/storage/oasis/nodeapi/file"
 	"github.com/oasisprotocol/nexus/storage/oasis/nodeapi/history"
@@ -24,9 +25,13 @@ func NewConsensusClient(ctx context.Context, sourceConfig *config.SourceConfig)
 	}
 	if sourceConfig.Cache != nil {
 		cachePath := filepath.Join(sourceConfig.Cache.CacheDir, "consensus")
-		nodeApi, err = file.NewFileConsensusApiLite(cachePath, nodeApi)
+		wrappedNodeApi, err := file.NewFileConsensusApiLite(cachePath, nodeApi)
 		if err != nil {
-			return nil, fmt.Errorf("error instantiating cache-based consensusApi: %w", err)
+			// Continue without a cache, but warn.
+			// (The "analyzer" tag is not technically true as we're not in an analyzer, but is helpful when reading logs)
+			log.NewDefaultLogger("init").With("analyzer", "consensus").Warn("error instantiating cache-based consensusApi, continuing without a cache", "kvstore_err", err)
+		} else {
+			nodeApi = wrappedNodeApi
 		}
 	}
 	return nodeApi, nil
@@ -41,9 +46,13 @@ func NewRuntimeClient(ctx context.Context, sourceConfig *config.SourceConfig, ru
 	}
 	if sourceConfig.Cache != nil {
 		cachePath := filepath.Join(sourceConfig.Cache.CacheDir, string(runtime))
-		nodeApi, err = file.NewFileRuntimeApiLite(runtime, cachePath, nodeApi)
+		wrappedNodeApi, err := file.NewFileRuntimeApiLite(runtime, cachePath, nodeApi)
 		if err != nil {
-			return nil, fmt.Errorf("error instantiating cache-based runtimeApi: %w", err)
+			// Continue without a cache, but warn.
+			// (The "analyzer" tag is not technically true as we're not in an analyzer, but is helpful when reading logs)
+			log.NewDefaultLogger("init").With("analyzer", "consensus").Warn("error instantiating cache-based runtimeApi, continuing without a cache", "kvstore_err", err)
+		} else {
+			nodeApi = wrappedNodeApi
 		}
 	}
 

storage/oasis/nodeapi/file/kvstore.go

@@ -37,7 +37,7 @@ type pogrebKVStore struct {
 	metrics *metrics.AnalysisMetrics // if nil, no metrics are emitted
 
 	// Address of the atomic variable that indicates whether the store is initialized.
-	// Synchronisation is required because the store is opened in background goroutine.
+	// Synchronisation is required because the store is opened in a background goroutine.
 	initialized uint32
 }
 
@@ -104,10 +104,14 @@ func (s *pogrebKVStore) init() error {
 // Initializes a new KVStore backed by a database at `path`, or opens an existing one.
 // `metrics` can be `nil`, in which case no metrics are emitted during operation.
 func OpenKVStore(logger *log.Logger, path string, metrics *metrics.AnalysisMetrics) (KVStore, error) {
+	// An unitialized `pogrebKVStore`. Its methods can still be used, they just do nothing:
+	// Reads will indicate a cache miss, and writes will fail.
 	store := &pogrebKVStore{
-		logger:  logger,
-		path:    path,
-		metrics: metrics,
+		path:        path,
+		logger:      logger,
+		metrics:     metrics,
+		db:          nil, // to be constructed during init()
+		initialized: 0,
 	}
 
 	// Open the database in background as it is possible it will do a full-reindex on startup after a crash: