1 files changed, 36 insertions, 0 deletions
diff --git a/configserver-flags/src/main/java/com/yahoo/vespa/configserver/flags/db/BootstrapFlagSource.java b/configserver-flags/src/main/java/com/yahoo/vespa/configserver/flags/db/BootstrapFlagSource.java
new file mode 100644
index 00000000000..0c467a0e7c8
--- /dev/null
+++ b/configserver-flags/src/main/java/com/yahoo/vespa/configserver/flags/db/BootstrapFlagSource.java
@@ -0,0 +1,36 @@
+// Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.configserver.flags.db;
+
+import com.yahoo.vespa.flags.FetchVector;
+import com.yahoo.vespa.flags.FlagId;
+import com.yahoo.vespa.flags.FlagSource;
+import com.yahoo.vespa.flags.RawFlag;
+import com.yahoo.vespa.flags.file.FlagDbFile;
+import com.yahoo.vespa.flags.json.FlagData;
+
+import java.nio.file.FileSystem;
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * A flag source that can be used in emergencies, see test for path and format of file.
+ *
+ * <p>Use file if the ZooKeeper flag makes it difficult to start the config server, would make irreparable damage,
+ * or is impossible to change through ZooKeeper due to a bug. This flag source should take precedence over ZooKeeper
+ * whenever it has specified the value for a flag.
+ *
+ * @author hakonhall
+ */
+public class BootstrapFlagSource implements FlagSource {
+    private final Map<FlagId, FlagData> flagData;
+
+    public BootstrapFlagSource(FileSystem fileSystem) {
+        // The flags on disk is read once now and never again.
+        this.flagData = new FlagDbFile(fileSystem).read();
+    }
+
+    @Override
+    public Optional<RawFlag> fetch(FlagId id, FetchVector vector) {
+        return Optional.ofNullable(flagData.get(id)).flatMap(data -> data.resolve(vector));
+    }
+}