Add --allow-downgrade CLI arg. If set it allows the downgrade and upd…

…ates the Besu version in the metadata file to the downgraded version.

Signed-off-by: Matthew Whitehead <matthew1001@gmail.com>

besu/src/main/java/org/hyperledger/besu/cli/BesuCommand.java

@@ -526,6 +526,12 @@ private InetAddress autoDiscoverDefaultIP() {
           "Minimum number of peers required before starting fast sync. Has only effect on PoW networks. (default: ${DEFAULT-VALUE})")
   private final Integer fastSyncMinPeerCount = FAST_SYNC_MIN_PEER_COUNT;
 
+  @Option(
+      names = {"--allow-downgrade"},
+      description =
+          "Allow an older version of Besu to start if it detects that a more recent version last wrote to the database. Warning - this could result in unrecoverable changes to the database so should only be used if a backup of the data has been taken before the downgrade. (default: ${DEFAULT-VALUE})")
+  private final Boolean allowDowngrade = false;
+
   @Option(
       names = {"--network"},
       paramLabel = MANDATORY_NETWORK_FORMAT_HELP,
@@ -3387,6 +3393,11 @@ public Path getDataPath() {
     public int getDatabaseVersion() {
       return dataStorageOptions.toDomainObject().getDataStorageFormat().getDatabaseVersion();
     }
+
+    @Override
+    public boolean getDowngradeAllowed() {
+      return allowDowngrade;
+    }
   }
 
   private void instantiateSignatureAlgorithmFactory() {

besu/src/main/java/org/hyperledger/besu/services/BesuConfigurationImpl.java

@@ -44,4 +44,9 @@ public Path getStoragePath() {
   public Path getDataPath() {
     return dataPath;
   }
+
+  @Override
+  public boolean getDowngradeAllowed() {
+    return false; // TODO
+  }
 }

ethereum/core/src/test/java/org/hyperledger/besu/ethereum/bonsai/AbstractIsolationTests.java

@@ -207,6 +207,11 @@ public Path getDataPath() {
               public int getDatabaseVersion() {
                 return 2;
               }
+
+              @Override
+              public boolean getDowngradeAllowed() {
+                return false;
+              }
             })
         .withMetricsSystem(new NoOpMetricsSystem())
         .build();

gradle/versions.gradle

@@ -233,5 +233,7 @@ dependencyManagement {
     dependency 'tech.pegasys.discovery:discovery:22.2.0'
 
     dependency 'com.github.oshi:oshi-core:6.4.1'
+
+    dependency 'org.apache.maven:maven-artifact:3.9.6'
   }
 }

plugin-api/src/main/java/org/hyperledger/besu/plugin/services/BesuConfiguration.java

@@ -44,4 +44,6 @@ public interface BesuConfiguration extends BesuService {
   default int getDatabaseVersion() {
     return 1;
   }
+
+  boolean getDowngradeAllowed();
 }

plugins/rocksdb/build.gradle

@@ -42,7 +42,7 @@ dependencies {
 
   implementation 'com.fasterxml.jackson.core:jackson-databind'
   implementation 'com.fasterxml.jackson.datatype:jackson-datatype-jdk8'
-  implementation 'org.apache.maven:maven-artifact:3.9.6'
+  implementation 'org.apache.maven:maven-artifact'
   implementation 'com.google.guava:guava'
   implementation 'info.picocli:picocli'
   implementation 'io.opentelemetry:opentelemetry-api'

plugins/rocksdb/src/main/java/org/hyperledger/besu/plugin/services/storage/rocksdb/RocksDBKeyValueStorageFactory.java

@@ -267,7 +267,7 @@ private int readDatabaseVersion(final BesuConfiguration commonConfiguration) thr
       databaseVersion = dbMetaData.getVersion();
       besuVersion = dbMetaData.getBesuVersion();
       LOG.info(
-          "Existing database detected at {}. DB version {}. Installed version {}. Compacting database...",
+          "Existing database detected at {}. DB version {}. Besu version {}. Compacting database...",
           dataDir,
           databaseVersion,
           besuVersion);
@@ -280,15 +280,29 @@ private int readDatabaseVersion(final BesuConfiguration commonConfiguration) thr
         if (versionComparison == 0) {
           // Versions match - no-op
         } else if (versionComparison < 0) {
-          final String message =
-              "Besu version "
-                  + installedVersion
-                  + " is lower than version "
-                  + dbBesuVersion
-                  + " that last updated the database."
-                  + ". Specify --downgrade to use different version.";
-          LOG.error(message);
-          throw new StorageException(message);
+          if (commonConfiguration.getDowngradeAllowed()) {
+            LOG.warn(
+                "Besu version {} is lower than version {} that last wrote to the database. Allowing startup because --allow-downgrade has been enabled.",
+                installedVersion,
+                dbBesuVersion);
+            // We've allowed startup at an older version of Besu. Since the version in the metadata
+            // file records the latest version of
+            // Besu to write to the database we'll update the metadata version to this
+            // downgraded-version. This avoids the need after a successful
+            // downgrade to keep specifying --allow-downgrade on every startup.
+            writeDatabaseMetadata(
+                databaseVersion, Optional.of(commonConfiguration.getBesuVersion()), dataDir);
+          } else {
+            final String message =
+                "Besu version "
+                    + installedVersion
+                    + " is lower than version "
+                    + dbBesuVersion
+                    + " that last updated the database."
+                    + ". Specify --allow-downgrade to allow Besu to start at the lower version (warning - this may have unrecoverable effects on the node database).";
+            LOG.error(message);
+            throw new StorageException(message);
+          }
         } else if (versionComparison > 0) {
           LOG.info(
               "Besu version {} is higher than version {} that last updated the DB. Updating DB metadata.",
@@ -297,6 +311,12 @@ private int readDatabaseVersion(final BesuConfiguration commonConfiguration) thr
           writeDatabaseMetadata(
               databaseVersion, Optional.of(commonConfiguration.getBesuVersion()), dataDir);
         }
+      } else {
+        // No besu version information was found in the metadata file, so update it with the current
+        // version and carry on
+        LOG.info("Adding Besu version to metadata file.");
+        writeDatabaseMetadata(
+            databaseVersion, Optional.of(commonConfiguration.getBesuVersion()), dataDir);
       }
     } else {
       databaseVersion = commonConfiguration.getDatabaseVersion();