Flag to enable compaction during initial sync

While compaction during initial sync makes thing much slower, it may be
preferred to not require to size the disk the double of the final
required space.

src/config.rs

@@ -41,6 +41,12 @@ pub struct Config {
     pub electrum_banner: String,
     pub electrum_rpc_logging: Option<RpcLogging>,
 
+    /// Enable compaction during initial sync
+    ///
+    /// By default compaction is off until initial sync is finished for performance reasons,
+    /// however, this requires much more disk space.
+    pub initial_sync_compaction: bool,
+
     #[cfg(feature = "liquid")]
     pub parent_network: BNetwork,
     #[cfg(feature = "liquid")]
@@ -191,6 +197,10 @@ impl Config {
                     .long("electrum-rpc-logging")
                     .help(&rpc_logging_help)
                     .takes_value(true),
+            ).arg(
+                Arg::with_name("initial_sync_compaction")
+                    .long("initial-sync-compaction")
+                    .help("Perform compaction during initial sync (slower but less disk space required)")
             );
 
         #[cfg(unix)]
@@ -403,6 +413,7 @@ impl Config {
             index_unspendables: m.is_present("index_unspendables"),
             cors: m.value_of("cors").map(|s| s.to_string()),
             precache_scripts: m.value_of("precache_scripts").map(|s| s.to_string()),
+            initial_sync_compaction: m.is_present("initial_sync_compaction"),
 
             #[cfg(feature = "liquid")]
             parent_network,

src/new_index/db.rs

@@ -90,7 +90,7 @@ impl DB {
         db_opts.set_compression_type(rocksdb::DBCompressionType::Snappy);
         db_opts.set_target_file_size_base(1_073_741_824);
         db_opts.set_write_buffer_size(256 << 20);
-        db_opts.set_disable_auto_compactions(true); // for initial bulk load
+        db_opts.set_disable_auto_compactions(!config.initial_sync_compaction); // for initial bulk load
 
         // db_opts.set_advise_random_on_open(???);
         db_opts.set_compaction_readahead_size(1 << 20);

tests/common.rs

@@ -113,6 +113,7 @@ impl TestRunner {
             asset_db_path: None, // XXX
             #[cfg(feature = "liquid")]
             parent_network: bitcoin::Network::Regtest,
+            initial_sync_compaction: false,
             //#[cfg(feature = "electrum-discovery")]
             //electrum_public_hosts: Option<crate::electrum::ServerHosts>,
             //#[cfg(feature = "electrum-discovery")]