Allow single-sync invocation using --sync-once commandline flag

internal/config_specification.toml

@@ -85,6 +85,10 @@ default = "10"
 name = "ignore_mempool"
 doc = "Don't sync mempool - queries will show only confirmed transactions."
 
+[[switch]]
+name = "sync_once"
+doc = "Exit after the initial sync is over (don't start Electrum server)."
+
 [[param]]
 name = "index_lookup_limit"
 type = "usize"

src/bin/electrs.rs

@@ -9,7 +9,9 @@ fn main() -> Result<()> {
     tracker
         .sync(&Daemon::connect(&config)?)
         .context("initial sync failed")?;
-
+    if config.sync_once {
+        return Ok(());
+    }
     // re-connect after initial sync (due to possible timeout during compaction)
     server::run(&config, Rpc::new(&config, tracker)?).context("server failed")
 }

src/config.rs

@@ -133,6 +133,7 @@ pub struct Config {
     pub index_batch_size: usize,
     pub index_lookup_limit: Option<usize>,
     pub ignore_mempool: bool,
+    pub sync_once: bool,
     pub server_banner: String,
     pub args: Vec<String>,
 }
@@ -294,6 +295,7 @@ impl Config {
             index_batch_size: config.index_batch_size,
             index_lookup_limit,
             ignore_mempool: config.ignore_mempool,
+            sync_once: config.sync_once,
             server_banner: config.server_banner,
             args: args.map(|a| a.into_string().unwrap()).collect(),
         };