Adding option for snapshot file in replay

Summary:
Adding a new option in `below replay` to be able to accept the compressed file from the `snapshot` and run replay using the files.

**Usage**
```
below replay -- --snapshot <snapshot_file> --time <timestamp>
```

Reviewed By: brianc118

Differential Revision: D34410231

fbshipit-source-id: 17af3214ed0a38fca86ac7dffb5b75d78b24363b

1 files changed, 34 insertions, 6 deletions

diff --git a/below/src/main.rs b/below/src/main.rs
index eda9ad7f..552d9179 100644
--- a/below/src/main.rs
+++ b/below/src/main.rs
@@ -37,7 +37,7 @@ use structopt::{
     clap::{AppSettings, Shell},
     StructOpt,
 };
-use tar::Builder as TarBuilder;
+use tar::{Archive, Builder as TarBuilder};
 use tempdir::TempDir;
 use users::{get_current_uid, get_user_by_uid};
 
@@ -209,6 +209,10 @@ enum Command {
         /// * 09/01/2020 17:00: below replay -r yy -t "09/03/2020 17:00"
         #[structopt(short = "r", verbatim_doc_comment)]
         yesterdays: Option<String>,
+        /// Replay from a snapshot file generated by the snapshot
+        /// command instead of from the store directory.
+        #[structopt(long)]
+        snapshot: Option<String>,
     },
     /// Debugging facilities (for development use)
     Debug {
@@ -620,11 +624,13 @@ fn real_main(init: init::InitToken) {
             ref host,
             ref port,
             ref yesterdays,
+            ref snapshot,
         } => {
             let time = time.clone();
             let host = host.clone();
             let port = port.clone();
             let days_adjuster = yesterdays.clone();
+            let snapshot = snapshot.clone();
             run(
                 init,
                 debug,
@@ -632,7 +638,16 @@ fn real_main(init: init::InitToken) {
                 Service::Off,
                 RedirectLogOnFail::Off,
                 |_, below_config, logger, errs| {
-                    replay(logger, errs, time, below_config, host, port, days_adjuster)
+                    replay(
+                        logger,
+                        errs,
+                        time,
+                        below_config,
+                        host,
+                        port,
+                        days_adjuster,
+                        snapshot,
+                    )
                 },
             )
         }
@@ -747,14 +762,27 @@ fn replay(
     host: Option<String>,
     port: Option<u16>,
     days_adjuster: Option<String>,
+    snapshot: Option<String>,
 ) -> Result<()> {
     let timestamp =
         cliutil::system_time_from_date_and_adjuster(time.as_str(), days_adjuster.as_deref())?;
 
-    let mut advance = if let Some(host) = host {
-        new_advance_remote(logger.clone(), host, port, timestamp)?
-    } else {
-        new_advance_local(logger.clone(), below_config.store_dir.clone(), timestamp)
+    let mut advance = match (host, snapshot) {
+        (None, None) => {
+            new_advance_local(logger.clone(), below_config.store_dir.clone(), timestamp)
+        }
+        (Some(host), None) => new_advance_remote(logger.clone(), host, port, timestamp)?,
+        (None, Some(snapshot)) => {
+            let mut tarball =
+                Archive::new(fs::File::open(&snapshot).context("Failed to open snapshot file")?);
+            let mut snapshot_dir = TempDir::new("snapshot_replay")?.into_path();
+            tarball.unpack(&snapshot_dir)?;
+            snapshot_dir.push(snapshot);
+            new_advance_local(logger.clone(), snapshot_dir, timestamp)
+        }
+        (Some(_), Some(_)) => {
+            bail!("--host and --snapshot are incompatible options")
+        }
     };
 
     // Fill the last_sample for forward iteration. If no previous sample exists,