always retry on specific errors from azcopy (#1196)

src/agent/onefuzz/src/az_copy.rs

@@ -20,6 +20,14 @@ use url::Url;
 const RETRY_INTERVAL: Duration = Duration::from_secs(5);
 const RETRY_COUNT: usize = 5;
 
+const ALWAYS_RETRY_ERROR_STRINGS: &[&str] = &[
+    // There isn't an ergonomic method to sync between the OneFuzz agent and fuzzers generating
+    // data.  As such, we should always retry azcopy commands that fail with errors that occur due
+    // to the fuzzers writing files while a sync is occurring.
+    // ref: https://github.com/microsoft/onefuzz/issues/1189
+    "source modified during transfer",
+];
+
 #[derive(Clone, Copy)]
 enum Mode {
     Copy,
@@ -106,21 +114,47 @@ async fn az_impl(mode: Mode, src: &OsStr, dst: &OsStr, args: &[&str]) -> Result<
     Ok(())
 }
 
+// Work around issues where azcopy fails with an error we should consider
+// "acceptable" to always retry on.
+fn should_always_retry(err: &anyhow::Error) -> bool {
+    let as_string = format!("{:?}", err);
+    for value in ALWAYS_RETRY_ERROR_STRINGS {
+        if as_string.contains(value) {
+            info!(
+                "azcopy failed with an error that always triggers a retry: {} - {:?}",
+                value, err
+            );
+            return true;
+        }
+    }
+    false
+}
+
 async fn retry_az_impl(mode: Mode, src: &OsStr, dst: &OsStr, args: &[&str]) -> Result<()> {
-    let counter = AtomicUsize::new(0);
+    let attempt_counter = AtomicUsize::new(0);
+    let failure_counter = AtomicUsize::new(0);
 
     let operation = || async {
-        let attempt_count = counter.fetch_add(1, Ordering::SeqCst);
-        let result = az_impl(mode, src, dst, args)
-            .await
-            .with_context(|| format!("azcopy {} attempt {} failed", mode, attempt_count + 1));
+        let attempt_count = attempt_counter.fetch_add(1, Ordering::SeqCst);
+        let mut failure_count = failure_counter.load(Ordering::SeqCst);
+        let result = az_impl(mode, src, dst, args).await.with_context(|| {
+            format!(
+                "azcopy {} attempt {} failed.  (failure {})",
+                mode,
+                attempt_count + 1,
+                failure_count + 1
+            )
+        });
         match result {
             Ok(()) => Ok(()),
-            Err(x) => {
-                if attempt_count >= RETRY_COUNT {
-                    Err(backoff::Error::Permanent(x))
+            Err(err) => {
+                if !should_always_retry(&err) {
+                    failure_count = failure_counter.fetch_add(1, Ordering::SeqCst);
+                }
+                if failure_count >= RETRY_COUNT {
+                    Err(backoff::Error::Permanent(err))
                 } else {
-                    Err(backoff::Error::Transient(x))
+                    Err(backoff::Error::Transient(err))
                 }
             }
         }