[pbs-devel] [RFC proxmox-backup 31/36] specs: add backup detection mode specification

[Christian Ebner]

Adds the specification for switching the detection mode used to
identify regular files which changed since a reference backup run.

Rather than being a flag selecting the mode, it is possible to pass
a list of archives for which to use metadata base file change
detection, allowing to run mixed modes with the same client
invocation.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 pbs-client/src/backup_specification.rs | 53 ++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/pbs-client/src/backup_specification.rs b/pbs-client/src/backup_specification.rs
index 619a3a9d..5b33b451 100644
--- a/pbs-client/src/backup_specification.rs
+++ b/pbs-client/src/backup_specification.rs
@@ -4,6 +4,7 @@ use proxmox_schema::*;
 
 const_regex! {
     BACKUPSPEC_REGEX = r"^([a-zA-Z0-9_-]+\.(pxar|img|conf|log)):(.+)$";
+    DETECTION_MODE_REGEX = r"^(data|metadata(:[a-zA-Z0-9_-]+\.pxar)*)$";
 }
 
 pub const BACKUP_SOURCE_SCHEMA: Schema =
@@ -11,6 +12,11 @@ pub const BACKUP_SOURCE_SCHEMA: Schema =
         .format(&ApiStringFormat::Pattern(&BACKUPSPEC_REGEX))
         .schema();
 
+pub const BACKUP_DETECTION_MODE_SPEC: Schema =
+    StringSchema::new("Backup source specification ([data|metadata(:<label>,...)]).")
+        .format(&ApiStringFormat::Pattern(&DETECTION_MODE_REGEX))
+        .schema();
+
 pub enum BackupSpecificationType {
     PXAR,
     IMAGE,
@@ -45,3 +51,50 @@ pub fn parse_backup_specification(value: &str) -> Result<BackupSpecification, Er
 
     bail!("unable to parse backup source specification '{}'", value);
 }
+
+/// Mode to detect file changes since last backup run
+pub enum BackupDetectionMode {
+    /// Regular mode, re-encode payload data
+    Data,
+    /// Compare metadata, reuse payload chunks if metadata unchanged
+    ///
+    /// Stores archive names for which to use the metadata mode
+    Metadata(Vec<String>),
+}
+
+impl BackupDetectionMode {
+    /// Check if the selected mode is metadata based file change detection
+    pub fn is_metadata(&self) -> bool {
+        match self {
+            Self::Data => false,
+            Self::Metadata(_) => true,
+        }
+    }
+
+    /// List of archive names, for which metadata based file change detection should be used
+    pub fn metadata_archive_names(&self) -> &[String] {
+        match self {
+            Self::Data => &[],
+            Self::Metadata(ref archives) => archives,
+        }
+    }
+}
+
+pub fn parse_backup_detection_mode_specification(
+    value: &str,
+) -> Result<BackupDetectionMode, Error> {
+    match (DETECTION_MODE_REGEX.regex_obj)().captures(value) {
+        Some(caps) => {
+            let mode = match caps.get(1).unwrap().as_str() {
+                "data" => BackupDetectionMode::Data,
+                ty if ty.starts_with("metadata") => {
+                    let archives = ty.split(':').skip(1).map(|s| s.to_string()).collect();
+                    BackupDetectionMode::Metadata(archives)
+                }
+                _ => bail!("invalid backup detection mode"),
+            };
+            Ok(mode)
+        }
+        None => bail!("unable to parse backup detection mode specification '{value}'"),
+    }
+}
-- 
2.39.2