diff --git a/services/backup/src/service/handlers/send_log.rs b/services/backup/src/service/handlers/send_log.rs
--- a/services/backup/src/service/handlers/send_log.rs
+++ b/services/backup/src/service/handlers/send_log.rs
@@ -1,4 +1,5 @@
 use tonic::Status;
+use tracing::{error, trace, warn};
 use uuid::Uuid;
 
 use crate::{
@@ -53,19 +54,40 @@
     &mut self,
     user_id: String,
   ) -> Result<(), Status> {
-    unimplemented!()
+    if self.user_id.is_some() {
+      warn!("user ID already provided");
+      return Err(Status::invalid_argument("User ID already provided"));
+    }
+    self.user_id = Some(user_id);
+    self.handle_internal().await
   }
   pub async fn handle_backup_id(
     &mut self,
     backup_id: String,
   ) -> Result<(), Status> {
-    unimplemented!()
+    if self.backup_id.is_some() {
+      warn!("backup ID already provided");
+      return Err(Status::invalid_argument("Backup ID already provided"));
+    }
+    tracing::Span::current().record("backup_id", &backup_id);
+    self.backup_id = Some(backup_id);
+    self.handle_internal().await
   }
   pub async fn handle_log_hash(
     &mut self,
     log_hash: Vec<u8>,
   ) -> Result<(), Status> {
-    unimplemented!()
+    if self.log_hash.is_some() {
+      warn!("Log hash already provided");
+      return Err(Status::invalid_argument("Log hash already provided"));
+    }
+    let hash_str = String::from_utf8(log_hash).map_err(|err| {
+      error!("Failed to convert data_hash into string: {:?}", err);
+      Status::aborted("Unexpected error")
+    })?;
+    tracing::Span::current().record("log_hash", &hash_str);
+    self.log_hash = Some(hash_str);
+    self.handle_internal().await
   }
   pub async fn handle_log_data(
     &mut self,
@@ -77,4 +99,36 @@
   pub async fn finish(self) -> Result<SendLogResponse, Status> {
     unimplemented!()
   }
+
+  // internal param handler helper
+  async fn handle_internal(&mut self) -> Result<(), Status> {
+    if self.should_receive_data {
+      error!("SendLogHandler is already expecting data chunks");
+      return Err(Status::failed_precondition("Log data chunk expected"));
+    }
+
+    // all non-data inputs must be set before receiving log contents
+    let (Some(backup_id), Some(_), Some(_)) = (
+      self.backup_id.as_ref(),
+      self.user_id.as_ref(),
+      self.log_hash.as_ref()
+    ) else { return Ok(()); };
+
+    let log_id = generate_log_id(backup_id);
+    tracing::Span::current().record("log_id", &log_id);
+    self.log_id = Some(log_id);
+
+    trace!("Everything prepared, waiting for data...");
+    self.should_receive_data = true;
+    Ok(())
+  }
+}
+
+fn generate_log_id(backup_id: &str) -> String {
+  format!(
+    "{backup_id}{sep}{uuid}",
+    backup_id = backup_id,
+    sep = ID_SEPARATOR,
+    uuid = Uuid::new_v4()
+  )
 }