Optional Idempotency id + check on emptyness

service-protocol/dev/restate/service/protocol.proto

@@ -318,7 +318,8 @@ message CallEntryMessage {
   // If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
   string key = 5;
 
-  string idempotency_key = 6;
+  // If present, it must be non empty.
+  optional string idempotency_key = 6;
 
   oneof result {
     bytes value = 14;
@@ -349,7 +350,8 @@ message OneWayCallEntryMessage {
   // If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
   string key = 6;
 
-  string idempotency_key = 7;
+  // If present, it must be non empty.
+  optional string idempotency_key = 7;
 
   // Entry name
   string name = 12;

src/service_protocol/generated/dev.restate.service.protocol.rs

@@ -361,8 +361,9 @@ pub struct CallEntryMessage {
     /// If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
     #[prost(string, tag = "5")]
     pub key: ::prost::alloc::string::String,
-    #[prost(string, tag = "6")]
-    pub idempotency_key: ::prost::alloc::string::String,
+    /// If present, it must be non empty.
+    #[prost(string, optional, tag = "6")]
+    pub idempotency_key: ::core::option::Option<::prost::alloc::string::String>,
     /// Entry name
     #[prost(string, tag = "12")]
     pub name: ::prost::alloc::string::String,
@@ -401,8 +402,9 @@ pub struct OneWayCallEntryMessage {
     /// If this invocation has a key associated (e.g. for objects and workflows), then this key is filled in. Empty otherwise.
     #[prost(string, tag = "6")]
     pub key: ::prost::alloc::string::String,
-    #[prost(string, tag = "7")]
-    pub idempotency_key: ::prost::alloc::string::String,
+    /// If present, it must be non empty.
+    #[prost(string, optional, tag = "7")]
+    pub idempotency_key: ::core::option::Option<::prost::alloc::string::String>,
     /// Entry name
     #[prost(string, tag = "12")]
     pub name: ::prost::alloc::string::String,

src/vm/errors.rs

@@ -125,6 +125,11 @@ pub const BAD_COMBINATOR_ENTRY: Error = Error::new_const(
     "The combinator cannot be replayed. This is most likely caused by non deterministic code.",
 );
 
+pub const EMPTY_IDEMPOTENCY_KEY: Error = Error::new_const(
+    codes::INTERNAL,
+    "Trying to execute an idempotent request with an empty idempotency key, this is not supported",
+);
+
 // Other errors
 
 #[derive(Debug, Clone, thiserror::Error)]

src/vm/mod.rs

@@ -11,7 +11,9 @@ use crate::service_protocol::messages::{
 };
 use crate::service_protocol::{Decoder, RawMessage, Version};
 use crate::vm::context::{EagerGetState, EagerGetStateKeys};
-use crate::vm::errors::{UnexpectedStateError, UnsupportedFeatureForNegotiatedVersion};
+use crate::vm::errors::{
+    UnexpectedStateError, UnsupportedFeatureForNegotiatedVersion, EMPTY_IDEMPOTENCY_KEY,
+};
 use crate::vm::transitions::*;
 use crate::{
     AsyncResultCombinator, AsyncResultHandle, CancelInvocationTarget, Error, GetInvocationIdTarget,
@@ -433,16 +435,23 @@ impl super::VM for CoreVM {
         ret
     )]
     fn sys_call(&mut self, target: Target, input: Bytes) -> VMResult<AsyncResultHandle> {
-        if target.idempotency_key.is_some() {
-            self.verify_feature_support("attach idempotency key to one way call", Version::V3)?;
+        if let Some(idempotency_key) = &target.idempotency_key {
+            self.verify_feature_support("attach idempotency key to call", Version::V3)?;
+            if idempotency_key.is_empty() {
+                self.do_transition(HitError {
+                    error: EMPTY_IDEMPOTENCY_KEY,
+                    next_retry_delay: None,
+                })?;
+                unreachable!();
+            }
         }
         self.do_transition(SysCompletableEntry(
             "SysCall",
             CallEntryMessage {
                 service_name: target.service,
                 handler_name: target.handler,
                 key: target.key.unwrap_or_default(),
-                idempotency_key: target.idempotency_key.unwrap_or_default(),
+                idempotency_key: target.idempotency_key,
                 parameter: input,
                 ..Default::default()
             },
@@ -461,16 +470,23 @@ impl super::VM for CoreVM {
         input: Bytes,
         delay: Option<Duration>,
     ) -> VMResult<SendHandle> {
-        if target.idempotency_key.is_some() {
+        if let Some(idempotency_key) = &target.idempotency_key {
             self.verify_feature_support("attach idempotency key to one way call", Version::V3)?;
+            if idempotency_key.is_empty() {
+                self.do_transition(HitError {
+                    error: EMPTY_IDEMPOTENCY_KEY,
+                    next_retry_delay: None,
+                })?;
+                unreachable!();
+            }
         }
         self.do_transition(SysNonCompletableEntry(
             "SysOneWayCall",
             OneWayCallEntryMessage {
                 service_name: target.service,
                 handler_name: target.handler,
                 key: target.key.unwrap_or_default(),
-                idempotency_key: target.idempotency_key.unwrap_or_default(),
+                idempotency_key: target.idempotency_key,
                 parameter: input,
                 invoke_time: delay
                     .map(|d| {