diff --git a/src/idempotency/server/request_htable.c b/src/idempotency/server/request_htable.c
index 92b0f0a..9005a6a 100644
--- a/src/idempotency/server/request_htable.c
+++ b/src/idempotency/server/request_htable.c
@@ -35,7 +35,9 @@ int idempotency_request_htable_add(IdempotencyRequestHTable *htable,
     current = *bucket;
     while (current != NULL) {
         if (current->req_id == request->req_id) {
-            request->output = current->output;
+            request->output.result = current->output.result;
+            memcpy(request->output.response, current->output.response,
+                    request->output.rsize);
             request->finished = current->finished;
             result = EEXIST;
             break;
diff --git a/src/idempotency/server/server_channel.c b/src/idempotency/server/server_channel.c
index d9d3dfc..9cdd462 100644
--- a/src/idempotency/server/server_channel.c
+++ b/src/idempotency/server/server_channel.c
@@ -287,3 +287,23 @@ void idempotency_channel_free(IdempotencyChannel *channel)
             channel_context.timeout_ctx.reserve_interval;
     }
 }
+
+int idempotency_request_alloc_init(void *element, void *args)
+{
+    static int i = 0;
+
+    IdempotencyRequest *request;
+    request = (IdempotencyRequest *)element;
+    request->allocator = (struct fast_mblock_man *)args;
+    request->output.rsize = request->allocator->info.element_size -
+        sizeof(IdempotencyRequest);
+    request->output.response = request + 1;
+
+    if (++i % 100 == 0) {
+        logInfo("i: %d, element_size: %d, rsize: %d", i,
+                request->allocator->info.element_size,
+                request->output.rsize);
+    }
+
+    return 0;
+}
diff --git a/src/idempotency/server/server_channel.h b/src/idempotency/server/server_channel.h
index 9909b37..c00f2bc 100644
--- a/src/idempotency/server/server_channel.h
+++ b/src/idempotency/server/server_channel.h
@@ -39,6 +39,8 @@ extern "C" {
                 &channel->request_htable, req_id);
     }
 
+    int idempotency_request_alloc_init(void *element, void *args);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/idempotency/server/server_handler.c b/src/idempotency/server/server_handler.c
index 027c76a..9264564 100644
--- a/src/idempotency/server/server_handler.c
+++ b/src/idempotency/server/server_handler.c
@@ -157,3 +157,38 @@ int sf_server_deal_report_req_receipt(struct fast_task_info *task,
     response->header.cmd = SF_SERVICE_PROTO_REPORT_REQ_RECEIPT_RESP;
     return 0;
 }
+
+IdempotencyRequest *sf_server_update_prepare_and_check(
+        struct fast_task_info *task, struct fast_mblock_man *
+        request_allocator, IdempotencyChannel *channel,
+        SFResponseInfo *response, int *result)
+{
+    SFProtoIdempotencyAdditionalHeader *adheader;
+    IdempotencyRequest *request;
+
+    if (!__sync_add_and_fetch(&channel->is_valid, 0)) {
+        response->error.length = sprintf(response->error.message,
+                "channel: %d is invalid", channel->id);
+        *result = SF_RETRIABLE_ERROR_CHANNEL_INVALID;
+        return NULL;
+    }
+
+    adheader = (SFProtoIdempotencyAdditionalHeader *)
+        (task->data + sizeof(SFCommonProtoHeader));
+    request = (IdempotencyRequest *)fast_mblock_alloc_object(request_allocator);
+    if (request == NULL) {
+        *result = ENOMEM;
+        return NULL;
+    }
+
+    request->finished = false;
+    request->req_id = buff2long(adheader->req_id);
+    *result = idempotency_channel_add_request(channel, request);
+    if (*result == EEXIST) {
+        if (!request->finished) {
+            *result = EAGAIN;
+        }
+    }
+
+    return request;
+}
diff --git a/src/idempotency/server/server_handler.h b/src/idempotency/server/server_handler.h
index eec28ca..7956fff 100644
--- a/src/idempotency/server/server_handler.h
+++ b/src/idempotency/server/server_handler.h
@@ -21,6 +21,11 @@ int sf_server_deal_report_req_receipt(struct fast_task_info *task,
         int *task_type, IdempotencyChannel **channel,
         SFResponseInfo *response);
 
+IdempotencyRequest *sf_server_update_prepare_and_check(
+        struct fast_task_info *task, struct fast_mblock_man *
+        request_allocator, IdempotencyChannel *channel,
+        SFResponseInfo *response, int *result);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/idempotency/server/server_types.h b/src/idempotency/server/server_types.h
index efe400f..33f4f01 100644
--- a/src/idempotency/server/server_types.h
+++ b/src/idempotency/server/server_types.h
@@ -5,14 +5,17 @@
 #include "fastcommon/fast_mblock.h"
 #include "fastcommon/fast_timer.h"
 
+typedef struct idempotency_request_result {
+    int rsize;   //response size defined by application
+    int result;
+    void *response;
+} IdempotencyRequestResult;
+
 typedef struct idempotency_request {
     uint64_t req_id;
     volatile int ref_count;
     bool finished;
-    struct {
-        int result;
-        int inc_alloc;
-    } output;
+    IdempotencyRequestResult output;
     struct fast_mblock_man *allocator;  //for free
     struct idempotency_request *next;
 } IdempotencyRequest;
diff --git a/src/sf_proto.h b/src/sf_proto.h
index 612ce77..320db81 100644
--- a/src/sf_proto.h
+++ b/src/sf_proto.h
@@ -64,6 +64,10 @@ typedef struct sf_common_proto_header {
     char padding[3];
 } SFCommonProtoHeader;
 
+typedef struct sf_proto_idempotency_additional_header {
+    char req_id[8];
+} SFProtoIdempotencyAdditionalHeader;
+
 typedef struct sf_proto_setup_channel_req {
     char channel_id[4]; //for hint
     char key[4];        //for validate when channel_id > 0