# Server push (IRPCServerDataPush)

Location: [gRPC API](https://developer.m-files.com/APIs/gRPC-API/index.md) > [Vault API](https://developer.m-files.com/APIs/gRPC-API/vault/index.md)

HTML version: https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/

A server-to-client channel: the server pushes requests and notifications to a logged-in client
over a long-lived stream.

- **gRPC service:** `MFiles.IRPCServerDataPush`
- **Book and level:** [Vault API](https://developer.m-files.com/APIs/gRPC-API/vault/index.md), standard
- **Methods:** 2
- **Proto file:** [`mfiles/IRPCServerDataPush.proto`](https://developer.m-files.com/APIs/gRPC-API/downloads/proto/mfiles/IRPCServerDataPush.proto)

<a id="overview"></a>

## Overview

Some operations need something from the user while the server is processing a call, for
example an electronic signature for a workflow state transition, or credentials for a vault
application or external repository. The server asks for it over the push channel of the
session, and the client answers with a separate call. M-Files clients use this service;
applications that perform such operations interactively need it too.

**Lifecycle**

1. Log in, then call [OpenServerDataPush](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/OpenServerDataPush/index.md)
   with the session's `mfiles-session-id-bin` metadata. It is a server-streaming call that stays
   open, without messages, until the server has something to push. Do not set a short deadline
   on it. Session assertions are not accepted.
2. Each session has at most one channel. Opening a new one ends the previous stream with status
   `OK`. Logging out also ends the stream with `OK`. If the stream ends while the session is
   still valid, open it again.
3. Each message is a [ServerDataPushItem](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/OpenServerDataPush/index.md#response). Its
   `request_data.type` tells what it is:
   - `SERVER_DATA_PUSH_REQUEST_TYPE_ELECTRONIC_SIGNATURE_REQUEST`: sign an operation. Needs a
     response.
   - `SERVER_DATA_PUSH_REQUEST_TYPE_EXTENSION_AUTHENTICATION_REQUEST`: authenticate the user to a
     vault application or external repository. Needs a response.
   - `SERVER_DATA_PUSH_REQUEST_TYPE_OBJECTS_CHANGED_NOTIFICATION`: object versions that the
     server changed on behalf of this session; refresh any cached copies. No response.
4. Answer a request with
   [SendDataPushResponse](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/SendDataPushResponse/index.md), passing its
   `response_id`. If preparing the answer takes time (the user is typing), send
   [SendPushDataPendingHeartbeat](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/SendPushDataPendingHeartbeat/index.md) with the
   same ID every few seconds.

**Timing.** While the original call waits for the answer, the server gives up, and fails the
original call, if the request is not delivered to an open channel within about 10 seconds, or
if neither an answer nor a heartbeat arrives within about 35 seconds. In the latter case the
server also closes the push channel; open it again. When the waiting call holds a database
transaction, the server waits at most about 20 seconds and then fails the call with an error
that asks the client to retry it. These are server defaults that administrators can change.

**Open the channel early.** Operations that need a response from the client fail if the session
has never opened a push channel. Requests that arrive while no stream is open are queued and
delivered when the next stream opens.

<a id="methods"></a>

## Methods

| Method | Summary | Facts |
|---|---|---|
| [OpenServerDataPush](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/OpenServerDataPush/index.md) | Opens the session's push channel: a stream of requests and notifications from the server. | `write` `session` `server streaming` |
| [SendDataPushResponse](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/SendDataPushResponse/index.md) | Sends the client's answer to a push request received from [OpenServerDataPush](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCServerDataPush/OpenServerDataPush/index.md). | `write` `session` |