fix: check ws max send buffer size over time

docs/src/installation/command_line.md

@@ -35,7 +35,8 @@ Signal K Server provides the following command line options and environment vari
 | `PLUGINS_WITH_UPDATE_DISABLED` | A comma separated list of plugin that will not be updated. |
 | `SECURITYSTRATEGY` | Override the security strategy module name. |
 | `WSCOMPRESSION` | Compress websocket messages _(default is false)_. |
-| `MAXSENDBUFFERSIZE` | The maximum number of bytes allowed in the server's send buffer of a WebSocket connection. The connection will be terminated if this is exceeded. Guards against slow or dysfunctional clients that can not cope with the message volume _(default is 512 * 1024 bytes)_. |
+| `MAXSENDBUFFERSIZE` | The maximum number of bytes allowed in the server's send buffer of a WebSocket connection. The connection will be terminated if this is exceeded for MAXSENDBUFFERCHECKTIME milliseconds. Guards against slow or dysfunctional clients that can not cope with the message volume _(default is 512 * 1024 bytes)_. |
+| `MAXSENDBUFFERCHECKTIME` | The maximum number of bytes allowed in the server's send buffer of a WebSocket connection. The connection will be terminated if this is exceeded. Guards against slow or dysfunctional clients that can not cope with the message volume _(default is 512 * 1024 bytes)_. |
 | `SIGNALK_SERVER_IS_UPDATABLE` | Allows the server to be updated through the GUI even if it is not installed in the standard paths _(default is false)_. If set to true, the server must have been installed with `npm install -g signalk-server`. |
 | `SIGNALK_DISABLE_SERVER_UPDATES` | Disables server updates in the GUI _(default is false)_. |
 | `DEBUG` | A comma-separated list of tags for debugging the specified module _(e.g signalk-server*,signalk-provider-tcp)_. Can now be defined directly in the graphical interface.  More help on how to use the debug here: `https://www.npmjs.com/package/debug#wildcards` |

src/interfaces/ws.js

@@ -736,6 +736,10 @@ function startServerLog(app, spark) {
 function getAssertBufferSize(config) {
   const MAXSENDBUFFERSIZE =
     process.env.MAXSENDBUFFERSIZE || config.maxSendBufferSize || 4 * 512 * 1024
+  const MAXSENDBUFFERCHECKTIME =
+    process.env.MAXSENDBUFFERCHECKTIME ||
+    config.maxSendBufferCheckTime ||
+    30 * 1000
   debug(`MAXSENDBUFFERSIZE:${MAXSENDBUFFERSIZE}`)
 
   if (MAXSENDBUFFERSIZE === 0) {
@@ -745,10 +749,23 @@ function getAssertBufferSize(config) {
   return (spark) => {
     debug(spark.id + ' ' + spark.request.socket.bufferSize)
     if (spark.request.socket.bufferSize > MAXSENDBUFFERSIZE) {
-      spark.end({
-        errorMessage: 'Server outgoing buffer overflow, terminating connection'
-      })
-      console.error('Send buffer overflow, terminating connection ' + spark.id)
+      if (!spark.bufferSizeExceeded) {
+        console.warn(
+          `${spark.id} outgoing buffer > max:${spark.request.socket.bufferSize}`
+        )
+        spark.bufferSizeExceeded = Date.now()
+      }
+      if (Date.now() - spark.bufferSizeExceeded > MAXSENDBUFFERCHECKTIME) {
+        spark.end({
+          errorMessage:
+            'Server outgoing buffer overflow, terminating connection'
+        })
+        console.error(
+          'Send buffer overflow, terminating connection ' + spark.id
+        )
+      }
+    } else {
+      spark.bufferSizeExceeded = undefined
     }
   }
 }