grid: events don't expire when using custom attributes in rows/columns

[faxm0dem]

When using custom attributes instead of the default host/service axes, the events never expire in the grid view. Here's a minimal test case:

• riemann.config

(let [host "127.0.0.1"]
  (tcp-server :host host :port 55555)
  (udp-server :host host :port 55555)
  (ws-server  :host host :port 55556))

(periodically-expire 5)

(let [index (default {:ttl 5 :state "ok"} (update-index (index)))]
  (streams index))

• riemann_dash-config.json

{
  "server":"localhost:55556",
  "server_type":"ws",
  "workspaces":[
    {
      "name":"test",
      "view":{
        "type":"Balloon",
        "weight":1,
        "id":"f6886a97daedb6df8ff1702075795533d6411dd1",
        "version":7,
        "child":{
          "type":"VStack",
          "weight":1,
          "id":"3dcfa12de6e2c1b033b7b49591e065bd419fc15c",
          "version":7,
          "children":[
            {
              "type":"Grid",
              "weight":1,
              "id":"92a8b2a3f2fbc3873d74c55ae81ffe03357875da",
              "version":6,
              "title":"test",
              "query":"tagged \"test\"",
              "max":"",
              "rows":"foo",
              "cols":"bar",
              "row_sort":"lexical",
              "col_sort":"lexical"
            },
            {
              "type":"Grid",
              "weight":1,
              "id":"b3164ce0e44b449e9d520a0aabf60e770b2a0625",
              "version":1,
              "title":"",
              "query":"tagged \"test\"",
              "max":"",
              "rows":"",
              "cols":"",
              "row_sort":"lexical",
              "col_sort":"lexical"
            }
          ]
        }
      },
      "id":"1b45a0bde6a77d7267102a18dfaf891bfbad9531"
    }
  ]
}

• events

riemann-client send -t test -a foo=bar -a bar=baz localhost 55555
riemann-client send -t test -a foo=baz -a bar=bar localhost 55555

Initial state: After 5 seconds: