The current task log header looks like this:

[taskcluster 2019-05-03T12:07:58.186Z] Worker Type (macos) settings:
[taskcluster 2019-05-03T12:07:58.186Z]   {
[taskcluster 2019-05-03T12:07:58.186Z]     "config": {
[taskcluster 2019-05-03T12:07:58.186Z]       "deploymentId": "",
[taskcluster 2019-05-03T12:07:58.186Z]       "runTasksAsCurrentUser": true
[taskcluster 2019-05-03T12:07:58.186Z]     },
[taskcluster 2019-05-03T12:07:58.186Z]     "generic-worker": {
[taskcluster 2019-05-03T12:07:58.186Z]       "go-arch": "amd64",
[taskcluster 2019-05-03T12:07:58.186Z]       "go-os": "darwin",
[taskcluster 2019-05-03T12:07:58.186Z]       "go-version": "go1.10.3",
[taskcluster 2019-05-03T12:07:58.186Z]       "release": "https://github.com/taskcluster/generic-worker/releases/tag/v11.0.1",
[taskcluster 2019-05-03T12:07:58.186Z]       "revision": "a0a5271ddad42022606ca47a6c16f84c128223ab",
[taskcluster 2019-05-03T12:07:58.186Z]       "source": "https://github.com/taskcluster/generic-worker/commits/a0a5271ddad42022606ca47a6c16f84c128223ab",
[taskcluster 2019-05-03T12:07:58.186Z]       "version": "11.0.1"
[taskcluster 2019-05-03T12:07:58.186Z]     }
[taskcluster 2019-05-03T12:07:58.186Z]   }
[taskcluster 2019-05-03T12:07:58.186Z] Task ID: cPGC8byaTb6lxOVuPCmgkA
[taskcluster 2019-05-03T12:07:58.186Z] === Task Starting ===

In this case, the worker type name (macos) isn't very definitive; so a user needs to dig up the original taskId to find out which provisionerId it had. In the case that the task log has expired, it isn't possible to see what it was. Therefore it would be better to include the provisionerId too in the header, i.e. in the above case, we would instead log:

[taskcluster 2019-05-03T12:07:58.186Z] Worker Type (proj-servo/macos) settings:

Released in generic-worker 14.1.1.