Class WebEngineStats

The counts of the web engines the client sessions of this server arrived on: how many are connected now and how many connected since the server started, per status and per group row (design CC-DESIGN-WEBVIEW-WARNING section 8.2, work order CC-WEBENGINE-SERVER). This is what ServerAdmin shows: the ruling asks for "how many sessions arrive unpatched".

In memory, since the server started (design D-11). Nothing is persisted: the counts start at zero with the server and the log line of WebEngineAdvisor is the history. In a hub cluster each server has its own counts.

A group row is one combination of application, platform, product, OS major, engine major and status: "demo, Android, Android System WebView, 7, 119, ENDED". A session is counted in exactly one row, and in the totals of its status:

• connect(String, WebEngineStatus, Instant) counts a new session: one more connect and one more active session;
• move(WebEngineStats.Group, String, WebEngineStatus, Instant) moves a session that was classified again, at a reconnect, to the row of its new verdict: the active counts follow, and NO connect is counted a second time;
• disconnect(WebEngineStats.Group) ends a session: one less active.

Bounded. The OS and engine majors of a row come from the client's user agent, which the peer controls, so the number of rows is capped at 1000: a session whose row would be one too many is counted in the shared overflow row of its status (application null) and in the totals, which are always exact.

Thread safe: every method takes the one monitor of the instance, held for a map lookup and a few additions. No clock inside: "now" is a parameter.