Session events

[Kobzol]

This PR adds session close event, enables querying for multiple event types and adds event tests.

It takes a while before the events are written to the DB, so the test sleeps for 1 sec. But since testing this interface is non-critical, I think that it can be marked as a slow test and it's not a problem that it is a bit flaky.

[spirali]

Is not better to use "IN" operator?
i.e. something like this?

        let modes : Vec<_> = v.iter().map(|e| make_where_string(&e.mode)).collect();
        where_conds.push(format!("event_type IN ({})", modes.join(",")));
        for event in v {
            args.push(&event.value);
        }

(And I also prefere collect than mut vec & push :)

[spirali]

Ah I see it now, my suggestion is not right. We would need to introduce whole "mode" with "in".

[Kobzol]

I usually use prepared statements for SQL and IN isn't allowed there :-) I thought about it, but it would complicate the code a bit, so I just reused the existing WHERE infrastructure. I'll rewrite it to collect, I didn't use it because the args need for anyway.

[Kobzol]

The collect is a bit problematic because of the error semantics. To match the rest of the function, it should return an error if any of the parameters are wrong. Is there an idiomatic way to do this in Rust? Something like v.iter().map(|e| make_where_string(&e.mode)?).collect() (but I can't use the question mark in the map). It could be rewritten to check whether the vector contains any errors, but then I'd say the for is simpler :-)

[spirali]

It is quite simple, just move "?" outside: v.iter().map(|e| make_where_string(&e.mode)).collect()?. The magic is that collecting into Result<Vec> will propage the error (it actually stops the iterator on the first error). e.g.: https://stackoverflow.com/questions/26368288/how-do-i-stop-iteration-and-return-an-error-when-iteratormap-returns-a-result

[Kobzol]

Whoa! That is awesome, thanks.

[spirali]

LGTM 👍
1 second delay is ok now (it it would be ideal to make the writing delay configurable via env variable (some of other delays already have such configuration) and set its value near the zero for this particular test, but as far as we do not have lots of these tests, it is not necessary)

[Kobzol]

Actually I wasn't able to get this to pass with a timeout lower than 1 sec. It certainly didn't work with 0.5 sec.

[Kobzol]

Can I add requests dependency to the Dockerfile? I use it in the HTTP tests.

[spirali]

Yes, it is no problem. Generally, it is ok to add any library in pip that is reasonably trustworthy and maintained.

[Kobzol]

Ok, then I think this can be merged, I rebased it on top of master.