Index User lookup by key to address DB connection pool exhaustion

[nilbus]

I noticed in BugSnag that we were still seeing this error:

ActiveRecord::ConnectionTimeoutErrorapi/v1/routes/core.rb:46
could not obtain a connection from the pool within 5.000 seconds (waited 5.567 seconds); all pooled connections were in use

These tracebacks were not originating at many various database calls like I would expect, but rather all at the same one, which indicates to me that this one call is responsible for a large portion of our database time.

        def find_user
          User.where(key: params[:key]).first if params[:key]
        end

Sure enough, there is no index for this common user lookup. Without it, the DB must scan all 150k users for each user lookup by key.

I think this should help with the ongoing connection pool issue! 🏇 ✨

[nilbus]

I would have made this a unique index, except that we actually have duplicate users in our production database. One example:

# select id, username, key, updated_at from users where key='[redacted]';
  id   |    key     |         updated_at
-------+------------+----------------------------
 14804 | [redacted] | 2014-06-05 11:59:17.267012
 14805 | [redacted] | 2014-06-05 11:59:13.151091

These could be due to a race condition with active-record uniqueness constraints, like if a user double-submits the sign-up form.

[kytrinyx]

Oh my goodness, I can't believe I missed that. Thank you! ✨

[kytrinyx]

This is saying 0 files changed. I'm seeing one commit with no changes. Would you take a look? (I can also make a migration to add the key, just curious what's going on here).

[nilbus]

Easy enough to miss. :-)

…

On Sat, Jul 8, 2017 at 11:30 AM Katrina Owen ***@***.***> wrote: Oh my goodness, I can't believe I missed that. Thank you! ✨ — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3584 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD8716p26VKVgBB6od2ZsfncpfD2cCsks5sL6CJgaJpZM4ORtPV> .

[nilbus]

ha, that's a commit failure on my part. I'll fix that when I get back home to my computer.

…

On Sat, Jul 8, 2017 at 11:31 AM Katrina Owen ***@***.***> wrote: This is saying 0 files changed. I'm seeing one commit with no changes. Would you take a look? (I can also make a migration to add the key, just curious what's going on here). — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3584 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD870PD8hPjEOl45RBBi8IsOwBHMzs3ks5sL6C-gaJpZM4ORtPV> .

[nilbus]

@kytrinyx All fixed. Sorry about that!

[kytrinyx]

Sweet, thanks!