a584f8de46
The `MailerImpl` gains a few new fields (`retryBase`, & `retryMax`). These are used with `core.RetryBackoff` in `reconnect()` to implement exponential backoff in a reconnect attempt loop. Both `expiration-mailer` and `notify-mailer` are modified to add CLI args for these 2 flags and to wire them into the `MailerImpl` via its `New()` constructor. In `MailerImpl`'s `SendMail()` function it now detects when `sendOne` returns an `io.EOF` error indicating that the server closed the connection unexpectedly. When this case occurs `reconnect()` is invoked. If the reconnect succeeds then we invoke `sendOne` again to try and complete the message sending operation that was interrupted by the disconnect. For integration testing purposes I modified the `mail-test-srv` to support a `-closeChance` parameter between 0 and 100. This controls what % of `MAIL` commands will result in the server immediately closing the client connection before further processing. This allows us to simulate a flaky mailserver. `test/startservers.py` is modified to start the `mail-test-srv` with a 35% close chance to thoroughly test the reconnection logic during the existing `expiration-mailer` integration tests. I took this as a chance to do some slight clean-up of the `mail-test-srv` code (mostly removing global state). For unit testing purposes I modified the mailer `TestConnect` test to abstract out a server that can operate similar to `mail-test-serv` (e.g. can close connections artificially). This is testing a server that **closes** a connection, and not a server that **goes away/goes down**. E.g. the `core.RetryBackoff` sleeps themselves are not being tested. The client is disconnected and attempts a reconnection which always succeeds on the first try. To test a "gone away" server would require a more substantial rewrite of the unit tests and the `mail-test-srv`/integration tests. I think this matches the experience we have with MailChimp/Mandril closing long lived connections. |
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| .. | ||
| http.go | ||
| http_test.go | ||
| main.go | ||