tornado: Log to files by port number.

Without an explicit port number, the `stdout_logfile` values for each
port are identical.  Supervisor apparently decides that it will
de-conflict this by appending an arbitrary number to the end:

```
/var/log/zulip/tornado.log
/var/log/zulip/tornado.log.1
/var/log/zulip/tornado.log.10
/var/log/zulip/tornado.log.2
/var/log/zulip/tornado.log.3
/var/log/zulip/tornado.log.7
/var/log/zulip/tornado.log.8
/var/log/zulip/tornado.log.9
```

This is quite confusing, since most other files in `/var/log/zulip/`
use `.1` to mean logrotate was used.  Also note that these are not all
sequential -- 4, 5, and 6 are mysteriously missing, though they were
used in previous restarts.  This can make it extremely hard to debug
logs from a particular Tornado shard.

Give the logfiles a consistent name, and set them up to logrotate.

puppet/zulip/files/logrotate/zulip

@@ -16,6 +16,8 @@
     create 644 zulip zulip
 }
 
+/var/log/zulip/tornado-*.log
+/var/log/zulip/tornado.log
 /var/log/zulip/server.log
 {
     missingok

puppet/zulip/templates/supervisor/zulip.conf.template.erb

@@ -34,7 +34,7 @@ stopsignal=TERM                 ; signal used to kill process (default TERM)
 stopwaitsecs=30                ; max num secs to wait b4 SIGKILL (default 10)
 user=zulip                    ; setuid to this UNIX account to run the program
 redirect_stderr=true           ; redirect proc stderr to stdout (default false)
-stdout_logfile=/var/log/zulip/tornado.log         ; stdout log path, NONE for none; default AUTO
+stdout_logfile=/var/log/zulip/tornado-98%(process_num)02d.log         ; stdout log path, NONE for none; default AUTO
 stdout_logfile_maxbytes=100MB   ; max # logfile bytes b4 rotation (default 50MB)
 stdout_logfile_backups=10     ; # of stdout logfile backups (default 10)
 directory=/home/zulip/deployments/current/

zerver/tornado/django_api.py

@@ -1,5 +1,6 @@
 from functools import lru_cache
 from typing import Any, Container, Dict, Iterable, List, Mapping, Optional, Sequence, Tuple, Union
+from urllib.parse import urlparse
 
 import orjson
 import requests
@@ -34,9 +35,11 @@ class TornadoAdapter(HTTPAdapter):
         try:
             resp = super().send(request, stream=stream, timeout=timeout, verify=verify, cert=cert, proxies=merged_proxies)
         except ConnectionError:
+            parsed_url = urlparse(request.url)
+            logfile = f"tornado-{parsed_url.port}.log" if settings.TORNADO_PROCESSES > 1 else "tornado.log"
             raise ConnectionError(
                 f"Django cannot connect to Tornado server ({request.url}); "
-                f"check {settings.ERROR_FILE_LOG_PATH} and tornado.log"
+                f"check {settings.ERROR_FILE_LOG_PATH} and {logfile}"
             )
         resp.raise_for_status()
         return resp