[sr-dev] [kamailio/kamailio] [presence] [dialog events] BLF problem: "early" state persisting after "terminated" (Issue #3192)

[liviu-rolo]

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### Description

Relevant modules and parameters in configuration:
```
loadmodule "presence.so"
loadmodule "dialog.so"
loadmodule "presence_xml.so"
loadmodule "pua.so"
loadmodule "presence_dialoginfo.so"
loadmodule "pua_dialoginfo.so"

modparam("dialog", "db_mode", 1)
modparam("presence", "subs_db_mode", 2)
modparam("presence", "db_table_lock_type", 0)
modparam("pua", "db_mode", 2)
modparam("pua", "db_table_lock_write", 0)
```

Using 2 UDP receiver processes.

User1 is watching (has` SUBSCRIBE`d to) User2, which is called by User3 (call1). User2 doesn't answer, phone is ringing. User1 now also calls User2 (call2), but we don't support receiving a second call so, for this `INVITE`, after 183, almost immediately, a 486 "Busy Here" message is sent and the call is cancelled (call2 finished). The 183 reply generates an "**early**" state on the UDP1 process, while 486 goes to "**terminated**" on the UDP2 process. The `PUBLISH` messages are processed almost concomitantly. The problem is that "**early**" state arrives to the subscriber (User1) after the "**terminated**" one (seen with `sngrep`) so the phone button keeps blinking for a while (... and the state cannot be changed by other call while the "**early**" event is still in the `presentity` table of the database). 
I suspect a concurrency problem since I didn't reproduce it with only one UDP receiver process. Even if the "**terminated**" lifetime is much smaller (11s vs minutes), I strongly believe it is still there when the "**early**" state is written. Does the "**early**" event checks the database/memory for a "**terminated**" event for the same call ID? Is it because of the missing locks maybe (`db_table_lock_type`, `db_table_lock_write`) ?

### Troubleshooting

#### Reproduction

Using 2 UDP receiver processes.

User1 is watching (has `SUBSCRIBE`d to) User2, which is called by User3 (call1). User2 doesn't answer, phone is ringing. User1 now also calls User2 (call2), but we don't support receiving a second call so, for this `INVITE`, after 183, almost immediately, a 486 "Busy Here" message is sent and the call is cancelled (call2 finished). 

I would not say that it is systematic, but easy enough to reproduce.

#### Debugging Data

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#### Log Messages

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#### SIP Traffic

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```
(paste your sip traffic here)
```

### Possible Solutions

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### Additional Information

  * **Kamailio Version** - output of `kamailio -v`

```
version: kamailio 5.5.4 (x86_64/linux)
flags: , EXTRA_DEBUGUSE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES
ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB
poll method support: poll, epoll_lt, epoll_et, sigio_rt, select.
id: unknown
compiled with gcc 8.3.0
```

* **Operating System**:
Docker image around

```
$ lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux 10 (buster)
Release:	10
Codename:	buster
(paste your output here)
```


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