Bug 23640: Flushing L1 on every SIP connection

Bug 23640: Flushing L1 on every SIP connection

This patch flushes the L1 cache on each SIP connection
(ie every invocation of process_request).

This means each SIP connection will fetch values from the
L2 cache (ie memcached) and persist the L1 cache (in Perl
memory cache) only until a new SIP connection comes in.

Without this patch, the L1 cache persists for the length
of the server process, which means the L1 cache will become
stale very quickly, which can lead to unexpected behaviour.

Test plan:
1. Enable IssueLog
2. Start SIP server
    2a. change to Koha git directory
    2b. koha-shell kohadev
    2c. perl C4/SIP/SIPServer.pm /etc/koha/sites/kohadev/SIPconfig.xml
3. Issue book via SIP

    perl misc/sip_cli_emulator.pl -a 127.0.0.1 -p 6001 -su term1 -sp term1 -l CPL --patron 1 --item 3999900000001 -m checkout

4. Check action_logs for "CIRCULATION ISSUE <borrowernumber> <biblionumber>" line

    http://localhost:8081/cgi-bin/koha/tools/viewlog.pl

5. Disable IssueLog

6. Check in the book and then check it out again

    perl misc/sip_cli_emulator.pl -a 127.0.0.1 -p 6001 -su term1 -sp term1 -l CPL --patron 1 --item 3999900000001 -m checkin
    perl misc/sip_cli_emulator.pl -a 127.0.0.1 -p 6001 -su term1 -sp term1 -l CPL --patron 1 --item 3999900000001 -m checkout

7. Check action_logs for "CIRCULATION ISSUE <borrowernumber> <biblionumber>" line

    http://localhost:8081/cgi-bin/koha/tools/viewlog.pl

8. Note results

Without the patch, you'll see a 2nd checkout.

With the patch, you won't see the 2nd checkout.

(Note: After applying the patch, you have to restart the SIP server.)

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>