fts_solr crashs

[M. Koehler]

Hi,

I´ve set up in dovecot 2.2.24-1~auto+49 (from dovecot repo) fts_solr and 
fts_tika - jetti8 (from Debian Jessie) and latest tika-server running on 
a seperate machine. But if I want to rescan all messages for reindexing 
for instance all attachments with "doveadm -v index -u user at domain.tld 
INBOX" with 3137 mail in the INBOX  it counts and then by 2900 mails the 
doveadm crashes with the following error message:

doveadm(user at domain.tld): Info: INBOX: Caching mails seq=1..3137
2900/3137doveadm(user at domain.tld): Error: fts_solr: Indexing failed: 500 
Java heap space  java.lang.OutOfMemoryError: Java heap space
doveadm(user at domain.tld): Panic: file http-client-request.c: line 769 
(http_client_request_send_payload): assertion failed: (ret == 0)
doveadm(user at domain.tld): Error: Raw backtrace: 
/usr/lib/dovecot/libdovecot.so.0(+0x8dc1e) [0x7f269375ec1e] -> 
/usr/lib/dovecot/libdovecot.so.0(+0x8dc98) [0x7f269375ec98] -> 
/usr/lib/dovecot/libdovecot.so.0(i_fatal+0) [0x7f26936fd02e] -> 
/usr/lib/dovecot/libdovecot.so.0(http_client_request_send_payload+0xc8) 
[0x7f2693716b88] -> 
/usr/lib/dovecot/modules/lib21_fts_solr_plugin.so(solr_connection_post_more+0x49) 
[0x7f2691c538b9] -> 
/usr/lib/dovecot/modules/lib21_fts_solr_plugin.so(+0x361e) 
[0x7f2691c4f61e] -> 
/usr/lib/dovecot/modules/lib20_fts_plugin.so(+0x9a17) [0x7f2692ad5a17] 
-> /usr/lib/dovecot/modules/lib20_fts_plugin.so(+0x9e20) 
[0x7f2692ad5e20] -> 
/usr/lib/dovecot/modules/lib20_fts_plugin.so(fts_build_mail+0x999) 
[0x7f2692ad6809] -> 
/usr/lib/dovecot/modules/lib20_fts_plugin.so(+0x1056e) [0x7f2692adc56e] 
-> /usr/lib/dovecot/libdovecot-storage.so.0(mail_precache+0x29) 
[0x7f2693a1f7b9] -> doveadm(+0x2e947) [0x7f26943be947] -> 
doveadm(+0x28daf) [0x7f26943b8daf] -> doveadm(+0x2989d) [0x7f26943b989d] 
-> doveadm(doveadm_cmd_ver2_to_mail_cmd_wrapper+0x278) [0x7f26943ba788] 
-> doveadm(doveadm_cmd_run_ver2+0x560) [0x7f26943c8c70] -> 
doveadm(doveadm_cmd_try_run_ver2+0x37) [0x7f26943c8cc7] -> 
doveadm(main+0x1df) [0x7f26943aa33f] -> 
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f2693347b45] 
-> doveadm(+0x1a716) [0x7f26943aa716]

I don´t see any shortages on the seperate solr machine. What could I do? 
How do I get more details to locate the problem?!

Thanks a lot and regards,

Michael