mdb_env_open: Too many open files
xmrblocks kill itself. This happen everyday, any clue?

I am on Ubuntu 16.04

>(2017-02-27 22:30:57) [INFO    ] Response: 0x7ef82050dc40 / 200 0
(2017-02-27 22:31:22) [INFO    ] Request: 127.0.0.1:38350 0x7ef820511840 HTTP/1.0 GET /tx/deb7a00f90c4c5e1c09ace7beda54be3f15d2f8139b9c2ac59ce580d467704a5
(2017-02-27 22:31:22) [INFO    ] Response: 0x7ef820511840 /tx/deb7a00f90c4c5e1c09ace7beda54be3f15d2f8139b9c2ac59ce580d467704a5 200 0
(2017-02-27 22:34:53) [INFO    ] Request: 127.0.0.1:38378 0x7ef820515440 HTTP/1.0 GET /tx/b90b7198d86cf321ce47fb0196e1a138b999bbe0786c98d219605aff28dafde0/1
mdb_env_open: Too many open files
(2017-02-27 22:34:53) [INFO    ] Response: 0x7ef820515440 /tx/b90b7198d86cf321ce47fb0196e1a138b999bbe0786c98d219605aff28dafde0/1 200 0
Killed


>(2017-02-28 22:44:16) [INFO    ] Request: 127.0.0.1:56490 0x7fc62c510ec0 HTTP/1.0 GET /tx/d74f3367395934fc3c7ce1d7683631c1dcc8786069f065f40310ac14476cad07/1
(2017-02-28 22:44:16) [INFO    ] Response: 0x7fc62c510ec0 /tx/d74f3367395934fc3c7ce1d7683631c1dcc8786069f065f40310ac14476cad07/1 200 0
(2017-02-28 22:45:16) [INFO    ] Request: 127.0.0.1:56502 0x7fc62c514ac0 HTTP/1.0 GET /tx/4dbeb57856e3a61cf0684fe0f331ff03e97185aa617f95e52fd5c8ce93d1a671
mdb_env_open: Too many open files
mdb_env_open: Too many open files
mdb_env_open: Too many open files
mdb_env_open: Too many open files
(2017-02-28 22:45:16) [INFO    ] Response: 0x7fc62c514ac0 /tx/4dbeb57856e3a61cf0684fe0f331ff03e97185aa617f95e52fd5c8ce93d1a671 200 0
Killed