It frequently logs the message below. It seems not helpful.

{"timestamp":1442987404.9433253,"message":"collector.started","log_level":"info","source":"collector","data":{},"thread_id":70132569199380,"fiber_id":70132570371720,"process_id":19392,"file":"/var/vcap/packages/collector/lib/collector/config.rb","lineno":45,"method":"setup_logging"}

the only possible error message from the bosh debug log is
"ntp":{"message":"bad ntp server"}

But I don't think, it is related to the failure of stats_z1 updating.

I, [2015-09-23 04:55:59 #2392] [canary_update(stats_z1/0)] INFO --
DirectorJobRunner: Checking if stats_z1/0 has been updated after
63.333333333333336 seconds
D, [2015-09-23 04:55:59 #2392] [canary_update(stats_z1/0)] DEBUG --
DirectorJobRunner: SENT: agent.7d3452bd-679e-4a97-8514-63a373a54ffd
{"method":"get_state","arguments":[],"reply_to":"director.c5b97fc1-b972-47ec-9412-a83ad240823b.473fda64-6ac3-4a53-9ebc-321fc7eabd7a"}
D, [2015-09-23 04:55:59 #2392] [] DEBUG -- DirectorJobRunner: RECEIVED:
director.c5b97fc1-b972-47ec-9412-a83ad240823b.473fda64-6ac3-4a53-9ebc-321fc7eabd7a
{"value":{"properties":{"logging":{"max_log_file_size":""}},"job":{"name":"stats_z1","release":"","template":"fluentd","version":"4c71c87bbf0144428afacd470e2a5e32b91932fc","sha1":"b141c6037d429d732bf3d67f7b79f8d7d80aac5d","blobstore_id":"d8451d63-2e4f-4664-93a8-a77e5419621d","templates":[{"name":"fluentd","version":"4c71c87bbf0144428afacd470e2a5e32b91932fc","sha1":"b141c6037d429d732bf3d67f7b79f8d7d80aac5d","blobstore_id":"d8451d63-2e4f-4664-93a8-a77e5419621d"},{"name":"collector","version":"889b187e2f6adc453c61fd8f706525b60e4b85ed","sha1":"f5ae15a8fa2417bf984513e5c4269f8407a274dc","blobstore_id":"3eeb0166-a75c-49fb-9f28-c29788dbf64d"},{"name":"metron_agent","version":"e6df4c316b71af68dfc4ca476c8d1a4885e82f5b","sha1":"42b6d84ad9368eba0508015d780922a43a86047d","blobstore_id":"e578bfb0-9726-4754-87ae-b54c8940e41a"},{"name":"apaas_collector","version":"8808f0ae627a54706896a784dba47570c92e0c8b","sha1":"b9a63da925b40910445d592c70abcf4d23ffe84d","blobstore_id":"3e6fa71a-07f7-446a-96f4-3caceea02f2f"}]},"packages":{"apaas_collector":{"name":"apaas_collector","version":"f294704d51d4517e4df3d8417a3d7c71699bc04d.1","sha1":"5af77ceb01b7995926dbd4ad7481dcb7c3d94faf","blobstore_id":"fa0e96b9-71a6-4828-416e-dde3427a73a9"},"collector":{"name":"collector","version":"ba47450ce83b8f2249b75c79b38397db249df48b.1","sha1":"0bf8ee0d69b3f21cf1878a43a9616cb7e14f6f25","blobstore_id":"722a5455-f7f7-427d-7e8d-e562552857bc"},"common":{"name":"common","version":"99c756b71550530632e393f5189220f170a69647.1","sha1":"90159de912c9bfc71740324f431ddce1a5fede00","blobstore_id":"37be6f28-c340-4899-7fd3-3517606491bb"},"fluentd-0.12.13":{"name":"fluentd-0.12.13","version":"71d8decbba6c863bff6c325f1f8df621a91eb45f.1","sha1":"2bd32b3d3de59e5dbdd77021417359bb5754b1cf","blobstore_id":"7bc81ac6-7c24-4a94-74d1-bb9930b07751"},"metron_agent":{"name":"metron_agent","version":"997d87534f57cad148d56c5b8362b72e726424e4.1","sha1":"a21404c50562de75000d285a02cd43bf098bfdb9","blobstore_id":"6c7cf72c-9ace-40a1-4632-c27946bf631e"},"ruby-2.1.6":{"name":"ruby-2.1.6","version":"41d0100ffa4b21267bceef055bc84dc37527fa35.1","sha1":"8a9867197682cabf2bc784f71c4d904bc479c898","blobstore_id":"536bc527-3225-43f6-7aad-71f36addec80"}},"configuration_hash":"a73c7d06b0257746e95aaa2ca994c11629cbd324","networks":{"private_cf_subnet":{"cloud_properties":{"name":"random","net_id":"1e1c9aca-0b5a-4a8f-836a-54c18c21c9b9","security_groups":["az1_cf_management_secgroup_bosh_cf_ssh_cf2","az1_cf_management_secgroup_cf_private_cf2","az1_cf_management_secgroup_cf_public_cf2"]},"default":["dns","gateway"],"dns":["192.168.110.8","133.162.193.10","133.162.193.9","192.168.110.10"],"dns_record_name":"0.stats-z1.private-cf-subnet.cf-apaas.microbosh","gateway":"192.168.110.11","ip":"192.168.110.204","netmask":"255.255.255.0"}},"resource_pool":{"cloud_properties":{"instance_type":"S-1"},"name":"small_z1","stemcell":{"name":"bosh-openstack-kvm-ubuntu-trusty-go_agent","version":"2989"}},"deployment":"cf-apaas","index":0,"persistent_disk":0,"persistent_disk_pool":null,"rendered_templates_archive":{"sha1":"0ffd89fa41e02888c9f9b09c6af52ea58265a8ec","blobstore_id":"4bd01ae7-a69a-4fe5-932b-d98137585a3b"},"agent_id":"7d3452bd-679e-4a97-8514-63a373a54ffd","bosh_protocol":"1","job_state":"failing","vm":{"name":"vm-12d45510-096d-4b8b-9547-73ea5fda00c2"},"ntp":{"message":"bad
ntp server"}}}