TNK様

お世話になっております。

> ログ監視のアイテムは、zabbix_getでは取得できません。
こちらについては取得できない認識でしたが、ひょっとしたら最近のアップデートなどで使用が変わったかもしれないと思い
念の為結果を記載させていただきました。

> OS上のユーザーのグループの変更を行ったのであれば、Zabbixエー
> ジェントの再起動も必ず行ってください。

こちら、さっそくエージェントの再起動を行いましたが結果は変わらずでした。

> アイテムとして設定して、取得できないのであれば、Zabbixエージ
> ェントやZabbixサーバーのログを確認してください。

通常のログレベルではこれと行ったものは見られませんでした。
そのためデバッグレベルに変更してログを採取しました。

エージェント側
/etc/zabbix/zabbix_agentd.confのDebugLevelを5にしてエージェントの再起動しました。
この状態でエラーを発生させ、ログを見てみました。関係ありそうなところ（retry_time=0が含まれている行および前後2行）のみ抜粋します
※本当はここをチェックしたほうがいいというのがありましたらご指摘いただきたいです。

10620:20180705:103101.430 In process_value() key:'dev:log[/var/log/td-agent/td-agent.log]' value:'2018-07-05 10:31:00 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 10:31:01 +0900 chunk="570367fc94be0f759a64db6a05b32634" error_class=Mysql2::Error::ConnectionError error="Access denied for user 'root'@'xxxxxxxxx' (using password: YES)"'
10620:20180705:103101.430 In send_buffer() host:'10.146.0.3' port:10051 entries:0/100
10620:20180705:103101.430 End of send_buffer():SUCCEED
--
10620:20180705:103101.430 In process_value() key:'dev:log[/var/log/td-agent/td-agent.log]' value:' 2018-07-05 10:31:00 +0900 [warn]: #0 suppressed same stacktrace'
10620:20180705:103101.430 In send_buffer() host:'10.146.0.3' port:10051 entries:1/100
10620:20180705:103101.430 JSON before sending [{"request":"agent data","data":[{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":"2018-07-05 10:31:00 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 10:31:01 +0900 chunk=\"570367fc94be0f759a64db6a05b32634\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":362,"clock":1530754261,"ns":430345647}],"clock":1530754261,"ns":430828438}]
10620:20180705:103101.431 JSON back [{"response":"success","info":"processed: 1; failed: 0; total: 1; seconds spent: 0.000091"}]
10620:20180705:103101.431 In check_response() response:'{"response":"success","info":"processed: 1; failed: 0; total: 1; seconds spent: 0.000091"}'

サーバ側
※時間にずれがありますが、発生させたエラーは同じものです
30217:20180705:111858.747 trapper got '{"request":"agent data","data":[{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":"2018-07-05 11:18:58 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":3617,"clock":1530757138,"ns":746734477}],"clock":1530757138,"ns":747120184}'
30229:20180705:111858.902 query [txnlev:1] [insert into history_log (id,itemid,clock,ns,timestamp,source,severity,value,logeventid) values (196308,30539,1530757138,746867656,0,'',0,'2018-07-05 11:18:58 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk="570372b4e8613e6cdad5efeb418f5083" error_class=Mysql2::Error::ConnectionError error="Access denied for user \'root\'@\'xxxxxxxxxxxxxxxxxxxxx\' (using password: YES)"',0);
30219:20180705:111903.758 trapper got '{"request":"agent data","data":[{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":" 2018-07-05 11:18:58 +0900 [warn]: #0 suppressed same stacktrace","lastlogsize":3683,"clock":1530757138,"ns":747909141},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,\"retry_time=0\"]","value":"2018-07-05 11:18:58 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":3617,"mtime":1530757138,"clock":1530757138,"ns":748578399},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,\"retry_time=0\"]","lastlogsize":3683,"mtime":1530757138,"clock":1530757138,"ns":748730056},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","value":"2018-07-05 11:18:58 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":3617,"mtime":1530757138,"clock":1530757138,"ns":749254955},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","lastlogsize":3683,"mtime":1530757138,"clock":1530757138,"ns":749431972},{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":"2018-07-05 11:18:59 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":3979,"clock":1530757139,"ns":750109191},{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":" 2018-07-05 11:18:59 +0900 [warn]: #0 suppressed same stacktrace","lastlogsize":4045,"clock":1530757139,"ns":750206412},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,\"retry_time=0\"]","value":"2018-07-05 11:18:59 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":3979,"mtime":1530757139,"clock":1530757139,"ns":750810367},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,\"retry_time=0\"]","lastlogsize":4045,"mtime":1530757139,"clock":1530757139,"ns":750972471},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","value":"2018-07-05 11:18:59 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":3979,"mtime":1530757139,"clock":1530757139,"ns":751475149},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","lastlogsize":4045,"mtime":1530757139,"clock":1530757139,"ns":751625964},{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":"2018-07-05 11:19:00 +0900 [warn]: #0 failed to flush the buffer. retry_time=1 next_retry_seconds=2018-07-05 11:19:00 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":4341,"clock":1530757140,"ns":752341723},{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":" 2018-07-05 11:19:00 +0900 [warn]: #0 suppressed same stacktrace","lastlogsize":4407,"clock":1530757140,"ns":752430036},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,\"retry_time=0\"]","lastlogsize":4407,"mtime":1530757140,"clock":1530757140,"ns":753052354},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","value":"2018-07-05 11:19:00 +0900 [warn]: #0 failed to flush the buffer. retry_time=1 next_retry_seconds=2018-07-05 11:19:00 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":4341,"mtime":1530757140,"clock":1530757140,"ns":753552067},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","lastlogsize":4407,"mtime":1530757140,"clock":1530757140,"ns":753701740},{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":"2018-07-05 11:19:02 +0900 [warn]: #0 failed to flush the buffer. retry_time=2 next_retry_seconds=2018-07-05 11:19:02 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":4703,"clock":1530757142,"ns":755938688},{"host":"dev","key":"log[/var/log/td-agent/td-agent.log]","value":" 2018-07-05 11:19:02 +0900 [warn]: #0 suppressed same stacktrace","lastlogsize":4769,"clock":1530757142,"ns":756032988},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,\"retry_time=0\"]","lastlogsize":4769,"mtime":1530757142,"clock":1530757142,"ns":756733967},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","value":"2018-07-05 11:19:02 +0900 [warn]: #0 failed to flush the buffer. retry_time=2 next_retry_seconds=2018-07-05 11:19:02 +0900 chunk=\"570372b4e8613e6cdad5efeb418f5083\" error_class=Mysql2::Error::ConnectionError error=\"Access denied for user 'root'@'xxxxxxxxxxxxxxxxxxxxx' (using password: YES)\"","lastlogsize":4703,"mtime":1530757142,"clock":1530757142,"ns":757184231},{"host":"dev","key":"logrt[/var/log/td-agent/td-agent.log,error_class=Mysql2::Error]","lastlogsize":4769,"mtime":1530757142,"clock":1530757142,"ns":757401900}],"clock":1530757143,"ns":758161526}'

ログ中にあるhistory_logについても参照してみましたが、valueカラムにはデータは入っているようでした。

MariaDB [zabbix]> select * from history_log where value like '%retry_time=0%' order by id desc limit 1\G
*************************** 1. row ***************************
id: 196315
itemid: 30544
clock: 1530757139
timestamp: 0
source:
severity: 0
value: 2018-07-05 11:18:59 +0900 [warn]: #0 failed to flush the buffer. retry_time=0 next_retry_seconds=2018-07-05 11:18:59 +0900 chunk="570372b4e8613e6cdad5efeb418f5083" error_class=Mysql2::Error::ConnectionError error="Access denied for user 'root'@'xxxxxxxxxxxx' (using password: YES)"
logeventid: 0
ns: 751642451
1 row in set (0.00 sec)

MariaDB [zabbix]>