Unable to collect data from MongoDB Arbiter with enabled authentication

[pnedkov]

In the past I had similar issue: #4163. I decided to file a new one since the versions are different and I provided more relevant and detailed information here.

Relevant telegraf.conf:

System info:

CentOS 7.7
Telegraf 1.12.6
MongoDB 3.2.22
InfluxDB 1.7.9

Steps to reproduce:

1. Setup three MongoDB nodes in a replica set - Primary, Secondary, Arbiter

replSet=rs0
auth=true
keyFile=/var/lib/mongo-keyfile

2. Create user in the MongoDB Primary node in the "admin" database

db.createUser( { user: "adm", pwd: "password", roles: [ { role: "root", db: "admin" } ] } )

3. Setup InfluxDB
   /etc/influxdb/influxdb.conf:

[[udp]]
  enabled = true
  bind-address = ":4444"
  database = "testdb"

3. Setup Telegraf on all three MongoDB nodes - Primary, Secondary and Arbiter
   /etc/telegraf/telegraf.conf:

urls = ["udp://<influxdb_ip>:4444"]
database = "testdb"

4. On the MongoDB Primary and Secondary nodes create /etc/telegraf/telegraf.d/mongod.conf with the following content:

[[inputs.procstat]]
    exe = "mongod"

[[inputs.mongodb]]
    servers = ["mongodb://adm:password@127.0.0.1:27017"]
    col_stats_dbs = ["testdb"]

Hint: This will work.

5. On the MongoDB Arbiter node create /etc/telegraf/telegraf.d/mongod.conf with the following content:

[[inputs.procstat]]
    exe = "mongod"

[[inputs.mongodb]]
    servers = ["mongodb://127.0.0.1:27017"]

Hint: This fails.
Note: No username and password since there are no users on the MongoDB Arbiter.

6. Login to the InfluxDB and check if there are any measurements for all three MongoDB nodes

# influx
Connected to http://localhost:8086 version 1.7.9
InfluxDB shell version: 1.7.9
> 
> use testdb
Using database testdb
>
> show tag values from mongodb with key = "host";

Expected behavior:

Telegraf on the MongoDB Arbiter node should be able to login to the local mongod server, collect information and push it to the InfluxDB. The influxdb query should return all three MongoDB nodes:

show tag values from mongodb with key = "host";

Actual behavior:

After step 6 you will see that influxdb contains measurements only for MongoDB Primary and Secondary nodes. No data is coming from MongoDB Arbiter.

This error is logged in the Telegraf log file on the MongoDB Arbiter node:

[inputs.mongodb] Error in plugin: not authorized on local to execute command { find: "oplog.$main", filter: { ts: { $exists: true } }, sort: { $natural: 1 }, skip: 0, limit: 1, batchSize: 1, singleBatch: true }

Additional info:

Everything works as expected if you follow the exact steps to reproduce but using Telegraf 1.11.5. Something is wrong with Telegraf 1.12.6.

[pnedkov]

Confirmed, it works with 1.13.0-rc2. Thank you!