MongoDB exporter panics when DB connection is lost

 go build

./mongodb_exporter --mongodb.uri=mongodb://127.0.0.1:17001/admin --mongodb.global-conn-pool --discovering-mode --compatible-mode --collect-all
2022/03/26 00:12:25 Starting HTTP server for http://:9216/metrics ...


ERRO[0018] Cannot get topology info: cannot check if the instance is an arbiter: server selection error: context deadline exceeded, current topology: { Type: Single, Servers: [{ Addr: 127.0.0.1:17001, Type: Unknown, Last error: connection() error occured during connection handshake: dial tcp 127.0.0.1:17001: connect: connection refused }, ] }
ERRO[0018] error while checking mongodb connection: server selection error: context deadline exceeded, current topology: { Type: Single, Servers: [{ Addr: 127.0.0.1:17001, Type: Unknown, Last error: connection() error occured during connection handshake: dial tcp 127.0.0.1:17001: connect: connection refused }, ] }. mongo_up is set to 0
ERRO[0018] Cannot get node type to check if this is a mongos: server selection error: context deadline exceeded, current topology: { Type: Single, Servers: [{ Addr: 127.0.0.1:17001, Type: Unknown, Last error: connection() error occured during connection handshake: dial tcp 127.0.0.1:17001: connect: connection refused }, ] }
ERRO[0018] cannot auto discover databases and collections: cannot make the list of databases to list all collections: cannot get the database names list: server selection error: context deadline exceeded, current topology: { Type: Single, Servers: [{ Addr: 127.0.0.1:17001, Type: Unknown, Last error: connection() error occured during connection handshake: dial tcp 127.0.0.1:17001: connect: connection refused }, ] }
ERRO[0018] cannot auto discover databases and collections
ERRO[0018] cannot run getDiagnosticData: server selection error: context deadline exceeded, current topology: { Type: Single, Servers: [{ Addr: 127.0.0.1:17001, Type: Unknown, Last error: connection() error occured during connection handshake: dial tcp 127.0.0.1:17001: connect: connection refused }, ] }
ERRO[0018] cannot run getDiagnosticData: response is empty
ERRO[0018] cannot decode getDiagnosticData: <nil> for data field: unexpected data type
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0xac2625]

goroutine 124 [running]:
github.com/percona/mongodb_exporter/exporter.(*topologyInfo).baseLabels(0x0)
        /home/karl/go/src/github.com/percona/mongodb_exporter/exporter/topology_info.go:84 +0x45
github.com/percona/mongodb_exporter/exporter.(*diagnosticDataCollector).Collect(0xc000112f80, 0xc00014c900?)
        /home/karl/go/src/github.com/percona/mongodb_exporter/exporter/diagnostic_data_collector.go:69 +0x40c
github.com/prometheus/client_golang/prometheus.DescribeByCollect.func1()
        /home/karl/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/collector.go:90 +0x2b
created by github.com/prometheus/client_golang/prometheus.DescribeByCollect
 /home/karl/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/collector.go:89 +0x9c