panic in logging http middleware

[brancz]

Thanos, Prometheus and Golang version used: main-2021-03-11-b2474aa3

Object Storage Provider: GCS

What happened:

Panic in the http logging middleware when querying

What you expected to happen:

No panic :)

How to reproduce it (as minimally and precisely as possible): I'm not certain but I think my requests don't have a Host header, so this panics:

thanos/pkg/logging/http.go

Line 42 in b2474aa

port := strings.Split(r.Host, ":")[1]

Full logs to relevant components:

2021/03/12 09:56:26 http: panic serving 10.0.7.7:43392: runtime error: index out of range [1] with length 1                                                                                                                                   
goroutine 13538 [running]:                                                                                                                                                                                                                    
net/http.(*conn).serve.func1(0xc00037cdc0)                                                                                                                                                                                                    
        /usr/local/go/src/net/http/server.go:1801 +0x147                                                                                                                                                                                      
panic(0x1a9fbe0, 0xc00035fc40)                                                                                                                                                                                                                
        /usr/local/go/src/runtime/panic.go:975 +0x47a                                                                                                                                                                                         
github.com/thanos-io/thanos/pkg/logging.(*HTTPServerMiddleware).HTTPMiddleware.func1(0x7fb741825850, 0xc00007af50, 0xc0004a6c00)                                                                                                              
        /home/circleci/project/pkg/logging/http.go:42 +0x3ef                                                                                                                                                                                  
net/http.HandlerFunc.ServeHTTP(0xc00038f9e0, 0x7fb741825850, 0xc00007af50, 0xc0004a6c00)                                                                                                                                                      
        /usr/local/go/src/net/http/server.go:2042 +0x44                                                                                                                                                                                       
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerResponseSize.func1(0x7fb741825850, 0xc00007af00, 0xc0004a6c00)                                                                                                       
        /home/circleci/go/pkg/mod/github.com/prometheus/client_golang@v1.9.0/prometheus/promhttp/instrument_server.go:198 +0xe9                                                                                                               
net/http.HandlerFunc.ServeHTTP(0xc00038fda0, 0x7fb741825850, 0xc00007af00, 0xc0004a6c00)                                                                                                                                                      
        /usr/local/go/src/net/http/server.go:2042 +0x44                                                                                                                                                                                       
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerCounter.func1(0x7fb741825850, 0xc00007aeb0, 0xc0004a6c00)                                                                                                            
        /home/circleci/go/pkg/mod/github.com/prometheus/client_golang@v1.9.0/prometheus/promhttp/instrument_server.go:101 +0xda                                                                                                               
net/http.HandlerFunc.ServeHTTP(0xc000156060, 0x7fb741825850, 0xc00007aeb0, 0xc0004a6c00)                                                                                                                                                      
        /usr/local/go/src/net/http/server.go:2042 +0x44                                                                                                                                                                                       
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerRequestSize.func1(0x7fb741825850, 0xc00007adc0, 0xc0004a6c00)                                                                                                        
        /home/circleci/go/pkg/mod/github.com/prometheus/client_golang@v1.9.0/prometheus/promhttp/instrument_server.go:165 +0xe9                                                                                                               
net/http.HandlerFunc.ServeHTTP(0xc000156570, 0x7fb741825850, 0xc00007adc0, 0xc0004a6c00)                                                                                                                                                      
        /usr/local/go/src/net/http/server.go:2042 +0x44                                                                                                                                                                                       
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerDuration.func1(0x1e27300, 0xc000122380, 0xc0004a6c00)                                                                                                                
        /home/circleci/go/pkg/mod/github.com/prometheus/client_golang@v1.9.0/prometheus/promhttp/instrument_server.go:68 +0x11c                                                                                                               
net/http.HandlerFunc.ServeHTTP(...)                                                                                                                                                                                                           
        /usr/local/go/src/net/http/server.go:2042                                                                                                                                                                                             
main.runQueryFrontend.func1.1(0x1e27300, 0xc000122380, 0xc0004a6b00)                                                                                                                                                                          
        /home/circleci/project/cmd/thanos/query_frontend.go:238 +0x365                                                                                                                                                                        
net/http.HandlerFunc.ServeHTTP(0xc00021f3b0, 0x1e27300, 0xc000122380, 0xc0004a6b00)                                                                                                                                                           
        /usr/local/go/src/net/http/server.go:2042 +0x44                                                                                                                                                                                       
net/http.(*ServeMux).ServeHTTP(0xc0002dedc0, 0x1e27300, 0xc000122380, 0xc0004a6b00)                                                                                                                                                           
        /usr/local/go/src/net/http/server.go:2417 +0x1ad                                                                                                                                                                                      
net/http.serverHandler.ServeHTTP(0xc00003a2a0, 0x1e27300, 0xc000122380, 0xc0004a6b00)                                                                                                                                                         
        /usr/local/go/src/net/http/server.go:2843 +0xa3                                                                                                                                                                                       
net/http.(*conn).serve(0xc00037cdc0, 0x1e2ea00, 0xc000398280)                                                                                                                                                                                 
        /usr/local/go/src/net/http/server.go:1925 +0x8ad                                                                                                                                                                                      
created by net/http.(*Server).Serve                                                                                                                                                                                                           
        /usr/local/go/src/net/http/server.go:2969 +0x36c

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