aa27bbe33f
This change should simplify the pipeline's job. Reference issue: https://github.com/ooni/probe/issues/1817. I previously dismissed this possibility, but now it seems clear it is simpler to have a very tabular data format internally and to convert such a format to OONI's data format when serializing. The OONI data format is what the pipeline expects, but processing is easier with a more linear/tabular format.
98 lines
2.7 KiB
Markdown
98 lines
2.7 KiB
Markdown
|
|
# Chapter XII: Following redirections.
|
|
|
|
This program shows how to combine the URL measurement
|
|
"step" introduced in the previous chapter with
|
|
following redirections. If we say that the previous
|
|
chapter performed a "web step", then we can say
|
|
that here we're performing multiple "web steps".
|
|
|
|
(This file is auto-generated. Do not edit it directly! To apply
|
|
changes you need to modify `./internal/tutorial/measurex/chapter12/main.go`.)
|
|
|
|
## main.go
|
|
|
|
The beginning of the program is pretty much the
|
|
same, except that here we need to define a
|
|
`measurement` container type that will contain
|
|
the result of each "web step".
|
|
|
|
```Go
|
|
package main
|
|
|
|
import (
|
|
"context"
|
|
"encoding/json"
|
|
"flag"
|
|
"fmt"
|
|
"time"
|
|
|
|
"github.com/ooni/probe-cli/v3/internal/measurex"
|
|
"github.com/ooni/probe-cli/v3/internal/runtimex"
|
|
)
|
|
|
|
type measurement struct {
|
|
URLs []*measurex.ArchivalURLMeasurement
|
|
}
|
|
|
|
func print(v interface{}) {
|
|
data, err := json.Marshal(v)
|
|
runtimex.PanicOnError(err, "json.Marshal failed")
|
|
fmt.Printf("%s\n", string(data))
|
|
}
|
|
|
|
func main() {
|
|
URL := flag.String("url", "http://facebook.com/", "URL to fetch")
|
|
timeout := flag.Duration("timeout", 60*time.Second, "timeout to use")
|
|
flag.Parse()
|
|
ctx, cancel := context.WithTimeout(context.Background(), *timeout)
|
|
defer cancel()
|
|
all := &measurement{}
|
|
mx := measurex.NewMeasurerWithDefaultSettings()
|
|
cookies := measurex.NewCookieJar()
|
|
headers := measurex.NewHTTPRequestHeaderForMeasuring()
|
|
```
|
|
|
|
Everything above this line is like in chapter11. What changes
|
|
now is that we're calling `MeasureURLAndFollowRedirections`
|
|
instead of `MeasureURL`.
|
|
|
|
Rather than returning a single measurement, this function
|
|
returns a channel where it posts the result of measuring
|
|
the original URL along with all its redirections. Internally,
|
|
`MeasureURLAndFollowRedirections` calls `MeasureURL`.
|
|
|
|
We accumulate the results in `URLs` and print `m`. The channel
|
|
is closed when done by `MeasureURLAndFollowRedirections`, so we leave the loop.
|
|
|
|
```Go
|
|
for m := range mx.MeasureURLAndFollowRedirections(ctx, *URL, headers, cookies) {
|
|
all.URLs = append(all.URLs, measurex.NewArchivalURLMeasurement(m))
|
|
}
|
|
print(all)
|
|
}
|
|
|
|
```
|
|
|
|
## Running the example program
|
|
|
|
Let us perform a vanilla run first:
|
|
|
|
```bash
|
|
go run -race ./internal/tutorial/measurex/chapter12 | jq
|
|
```
|
|
|
|
Take a look at the JSON. You should see several redirects
|
|
and that we measure each endpoint of each redirect, including
|
|
QUIC endpoints that we discover on the way.
|
|
|
|
Exercise: remove code for converting to OONI data format
|
|
and compare output with previous chapter. See any difference?
|
|
|
|
## Conclusion
|
|
|
|
We have introduced `MeasureURLAndFollowRedirect`, the
|
|
top-level API for fully measuring a URL and all the URLs
|
|
that derive from such an URL via redirection.
|
|
|