Why am I getting 'open stack of elements exceeds 512 nodes' when parsing an image URL with GoQuery?
Asked by
CuriousCoder92
Hi everyone! I'm a beginner learning Go, and I'm working on building a web crawler using the goquery library for HTML parsing. However, I've hit an issue when my crawler tries to parse a page for an image (like a .png file). I keep getting the error "html: open stack of elements exceeds 512 nodes".
Here's a simple piece of code that reproduces the error:
```go
package main
import (
"net/http"
"github.com/PuerkitoBio/goquery"
)
func main() {
url := "https://nicolasgatien.com/images/root-game.png"
resp, err := http.Get(url)
if err != nil {
panic(err)
}
defer resp.Body.Close()
println(url)
_, err = goquery.NewDocumentFromReader(resp.Body)
if err != nil {
panic(err)
}
}
```
I'm puzzled because the page seems quite simple – it contains a node, a node, and just one ![]()
node. Can someone explain what the "open stack of elements" error means and why it exceeds 512 nodes when the content looks simple? I even considered if it might be an issue with content length, but larger responses don't cause this error. Any insights would be appreciated!
Answers
The error could stem from too many recursive calls happening somewhere in your code. It's a bit confusing since your script looks straightforward and only makes one request, but the page you're trying to access could contain scripts that lead to recursion. Just something to keep in mind!
Reply to this answer
The issue is that you're trying to parse a PNG file as if it were HTML. GoQuery is expecting content with a `text/html` Content-Type, but your URL returns `image/png`. To fix this, check the Content-Type before parsing it. Here's a snippet that avoids the error by ensuring you're only parsing HTML:
```go
resp, err := http.Get(url)
if err != nil {
panic(err)
}
defer resp.Body.Close()
if resp.Header.Get("Content-Type") != "text/html" {
println("Not HTML, skipping:", url)
return
}
doc, err := goquery.NewDocumentFromReader(resp.Body)
if err != nil {
panic(err)
}
```
Just make sure to feed only HTML pages to GoQuery, and that should solve your stack error issue!
CuriousCoder92: Ooooh! Okay, great. This fixed my problem, thank you! :D
Reply to this answer
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Answers are reviewed before publication.
CuriousCoder92: How would the script I posted above be resulting in recursion? It's making one request, and then trying to parse the response. Are you saying the page itself might have a recursive script inside it?