Best way to buffer upstream responses in reverse proxy

[Prabhu Chawandi]

Hello,

     For a single request from a client, I have to make multiple upstream requests and send a single response back to the client. 

I am looking for best way to buffer in the proxy and write all at once, where GC is not hurting the performance, seamlessly work for multiple client request simultaneously. 

Regards,

pc

  

  

   

  

[Tamás Gulácsi]

Start simple: use a *bytes.Buffer, and help the GC with using a sync.Pool for those buffers.

[Prabhu Chawandi]

Thank you for the pointers. I will dig more into them. 

Thanks,

Prabhu

On Sat, Jan 18, 2020 at 12:10 PM Tamás Gulácsi <tgula...@gmail.com> wrote:

Start simple: use a *bytes.Buffer, and help the GC with using a sync.Pool for those buffers.

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[Prabhu Chawandi]

Hello,

   I am able to buffer in types.Buffer the multiple response before writing back to client, I am hit at a problem of JSON formatting the final output.

Example: after first response buf = {...}, after second buf={...}{...}.

Now it will be returned as is, which is not in proper json format. I need to make this like [{...},{...}] 

Any hints to achieve this?

Regards,

Prabhu

[Tamás Gulácsi]

Just put the missing [,] chars wher it's required with buf.WriteByte.

[Prabhu Chawandi]

Yes, I also need to put '[' at first and ']' at last position. But I was checking if there is any better way to do it. I was even having question how can someone make it better without unmarshalling JSON and remarshalling merged object.

On Mon, Jan 20, 2020 at 4:12 AM Tamás Gulácsi <tgula...@gmail.com> wrote:

Just put the missing [,] chars wher it's required with buf.WriteByte.

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[Tamás Gulácsi]

Please define "better".

For complexity and speed, appending "[", inserting ",", and appending "]" at the end is the simplest and fastest solution.

If you want to check for syntax and completeness, then you should unmarshal, append, and then marshal again.

But if not needed, it's just complexity and resource hog.

You can hide it in a function/library, but anyway, any solution would do one of the two solutions specified here.

So it will be either "hacky" or "bloat".

At least when the "hacky" solution is in plain sight, you'll know where to check first when syntax errors araise :-)

Tamás

2020. január 20., hétfő 10:19:26 UTC+1 időpontban pc a következőt írta:

Yes, I also need to put '[' at first and ']' at last position. But I was checking if there is any better way to do it. I was even having question how can someone make it better without unmarshalling JSON and remarshalling merged object.

On Mon, Jan 20, 2020 at 4:12 AM Tamás Gulácsi <tgula...@gmail.com> wrote:

Just put the missing [,] chars wher it's required with buf.WriteByte.

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[Prabhu Chawandi]

As responses coming from upstream server, because my application acting as proxy server and it will not have  visibility of the fields of the responses coming.

So, think appending the characters to meet JSON format is only way. Am I right assuming so?

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[robfig]

You could use json iterator’s Stream type if you prefer to feel better by having it wrapped in a library. It does the same thing of course. As the name suggests it can be used to incrementally write the json to a writer if that’s what you’d like.
https://godoc.org/github.com/json-iterator/go#Stream

[Prabhu Chawandi]

Yes, I ended up using this package. Thanks.

On Wed, Jan 22, 2020 at 2:35 AM robfig <rob...@gmail.com> wrote:

You could use json iterator’s Stream type if you prefer to feel better by having it wrapped in a library. It does the same thing of course. As the name suggests it can be used to incrementally write the json to a writer if that’s what you’d like.
https://godoc.org/github.com/json-iterator/go#Stream

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