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Re: question about filter

June 16, 2011 10:22AM
Hello mates,
I continued to work on the issue I found in my module. I wrote another
simpler module that just collect first 128 KB of each served file and
write them in a file.
Unfortunately for one and the same served file I found different content
in dump files and this is very confusing situation. Maybe my function
that collect separated buffers from the chains is wrong?
The function skip only ngx_buf_special flagged buffers ....
Should I skip something else?

The test module is attached;

Thanks in advance
Anatoli Marinov

On 06/15/2011 02:16 PM, Anatoli Marinov wrote:
> Hello Colleagues,
>
> I am trying to write a filter that should buffer some data coming from
> upstream. When the filter has collected enough data (for example 3
> MB), special function will estimate the desired limit rate related to
> the data from the buffer (the files are mp4 so limit rate will be set
> according to the mp4 bitrate).
> In most cases it works but sometime for one and the same file I got
> different data in the buffer ?!?!?!. The data is similar but invalid
> so the mp4 parsing function cannot use it.
> When the file exists in the local cache everything is ok. The issue
> appears only when the file comes from upstream.
>
> What could be the reason to receive different data in the filter?
> I am using nginx 1.0.2 on 64b machine with linux.
>
> My example code:
>
> static void ngx_http_throttling_collect(ngx_http_request_t *r,
> ngx_http_throttling_ctx_t *ctx, ngx_chain_t *in)
> {
> ngx_chain_t *ch_in;
> ngx_buf_t *buf;
> ngx_int_t read_bytes, in_b_size, local_b_space, len;
>
> ch_in = in;
>
> for(ch_in = in; ch_in != NULL; ch_in = ch_in->next) {
>
> if(ch_in->buf == NULL) {
> continue;
> }
>
> buf = ch_in->buf;
>
> if(ngx_buf_special(buf)) {
> NGX_HTTP_LLOG(r->connection->log, "r[%p] buff is
> special\n", r);
> continue;
> }
>
> /* try to recognize the resource */
> if(ctx->buff_type == THROTLING_UNKNOWN) {
> if(buf->temp_file == 0) {
> ctx->buff_type = THROTLING_USE_FILE;
> } else {
> ctx->buff_type = THROTLING_USE_MEM;
> }
> }
>
> if(ctx->buff_type == THROTLING_USE_FILE) {
> read_bytes = read(buf->file->fd, ctx->b.last,
> NGX_HTTP_THRT_BUFF_SIZE);
>
> if(read_bytes != NGX_HTTP_THRT_BUFF_SIZE) {
> ctx->state = THROTTLING_CANNOT_GET_FORMAT_INFO;
> r->limit_rate = ctx->lconf->default_rate_limit;
> r->limit_rate_after = r->limit_rate *
> ctx->lconf->full_speed_sec;
> return;
> }
>
> ctx->b.last += read_bytes;
> ngx_http_throttling_process_buffer(r, ctx);
> } else {
> in_b_size = buf->last - buf->start;
> local_b_space = NGX_HTTP_THRT_BUFF_SIZE -
> CDN_BUFF_DATA_LEN(&ctx->b);
>
> if(local_b_space == 0) {
> ngx_http_throttling_process_buffer(r, ctx);
> return;
> }
>
> len = local_b_space < in_b_size ? local_b_space
> : in_b_size;
>
> if(len) {
> ctx->b.last = ngx_copy(ctx->b.last, buf->start, len);
> }
> }
> }
> }
>
>
> Thanks for all ideas in advance.
>
>
> _______________________________________________
> nginx-devel mailing list
> nginx-devel@nginx.org
> http://nginx.org/mailman/listinfo/nginx-devel

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Subject Author Views Posted

question about filter

toli 1618 June 15, 2011 07:18AM

Re: question about filter

toli 760 June 16, 2011 10:22AM



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