I believe http-parser will fail only in a strict mode. May I ask you to share more details with us?

When the http response header is something like this:

HTTP/1.1 200 OK\r\n
Content-Length : 123\r\n
\r\n
body data

Please pay attention to the white spaces after Content-Length and before the colon.

I encountered this error in Mesos project: apache/mesos@b2c92ee#diff-cce67628b066393859924dbdfc3e0fb5L658

The bug URL: https://issues.apache.org/jira/browse/MESOS-5063

I indeed see the whitespace before the colon, but still not sure what kind of failure you are experiencing. From what I have tried a week ago, it really looked like http-parser supports whitespace before the colon.

May I ask you help me understand it?

Yes, I thought http-parser 2.6.2 solved this issue, but actually not.

You can insert a white space in this line, then do a make action, it will show you errors.

https://github.com/nodejs/http-parser/blob/v2.6.2/test.c#L1172

More detailed:

data = "HTTP/1.1 200 OK\r\nContent-Length : 12\r\n\r\nHello World!";
length = 52;
size_t parsed = http_parser_execute(&parser, &settings, data, length);

The parsed and the real length are not same.

@indutny Could you take a look about this issue? Thanks.

Set the HTTP_PARSER_STRICT=0 solved my issue, thanks.