10000 concurrency problems with fpm · Issue #399 · phpredis/phpredis · GitHub
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edlerd opened this issue Oct 30, 2013 · 1 comment
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concurrency problems with fpm #399

edlerd opened this issue Oct 30, 2013 · 1 comment

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@edlerd
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edlerd commented Oct 30, 2013

We are using phpredis on a high traffic site. Recently changing to php-fpm and since we are having occasional segfaults.

From our research we suggest it is a concurrency problem due to wrong separation of persistent connection.

Here is an excerpt of a gdb stacktrace from on of the core dumps:

(gdb) bt
#0  0x000000000065c75d in _php_stream_write (stream=0x23856a0, 
    buf=0x2154778 "*2\r\n$3\r\nTTL\r\n$48\r\nDataCollect:15930455cf71f0fb5c8c429412949b4f6c0d\r\n", count=68)
    at /build/buildd/php5-5.3.10/main/streams/streams.c:1098
#1  0x00007f37ce048292 in redis_sock_write () from /usr/lib/php5/20090626/redis.so
#2  0x00007f37ce0367b0 in generic_ttl () from /usr/lib/php5/20090626/redis.so

So the problem is in stream.c. The line where the segfault happens is marked:

PHPAPI int _php_stream_set_option(php_stream *stream, int option, int value, void *ptrparam TSRMLS_DC)
{
        int ret = PHP_STREAM_OPTION_RETURN_NOTIMPL;

        if (stream->ops->set_option) { // segfault happens here
                ret = stream->ops->set_option(stream, option, value, ptrparam TSRMLS_CC);
        }    

        if (ret == PHP_STREAM_OPTION_RETURN_NOTIMPL) {
                switch(option) {
                        case PHP_STREAM_OPTION_SET_CHUNK_SIZE:
                                ret = stream->chunk_size;
                                stream->chunk_size = value;
                                return ret; 

                        case PHP_STREAM_OPTION_READ_BUFFER:
                                /* try to match the buffer mode as best we can */
                                if (value == PHP_STREAM_BUFFER_NONE) {
                                        stream->flags |= PHP_STREAM_FLAG_NO_BUFFER;
                                } else if (stream->flags & PHP_STREAM_FLAG_NO_BUFFER) {
                                        stream->flags ^= PHP_STREAM_FLAG_NO_BUFFER;
                                }    
                                ret = PHP_STREAM_OPTION_RETURN_OK;
                                break;

                        default:
                                ;    
                }    
        }

        return ret; 
}

Of course one solution would be to deactivate persistent connections, but the performace loss is not so nice. Any ideas how to solve it?
@edlerd edlerd mentioned this issue Dec 18, 2013
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@michael-grunder
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Closing via #415

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@michael-grunder @edlerd
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