Hi Kay, On Tue, Jan 20, 2009 at 12:00 PM, Kay Röpke <[email protected]> wrote: > Hi! > > On Jan 19, 2009, at 4:54 PM, nick loeve wrote: >
[snip] >> >> So, my question: >> >> Does mysqlproxy require a backend connection from the connection pool >> for every query coming in the front-end or can it also handle a >> 'backlog'? > > There is no "backlog" yet, so currently you have to have a free connection > for each incoming connection, yes, > since we cannot multiplex multiple queries onto one mysqld thread. > IOW, each incoming connection will allocate a new or reuse an idle > connection from the proxy to the server, up to the thread limit of the > server (which is probably when you start seeing the connection lost errors). Ok, makes sense. I had a closer look at the chassis/plugin source last night, and we are currently evaluating what it would take to add this 'backlog' functionality, either as a patch for the proxy-plugin or a stripped down proxy-plugin. Our initial idea to get the multiplexing behaviour is: A process similar to the query injection system, whereby we globally queue a front-end connection with its pending query, and once an active 'network_mysqld_con' passes the send_query_reponse phase (including injected queries etc), we pop from the queue, swap out the network_mysqld_con->client with the network_socket from the queue item and inject the pending query. While there is a backlog this process will be repeated. I haven't thought this through entirely, but any suggestions would be helpful. > >> My lua script to do the query funneling is currently >> returning 'Lost connection to MySQL server during query' errors to the >> client if I have more clients connected and sending queries than I >> have back-end connections open. > > Any chance you could share snippets of that script? Makes it a bit easier to > discuss. > also, which version of proxy are you using? Im using 0.7.0 (well lp:mysql-proxy trunk) I have attached, a cut down version of my test lua script, but I understand the limitations I was confused about earlier. > > regarding your follow-up: >> >> (critical) proxy-plugin.c.1087: I have no server backend, closing >> connection >> (critical) network-mysqld.c.1181: plugin_call(CON_STATE_READ_QUERY) failed >> >> Yet i do not define a read_query_result in my lua script (and so I do >> not play with backends/connections/proxy.* return status etc), which >> leads me to ask if you need a connection available in the pool for a >> back-end for every query coming in the front-end. > > the last message is not from the "proxy" itself, but the chassis which is > handling the low-level network stuff. > the CON_STATE_READ_QUERY is the state in the protocol, there doesn't > necessarily has to be a lua callback for it. it's merely the place where > proxy does the default behavior. Yep, that is clear now also. Thanks for your comments, -- Nick Loeve
mysqlproxy-pool-and-funnel.lua
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