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HttpDrizzleModule

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[edit] Name

drizzle-nginx-module - Upstream module for talking to MySQL and Drizzle directly

This module is not distributed with the Nginx source. See the installation instructions.

[edit] Status

This module is already production ready and is powering the Taobao LineZing site.

[edit] Version

This document describes ngx_drizzle v0.1.2rc1 released on 8 October 2011.

[edit] Synopsis 

    http {
        ...
 
        upstream cluster {
            # simple round-robin
            drizzle_server 127.0.0.1:3306 dbname=test
                 password=some_pass user=monty protocol=mysql;
            drizzle_server 127.0.0.1:1234 dbname=test2
                 password=pass user=bob protocol=drizzle;
        }
 
        upstream backend {
            drizzle_server 127.0.0.1:3306 dbname=test
                 password=some_pass user=monty protocol=mysql;
        }
 
        server {
            location /mysql {
                set $my_sql 'select * from cats';
                drizzle_query $my_sql;
 
                drizzle_pass backend;
 
                drizzle_connect_timeout    500ms; # default 60s
                drizzle_send_query_timeout 2s;    # default 60s
                drizzle_recv_cols_timeout  1s;    # default 60s
                drizzle_recv_rows_timeout  1s;    # default 60s
            }
 
            ...
 
            # for connection pool monitoring
            location /mysql-pool-status {
                allow 127.0.0.1;
                deny all;
 
                drizzle_status;
            }
        }
    }

[edit] Description

This is an nginx upstream module integrating libdrizzle into Nginx in a non-blocking and streamming way.

Essentially it provides a very efficient and flexible way for nginx internals to access MySQL, Drizzle, as well as other RDBMS's that support the Drizzle or MySQL wired protocol. Also it can serve as a direct REST interface to those RDBMS backends.

This module does not generate human-readable outputs, rather, in a binary format called Resty-DBD-Stream (RDS) designed by ourselves. You usually need other components, like HttpRdsJsonModule, HttpRdsCsvModule, or LuaRdsParser, to work with this module. See Output Format for details.

[edit] Keepalive connection pool

This module also provides a builtin per-worker connection pool mechanism for MySQL or Drizzle TCP connections.

Here's a sample configuration: 

    upstream backend {
        drizzle_server 127.0.0.1:3306 dbname=test
             password=some_pass user=monty protocol=mysql;
        drizzle_keepalive max=100 mode=single overflow=reject;
    }

For now, the connection pool uses a simple LIFO algorithm to assign idle connections in the pool. That is, most recently (successfully) used connections will be reused first the next time. And new idle connections will always replace the oldest idle connections in the pool even if the pool is already full.

See the drizzle_keepalive directive for more details.

[edit] Last Insert ID

If you want to get LAST_INSERT_ID, then ngx_drizzle already returns that automatically for you when you're doing a SQL insert query. Consider the following sample nginx.conf snippet: 

    location /test {
        echo_location /mysql "drop table if exists foo";
        echo;
        echo_location /mysql "create table foo (id serial not null, primary key (id), val real);";
        echo;
        echo_location /mysql "insert into foo (val) values (3.1415926);";
        echo;
        echo_location /mysql "select * from foo;";
        echo;
    }
 
    location /mysql {
        drizzle_pass backend;
        drizzle_module_header off;
        drizzle_query $query_string;
        rds_json on;
    }

Then request GET /test gives the following outputs: 

    {"errcode":0}
    {"errcode":0}
    {"errcode":0,"insert_id":1,"affected_rows":1}
    [{"id":1,"val":3.1415926}]

You can see the insert_id field (as well as the affected_rows field in the 3rd JSON response.

[edit] Directives

[edit] drizzle_server

syntax: drizzle_server <host> user=<user> password=<pass> dbname=<database>

syntax: drizzle_server <host>:<port> user=<user> password=<pass> dbname=<database> protocol=<protocol> charset=<charset>

default: no

context: upstream

Directive assigns the name and the parameters of server. For the name it is possible to use a domain name, an address, with an optional port (default: 3306). If domain name resolves to several addresses, then all are used.

The following options are supported:

user=<user>

MySQL/Drizzle user name <user> for login.

password=<pass>

Specify mysql password <pass>for login.

dbname=<database>

Specify default MySQL database <database> for the connection. Note that MySQL does allow referencing tables belonging to different databases by qualifying table names with database names in SQL queries.

protocol=<protocol>

Specify which wire protocol to use, drizzle or mysql. Default to drizzle.

charset=<charset>

Explicitly specify the character set for the MySQL connections. Setting this option to a non-empty value will make this module send out a set names '<charset>' query right after the mysql connection is established.
If the default character encoding of the MySQL connection is already what you want, you needn't set this option because it has extra runtime cost.
Here is a small example: 
    drizzle_server foo.bar.com:3306 user=monty password=some_pass
                                    dbname=test protocol=mysql
                                    charset=utf8;

Please note that for the mysql server, "utf-8" is not a valid encoding name while utf8 is.

[edit] drizzle_keepalive

syntax: drizzle_keepalive max=<size> mode=<mode>

default: drizzle_keepalive max=0 mode=single

context: upstream

Configures the keep-alive connection pool for MySQL/Drizzle connections.

The following options are supported:

max=<num>

Specify the capacity of the connection pool for the current upstream block. The <num> value must be non-zero. If set to 0, it effectively disables the connection pool. This option is default to 0.

mode=<mode>

This supports two values, single and multi. The single mode means the pool does not distinguish various drizzle servers in the current upstream block while multi means the pool will merely reuse connections which have identical server host names and ports. Note that even under multi, differences between dbname or user parameters will be silently ignored. Default to single.

overflow=<action>

This option specifies what to do when the connection pool is already full while new database connection is required. Either reject or ignore can be specified. In case of reject, it will reject the current request, and returns the 503 Service Unavailable error page. For ignore, this module will go on creating a new database connection.

[edit] drizzle_query

syntax: drizzle_query <sql>

default: no

context: http, server, location, location if

Specify the SQL queries sent to the Drizzle/MySQL backend.

Nginx variable interpolation is supported, but you must be careful with SQL injection attacks. You can use the set_quote_sql_str directive, for example, to quote values for SQL interpolation: 

    location /cat {
        set_unescape_uri $name $arg_name;
        set_quote_sql_str $quoted_name $name;
 
        drizzle_query "select * from cats where name = $quoted_name";
        drizzle_pass my_backend;
    }

[edit] drizzle_pass

syntax: drizzle_pass <remote>

default: no

context: location, location if

phase: content

This directive specifies the Drizzle or MySQL upstream name to be queried in the current location. The <remote> argument can be any upstream name defined with the drizzle_server directive.

Nginx variables can also be interpolated into the <remote> argument, so as to do dynamic backend routing, for example: 

    upstream moon { drizzle_server ...; }
 
    server {
        location /cat {
            set $backend 'moon';
 
            drizzle_query ...;
            drizzle_pass $backend;
        }
    }

[edit] drizzle_connect_timeout

syntax: drizzle_connect_time <time>

default: drizzle_connect_time 60s

context: http, server, location, location if

Specify the (total) timeout for connecting to a remote Drizzle or MySQL server.

The <time> argument can be an integer, with an optional time unit, like s (second), ms (millisecond), m (minute). The default time unit is s, i.e., "second". The default setting is 60s.

[edit] drizzle_send_query_timeout

syntax: drizzle_send_query_timeout <time>

default: drizzle_send_query_timeout 60s

context: http, server, location, location if

Specify the (total) timeout for sending a SQL query to a remote Drizzle or MySQL server.

The <time> argument can be an integer, with an optional time unit, like s (second), ms (millisecond), m (minute). The default time unit is s, ie, "second". The default setting is 60s.

[edit] drizzle_recv_cols_timeout

syntax: drizzle_recv_cols_timeout <time>

default: drizzle_recv_cols_timeout 60s

context: http, server, location, location if

Specify the (total) timeout for receiving the columns metadata of the result-set to a remote Drizzle or MySQL server.

The <time> argument can be an integer, with an optional time unit, like s (second), ms (millisecond), m (minute). The default time unit is s, ie, "second". The default setting is 60s.

[edit] drizzle_recv_rows_timeout

syntax: drizzle_recv_rows_timeout <time>

default: drizzle_recv_rows_timeout 60s

context: http, server, location, location if

Specify the (total) timeout for receiving the rows data of the result-set (if any) to a remote Drizzle or MySQL server.

The <time> argument can be an integer, with an optional time unit, like s (second), ms (millisecond), m (minute). The default time unit is s, ie, "second". The default setting is 60s.

[edit] drizzle_buffer_size

syntax: drizzle_buffer_size <size>

default: drizzle_buffer_size 4k/8k

context: http, server, location, location if

Specify the buffer size for drizzle outputs. Default to the page size (4k/8k). The larger the buffer, the less streammy the outputing process will be.

[edit] drizzle_module_header

syntax: drizzle_module_header on|off

default: drizzle_module_header on

context: http, server, location, location if

Controls whether to output the drizzle header in the response. Default on.

The drizzle module header looks like this: 

    X-Resty-DBD-Module: ngx_drizzle 0.1.0

[edit] drizzle_status

syntax: drizzle_status

default: no

context: location, location if

phase: content

When specified, the current Nginx location will output a status report for all the drizzle upstream servers in the virtual server of the current Nginx worker process.

The output looks like this: 

    worker process: 15231
 
    upstream backend
      active connections: 0
      connection pool capacity: 10
      overflow: reject
      cached connection queue: 0
      free'd connection queue: 10
      cached connection successfully used count:
      free'd connection successfully used count: 3 0 0 0 0 0 0 0 0 0
      servers: 1
      peers: 1
 
    upstream backend2
      active connections: 0
      connection pool capacity: 0
      servers: 1
      peers: 1

Note that, this is not the global statistics if you do have multiple Nginx worker processes configured in your nginx.conf.

[edit] Variables

This module creates the following Nginx variables:

[edit] $drizzle_thread_id

This variable will be assigned a textual number of the underlying MySQL or Drizzle query thread ID when the current SQL query times out. This thread ID can be further used in a SQL kill command to cancel the timed-out query.

Here's an example: 

    drizzle_connect_timeout 1s;
    drizzle_send_query_timeout 2s;
    drizzle_recv_cols_timeout 1s;
    drizzle_recv_rows_timeout 1s;
 
    location /query {
        drizzle_query 'select sleep(10)';
        drizzle_pass my_backend;
        rds_json on;
 
        more_set_headers -s 504 'X-Mysql-Tid: $drizzle_thread_id';                                   
    }
 
    location /kill {
        drizzle_query "kill query $arg_tid";
        drizzle_pass my_backend;
        rds_json on;
    }
 
    location /main {
        content_by_lua '
            local res = ngx.location.catpure("/query")
            if res.status ~= ngx.HTTP_OK then
                local tid = res.header["X-Mysql-Tid"]
                if tid and tid ~= "" then
                    ngx.location.capture("/kill", { args = {tid = tid} })
                end
                return ngx.HTTP_INTERNAL_SERVER_ERROR;
            end
            ngx.print(res.body)
        '
    }

where we make use of HttpHeadersMoreModule, HttpLuaModule, and HttpRdsJsonModule too. When the SQL query timed out, we'll explicitly cancel it immediately. One pitfall here is that you have to add these modules in this order while building Nginx:

Such that, their output filters will work in the reversed order, i.e., first convert RDS to JSON, and then add our X-Mysql-Tid custom header, and finally capture the whole (subrequest) response with the Lua module. You're recommended to use the OpenResty bundle though, it ensures the module building order automatically for you.

[edit] Output Format

This module generates binary query results in a format that is shared among the various Nginx database driver modules like ngx_postgres. This data format is named Resty DBD Stream (RDS).

If you're a web app developer, you may be more interested in

For the HTTP response header part, the 200 OK status code should always be returned. The Content-Type header must be set to application/x-resty-dbd-stream. And the driver generating this response also sets a X-Resty-DBD header. For instance, this module adds the following output header: 

    X-Resty-DBD-Module: drizzle 0.1.0

where 0.1.0 is this module's own version number. This X-Resty-DBD-Module header is optional though.

Below is the HTTP response body format (version 0.0.3):

[edit] RDS Header Part

The RDS Header Part consists of the following fields:

uint8_t

endian type (1 means big-endian and little endian otherwise)

uint32_t

format version (v1.2.3 is represented as 1002003 in decimal)

uint8_t

result type (0 means normal SQL result type, fixed for now)

uint16_t

standard error code

uint16_t

driver-specific error code

uint16_t

driver-specific error string length

u_char *

driver-specific error string data

uint64_t

database rows affected

uint64_t

insert id (if none, 0)

uint16_t

column count

[edit] RDS Body Part

When the column count field in the RDS Header Part is zero, then the whole RDS Body Part is omitted.

The RDS Body Part consists of two sections, Columns and Rows.

[edit] Columns

The columns part consists of zero or more column data. The number of columns is determined by column count field in RDS Header Part.

Each column consists of the following fields

uint16_t

non-zero value for standard column type code and for the column list terminator and zero otherwise.

uint16_t

driver-specific column type code

uint16_t

column name length

u_char *

column name data

[edit] Rows

The rows part consists of zero or more row data, terminated by a 8-bit zero.

Each row data consists of a Row Flag and an optional Fields Data part.

[edit] Row Flag

uint8_t

valid row (1 means valid, and 0 means the row list terminator)

[edit] Fields Data

The Fields Data consists zero or more fields of data. The field count is predetermined by the column number</code) specified in RDS Header Part.

uint32_t

field length ((uint32_t) -1 represents NULL)

u_char *

field data in textual representation), is empty (0) if field length == (uint32_t) -1

[edit] RDS buffer Limitations

On the nginx output chain link level, the following components should be put into a single <code>ngx_buf_t struct:

  • the header
  • each column and the column list terminator
  • each row's valid flag byte and row list terminator
  • each field in each row (if any) but the field data can span multiple bufs.

[edit] Status Code

If the MySQL error code in MySQL's query result is not OK, then a 500 error page is returned by this module, except for the table non-existent error, which results in the 410 Gone error page.

[edit] Caveats

[edit] Trouble Shooting

  • When you see the following error message in error.log: 
        failed to connect: 15: drizzle_state_handshake_result_read:
          old insecure authentication mechanism not supported in upstream, ...
then you may checkout if your MySQL is too old (at least 5.x is required) or your mysql config file explicitly forces the use of old authentication method (you should remove the old-passwords line from your my.cnf and add the line secure_auth 1).
  • When you see the following error message in error.log: 
        failed to connect: 23: Access denied for user 'root'@'ubuntu'
          (using password: YES) while connecting to drizzle upstream, ...
You should check if your MySQL account does have got TCP login access on your MySQL server side. A quick check is to use MySQL's official client to connect to your server: 
        mysql --protocol=tcp -u user --password=password -h foo.bar.com dbname
Note that the --protocol=tcp option is required here, or your MySQL client may use Unix Domain Socket to connect to your MySQL server.

[edit] Known Issues

  • Calling mysql procedures are currently not supported because the underlying libdrizzle library does not support the CLIENT_MULTI_RESULTS flag yet :( But we'll surely work on it.
  • Multiple SQL statements in a single query are not supported due to the lack of CLIENT_MULTI_STATEMENTS support in the underlying libdrizzle library.
  • This module does not (yet) work with the RTSIG event model.

[edit] Installation

You're recommended to install this module as well as HttpRdsJsonModule via the ngx_openresty bundle:

http://openresty.org

The installation steps are usually as simple as ./configure --with-http_drizzle_module && make && make install (But you still need to install the libdrizzle library manually, see http://openresty.org/#DrizzleNginxModule for detailed instructions.

Alternatively, you can compile this module with Nginx core's source by hand:

  • You should first install libdrizzle 1.0 which is now distributed with the drizzle project and can be obtained from https://launchpad.net/drizzle. The latest drizzle7 release does not support building libdrizzle 1.0 separately and requires a lot of external dependencies like Boost and Protobuf which are painful to install. The last version supporting building libdrizzle 1.0 separately is 2011.07.21. You can download it from http://agentzh.org/misc/nginx/drizzle7-2011.07.21.tar.gz . Which this version of drizzle7, installation of libdrizzle 1.0 is usually as simple as 
        tar xzvf drizzle7-2011.07.21.tar.gz
        cd drizzle7-2011.07.21/
        ./configure --without-server
        make libdrizzle-1.0
        make install-libdrizzle-1.0
Ensure that you have the python command point to a python2 interpreter. It's known that on recent : Arch Linux distribution, python is linked to python3 by default, and while running make libdrizzle-1.0 will yield the error 
        File "config/pandora-plugin", line 185
            print "Dependency loop detected with %s" % plugin['name']
                                                     ^
        SyntaxError: invalid syntax
        make: *** [.plugin.scan] Error 1
You can fix this by pointing python to python2.
  • Download the latest version of the release tarball of this module from drizzle-nginx-module file list.
  • Grab the nginx source code from nginx.org, for example, the version 1.2.1 (see nginx compatibility), and then build the source with this module: 
        wget 'http://nginx.org/download/nginx-1.2.1.tar.gz'
        tar -xzvf nginx-1.2.1.tar.gz
        cd nginx-1.2.1/
 
        # if you have installed libdrizzle to the prefix /opt/drizzle, then
        # specify the following environments:
        # export LIBDRIZZLE_INC=/opt/drizzle/include/libdrizzle-1.0
        # export LIBDRIZZLE_LIB=/opt/drizzle/lib
 
        # Here we assume you would install you nginx under /opt/nginx/.
        ./configure --prefix=/opt/nginx \
                    --add-module=/path/to/drizzle-nginx-module
 
        make -j2
        make install

You usually also need HttpRdsJsonModule to obtain JSON output from the binary RDS output generated by this upstream module.

[edit] Compatibility

If you're using MySQL, then MySQL 5.0 ~ 5.5 is required. We're not sure if MySQL 5.6+ work; reports welcome!

This module has been tested on Linux and Mac OS X. Reports on other POSIX-compliant systems will be highly appreciated.

The following versions of Nginx should work with this module:

  • 1.2.x (last tested: 1.2.1)
  • 1.1.x (last tested: 1.1.5)
  • 1.0.x (last tested: 1.0.8)
  • 0.8.x (last tested: 0.8.55)
  • 0.7.x >= 0.7.44 (last tested version is 0.7.67)

Earlier versions of Nginx like 0.6.x and 0.5.x will not work.

If you find that any particular version of Nginx above 0.7.44 does not work with this module, please consider reporting a bug.

[edit] Report Bugs

Although a lot of effort has been put into testing and code tuning, there must be some serious bugs lurking somewhere in this module. So whenever you are bitten by any quirks, please don't hesitate to

  1. create a ticket on the issue tracking interface provided by GitHub,
  2. or send a bug report or even patches to the nginx mailing list.

[edit] Source Repository

Available on github at chaoslawful/drizzle-nginx-module.

[edit] Test Suite

This module comes with a Perl-driven test suite. The test cases are declarative too. Thanks to the Test::Nginx module in the Perl world.

To run it on your side: 

    $ PATH=/path/to/your/nginx-with-echo-module:$PATH prove -r t

Because a single nginx server (by default, localhost:1984) is used across all the test scripts (.t files), it's meaningless to run the test suite in parallel by specifying -jN when invoking the prove utility.

[edit] TODO

  • add the MySQL transaction support.
  • add multi-statement MySQL query support.
  • implement the "drizzle_max_output_size" directive. When the RDS data is larger then the size specified, the module will try to terminate the output as quickly as possible but will still ensure the resulting response body is still in valid RDS format.
  • implement the drizzle_upstream_next mechanism for failover support.
  • add support for multiple "drizzle_query" directives in a single location.
  • implement weighted round-robin algorithm for the upstream server clusters.
  • add the max_idle_time option to the drizzle_server directive, so that the connection pool will automatically release idle connections for the timeout you specify.
  • add the min option to the "drizzle_server" directive so that the connection pool will automatically create that number of connections and put them into the pool.
  • add Unix domain socket support in the drizzle_server directive.
  • make the drizzle_query directive reject variables that have not been processed by a drizzle_process directive. This will pretect us from SQL injections. There will also be an option ("strict=no") to disable such checks.

[edit] Changes

[edit] v0.1.1

  • fixed segmentation faults on 32-bit systems. thanks @榄忎笘姹 and @stefanli for reporting this issue.
  • documented the $drizzle_thread_id variable.
  • added lots of debug outputs (enabled by the --with-debug option while building Nginx or OpenResty), inspired by github issue #10.
  • fixed issues regarding defining global variables in C header files: we should have defined rds_rough_col_type_t as a type rather than a global variable. thanks @濮滃ぇ鐐.
  • documented the python -> python3 pitfall while building libdrizzle 1.0 on at least ArchLinux.
  • fixed the automatic libdrizzle searching algorithm in the config file: now we should look under libdrizzle-1.0/ instead. thanks 鏀涔 (Calio) for reporting this issue.

[edit] Authors

  • chaoslawful (鐜嬫檽鍝) <chaoslawful at gmail dot com>
  • Zhang "agentzh" Yichun (绔犱害鏄) <agentzh at gmail dot com>
  • Piotr Sikora <piotr.sikora at frickle dot com>

[edit] Copyright & License

This module is licenced under the BSD license.

Copyright (C) 2009, 2010, 2011, Taobao Inc., Alibaba Group ( http://www.taobao.com ).

Copyright (C) 2009, 2010, 2011, by Xiaozhe Wang (chaoslawful) <chaoslawful@gmail.com>.

Copyright (C) 2009, 2010, 2011, by Zhang "agentzh" Yichun (绔犱害鏄) <agentzh@gmail.com>.

Copyright (C) 2010, 2011, by FRiCKLE Piotr Sikora <info@frickle.com>.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

[edit] See Also

Retrieved from "http://wiki.nginx.org/index.php?title=HttpDrizzleModule&oldid=2389"