postgresql मणि async . का उपयोग करना

pg लाइब्रेरी PostgreSQL के एसिंक्रोनस एपीआई के लिए पूर्ण समर्थन प्रदान करती है। मैंने एक उदाहरण जोड़ा है samples/ . के लिए इसका उपयोग कैसे करें निर्देशिका:

#!/usr/bin/env ruby

require 'pg'

# This is a example of how to use the asynchronous API to query the
# server without blocking other threads. It's intentionally low-level;
# if you hooked up the PGconn#socket to some kind of reactor, you
# could make this much nicer.

TIMEOUT = 5.0 # seconds to wait for an async operation to complete
CONN_OPTS = {
    :host     => 'localhost',
    :dbname   => 'test',
    :user     => 'jrandom',
    :password => 'banks!stealUR$',
}

# Print 'x' continuously to demonstrate that other threads aren't
# blocked while waiting for the connection, for the query to be sent,
# for results, etc. You might want to sleep inside the loop or 
# comment this out entirely for cleaner output.
progress_thread = Thread.new { loop { print 'x' } }

# Output progress messages
def output_progress( msg )
    puts "\n>>> #{msg}\n"
end

# Start the connection
output_progress "Starting connection..."
conn = PGconn.connect_start( CONN_OPTS ) or 
    abort "Unable to create a new connection!"
abort "Connection failed: %s" % [ conn.error_message ] if
    conn.status == PGconn::CONNECTION_BAD

# Now grab a reference to the underlying socket so we know when the
# connection is established
socket = IO.for_fd( conn.socket )

# Track the progress of the connection, waiting for the socket to 
# become readable/writable before polling it
poll_status = PGconn::PGRES_POLLING_WRITING
until poll_status == PGconn::PGRES_POLLING_OK ||
      poll_status == PGconn::PGRES_POLLING_FAILED

    # If the socket needs to read, wait 'til it becomes readable to
    # poll again
    case poll_status
    when PGconn::PGRES_POLLING_READING
        output_progress "  waiting for socket to become readable"
        select( [socket], nil, nil, TIMEOUT ) or
            raise "Asynchronous connection timed out!"

    # ...and the same for when the socket needs to write
    when PGconn::PGRES_POLLING_WRITING
        output_progress "  waiting for socket to become writable"
        select( nil, [socket], nil, TIMEOUT ) or
            raise "Asynchronous connection timed out!"
    end

    # Output a status message about the progress
    case conn.status
    when PGconn::CONNECTION_STARTED
        output_progress "  waiting for connection to be made."
    when PGconn::CONNECTION_MADE
        output_progress "  connection OK; waiting to send."
    when PGconn::CONNECTION_AWAITING_RESPONSE
        output_progress "  waiting for a response from the server."
    when PGconn::CONNECTION_AUTH_OK
        output_progress "  received authentication; waiting for " +
                        "backend start-up to finish."
    when PGconn::CONNECTION_SSL_STARTUP
        output_progress "  negotiating SSL encryption."
    when PGconn::CONNECTION_SETENV
        output_progress "  negotiating environment-driven " +
                        "parameter settings."
    end

    # Check to see if it's finished or failed yet
    poll_status = conn.connect_poll
end

abort "Connect failed: %s" % [ conn.error_message ] unless 
    conn.status == PGconn::CONNECTION_OK

output_progress "Sending query"
conn.send_query( "SELECT * FROM pg_stat_activity" )

# Fetch results until there aren't any more
loop do
    output_progress "  waiting for a response"

    # Buffer any incoming data on the socket until a full result 
    # is ready. 
    conn.consume_input
    while conn.is_busy
        select( [socket], nil, nil, TIMEOUT ) or
            raise "Timeout waiting for query response."
        conn.consume_input
    end

    # Fetch the next result. If there isn't one, the query is 
    # finished
    result = conn.get_result or break

    puts "\n\nQuery result:\n%p\n" % [ result.values ]
end

output_progress "Done."
conn.finish

if defined?( progress_thread )
    progress_thread.kill
    progress_thread.join
end

मेरा सुझाव है कि आप पर प्रलेखन पढ़ें। PQconnectप्रारंभ फ़ंक्शन और एसिंक्रोनस कमांड प्रोसेसिंग PostgreSQL मैनुअल का अनुभाग, और उसके बाद ऊपर दिए गए नमूने के साथ इसकी तुलना करें।

मैंने पहले EventMachine का उपयोग नहीं किया है, लेकिन अगर यह आपको पढ़ने योग्य/लिखने योग्य होने पर सॉकेट और कॉलबैक पंजीकृत करने देता है, तो मुझे लगता है कि इसमें डेटाबेस कॉल को एकीकृत करना काफी आसान होगा।

मैं इवेंट कोड को साफ करने के लिए फाइबर का उपयोग करने पर इल्या ग्रिगोरिक का लेख async API का उपयोग करना आसान बनाने के लिए, लेकिन यह एक तरीका है। मेरे पास एक टिकट है खुला यदि आप इसे स्वयं करने के लिए इच्छुक/प्रेरित हैं तो इसे ट्रैक करने के लिए।