This document discusses socket utilization in Node.js and how to improve it. It notes that while Node's HTTP module supports keep-alive, connections are only kept alive if there are pending requests, otherwise each request closes the connection. This can lead to high numbers of TIME_WAIT sockets and potential crashes. It recommends using libraries like request or keep-alive-agent to better manage sockets, and tuning options like maxSockets and idleTimeout. Tests show a keep-alive agent can increase throughput, response time, and transactions per second while avoiding issues from closed connections. Upgrading Node can also improve socket management across multiple hosts.

1. SOCKET UTILIZATION IN
NODE.JS
Akhilesh Gupta
@agupta03

2. Inefficient use of TCP sockets: Is HTTP keep-alive working?

3. Node’s HTTP module supports keep-alive

4. But there is a catch!

5. TCP Connection kept alive only if
PENDING requests in agent queue

6. If requests go out one-by-one
Connection closed each time

7. High QPS/Low Latency
High time-wait sockets
Eventual node CRASH
Houston, we’ve had a problem here!

8. NPM Libraries to the rescue!

9. mikeal/request : forever module
ceejbot/keep-alive-agent
TBEDP/agentkeepalive

10. TUNING UP YOUR F-35!
Monitor time_wait sockets
!
“If you can’t measure it, you can’t fix it”

11. TUNING UP YOUR F-35!
maxSockets
!
Concurrent sockets agent can have open/host

12. TUNING UP YOUR F-35!
idleTimeout
!
Time for which connection is unused before it is discarded

13. THE ENGINEERING
HAPPINESS GRAPH

14. Normal agent:
Keep alive agent (30 seconds):
Transactions:
60000 hits!
Availability:
100.00 %!
Elapsed time:
46.53 secs!
Data transferred:
14.88 MB!
Response time:
0.05 secs!
Transaction rate:
1289.49 trans/sec!
Throughput:
0.32 MB/sec!
Concurrency:
59.81!
Successful transactions:60000!
Failed transactions:
0!
Longest transaction:
0.45!
Shortest transaction:
0.00
Transactions:
60000 hits!
Availability:
100.00 %!
Elapsed time:
29.70 secs!
Data transferred:
14.88 MB!
Response time:
0.03 secs!
Transaction rate:
2020.20 trans/sec!
Throughput:
0.50 MB/sec!
Concurrency:
59.84!
Successful transactions:60000!
Failed transactions:
0!
Longest transaction:
0.15!
Shortest transaction:
0.01

15. TUNING UP YOUR F-35!
Upgrade to Node 0.5.3+
!
Agent holds sockets for any number of hosts