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Code Issues Releases Wiki Activity

[#278,!162] Minor cleanup in Congestion Handling per review.

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This commit is contained in:
Marcin Siodelski
2018-12-10 17:17:31 +01:00
parent 34239554b8
commit 1f94eaa3d8
1 changed files with 11 additions and 11 deletions
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doc/devel/congestion-handling.dox
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@@ -6,7 +6,7 @@
/** /**
@page congestionHandling Congestion Handling in Kea DHCP4/DHCP6 @page congestionHandling Congestion Handling in Kea DHCP Servers
@section background What is Congestion? @section background What is Congestion?
Congestion occurs when servers are subjected to client queries Congestion occurs when servers are subjected to client queries
@@ -27,12 +27,12 @@ simultaneously need leases such as recovery after a network outage.
@section introduction Congestion Handling Overview @section introduction Congestion Handling Overview
Kea 1.5 introduces a new feature referred to as Congestion Handling. The Kea 1.5.0 introduces a new feature referred to as Congestion Handling. The
goal of Congestion Handling is to help the servers mitigate the peak goal of Congestion Handling is to help the servers mitigate the peak
in traffic by fulfilling as many of the most relevant requests as possible in traffic by fulfilling as many of the most relevant requests as possible
until it subsides. until it subsides.
Prior to Kea 1.5, kea-dhcp4 and kea-dhcp6 read inbound packets directly Prior to Kea 1.5.0, Kea DHCP servers read inbound packets directly
from the interface sockets in the main application thread. This meant that from the interface sockets in the main application thread. This meant that
packets waiting to be processed were held in socket buffers themselves. Once packets waiting to be processed were held in socket buffers themselves. Once
these buffers fill any new packets are discarded. Under swamped conditions these buffers fill any new packets are discarded. Under swamped conditions
@@ -43,12 +43,12 @@ the FIFO socket buffers become increasingly stale.
Congestion Handling offers the ability to configure the server to use a Congestion Handling offers the ability to configure the server to use a
separate thread to read packets from the interface socket buffers. As the separate thread to read packets from the interface socket buffers. As the
thread reads packets from the buffers they are added to an internal "packet thread reads packets from the buffers they are added to an internal "packet
queue". The server's main application thread process packets from this queue queue". The server's main application thread processes packets from this queue
rather than the socket buffers. By structuring it this way, we've introduced rather than the socket buffers. By structuring it this way, we've introduced
a configurable layer which can make decisions on which packets to process, a configurable layer which can make decisions on which packets to process,
how to store them, and the order in which they are processed by the server. how to store them, and the order in which they are processed by the server.
The default packet queue implementation for both kea-dhcp4 and kea-dhcp6 The default packet queue implementation for both Kea DHCPv4 and DHCPv6 servers
is a simple ring buffer. Once it reaches capacity, new packets get added to is a simple ring buffer. Once it reaches capacity, new packets get added to
the back of queue by discarding packets from the front of queue. Rather than the back of queue by discarding packets from the front of queue. Rather than
always discarding the newest packets, we now always discard the oldest always discarding the newest packets, we now always discard the oldest
@@ -87,7 +87,7 @@ chapter for DHCPv6.
The two primary functions of interest are: The two primary functions of interest are:
-# isc::dhcp::PacketQueue::enqueuePacket() - This function is invoked by -# isc::dhcp::PacketQueue::enqueuePacket() - This function is invoked by
the receiver thread each time a packet has been read from a interface the receiver thread each time a packet has been read from an interface
socket buffer and should be added to the queue. It is passed a pointer to socket buffer and should be added to the queue. It is passed a pointer to
the unpacked client packet (isc::dhcp::Pkt4Ptr or isc::dhcp::Pkt6Ptr), and the unpacked client packet (isc::dhcp::Pkt4Ptr or isc::dhcp::Pkt6Ptr), and
a reference to the isc::dhcp::SocketInfo describing the interface socket a reference to the isc::dhcp::SocketInfo describing the interface socket
@@ -116,8 +116,8 @@ isc::util::thread::Mutex::Locker).
-# Its efficiency (or lack thereof) will have a direct impact on server -# Its efficiency (or lack thereof) will have a direct impact on server
performance. You will have to consider the dynamics of your deployment performance. You will have to consider the dynamics of your deployment
to determine where the trade-off between the volume of packets responded to determine where the trade-off lies between the volume of packets responded
to versus preferring to respond to some subset of those packets lies. to and preferring to respond to some subset of those packets.
@subsection packet-queue-derivation-factory Defining a Factory @subsection packet-queue-derivation-factory Defining a Factory
@@ -160,7 +160,7 @@ to construct a queue instance.
@subsection packet-queue-derivation-example An Example @subsection packet-queue-derivation-example An Example
Let's suppose you wish develop a queue for DHCPv4 and your implementation Let's suppose you wish to develop a queue for DHCPv4 and your implementation
requires two configurable parameters: capacity and threshold. Your class requires two configurable parameters: capacity and threshold. Your class
declaration might look something like this: declaration might look something like this:
@@ -293,7 +293,7 @@ to look something like this:
"hooks-libraries": [ "hooks-libraries": [
{ {
# Loading your hook library! # Loading your hook library!
"library": "/somepath/lib//libyour_packet_queue.so" "library": "/somepath/lib/libyour_packet_queue.so"
} }
# any other hook libs # any other hook libs
@@ -431,7 +431,7 @@ Server configuration for kea-dhcp6:
"hooks-libraries": [ "hooks-libraries": [
{ {
# Loading your hook library! # Loading your hook library!
"library": "/somepath/lib//libyour_packet_queue.so" "library": "/somepath/lib/libyour_packet_queue.so"
} }
# any other hook libs # any other hook libs