16
Using Edge and Origin Servers
Connecting to a cluster of edge servers
When edge servers are configured into a cluster, the clients probably do not know that edge
servers are present and servicing their connection requests. This is a secure and desirable
strategy for disguising the address of the origin server. A different scheme for connecting
clients to Flash Media Server is required.
With a cluster of proxies in place, when the client attempts to connect to Flash Media Server,
the call to the
NetConnection.connect()
method uses the User Datagram Protocol (UDP)
to initiate a local broadcast of an FPAD message. The other edge servers in the network that
receive the FPAD message respond to the client. The client automatically chooses the edge to
connect to. The edge then makes the connection to the origin server. This brief scenario
describes how a cluster of explicit proxies services outgoing connections to an origin server
Enrolling proxy servers in the cluster
Each proxy or edge in a cluster is dynamically assigned a numeric ID when it starts up. The
edge broadcasts a message announcing its presence. All edges in the cluster that are currently
running receive this message. Each edge responds with a message indicating its ID. The ID is
assigned from a sequence of numbers: 0, 1, 2, …, N-1, where N is the number of edges
allowed in the cluster.
The edge that is starting up waits for all of the responses to be received, then assigns itself the
first ID not found in the sequence. When an edge server shuts down, it broadcasts a message
announcing its exit from the cluster.
Accessing applications through an edge cluster
To maximize the conservation of network and bandwidth resources, Flash Media Server
directs to the same edge in a cluster all clients that request a connection to an application. All
the edge servers in the cluster automatically compute an affinity value based on the URI that
the client wishes to connect to. When a client broadcasts an auto discovery process message to
discover the available edges, an affinity value is returned in a message back to the client. After
the client receives responses from all of the currently active edges in the cluster, it
automatically selects the edge with the lowest affinity value to connect to.
The affinity value is dynamic; it adjusts to the increasing or decreasing workload of
connection requests and distributes the workload across edges in the cluster. For instance,
consider how the notion of affinity value applies in a cluster of three edges: edge0, edge1, and
edge2. As the workload on edge0 starts to peak, its connections start to spill over to edge1.
Both have a computed affinity value of 1. As edge1's load increases, its connections start to
spill over to edge2. Both have a computed affinity value of 2. As edge2's load increases, its
connections start to spill over back to edge0.
Summary of Contents for FIREWORKS 2-USING FIREWORKS
Page 1: ...Using Flash Media Server Edge Servers ...
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