Definition
Initial (dirty) discovery of members. Used to detect the coordinator (oldest member), either by mcasting PING requests to an IP MCAST address or connecting to a GossipRouter.
Each member responds with a packet {C, A}, where C=coordinator's address and A=own address. After milliseconds or replies, the joiner determines the coordinator from the responses, and sends a JOIN request to it (handled by GMS). If nobody responds, we assume we are the first member of a group.
Unlike TCPPING, PING employs dynamic discovery, meaning that the member does not have to know in advance where other group memebers are.
Configuration Example
Configuration example for IP MULTICAST.
<PING timeout="3000" num_initial_members="3" ></PING>
Configuration Parameters
| Name | Description |
|---|---|
| break_on_coord_rsp | Return from the discovery phase as soon as we have 1 coordinator response |
| discovery_timeout | Time (in ms) to wait for our own discovery message to be received. 0 means don't wait. If the discovery message is not received within discovery_timeout ms, a warning will be logged |
| id | Give the protocol a different ID if needed so we can have multiple instances of it in the same stack |
| level | Sets the logger level (see javadocs) |
| name | Give the protocol a different name if needed so we can have multiple instances of it in the same stack |
| num_initial_members | Minimum number of initial members to get a response from. Default is 2 |
| num_initial_srv_members | Minimum number of server responses (PingData.isServer()=true). If this value is greater than 0, we'll ignore num_initial_members |
| num_ping_requests | Number of discovery requests to be sent distributed over timeout. Default is 2 |
| return_entire_cache | Whether or not to return the entire logical-physical address cache mappings on a discovery request, or not. Default is false, except for TCPPING |
| stats | Determines whether to collect statistics (and expose them via JMX). Default is true |
| timeout | Timeout to wait for the initial members. Default is 3000 msec |
See also Protocol Configuration Common Parameters.
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