ZenMonitor v1.0.0 ZenMonitor.Local.Tables View Source

ZenMonitor.Local.Tables owns tables that are shared between multiple ZenMonitor.Local components.

See nodes/0 and references/0 for more information.

Link to this section Summary

Functions

Returns a specification to start this module under a supervisor

Invoked when the server is started. start_link/3 or start/3 will block until it returns

Nodes holds cached information about remote node compatibility

References holds the set of authoritative monitor references

Link to this section Functions

Returns a specification to start this module under a supervisor.

See Supervisor.

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

args is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning {:ok, state, {:continue, continue}} is similar to {:ok, state} except that immediately after entering the loop the c:handle_continue/2 callback will be invoked with the value continue as first argument.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

  • The GenServer is disabled by configuration but might be enabled later.
  • An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

Nodes holds cached information about remote node compatibility

This information is stored in one of the following structures:

For compatible nodes { remote_node, :compatible } ^—-key—-^ ^—value—^

For incompatible nodes { remote_node, {:incompatible, enforce_until, attempts} } ^—-key—-^ ^———————-value————————-^

enforce_until is the time (as reported by System.monotonic_time(:milliseconds)) after which this cache entry should no longer be enforced.

attempts is the number of consecutive connect attempts that have failed, this value is useful for calculating geometric backoff values

Link to this function references() View Source
references() :: :ets.tid()

References holds the set of authoritative monitor references

These references are stored in this structure:

{ {subscriber_pid, monitor_reference}, {remote_node, remote_pid} } ^——————-key————————-^ ^—————value————^

There is a compound key of {subscriber_pid, monitor_reference} this allows for lookup of a given reference (if the subscriber is known, by convention it will be the calling process, self()) or the retrieval of all active monitors for a subscriber.