This patch equips init with the ability to act as a server that forwards
session requests to its children. Session requests can be routed
depending of the requested service type and the session label
originating from init's parent.
The feature is configured by one or multiple <service> nodes hosted in
init's <config> node. The routing policy is selected by via the regular
server-side policy-selection mechanism, for example:
<config>
...
<service name="LOG">
<policy label="noux">
<child name="terminal_log" label="important"/>
</policy>
<default-policy> <child name="nitlog"/> </default-policy>
</service>
...
</config>
Each policy node must have a <child> sub node, which denotes name of the
server with the 'name' attribute. The optional 'label' attribute defines
the session label presented to the server, analogous to how the
rewriting of session labels works in session routes. If not specified,
the client-provided label is presented to the server as is.
Fixes#2247
This patch removes the formerly built-in policy of responding to
resource requests with handing out slack quota. Instead, resource
requests have to be answered by an update of the init configuration with
adjusted quota values.
Note that this patch may break run scripts that depend on init's
original policy. Those run scripts may be adjusted by increasing the
quota for the components that use to inflate their RAM usage during
runtime such that the specified quota suffices for the entire lifetime
of the component.
This patch improves init's dynamic reconfigurability with respect to
adjustments of the RAM quota assigned to the children.
If the RAM quota is decreased, init withdraws as much quota from the
child's RAM session as possible. If the child's RAM session does not
have enough available quota, a resource-yield request is issued to
the child. Cooparative children may respond to such a request by
releasing memory.
If the RAM quota is increased, the child's RAM session is upgraded.
If the configuration exceeds init's available RAM, init re-attempts
the upgrade whenever new slack memory becomes available (e.g., by
disappearing other children).
This patch enables init to apply changes of any server's <provides>
declarations in a differential way. Servers can in principle be extended
by new services without re-starting them. Of course, changes of the
<provides> declarations may affect clients or would-be clients as this
information is taken into account for the session routing.
The optional 'version' attribute allows for the forced restart of a
child with an otherwise unmodified start node. The specified value is
also reflected in the state report.
This patch covers the resolution of the ROM route for child binaries
via the generic label-rewriting mechanics. Now, the <binary> node has
become merely sytactic sugar for a route like the following:
<start name="test"/>
<route>
<service name="ROM" unscoped_label="test">
<parent label="test-binary-name"/> </service>
...
</route>
...
</start>
A change of the binary name has an effect on the child's ROM route to
the binary and thereby implicitly triggers a child restart due to the
existing re-validation of the routing.
This patch improves the accuracy of init's quota-saturation feature
(handing out all slack quota to a child by specifying an overly high RAM
quota for the child) and makes the RAM preserved by init configurable.
The preservation is specified as follows:
! <config>
! ...
! <resource name="RAM" preserve="1M"/>
! ...
! </config>
If not specified, init has a reasonable default of 160K (on 32 bit) and
320K (on 64 bit).
This patch lets init apply configuration changes to a running scenario
in a differential way. Children are restarted if any of their session
routes change, new children can be added to a running scenario, or
children can deliberately be removed.
Furthermore, the new version of init is able to propagate configuration
changes (modifications of <config> nodes) to its children without
restarting them.
