Yamcs Cascading Link¶

Class Name¶

org.yamcs.cascading.YamcsLink

In the examples/cascading directory of the main yamcs repository there is a configuration with two Yamcs instances upstream and downstream demonstrating the cascading functionality.

Configuration Options¶

upstreamName (string)

Required. The name of the upstream Yamcs server. The name is used on the local Yamcs for the command history entries and for the system (/yamcs) parameters.

yamcsUrl (string)

Required. The URL to connect to the upstream Yamcs server; The URL has to include http or https.

username (string)

Username to connect to the upstream Yamcs server (if authentication is enabled); has to be set together with password.

password (string)

Password to connect to the upstream Yamcs server (if authentication is enabled); has to be set together with username.

upstreamInstance (string)

Required. The instance of Yamcs on the upstream server.

verifyTls (boolean)

If the connection is over TLS (when yamcsUrl starts with https), this option can enable/disable the verification of the server certificate against local accepted CA list. Default: true

upstreamProcessor (string)

The processor to connect to on the upstream Yamcs server. Default: realtime

tm (boolean)

Subscribe telemetry containers (packets). The list of containers (packets) has to be specified using the containers option. Default: true

containers (list of strings)

Required if tm is true. The list of containers(packets) to subscribe to. The list has to contain fully qualified names of containers. At this moment both the local (downstream) MDB and the upstream MDB have to contain definitions for the containers specified in this list. However, the local MDB can contain a more refined version. For example the upstream MDB may define the container with just the header or a few parameters whereas the local MDB may define it in full and additionally other derived containers.

tmRealtimeStream (string)

Stream to which the TM packets will be sent. Default: "tm_realtime".

tmArchive (boolean)

Enables TM archival. Default: true.

tmArchiveStream (string)

Stream to which the TM packets will be archived. Default: "tm_dump".

gapFillingInterval (integer)

Number of seconds between each archive gap filling attempt. Default: 300.

pp (boolean)

Subscribe parameters (pp stands for "processed parameters"). The list of parameters has to be specified using the parameters option. Default: true

parameters (list of strings)

Required if pp is true. The list of parameters has to subscribe to. The list should contain fully qualified name of parameters which have to be present both in the local MDB and in the remote(upstream) MDB. Wildcards using glob patterns can be used.

The requirement to have the parameters in both MDBs is a a current limitation due to the fact that we do not add parameters dynamically to the MDB. One exception is the Yamcs system parameters (those in the /yamcs namespace) - these do not have to be present in the local MDB, they are created on the fly.

The /yamcs system parameters will be renamed such that /yamcs/a/b/c/parameter_name is saved in the local archive as /yamcs/upstreamName_a/b/c/parameter_name.

ppRealtimeStream (string)

Stream to which the parameter packets will be sent. Default: "pp_realtime".

tc (boolean)

Allow to send TC and subscribe to command history.

All the command history entries received from the upstream server will be renamed to the shape yamcs<uspstreamName>_OriginalEntryName.

Exception make those added in the keepUpstreamAcks configuration.

Default: true

keepUpstreamAcks (list of strings)

List of command acknowledgments names received from the upstream server to keep unmodified.

Default is "ccsds-seqcount" - this key is used by one of the CCSDS links to set the sequence count associated to the command and required in the simulation configuration to be able to verify the command execution (because the sequence count is reported in returning telemetry containing the command execution status).

event (boolean)

Subscribe to realtime events. The events on the upstream server will be mirrored to the local server.

Default: true

eventRealtimeStream (string)

Stream to which the events will be sent. Default: "events_realtime".

connectionAttempts (integer)

How many times to attempt reconnection if the connection fails. Reconnection will only be attempted once if the authentication fails.

Link disable/enable is required to reattempt the connection once this number has passed.

reconnectionDelay (integer)

If the connection fails or breaks, the time (in milliseconds) to wait before reconnection.

commandMapping (list of CommandMapData)

This option is used to configure the mapping between the downstream command names and the upstream command names. Each entry in the list can have the following structure:

type (string)

Required. Can take one of the values:

• DIRECT: maps all the arguments in the downstream command directly onto the arguments in the upstream commands. The command names can be changed using the local and upstream configuration options below.

• EMBEDDED_BINARY: encodes the downstream command to binary and sets the binary as an argument in the upstream command. The argument configuration option below is the name of the argument of the downstream command.

• DEFAULT: this is the default behavior before Yamcs 5.8.7; it assumes that upstream and downstream MDBs have the same commands.

local (string)

Required if type is DIRECT or EMBEDDED_BINARY Downstream path to be mapped. Can be either a path (ending with /) to a downstream subsystem or a specific downstream command.

upstream (string)

Required if type is DIRECT or EMBEDDED_BINARY Upstream path to be mapped. If the type is DIRECT and local is a path, then this can also be a path to an upstream subsystem. If local and upstream are paths, then the upstream command is found by replacing the path specified in local with the path specified in upstream

argument (string)

Required if type is EMBEDDED_BINARY. Argument in the upstream command that will be used for the embedded binary downstream command.

The list of commandMapping is checked in order - the first entry which matches the local entry will be used. If no entry matches the sent command, the command will fail.

failCommandIfNoMappingMatches (boolean)

Since Yamcs 5.9.7. If no mapping was found for the local command, setting this option to true will cause immediately the command to fail. If set to false (default) the command will not fail immediately and the link manager will try to send it on another link (if available).