Computations from an external library cannot be linked directly with
a Motr instance. The library is supposed to have an entry function named
void motr_lib_init(void). All the computations in the library must
have the following signature:
int comp(struct m0_buf *args, struct m0_buf *out,
struct m0_isc_comp_private *comp_data, int *rc)
See demo/libdemo.c for examples.
With spiel command (see spiel/spiel.h and demo/util.h) the library
can be loaded with any running Motr instance. A helper function
m0_isc_lib_register takes the library path which is (IMPORTANT!)
expected to be the same across all the nodes running Motr.
m0iscreg utility takes the path as an input and loads the library
into all the remote Motr instances.
On successful loading of the library, the output will look like this:
$ m0iscreg -e 192.168.180.171@tcp:12345:4:1 \
-x 192.168.180.171@tcp:12345:1:1 \
-f 0x7200000000000001:0x2c \
-p 0x7000000000000001:0x50 $PWD/libdemo.so
m0iscreg success
The four options are standard ones to connect to Motr:
$ m0iscreg -h Usage: m0iscreg OPTIONS libpath -e <addr> endpoint address -x <addr> ha-agent (hax) endpoint address -f <fid> process fid -p <fid> profile fid
The values for them can be taken from the output of hctl status
command. (We'll refer to them as <motr-opts> below.)
Note: m0iscreg utility can be used to load any future ISC-library
without modifications.
Currently, we demonstrate three simple computations: ping, min and
max. m0iscdemo utility can be used to invoke the computations and
see the result:
$ m0iscdemo -h Usage: m0iscdemo OPTIONS COMP OBJ_ID LEN Supported COMPutations: ping, min, max OBJ_ID is two uint64 numbers in hi:lo format (dec or hex) LEN is the length of object (in KiB)
Following are the steps to run the demo.
This functionality pings all the ISC services spanned by the object units. For each unit a separate ping request is sent, so the utility prints "Hello-World@<service-fid>" reply each of these requests.
Here is an example for the object with 1MB units:
$ m0iscdemo <motr-opts> ping 123:12371 4096 Hello-world @192.168.180.171@tcp:12345:2:2 Hello-world @192.168.180.171@tcp:12345:2:2 Hello-world @192.168.180.171@tcp:12345:2:2 Hello-world @192.168.180.171@tcp:12345:2:2
Note: the object length (or the amount to read) must be specified, as Motr does not store the objects lengths in their metadata. In the example above, 4MB length was specified for the object with 1MB units, so 4 ping requests were sent and, as result, 4 replies were printed as a result.
The cluster configuration in the above example consisted of a single node only, so all the units were located on the same node. That's why the endpoints addresses in the replies are identical.
Write an object with a real numbers strings delimited by the newline. The min/max in-storage computation can then be done on such object:
$ m0iscdemo <motr-opts> max 123:12371 4096 idx=132151 val=32767.627900 $ m0iscdemo <motr-opts> min 123:12371 4096 idx=180959 val=0.134330