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| 2 | |
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| 3 | Steps in adding a request to the server: |
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| 4 | |
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| 5 | 1) select a request name and number |
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| 6 | src/proto/pvfs2-req-proto.h |
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| 7 | |
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| 8 | 2) add a request and response struct |
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| 9 | src/proto/pvfs2-req-proto.h |
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| 10 | add entry to unions: PVFS_server_req and PVFS_server_resp |
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| 11 | |
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| 12 | 2a) add endecode functions if needed |
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| 13 | src/proto/endecode-funcs.h |
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| 14 | for each of these you add or modify you must also |
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| 15 | add a stub in include/pvfs2-encode-stubs.h |
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| 16 | |
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| 17 | 2b) update the protocol version number |
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| 18 | src/proto/pvfs2-req-proto.h |
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| 19 | increment PVFS2_PROTO_MINOR, assuming that the |
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| 20 | addition of this new request does not break backwards |
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| 21 | compatibility for other request types |
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| 22 | |
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| 23 | 3) add entries to decode/encode functions |
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| 24 | src/proto/PINT-le-bytefield.c |
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| 25 | lebf_initialize() - need code here to set up a request so it |
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| 26 | can be encoded and expression for extra message size if any |
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| 27 | lebf_encode_req() |
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| 28 | lebf_encode_resp() |
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| 29 | lebf_decode_req() |
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| 30 | lebf_decode_resp() |
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| 31 | lebf_decode_rel() (2 places) |
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| 32 | In this last entry, we free any resources allocated during |
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| 33 | decode - specifically array items |
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| 34 | This does not free resources allocated by SM code |
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| 35 | |
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| 36 | 4) add request specific scratch space to PINT_server_op |
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| 37 | src/server/pvfs2-server.h |
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| 38 | PINT_server_op -- only if required |
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| 39 | |
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| 40 | 5) write state machine -- se details below |
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| 41 | src/server/<reqname>.sm |
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| 42 | each state machine added must have a delcaration in |
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| 43 | src/server/pvfs2-server.h |
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| 44 | |
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| 45 | 6) update request scheduler |
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| 46 | src/server/request-scheduler/request-scheduler.c |
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| 47 | PINT_req_sched_target_handle() |
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| 48 | |
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| 49 | 7) add entry to server operation parameters table |
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| 50 | src/server/pvfs2-server.c |
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| 51 | init_req_table -- see src/server/prelude.sm |
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| 52 | prelude_perm_check() |
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| 53 | |
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| 54 | 8) add entry in final response state machine |
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| 55 | src/server/final-response.sm |
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| 56 | s_req_resp_type_map |
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| 57 | |
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| 58 | |
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| 59 | |
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| 60 | Writing State Machines |
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| 61 | |
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| 62 | Every state machine passes a PINT_server_op in to each state function. |
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| 63 | state machine initialized in src/server/pvfs2-server.c |
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| 64 | server_state_machine_start |
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| 65 | gets the s_op set up |
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| 66 | decodes request message |
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| 67 | sets s_op->req, s_op->resp |
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| 68 | |
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| 69 | Each state machine must first run the pvfs2_prelude_sm |
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| 70 | reads the attribs of the target object, if appropriate to s_op->attr |
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| 71 | does basic permission checking |
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| 72 | posts request to the scheduler |
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| 73 | |
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| 74 | State machines typically submit jobs, defined in |
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| 75 | src/io/job/job.h |
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| 76 | |
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| 77 | Each state machine must run the pvfs2_final_response_sm |
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| 78 | releases request from the scheduler |
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| 79 | sends response to the client |
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| 80 | s_op->resp must be filled in |
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| 81 | return status in js_p->error_code |
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| 82 | |
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| 83 | Cleanup must free any memory allocated by SM code |
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| 84 | |
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| 85 | State functions return 0 or 1 on error-free completion, |
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| 86 | 0 indicates an asynchronous call has been made and must be waited for |
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| 87 | 1 indicates no async call was made and should proceed to next state |
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| 88 | <0 indicates an error - use PVFS_EXXX codes defined in |
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| 89 | include/pvfs2-types.h |
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| 90 | |
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