[HECnet] Re: Tops-20 Finger Server Update

I thought I would update everyone with where things stand with the Tops-20 finger server. Johnny and I agreed that, by default, the response to a DECnet finger query is a sequences of records, each no longer than 132 bytes (more typically 90), terminated by a line-feed.   If the remote finger client or operating system can handle larger buffers, then it can connect with optional data=STREAM. Tops-20 will then dump everything in one giant record.  Only the Tops-20 finger client can handle this, although I suspect maybe a VAX client might also be able to do it. I had been making steady progress until I started stress testing it, meaning having a session active on MIM::, TOMMYT::, and VENTI2:: (local), each having a finger command in ready to go and then pushing carriage return on all three as simultaneously as possible. This started generating errors on MIM:: that the "object wasn't available".  What was going on was that the structure of the Tops-20 finger server really wasn't architected to have real time response for that much curiosity. It only opens a single SRV:117 (finger) object at a time, waits for a connection, reads the data, hands it off to an idle finger client fork via a pipe, and then gets a new SRV:117 object. In other words, it isn't until the finger client is started with the connection redirected to DECnet that the server is ready to accept another connection.  That has what I would consider to be noticeable latency, particularly on failure.    An error doesn't really matter for SMTP as it is a background task and just tries again, later. An interactive finger on the other hand, has a user sitting there waiting for a response, so it seemed to me that this wasn't really going to cutit. I took the model of the Tops-20 FAL server, which has a single control fork, looking for illness in sub-forks, all of which open their own FAL server object.  The new finger controller now starts separate FNGSRV sub-server forks, creating a FINGER sub-fork for each, gets all the communications lined up, and starts all the FNGSRV sub-forks to listen for connections. This has the advantage of not clobbering the system on FNGSRV startup because resources are gotten or creating sequentially, so there isn't much for a FNGSRV sub-fork to do except wait for a connection and manage its own single FINGER sub-fork. Startup resource allocation looks like this:      [Fork FNGSRV opening PIP:1;RECORD-LENGTH:200 for writing]      [Fork FNGSRV opening PIP:1.1 for reading]      [Fork FNGSRV opening SRV:117 for reading, writing]      [Fork FNGSRV opening PIP:2;RECORD-LENGTH:200 for writing]      [Fork FNGSRV opening PIP:2.2 for reading]      [Fork FNGSRV opening SRV:117 for reading, writing]      [Fork FNGSRV opening PIP:3;RECORD-LENGTH:200 for writing]      [Fork FNGSRV opening PIP:3.3 for reading]      [Fork FNGSRV opening SRV:117 for reading, writing] The resulting JFN's being:          JFN  File Mode      Bytes(Size)           2   FNGSRV.EXE.330             Read, Execute           3   FINGER.EXE.116             Read, Execute           15  PIP:1;RECORD-LENGTH:200    Append          0.(8)           16  PIP:1.1                    Read            0.(8)           17  SRV:117                    Read, Append   0.(8)           20  PIP:2;RECORD-LENGTH:200    Append          0.(8)           21  PIP:2.2                    Read            0.(8)           22  SRV:117                    Read, Append   0.(8)           23  PIP:3;RECORD-LENGTH:200    Append          0.(8)           24  PIP:3.3                    Read            0.(8)           25  SRV:117                    Read, Append   0.(8) The resulting fork structure is:       => FNGSRV (2): HALT at STARTS+13, 0.02719             Fork 12:HALT at 0, 0.00018                Fork 13: HALT at 0, 0.00016             Fork 10:HALT at 0, 0.00012                Fork 11: HALT at 0, 0.00012             Fork 6: HALT at 0, 0.00008                Fork 7: HALT at 0, 0.00007 So fork 2 is the finger server controller, forks 12, 10, and 6 are finger server sub-forks, and forks 13, 11, and 7 are the respective Tops-20 finger clients.  Times are in tens of microseconds, the maximum resolution that Tops-20 supports.  What can be seen is that fork creation is happening in sub-millisecond time.  This was notthe case in the 1980's with KL10's (I /think/), and modifications were necessary to Tops-20 and the EXEC to capture the increased resolution. I guess I'll have another version ready in about two weeks. _______________________________________________ HECnet mailing list -- hecnet(a)lists.dfupdate.se To unsubscribe send an email to hecnet-leave(a)lists.dfupdate.se