/Experiment ODB tree

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Creating the /Experiment tree

The /Experiment ODB tree is created automatically when the ODB is first created.

Purpose

The /Experiment ODB tree contains information relevent to the experiment. Other optional keys are added by mhttpd or by the user to customize their experiment.

Examples

When initially created, the /Experiment tree contains the following keys:

[local:midas:S]/>ls -lrt /experiment
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
Experiment                      DIR
   Name                         STRING  1     32    14s  0   RWD  midas
   Buffer sizes                 DIR
       SYSMSG                   DWORD   1     4     11h  0   RWD  100000
   Security                     DIR
       Enable non-localhost RPC BOOL    1     4     46s  0   RWD  n
       RPC ports                DIR
          ODBEdit               DWORD   1     4     38m  0   RWD  0
       RPC hosts                DIR
          Allowed hosts         STRING  10    256   38m  3   RWD
                                        [0]             localhost
                                        [1]
                                        [2]
                                        [3]
                                        [4]
                                        [5]
                                        [6]
                                        [7]
                                        [8]
                                        [9]
       Disable RPC hosts check  BOOL    1     4     46s  0   RWD  n

The following example shows the /Experiment tree for a typical experiment:

[local:midas:R]/>ls -lrt /experiment
Key name                        Type    #Val  Size  Last Opn Mode Value
---------------------------------------------------------------------------
Experiment                      DIR
   Name                         STRING  1     32    7s   0   RWD  midas
   Buffer sizes                 DIR
       SYSMSG                   DWORD   1     4     23h  0   RWD  100000
       SYSTEM                   DWORD   1     4     23h  0   RWD  640000000
       BUF0                     DWORD   1     4     23h  0   RWD  80000000
       BUF1                     DWORD   1     4     23h  0   RWD  80000000
       .......    other user-defined buffers not shown  
   Security                     DIR
       Enable non-localhost RPC BOOL    1     4     38m  0   RWD  n
       RPC ports                DIR
           ODBEdit              DWORD   1     4     38m  0   RWD  0
           Logger               DWORD   1     4     35m  0   RWD  0
           mhttpd               DWORD   1     4     23m  0   RWD  0
       RPC hosts                DIR
           Allowed hosts        STRING  10    256   38m  3   RWD
                                        [0]             localhost
                                        [1]
                                        [2]
                                        [3]
                                        [4]
                                        [5]
                                        [6]
                                        [7]
                                        [8]
                                        [9]
       Disable RPC hosts check  BOOL    1     4     38m  0   RWD  n
   Start-Stop Buttons           BOOL    1     4     8h   0   RWD  y
   Pause-Resume Buttons         BOOL    1     4     8h   0   RWD  n
  Status items                DIR
       Experiment Name -> /Experiment/Name
   MAX_EVENT_SIZE               DWORD   1     4     23h  0   RWD  4194304
   Midas server port            DWORD   1     4     3m   0   RWD  1175
   Transition debug flag        INT     1     4     23h  0   RWD  0
   Transition connect timeout   INT     1     4     23h  0   RWD  10000
   Transition timeout           INT     1     4     23h  0   RWD  120000
   edit on start                DIR
       experiment number        DWORD   1     4     2h   0   RWD  9499
       field                    STRING  1     32    2h   0   RWD  19000.2(0.0)G
       comment-> /Experiment/run parameters/comment
                                STRING  1     80    2h   0   RWD  Testing with low beam
       Number of channels -> /Run Parameters/number of channels
                                DWORD   1     4     2h   0   RWD  20
       Write Data -> /Logger/Write data
                                BOOL    1     4     2h   0   RWD  n
       Number of cycles -> /Equipment/FIFO_acq/frontend/hardware/num cycles
                                DWORD   1     4     2h   0   RWD  0
   Parameter Comments           DIR                   
       field                    STRING  1     32    >99d 0   RWD  Entered in Tesla unit
       Num cycles               STRING  1     80    >99d 0   RWD  Stop run after num cycles is reached. Enter 0 to disable (free running)
   Run Parameters               DIR
       Comment                  STRING  1     80    2h   0   RWD  Testing with low beam
       Run Description          STRING  1     256   7h   0   RWD  Sequencer Tests
       Number of channels       DWORD   1     4     2h   0   RWD  20
   Lock when running            DIR
       Num channels -> /Run Parameters/number of channels
                                DWORD   1     4     2h   0   RWD  20
   edit on sequence             DIR
       title                    STRING  1     128   2h   0   RWD  none
       experiment number        DWORD   1     4     2h   0   RWD  9438
       experimenter             STRING  1     32    2h   0   RWD  gls
       sample                   STRING  1     36    2h   0   RWD  NA
       run description -> /Experiment/run parameters/run description
                                STRING  1     256   7h   0   RWD  Sequencer Tests
       Write Data -> /Logger/Write data
                                BOOL    1     4     2h   0   RWD  n
       Number of cycles -> /Equipment/FIFO_acq/frontend/hardware/num cycles
                                DWORD   1     4     2h   0   RWD  0
   Prevent start on alarms      BOOL    1     4     22h  0   RWD  n
   Prevent start on required    BOOL    1     4     22h  0   RWD  n
   Status items                 DIR
       Experiment Name -> /Experiment/Name
                                STRING  1     32    7s   0   RWD  midas
   Start-Stop Buttons           BOOL    1     4     5h   0   RWD  y
   Pause-Resume Buttons         BOOL    1     4     5h   0   RWD  n

Keys in /Experiment tree

The keys in the ODB /Experiment tree are described in the following sections.

Name

• Type: STRING
• Default:

This key in the /Experiment tree contains the name of the experiment. It is created by the MIDAS system when the ODB is created.

---

Buffer Sizes subtree

• Type: DIR

This key in the /Experiment tree is a subtree to contain the sizes of the Midas Buffers for the experiment. Created by the MIDAS system with default values. The sizes can be changed to optimize the memory usage. See Event Buffer Size(s) for details. Other user-defined buffers may be present (e.g. for event filtering).

---

SYSMSG

• Type: DWORD
• Default: 100000 Bytes

This key in the /Experiment/Buffer Sizes subtree contains the size of SYSMSG buffer. This buffer is used for MIDAS messages. The default value of this key is defined by MESSAGE_BUFFER_SIZE in $MIDASSYS/include/msystem.h .

---

SYSTEM

• Type: DWORD
• Default: 32MiBytes

This key in the /Experiment/Buffer Sizes subtree contains the size of SYSTEM buffer. The default value of this key is DEFAULT_BUFFER_SIZE = 32 MiB (defined in midas.h). The actual SYSTEM buffer size is set by this key. To increase the SYSTEM buffer size (e.g. for very large events), see Event Buffer.

---

MAX_EVENT_SIZE

• Type: DWORD
• Default: 4MiBytes

This key in the /Experiment tree specifies the maximum event size that can be acquired. The default value of this key is DEFAULT_MAX_EVENT_SIZE = 4 MiB (defined in midas.h). The actual maximum event size is set by this key, and can be increased for larger events if needed (see Event Buffer for more information).

---

midas server port

• Type: DWORD
• Default: 1175

This key is created when mserver is started for the first time. It contains the default value of the port used by mserver. This is set to MIDAS_TCP_PORT = 1175 ( midas.h). A different port can be used by starting mserver with the -p argument.

NOTE

This key was added in May 2015 (see Security).

---

Start-Stop Buttons

• Type: BOOL
• Default: y

This key in the /Experiment tree is added automatically by mhttpd to allow the user to suppress the Start or Stop buttons from appearing on the Status Page. By default, Start/Stop buttons are shown.

---

Pause-Resume Buttons

• Type: BOOL
• Default: (no default, must be manually created)

This key in the /Experiment tree can be created and set to "n" to hide the Pause/Resume buttons on the Status Page (so that only Start/Stop buttons will be visible). If the key doesn't exist, or is set to "y", the Pause/Resume buttons will be shown.

---

Transition debug flag

• Type: INT
• Default: 0

This key in the /Experiment tree contains a flag that, if set to 1, causes messages reporting transition progress to be output.

---

Transition connect timeout

• Type: INT
• Default: 10000

This key in the /Experiment tree contains the value of timeout for remote rpc connect

---

Transition timeout

• Type: INT
• Default: 120000

This key in the /Experiment tree contains the value of timeout for transition (in ms)

---

Prevent start on alarms

• Type: BOOL
• Default: "n"

This key in the /Experiment tree if set true will prevent the run from starting if an alarm is true, i.e. the run start procedure will fail if an alarm has been Triggered for a client, provided a valid alarms class has been entered in the client's Alarm class key.

---

Prevent start on required program

• Type: BOOL
• Default: "n"

This key in the /Experiment tree if set true ("y") will prevent the run from starting if one of the required clients is not running. A client is flagged as "required" by setting the ODB key Required to "y".

---

Edit on Sequence subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameters which will be displayed for editing at the start of each Sequence. See Edit-on-Sequence Parameters for details.

---

Edit on Start subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameters which will be displayed for editing at the beginning of each run. See Edit-on-start Parameters for details.

---

Lock when running subtree

• Type: DIR

This optional subdirectory in the /Experiment tree contains user-defined links to ODB parameters to prevent them being changed when the run is in progress. See Lock when running for details.

---

Parameter Comments subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameter comments that give more information about the Edit-on-start Parameters. See creating parameter comments for details.

---

Run Parameters subtree

• Type: DIR

This optional subdirectory in the /Experiment tree may contain user-defined parameters or parameter(s) with reserved names (i.e. Run Description).

---

Run Description

• Type: STRING
• Default:

This ODB key is used by the Sequencer RUNDESCRIPTION command to store the run description.

---

<parameter name>

• Type: STRING
• Default:

The user may define parameters here e.g. for linking as Edit-on-start or Edit-on-Sequence parameters.

---

Status items subtree

• Type: DIR

NOTE: This key in the /Experiment tree is a subtree which by default (Hmmm no!) contains a link to the experiment name. Any links or keys created by the user in this optional subdirectory will be displayed on the mhttpd main status page.

This subtree may not be present by default. In order to make any ODB parameters visible in the status page, create first the subtree and a link to the experiment name inside this newly subtree such as:

cd /experiment
mkdir "Status items"
cd "Status items"
ln /experiment/name "Experiment Name"

Any following link to any ODB parameters will be displayed in the status page above the Equipment list.

---

Security subtree

• Type: DIR

This optional subtree in the /Experiment tree is created when the odbedit commands passwd or webpasswd are issued. It enables a user to set up security features. See Security.

---

Disable RPC hosts check

• Type: BOOL
• Default: "n"

Setting the key to "n" (the default) causes access by unauthorized hosts to be prevented by the system checking the RPC access control list (see RPC hosts/Allowed hosts).

If MIDAS clients have to connect from random hosts (i.e. dynamically assigned random DHCP addresses), one can disable the host name checks by setting this key to "y". This configuration is insecure and should only be done on a private network behind a firewall. See Note 1080.

NOTE

This key was added August 2015. Used by mserver to improve network Security for the MIDAS experiment.

---

Enable non-localhost RPC

• Type: BOOL
• Default: "n"

The default value of this key is "n", denying access by external network connections. If running an experiment that requires external network connections, this key must be set to "y" and the key RPC hosts must be filled. See Note 1080.

NOTE

This key was added August 2015. Used by mserver to improve network Security for the MIDAS experiment.

---

RPC ports subtree

• Type: DIR

This subtree in the /Experiment/Security subtree is new as of August 2015. It is created by the MIDAS system. It is part of the improved security features of MIDAS (See Security). This subdirectory contains the names of MIDAS clients and their fixed TCP port numbers. When a client is started for the first time, an entry named for the client will be created in this subtree.

---

<client-name>

• Type: STRING
• Default: 0

When a MIDAS client is started, a key will be created named for that client. It will contain the fixed TCP port number that the MIDAS client is using. Clients started on the local host will have TCP port numbers of 0 (default).

Once a remote frontend is bound to a fixed port, appropriate openings can be made in the firewall, etc. Default port number value will be 0 meaning "use random port", same as now. See [1].

NOTE

This feature was added August 2015. It is part of the improved security features of MIDAS (See Security).

---

RPC hosts subtree

• Type: DIR

This subtree in the /Experiment/Security subtree is new as of August 2015. It is created by the MIDAS system. It is part of the improved security features of MIDAS (See Security).

---

Allowed hosts

• Type: STRING array
• Default: "localhost"

This key in the /Experiment/Security/RPC hosts subtree is new as of August 2015 and is created by the system (i.e. midas.c).

It is part of the improved security features of MIDAS (See Security) and is used to maintain a Network Access Control list. The access control list array is self-growing - it will have at least 10 empty entries at the end at all times.

The default value for Allowed hosts[0] is "localhost", which will reject all external connections, even when permitted by Enable external RPC connections. The user will be required to enter the names of all machines that will run midas clients in this array. See [2].

All clients' db_watch() routines watch the access control list and automatically reload it when it is changed, so there is no need to restart clients.

---

The following keys in the /Experiment tree are OBSOLETE:

midas http port

• Type: INT
• Status: OBSOLETE
• Default: 8080

This key in the /Experiment tree is created when mhttpd is run for the first time. It contains the listening port for the HTTP server (default 8080). This will be redirected to the secure HTTPS port given by midas https port if the key http redirect to https is set to "y".

If the http port are supplied with the "--http" option when starting mhttpd, the port supplied will overwrite the default value stored in this key. See mhttpd for details.

NOTE

This Security feature was added to mhttpd in August 2015

As of March 2020, this key has been deprecated in favour of the Webserver ODB tree.

---

midas https port

• Type: INT
• Status: OBSOLETE
• Default: 8443

This key in the /Experiment tree is created when mhttpd is run for the first time. It contains the listening port (default 8443) for the secure HTTPS/SSL server (Mongoose).

If the https port is supplied with the "--https" option when starting mhttpd, the port supplied will overwrite the default value stored in this key. See mhttpd for details.

NOTE

This Security feature was added to mhttpd in August 2015

As of March 2020, this key has been deprecated in favour of the Webserver ODB tree.

---

http redirect to https

• Type: BOOL
• Status: OBSOLETE
• Default: y

This key in the /Experiment tree is created when mhttpd is run for the first time. If set to "y", connections to the http port (specified by the key midas http port will be redirected to hte https port (specified by the key midas https port, i.e. the listening port for the secure HTTPS/SSL server (Mongoose).

NOTE

This Security feature was added to mhttpd in August 2015

As of March 2020, this key has been deprecated in favour of the Webserver ODB tree.

---

mhttpd hosts subtree

• Type: DIR
• Status: OBSOLETE

This subtree in the /Experiment/Security subtree is new as of August 2015. It is created by the MIDAS system. It is part of the improved security features of MIDAS (See Security).

NOTE

As of March 2020, this key has been deprecated in favour of the Webserver ODB tree.

---

Allowed hosts

• Type: STRING array
• Status: OBSOLETE
• Default: "localhost"

This key in the /Experiment/Security/mhttpd hosts subtree is new as of August 2015 and is created by the system (i.e. midas.c).

It is part of the improved security features of MIDAS (See Security) and is used to maintain an access control list for mhttpd. An empty list means free access from everywhere. Access control is also controlled by the mhttpd "-a" command line arguments. Hosts supplied by the "-a" command line arguments are not added to the access control list by the system.

The access control list is watched by mhttpd, therefore there is no need to restart it after updating the list.

NOTE

As of March 2020, this key has been deprecated in favour of the Webserver ODB tree.

---

CSS File

• Type: STRING
• Status: OBSOLETE
• Default: "mhttpd.css"

This key in the /Experiment tree contains the name of the MIDAS stylesheet file for the use of those writing Custom Web Pages.

NOTE

Serving resource file is now done differently. See serving MIDAS resource file. Also mhttpd.css has be replaced by midas.css.

---

JS File

• Type: STRING
• Status: OBSOLETE
• Default: "mhttpd.js"

This key in the /Experiment tree contains the name of the Javascript library file for the use of those writing Custom Web Pages.

NOTE

Serving resource file is now done differently. See serving MIDAS resource files.

---

Menu Buttons

• Type: STRING
• Status: OBSOLETE
• Default: "Status, ODB, Messages, ELog, Alarms, Programs, History, Sequencer, Chat, Config, Help"

This key in the /Experiment tree is added automatically by mhttpd to allow the Menu buttons that appear on the Main Status Page to be customized by removing unnecessary buttons or by changing their order.

The Start/Stop/Pause/Resume buttons are not now included in Menu Buttons.

• To suppress/display the Start/Stop buttons use key Start-Stop Buttons.
• To display/suppress the Pause/Resume buttons, use key Pause-Resume Buttons.

Note

If MSCB support is built into MIDAS, the default will also include the MSCB Menu button (see MSCB Page).

---

Mongoose listening_port

• Type: STRING
• Status: OBSOLETE
• Default: "8080r,8443s"

This key in the /Experiment tree existed for a short time in midas versions May-August 2015.

It has been replaced by the ODB keys midas http port and midas https port.

This key in the /Experiment tree was created when mhttpd was run for the first time. It contained the listening ports for the secure HTTPS/SSL server (Mongoose). The ports are the HTTP port (default 8080) which is to be redirected to the secure HTTPS port (default 8443). If ports were supplied with the "--mg" option when starting mhttpd, their values will overwrite the default values stored in this key. See mhttpd for details.

---

Mongoose access_control_list

• Type: STRING
• Status: OBSOLETE
• Default: ""

This key in the /Experiment tree existed for a short time in midas versions May-August 2015.

Use the mhttpd hosts/Allowed hosts access control list or the mhttpd "-a hostname" parameter to restrict access.

This key in the /Experiment tree is created when mhttpd is run for the first time. It contains the access control list (ACL) for the Mongoose web server. By default, this key is empty and there is no access control. The format of the ACL is described under access_control_list at Mongoose Configuration Options.

---

The following keys in the /Experiment/Security subdirectory are OBSOLETE - replaced by the security features added Aug 2015

Password

• Type: STRING
• Status: OBSOLETE
• Default:

Notes

1. This feature pre-dates the improved Security features (August 2015)
2. Do not set this key except through the odbedit command passwd. Setting an unencrypted password will lock you out of the ODB unless odbedit is listed in the allowed programs subtree.
3. This security feature is not proof against malicious access. See Security for details.

This optional key in the /Experiment/Security subtree contains the encrypted password. This Key is created when the odbedit command passwd is issued. See Restrict user access for details.

---

Allowed Hosts subtree

• Type: DIR

Notes

• This subtree pre-dates the improved Security features (August 2015) and is not to be confused with RPC hosts/Allowed hosts array.
• This security feature is not proof against malicious access. See Security for details.

This subtree in the /Experiment/Security subtree is created when the odbedit command passwd is issued. When created, this subtree is empty. Optionally, it may contain user-defined names of remote hosts allowed to have free access (i.e. without password) to the current experiment.

---

Allowed programs subtree

• Type: DIR

Notes

• This subtree pre-dates the improved Security features (August 2015)
• This feature is not proof against malicious access. See Security for details.

This optional subtree in the /Experiment/Security subtree is created when the odbedit command passwd is issued. When created, this subtree is empty. Optionally, it may contain user-defined names of clients allowed to have free access (i.e. without password) to the current experiment. See Security #Allowed programs.

---

Web Password

• Type: STRING
• Status: OBSOLETE
• Default:

Notes

• This key pre-dates (and has been superceded by) the improved Security features (August 2015)
• This feature is not proof against malicious access. See Security for details.

If restriction on user web access has been set up, this key in the /Experiment/Security subtree will contain an encrypted password for Web server access. This key is created by using the odbedit command webpasswd.

If this key is present, the user will be requested to provide the "Web Password" when accessing the requested experiment in "Write Access" mode. The "Read Only Access" mode is still available (without a password) to all users.

---