Maapi session: database is locked by session failure

CDB and CDB API
1

I was trying to write to the cdb using maapi.
I can see the two parameters that I wrote to cdb just fine with the show command… however, if I try to overwrite either of them, I am getting a message that says “database is locked by session” and it is pointing to the maapi_start_user_session()
Any ideas what I am missing here?

    syslog(LOG_INFO, "%s: ", __FUNCTION__);
    addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    addr.sin_family = AF_INET;
    addr.sin_port = htons(CONFD_PORT);

    if ((msock = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        syslog(LOG_ERR, "%s: Failed to open socket", __FUNCTION__);
        return CN_ERROR;
    }

    /* using MAAPI to connect to CDB to update configuration data */
    if (maapi_connect(msock, (struct sockaddr*) &addr,
                      sizeof(struct sockaddr_in)) < 0) {
        syslog(LOG_ERR, "%s: Failed to maapi_connect() to confd", __FUNCTION__);
        maapi_close(msock);
        return CN_ERROR;
    }

    if (maapi_load_schemas(msock) != CONFD_OK) {
        syslog(LOG_ERR, "%s: Failed to maapi_load_schemas() to confd", __FUNCTION__);
        maapi_close(msock);
        return CN_ERROR;
    }

    ip.af = AF_INET;
    inet_pton(AF_INET, "0.0.0.0", &ip.ip.v4);

    if ((maapi_start_user_session(msock, NULL, "system", NULL, 0,
                            &ip, CONFD_PROTO_TCP)) != CONFD_OK) {
        syslog(LOG_ERR, "%s: Failed to start maapi user session", __FUNCTION__);
        maapi_close(msock);
        return CONFD_ERR;
    }

    iDB = CONFD_RUNNING;
   // Start MAAPI transaction
    if ((maapi_thandle = maapi_start_trans(
                msock, (enum confd_dbname)iDB, CONFD_READ_WRITE)) < 0 ) {
        syslog(LOG_ERR, "%s: failed to start maapi transaction", __FUNCTION__);
        maapi_close(msock);
        return CONFD_ERR;
    }

    syslog(LOG_INFO, "setting link mode to be differerntiated");
    maapi_set_namespace(msock, maapi_thandle, link__ns);
    if (maapi_set_elem2(msock, maapi_thandle, "differentiated", "/link/mode") != CONFD_OK) {
        syslog(LOG_ERR, "link-mode init failed");
    }

    syslog(LOG_INFO, "setting cos-classifier to be pcp");
    if (maapi_set_elem2(msock, maapi_thandle, "pcp", "/link/cos-classifier") != CONFD_OK) {
        syslog(LOG_ERR, "cos-classifier init to pcp failed");
    }

    if (maapi_apply_trans(msock, maapi_thandle, 0) != CONFD_OK) {
        syslog(LOG_ERR, "%s: failed to apply transaction", __FUNCTION__);
    }

    if (maapi_finish_trans(msock, maapi_thandle) != CONFD_OK) {
        syslog(LOG_ERR, "%s: failed to finish transaction", __FUNCTION__);
    }
    syslog(LOG_INFO, "%s: Changes applied to CDB successfully", __FUNCTION__);

    if (maapi_end_user_session(msock) != CONFD_OK) {
        syslog(LOG_ERR, "%s: failed to end user session", __FUNCTION__);
    }

    maapi_close(msock);
2

Actually I just realized from the logs that it is the maapi_apply_trans() that failed. I am not sure what I am doing wrong…

3

My yang definitions are:

     leaf mode {
          type cndlp-types:cndlp-link-mode;
          tailf:info "Mode of operation for traffic treatment";
      }
      leaf cos-classifier {
          when "../mode = 'differentiated'";
          type cndlp-types:cndlp-classifier-mode;
          tailf:info "Mode of traffic treatment based on vlan or pcp";
      }
4

From syslog, I see the following (dpm is name of my daemon):

<INFO>: 2017-09-18T21:05:21.3063 qemux86-64 dpm: update_config_cdb:
<INFO>: 2017-09-18T21:05:21.3437 qemux86-64 dpm: setting link mode to be differerntiated
<INFO>: 2017-09-18T21:05:21.4014 qemux86-64 dpm: setting cos-classifier to be pcp
<ERR>: 2017-09-18T21:05:51.4173 qemux86-64 confd[1067]: - CDB client (dpm) timed out, waiting for call to sync_subscription
<INFO>: 2017-09-18T21:05:51.4182 qemux86-64 confd[1067]: devel-cdb Restored running from snapshot
<ERR>: 2017-09-18T21:05:51.4264 qemux86-64 dpm: update_config_cdb: failed to apply transaction
5

You might want to understand why the Sync Subscription is not done by your daemon.

Check also who has a read lock. I think this is the reason why you can’t update the second time.

6

@nabil, can you please help me out how to find

  • who has read lock
  • how to see why sync subscription is not done? Is there any API that I am missing to invoke?
7

BTW. This is happening when I try to handle delete command that deletes all configuration but I had to update the CDB with default values. I was triggering maapi calls to CDB to update few parameters to default values during COMMIT phase.

8

This needs some look up in the code and some debugging.
Don’t trigger MAAPI calls during a transaction commit, to change configuration. This is where you are getting deadlocked, unless you implement transaction hooks.

I recommend you look at transaction hooks that will allow your application to participate in a configuration change transaction. This way you can attach a MAAPI Session to the transaction and do whatever you need before the validation phase kicks in.

You can find information about this in the user guide:
10.6. Hooks