rjlopes wrote
Consider a scenario where I have a provider queue with several modems attached to it.
If 10 sms enter the queue at the same time how are they processed? And if they enter at a rate of 1 per hour?
In Unix "at the same time" means that all files have the same timestamp, because the time resolution is one second. Oldest file is processed first, but with same timestamps files are selected by the alphabetic order of a name.
Each modem will try to get a file. When smsd is started, modem processes are searching for files almost simultaneously. Later, when some messages are sent and received, they are not searching exactly at the same time. In cannot be known, or defined, which modem will get the next message. The modem which will see the message first, will send it.
rjlopes wrote
Are the messages send to the first declared modem on the queue and only try the next one if the first is down or busy?
No. Any modem can pick up the message. If the first modem is busy, it does not search for files, but other modems will search (if not busy too).
rjlopes wrote
Are they distributed fairly among the modems?
Can this by configured?
There are no configuration options for this. When sending large number of messages with several modems, all modems will always have something to send. Also, usually the time of sending does matter, not the number of messages. Longer messages take more time, and in some cases there can be retries, or failures. Because of this, smsd does not even try to distribute messages "fairly".
If you need that the balance of each SIM is used evenly, you need to create an external "load balancing". This kind of a functionality can be done with a
checkhandler. In the
scripts directory of a package, there is a sample script
load_balancing.sh. I include it here:
#!/bin/bash
# ---------------------------------------------------------------------------------------
# This example is for three modems, named GSM1, GSM2 and GSM3
# using queues Q1, Q2 and Q3.
# In the global part of smsd.conf, enable message counters:
# stats = /var/spool/sms/stats
# Use zero value for interval if statistics files are not used:
# stats_interval = 0
#
# Enable checkhandler (this script):
# checkhandler = /usr/local/bin/load_balancing.sh
#
# Define queues and providers:
# [queues]
# Q1 = /var/spool/sms/Q1
# Q2 = /var/spool/sms/Q2
# Q3 = /var/spool/sms/Q3
#
# [providers]
# Q1 = 0,1,2,3,4,5,6,7,8,9,s
# Q2 = 0,1,2,3,4,5,6,7,8,9,s
# Q3 = 0,1,2,3,4,5,6,7,8,9,s
#
# Add queue definition for each modem:
# [GSM1]
# queues = Q1
# etc...
# ---------------------------------------------------------------------------------------
STATSDIR=/var/spool/sms/stats
read_counter()
{
RESULT=0
FILE=$STATSDIR/$1.counter
if [[ -e $FILE ]]
then
COUNTER=`formail -zx $1: < $FILE`
if [ "$COUNTER" != "" ]; then
RESULT=$COUNTER
fi
fi
return $RESULT
}
# If there is Queue (or Provider) defined, load balancing is ignored:
QUEUE=`formail -zx Queue: < $1`
if [ "$QUEUE" = "" ]; then
QUEUE=`formail -zx Provider: < $1`
if [ "$QUEUE" = "" ]; then
# Read current counters:
read_counter GSM1
COUNTER1=$?
read_counter GSM2
COUNTER2=$?
read_counter GSM3
COUNTER3=$?
QUEUE=Q1
COUNTER=$COUNTER1
if [ $COUNTER2 -lt $COUNTER ]; then
QUEUE=Q2
COUNTER=$COUNTER2
fi
if [ $COUNTER3 -lt $COUNTER ]; then
QUEUE=Q3
COUNTER=$COUNTER3
fi
TMPFILE=`mktemp /tmp/smsd_XXXXXX`
cp $1 $TMPFILE
formail -f -I "Queue: $QUEUE" < $TMPFILE > $1
unlink $TMPFILE
fi
fi
exit 0
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