[docker-orchagent] Call sonic-cfggen Once (sonic-net#4936)

Optimizing number of calls made to sonic-cfggen during service
start up as it adds to total system boot up time.

signed-off-by: Tamer Ahmed <[email protected]>

**- Why I did it**
sonic-cfggen call is slow and it adds to system start up time

**- How I did it**
places all required variable into single template and called into sonic-cfggen using this template

**- How to verify it**
***-Test 1***
there is an average saving of .5 to 1 sec between old script and new script
```
root@str-s6000-acs-14:/# time ./orchagent_old.sh
/usr/bin/orchagent -d /var/log/swss -b 8192 -m f4:8e:38:16:bc:8d

real	0m3.546s
user	0m2.365s
sys	0m0.585s

root@str-s6000-acs-14:/# time ./orchagent_new.sh
/usr/bin/orchagent -d /var/log/swss -b 8192 -m f4:8e:38:16:bc:8d

real	0m2.058s
user	0m1.650s
sys	0m0.363s
```
***-Test 2***
Built an image with this change and orchagent is running with intended params:
```
admin@str-s6000-acs-14:~$ ps -ef | grep orchagent
root      2988  1901  1 02:09 pts/0    00:00:02 /usr/bin/orchagent -d /var/log/swss -b 8192 -m f4:8e:38:16:bc:8d
```

signed-off-by: Tamer Ahmed <[email protected]>

dockers/docker-orchagent/orchagent.sh

@@ -1,10 +1,18 @@
 #!/usr/bin/env bash
 
-# Export platform information. Required to be able to write
-# vendor specific code.
-export platform=`sonic-cfggen -y /etc/sonic/sonic_version.yml -v asic_type`
+EXIT_SWSS_VARS_FILE_NOT_FOUND=1
+SWSS_VARS_FILE=/usr/share/sonic/templates/swss_vars.j2
 
-MAC_ADDRESS=$(sonic-cfggen -d -v 'DEVICE_METADATA.localhost.mac')
+if [ ! -f "$SWSS_VARS_FILE" ]; then
+    echo "SWSS vars template file not found"
+    exit $EXIT_SWSS_VARS_FILE_NOT_FOUND
+fi
+
+# Retrieve SWSS vars from sonic-cfggen
+SWSS_VARS=$(sonic-cfggen -d -y /etc/sonic/sonic_version.yml -t $SWSS_VARS_FILE)
+platform=$(echo $SWSS_VARS | jq -r '.asic_type')
+
+MAC_ADDRESS=$(echo $SWSS_VARS | jq -r '.mac')
 if [ "$MAC_ADDRESS" == "None" ] || [ -z "$MAC_ADDRESS" ]; then
     MAC_ADDRESS=$(ip link show eth0 | grep ether | awk '{print $2}')
     logger "Mac address not found in Device Metadata, Falling back to eth0"
@@ -27,7 +35,7 @@ ORCHAGENT_ARGS+="-b 8192 "
 # ID field could be integers just to denote the asic instance like 0,1,2...
 # OR could be PCI device ID's which will be strings like "03:00.0"
 # depending on what the SAI/SDK expects.
-asic_id=`sonic-cfggen -d -v DEVICE_METADATA.localhost.asic_id`
+asic_id=$(echo $SWSS_VARS | jq -r '.asic_id')
 if [ -n "$asic_id" ]
 then
     ORCHAGENT_ARGS+="-i $asic_id "
@@ -51,7 +59,7 @@ elif [ "$platform" == "mellanox" ]; then
 elif [ "$platform" == "innovium" ]; then
     ORCHAGENT_ARGS+="-m $MAC_ADDRESS"
 else
-    MAC_ADDRESS=`sonic-cfggen -d -v 'DEVICE_METADATA.localhost.mac'`
+    # Should we use the fallback MAC in case it is not found in Device.Metadata
     ORCHAGENT_ARGS+="-m $MAC_ADDRESS"
 fi
 

dockers/docker-orchagent/swss_vars.j2

@@ -0,0 +1,6 @@
+{
+    "asic_type": "{{ asic_type }}",
+    "asic_id": "{{ DEVICE_METADATA.localhost.asic_id }}",
+    "mac": "{{ DEVICE_METADATA.localhost.mac }}"
+}
+