[telemetry] Call sonic-cfggen Once (#4901)

sonic-cfggen call is slow and this is taking place in the SONiC
boot up process. The change uses templates to assemble all required
vars into single template file. With this change, telemetry now calls
once into sonic-cfggen.

signed-off-by: Tamer Ahmed <tamer.ahmed@microsoft.com>

dockers/docker-base-buster/Dockerfile.j2

@@ -64,7 +64,9 @@ RUN apt-get update &&        \
         net-tools            \
 # for arm arch: Installing j2cli dependency package MarkupSafe from source relies on weeksetuptools and wheel
         python-setuptools    \
-        python-wheel
+        python-wheel         \
+# for processing/handling json files in bash environment
+        jq
 
 # For templating
 RUN pip install j2cli

dockers/docker-base-stretch/Dockerfile.j2

@@ -62,7 +62,9 @@ RUN apt-get update &&        \
         net-tools            \
 # for arm arch: Installing j2cli dependency package MarkupSafe from source relies on weeksetuptools and wheel
         python-setuptools    \
-        python-wheel
+        python-wheel         \
+# for processing json files in bash environment
+        jq
 
 # For templating
 RUN pip install j2cli

dockers/docker-sonic-telemetry/Dockerfile.j2

@@ -22,7 +22,7 @@ RUN apt-get clean -y      && \
     apt-get autoremove -y && \
     rm -rf /debs
 
-COPY ["start.sh", "telemetry.sh", "dialout.sh", "/usr/bin/"]
+COPY ["start.sh", "telemetry.sh", "dialout.sh", "telemetry_vars.j2", "/usr/bin/"]
 COPY ["supervisord.conf", "/etc/supervisor/conf.d/"]
 COPY ["files/supervisor-proc-exit-listener", "/usr/bin"]
 COPY ["critical_processes", "/etc/supervisor"]

dockers/docker-sonic-telemetry/telemetry.sh

@@ -2,36 +2,38 @@
 
 # Try to read telemetry and certs config from ConfigDB.
 # Use default value if no valid config exists
-X509=`sonic-cfggen -d -v "DEVICE_METADATA['x509']"`
-gnmi=`sonic-cfggen -d -v "TELEMETRY['gnmi']"`
-certs=`sonic-cfggen -d -v "TELEMETRY['certs']"`
+TELEMETRY_VARS=$(sonic-cfggen -d -t telemetry_vars.j2)
+TELEMETRY_VARS=${TELEMETRY_VARS//[\']/\"}
+X509=$(echo $TELEMETRY_VARS | jq -r '.x509')
+GNMI=$(echo $TELEMETRY_VARS | jq -r '.gnmi')
+CERTS=$(echo $TELEMETRY_VARS | jq -r '.certs')
 
 TELEMETRY_ARGS=" -logtostderr"
 export CVL_SCHEMA_PATH=/usr/sbin/schema
 
-if [ -n "$certs" ]; then
-    SERVER_CRT=`sonic-cfggen -d -v "TELEMETRY['certs']['server_crt']"`
-    SERVER_KEY=`sonic-cfggen -d -v "TELEMETRY['certs']['server_key']"`
+if [ -n "$CERTS" ]; then
+    SERVER_CRT=$(echo $CERTS | jq -r '.server_crt')
+    SERVER_KEY=$(echo $CERTS | jq -r '.server_key')
     if [ -z $SERVER_CRT  ] || [ -z $SERVER_KEY  ]; then
         TELEMETRY_ARGS+=" --insecure"
     else
         TELEMETRY_ARGS+=" --server_crt $SERVER_CRT --server_key $SERVER_KEY "
     fi
 
-    CA_CRT=`sonic-cfggen -d -v "TELEMETRY['certs']['ca_crt']"`
+    CA_CRT=$(echo $CERTS | jq -r '.ca_crt')
     if [ ! -z $CA_CRT ]; then
         TELEMETRY_ARGS+=" --ca_crt $CA_CRT"
     fi
 elif [ -n "$X509" ]; then
-    SERVER_CRT=`sonic-cfggen -d -v "DEVICE_METADATA['x509']['server_crt']"`
-    SERVER_KEY=`sonic-cfggen -d -v "DEVICE_METADATA['x509']['server_key']"`
+    SERVER_CRT=$(echo $X509 | jq -r '.server_crt')
+    SERVER_KEY=$(echo $X509 | jq -r '.server_key')
     if [ -z $SERVER_CRT  ] || [ -z $SERVER_KEY  ]; then
         TELEMETRY_ARGS+=" --insecure"
     else
         TELEMETRY_ARGS+=" --server_crt $SERVER_CRT --server_key $SERVER_KEY "
     fi
 
-    CA_CRT=`sonic-cfggen -d -v "DEVICE_METADATA['x509']['ca_crt']"`
+    CA_CRT=$(echo $X509 | jq -r '.ca_crt')
     if [ ! -z $CA_CRT ]; then
         TELEMETRY_ARGS+=" --ca_crt $CA_CRT"
     fi
@@ -40,19 +42,20 @@ else
 fi
 
 # If no configuration entry exists for TELEMETRY, create one default port
-if [ -z "$gnmi" ]; then
-    sonic-db-cli CONFIG_DB hset "TELEMETRY|gnmi" port 8080
+if [ -z "$GNMI" ]; then
+    PORT=8080
+    sonic-db-cli CONFIG_DB hset "TELEMETRY|gnmi" port $PORT
+else
+    PORT=$(echo $GNMI | jq -r '.port')
 fi
-
-PORT=`sonic-cfggen -d -v "TELEMETRY['gnmi']['port']"`
 TELEMETRY_ARGS+=" --port $PORT"
 
-CLIENT_AUTH=`sonic-cfggen -d -v "TELEMETRY['gnmi']['client_auth']"`
+CLIENT_AUTH=$(echo $GNMI | jq -r '.client_auth')
 if [ -z $CLIENT_AUTH ] || [ $CLIENT_AUTH == "false" ]; then
     TELEMETRY_ARGS+=" --allow_no_client_auth"
 fi
 
-LOG_LEVEL=`sonic-cfggen -d -v "TELEMETRY['gnmi']['log_level']"`
+LOG_LEVEL=$(echo $GNMI | jq -r '.log_level')
 if [ ! -z $LOG_LEVEL ]; then
     TELEMETRY_ARGS+=" -v=$LOG_LEVEL"
 else

dockers/docker-sonic-telemetry/telemetry_vars.j2

@@ -0,0 +1,5 @@
+{
+    "certs": "{% if "certs" in TELEMETRY.keys() %}{{ TELEMETRY["certs"] }}{% endif %}",
+    "gnmi" : "{% if "gnmi" in TELEMETRY.keys() %}{{ TELEMETRY["gnmi"] }}{% endif %}",
+    "x509" : "{% if "x509" in DEVICE_METADATA.keys() %}{{ DEVICE_METADATA["x509"] }}{% endif %}"
+}