Error Fetching Children for Path

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Symptom

Deployment of API proxy revisions through the Edge UI or Edge management API fails with the ZooKeeper error "Error while fetching children for path".

Error Messages

Error in deployment for environment prod. 
The revision is deployed, but traffic cannot flow. com.apigee.repository.RepositoryException{ code = repository.zookeeper.UnExpectedError, message = Unexpected error Error while fetching children for path : /organizations/myorg/environments/prod/apiproxies/tinkerbell/revisions, associated contexts = []};

Possible Causes

The typical cause for this error is a network connectivity issue between the Message Processor and ZooKeeper.

Diagnosis

Note: Only Edge Private Cloud users can perform the following steps. If you are on Edge Public Cloud, contact Apigee Edge Support.

Get the deployment status output for the specific API that shows the error using the following management API call:

curl -v http://<management-server-IPaddress>:<port#>/organizations/<orgname>/environments/<envname>/apis/<apiname>/deployments -u <username>

Sample deployment status output showing the error:

{ 
"environment" : [ { 
"name" : "prod", 
"revision" : [ { 
"configuration" : { 
"basePath" : "/", 
"steps" : [ ] 
}, 
"name" : "1", 
"server" : [ { 
"error" : "com.apigee.repository.RepositoryException: com.apigee.zookeeper.ZooKeeperException{ code = zookeeper.ErrorFetchingChildren, message = Error while fetching children for path : /organizations/gsc/environments/prod/apiproxies/apigee_test/revisions, associated contexts = []}", 
"status" : "error", 
"type" : [ "message-processor" ], 
"uUID" : "01fc5b23-8ad3-40bf-b059-2fc82cdac111" 
},

Check the Message Processor (/opt/apigee/var/log/edge-message-processor/system.log).

Sample error from Message Processor log

2017-05-29 01:25:40,592  main ERROR KERNEL - MicroKernel.deployAll() : MicroKernel.deployAll() : Error in deploying the deployment : WebService
com.apigee.zookeeper.ZooKeeperException: Error while checking path existence for path : /regions/dc-2/pods/gateway/servers/099c2603-93a4-4b73-ae03-a55d130adb80/reachable
        at com.apigee.zookeeper.impl.ZooKeeperServiceImpl.exists(ZooKeeperServiceImpl.java:410) ~[zookeeper-1.0.0.jar:na]
        at com.apigee.zookeeper.impl.ZooKeeperServiceImpl.exists(ZooKeeperServiceImpl.java:394) ~[zookeeper-1.0.0.jar:na]
        at com.apigee.services.repository.zookeeper.ZKRepository.exists(ZKRepository.java:280) ~[repository-impl-1.0.0.jar:na]
        at com.apigee.services.repository.RepositoryServiceImpl.exists(RepositoryServiceImpl.java:234) ~[repository-impl-1.0.0.jar:na]
        at com.apigee.registration.info.StatusBuilder.build(StatusBuilder.java:26) ~[registration-1.0.0.jar:na]
        at com.apigee.registration.ServerRegistrationServiceImpl.buildServerInfo(ServerRegistrationServiceImpl.java:856) ~[registration-1.0.0.jar:na]
        at com.apigee.registration.ServerRegistrationServiceImpl.start(ServerRegistrationServiceImpl.java:122) ~[registration-1.0.0.jar:na]
        at com.apigee.kernel.service.deployment.ServiceDeployer.startService(ServiceDeployer.java:167) ~[microkernel-1.0.0.jar:na]
        at com.apigee.kernel.service.deployment.ServiceDeployer.deploy(ServiceDeployer.java:70) ~[microkernel-1.0.0.jar:na]
        at com.apigee.kernel.service.deployment.ServiceDeployer.deployDependantServices(ServiceDeployer.java:356) ~[microkernel-1.0.0.jar:na]
        at com.apigee.kernel.service.deployment.ServiceDeployer.deploy(ServiceDeployer.java:76) ~[microkernel-1.0.0.jar:na]
        at com.apigee.kernel.service.deployment.ServiceDeployer.deployDependantServices(ServiceDeployer.java:356) ~[microkernel-1.0.0.jar:na]
        at com.apigee.kernel.service.deployment.ServiceDeployer.deploy(ServiceDeployer.java:76) ~[microkernel-1.0.0.jar:na]
        at com.apigee.kernel.MicroKernel.deployAll(MicroKernel.java:178) [microkernel-1.0.0.jar:na]
        at com.apigee.kernel.MicroKernel.start(MicroKernel.java:139) [microkernel-1.0.0.jar:na]
        at com.apigee.kernel.MicroKernel.start(MicroKernel.java:135) [microkernel-1.0.0.jar:na]
        at com.apigee.kernel.MicroKernel.main(MicroKernel.java:84) [microkernel-1.0.0.jar:na]
Caused by: org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /regions/dc-2/pods/gateway/servers/099c2603-93a4-4b73-ae03-a55d130adb80/reachable
        at org.apache.zookeeper.KeeperException.create(KeeperException.java:99) ~[zookeeper-3.4.6.jar:3.4.6-1569965]
        at org.apache.zookeeper.KeeperException.create(KeeperException.java:51) ~[zookeeper-3.4.6.jar:3.4.6-1569965]
        at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1045) ~[zookeeper-3.4.6.jar:3.4.6-1569965]
        at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1073) ~[zookeeper-3.4.6.jar:3.4.6-1569965]
        at com.apigee.zookeeper.impl.ZooKeeperServiceImpl.exists(ZooKeeperServiceImpl.java:402) ~[zookeeper-1.0.0.jar:na]
        ... 16 common frames omitted

If you observe a similar error as shown in the above example, then perform the following steps:
1. Test the connectivity from the Message Processor to ZooKeeper servers on port 2181 using the following steps:
  1. If telnet is available, then use telnet:
```
telnet <ZooKeeper-IP> 2181
```
  2. If telnet is not available, use netcat to check the connectivity as follows:
```
nc -vz <ZooKeeper-IP> 2181
```
  3. If you get the response "Connection Refused" or "Connection timed out", engage your network operations team. Go to Resolution section below.
If you observe any other, then contact Apigee Edge Support.

Resolution

Note: Only Edge Private Cloud users can perform the following steps. If you are on Edge Public Cloud, contact Apigee Edge Support.

Work with your network team to:
1. 1. Ensure connectivity is allowed between the Message Processor and all ZooKeeper nodes on port 2181.
  2. Remove any firewall restrictions or security rules setup from Message Processors to allow connectivity to port 2181 on the ZooKeeper servers.
2. If there is network issue on the Message Processor, then restarting the specific Message Processor that shows the error (as per the deployment status output) might fix the issue. Restart the specific Message Processor:
```
/opt/apigee/apigee-service/bin/apigee-service edge-message-processor restart
```
If the problem persists, contact Apigee Edge Support.