Chapter 8. Troubleshooting the API infrastructure

When you are first integrating your API with APIcast Hosted on the Service Integration screen, you might get some of the following errors shown on the page or returned by the test call you make to check for a successful integration.

After you have successfully tested the integration with APIcast self-managed, you might want to host the API gateway yourself. Following are some errors you may encounter when you first install your self-managed gateway and call your API through it.

Following are some other symptoms that may point to an incorrect APIcast self-managed integration:

Availability issues are normally characterised by upstream timed out errors in your nginx error.log; example:

upstream timed out (110: Connection timed out) while connecting to upstream, client: X.X.X.X, server: api.example.com, request: "GET /RESOURCE?CREDENTIALS HTTP/1.1", upstream: "http://Y.Y.Y.Y:80/RESOURCE?CREDENTIALS", host: "api.example.com"

If you are experiencing intermittent 3scale availability issues, following may be the reasons for this:

Log in to the machine where the gateway is running. If this fails, your gateway server might be down.

After you have logged in, check that the NGINX process is running. For this, run ps ax | grep nginx or htop.

NGINX is running if you see nginx master process and nginx worker process in the list.

Following are some common errors you might see in the gateway logs, for example in error.log:

If you are using NGINX as your API gateway, the following message displays in the nginx error logs when the gateway is unable to contact 3scale.

2015/11/20 11:33:51 [error] 3578#0: *1 upstream timed out (110: Connection timed out) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /api/activities.json?user_key=USER_KEY HTTP/1.1", subrequest: "/threescale_authrep", upstream: "https://54.83.62.186:443/transactions/authrep.xml?provider_key=YOUR_PROVIDER_KEY&service_id=SERVICE_ID&usage[hits]=1&user_key=USER_KEY&log%5Bcode%5D=", host: "localhost"

Here, note the upstream value. This IP corresponds to one of the IPs that the 3scale product resolves to. This implies that there is a problem reaching 3scale. You can do a reverse DNS lookup to check the domain for an IP by calling nslookup.

For example, because the API gateway is unable to reach 3scale, it does not mean that 3scale is down. One of the most common reasons for this would be firewall rules preventing the API gateway from connecting to 3scale.

There may be network issues between the gateway and 3scale that could cause connections to timeout. In this case, you should go through the steps in troubleshooting generic connectivity issues to identify where the problem lies.

To rule out networking issues, use traceroute or MTR to check the routing and packet transmission. You can also run the same command from a machine that is able to connect to 3scale and your API gateway and compare the output.

Additionally, to see the traffic that is being sent between your API gateway and 3scale, you can use tcpdump as long as you temporarily switch to using the HTTP endpoint for the 3scale product (su1.3scale.net).

Ensure you have the resolver directive added to your nginx.conf.

For example, in nginx.conf:

http {
  lua_shared_dict api_keys 10m;
  server_names_hash_bucket_size 128;
  lua_package_path ";;$prefix/?.lua;";
  init_by_lua 'math.randomseed(ngx.time()) ; cjson = require("cjson")';

  resolver 8.8.8.8 8.8.4.4;

You can substitute the Google DNS (8.8.8.8 and 8.8.4.4) with your preferred DNS.

To check DNS resolution from your API gateway, call nslookup as follows with the specified resolver IP:

nslookup su1.3scale.net 8.8.8.8
;; connection timed out; no servers could be reached

The above example shows the response returned if Google DNS cannot be reached. If this is the case, you must update the resolver IPs. You might also see the following alert in your nginx error.log:

2016/05/09 14:15:15 [alert] 9391#0: send() failed (1: Operation not permitted) while resolving, resolver: 8.8.8.8:53

Finally, run dig any su1.3scale.net to see the IP addresses currently in operation for the 3scale Service Management API. Note that this is not the entire range of IP addresses that might be used by 3scale. Some may be swapped in and out for capacity reasons. Additionally, you may add more domain names for the 3scale service in the future. For this you should always test against the specific address that are supplied to you during integration, if applicable.

If you want to check the request your API gateway is making to 3scale for troubleshooting purposes only you can add the following snippet to the 3scale authrep location in nginx.conf (/threescale_authrep for API Key and App\_id authentication modes):

body_filter_by_lua_block{
  if ngx.req.get_headers()["X-3scale-debug"] == ngx.var.provider_key then
    local resp = ""
    ngx.ctx.buffered = (ngx.ctx.buffered or "") .. string.sub(ngx.arg[1], 1, 1000)
    if ngx.arg[2] then
      resp = ngx.ctx.buffered
    end

    ngx.log(0, ngx.req.raw_header())
    ngx.log(0, resp)
  end
}

This snippet will add the following extra logging to the nginx error.log when the X-3scale-debug header is sent, e.g. curl -v -H 'X-3scale-debug: YOUR_PROVIDER_KEY' -X GET "https://726e3b99.ngrok.com/api/contacts.json?access_token=7c6f24f5"

This will produce the following log entries:

2016/05/05 14:24:33 [] 7238#0: *57 [lua] body_filter_by_lua:7: GET /api/contacts.json?access_token=7c6f24f5 HTTP/1.1
Host: 726e3b99.ngrok.io
User-Agent: curl/7.43.0
Accept: */*
X-Forwarded-Proto: https
X-Forwarded-For: 2.139.235.79

 while sending to client, client: 127.0.0.1, server: pili-virtualbox, request: "GET /api/contacts.json?access_token=7c6f24f5 HTTP/1.1", subrequest: "/threescale_authrep", upstream: "https://54.83.62.94:443/transactions/oauth_authrep.xml?provider_key=REDACTED&service_id=REDACTED&usage[hits]=1&access_token=7c6f24f5", host: "726e3b99.ngrok.io"
2016/05/05 14:24:33 [] 7238#0: *57 [lua] body_filter_by_lua:8: <?xml version="1.0" encoding="UTF-8"?><error code="access_token_invalid">access_token "7c6f24f5" is invalid: expired or never defined</error> while sending to client, client: 127.0.0.1, server: pili-virtualbox, request: "GET /api/contacts.json?access_token=7c6f24f5 HTTP/1.1", subrequest: "/threescale_authrep", upstream: "https://54.83.62.94:443/transactions/oauth_authrep.xml?provider_key=REDACTED&service_id=REDACTED&usage[hits]=1&access_token=7c6f24f5", host: "726e3b99.ngrok.io"

The first entry (2016/05/05 14:24:33 [] 7238#0: *57 [lua] body_filter_by_lua:7:) prints out the request headers sent to 3scale, in this case: Host, User-Agent, Accept, X-Forwarded-Proto and X-Forwarded-For.

The second entry (2016/05/05 14:24:33 [] 7238#0: *57 [lua] body_filter_by_lua:8:) prints out the response from 3scale, in this case: <error code="access_token_invalid">access_token "7c6f24f5" is invalid: expired or never defined</error>.

Both will print out the original request (GET /api/contacts.json?access_token=7c6f24f5) and subrequest location (/threescale_authrep) as well as the upstream request (upstream: "https://54.83.62.94:443/transactions/threescale_authrep.xml?provider_key=REDACTED&service_id=REDACTED&usage[hits]=1&access_token=7c6f24f5".) This last value allows you to see which of the 3scale IPs have been resolved and also the exact request made to 3scale.

It is also possible that 3scale is available but is returning an error to your API gateway which would prevent calls going through to your API. Try to make the authorization call directly in 3scale and check the response. If you get an error, check the #troubleshooting-api-error-codes[Error Codes] section to see what the issue is.

You can also turn on the 3scale debug headers by making a call to your API with the X-3scale-debug header, example:

curl -v -X GET "https://api.example.com/endpoint?user_key" X-3scale-debug: YOUR_SERVICE_TOKEN

This will return the following headers with the API response:

X-3scale-matched-rules: /, /api/contacts.json
< X-3scale-credentials: access_token=TOKEN_VALUE
< X-3scale-usage: usage[hits]=2
< X-3scale-hostname: HOSTNAME_VALUE

You can also check the integration errors on your Admin Portal to check for any issues reporting traffic to 3scale. See https://YOUR_DOMAIN-admin.3scale.net/apiconfig/errors.

One of the reasons for integration errors can be sending credentials in the headers with underscores_in_headers directive not enabled in server block.

Try directing a browser to the IP address (or domain name) of your gateway server. If this fails, ensure that you have opened the firewall on the relevant ports.

If possible, try to connect to the API gateway from the client using one of the methods outlined earlier (telnet, curl, etc.) If the connection fails, the problem lies in the network between the two.

Otherwise, you should move on to troubleshooting the client making the calls to the API.

If a request is not returning the expected result, test with a different HTTP client. For example, if you are calling an API with a Java HTTP client and you see something wrong, cross-check with cURL.

You can also call the API through a proxy between the client and the gateway to capture the exact parameters and headers being sent by the client.

Use a tool like Wireshark to see the requests being made by the client. This will allow you to identify if the client is making calls to the API and the details of the request.